DEPARTMENT OF COMMERCE

BUREAU OF STANDARDS

' S. W. STRATTON, Dirictor

WAR WORK

OF THE

BUREAU OF STANDARDS

APRIL 1, 1921

MISCELLANEOUS PUBLICATIONS

OF THE

BUREAU OF STANDARDS

No. 46

PRICE, 70 CENTS

Sold only by the Superintendent of Documents, Government Printing Office, Washington, D. C.

WASHINGTON

GOVERNMENT PRINTING OFFICB

DEPARTMENT OF COMMERCE

BUREAU OF STANDARDS

S. W. STRATTON, Dirzctor

WAR WORK

OF THE

BUREAU OF STANDARDS

APRIL 1, 1921

MISCELLANEOUS PUBLICATIONS

OF THE

BUREAU OF STANDARDS

No. 46

PRICE, 70 CENTS

Sold only by the Superintendent of Documents, Government Printing Office, Washington, D. C.

WASHINGTON

GOVERNMENT PRINTING OFFICE

1921

WAR WORK OF THE BUREAU OF STANDARDS

CONTENTS

Page

Introduction 10 Aeronautic instruments n

Information n

Testing and investigation 13 Development 14 Instrument collection 16 Magnetic compasses 16 Aeronautic power plants 16 Description of altitude laboratory 16 Operating conditions studied in the laboratory . 19

Carbureter performance as affected by altitude 20

Aircraft cooling radiators 21 Airplane-engine fuels 23

Ignition systems 24

Lubrication of aircraft engines 30

Miscellaneous investigations 31

Aircraft construction 32

Metal construction for airplanes 32

Design of variable-camber airplane wing 34

Laminated wooden members for airplane construction 35

Various wood species as spruce substitutes 36

Artificial drying processes for wood 36

Wood protective coatings 37

Aircraft materials 37

Airplane dopes 37

Paper as a substitute for linen in airplane construction 37

Development of satisfactory cotton fabric for airplane wings 37

Balloon fabrics 38

Investigation of the thermal expansion of materials used in the aircraft- engine construction 38

Aircraft (miscellaneous) 38

Instruments for measuring tautness of airplane wires and cables 38

Synchronizing devices for airplane guns 40

Recovery of helium from natural gas 47

Airplane dopes 48

Introduction 48

Function and history of dopes 50

Composition of dopes 51 Cellulose nitrate dopes 52 Cellulose acetate dopes ' 52 Dope covers 54

Application of dopes 55 Fireproofed dopes . 56

Relation of dopes to fabrics 57 Balloon gases 57 Compilation of information 57 Laboratory and field work upon the generation of hydrogen 58

3
4 WAR WORK OF THE BUREAU OF STANDARDS

Balloon gases—Continued. page Tests of hydrogen plant at Langley Field 58

Inflammability of mixtures of hydrogen and helium and the ignition of balloons by incendiary bullets 59

Gas-leak detectors 59

Means for determining the specific gravity of balloon gas 59

Calibration of testing machines 59

Comparison bars for calibration 60

Preferable calibration methods 60

Hardness machines and extensometers 61 Chemical investigations (miscellaneous) 61 Ferrous materials 61 Nonferrous materials 62 Platinum metals and platinum substitutes 64

Prevention of corrosion 66

Removing metal fouling from rifle barrels 68

Soap ... .......... .'. 69

Carbon tetrachloride fire-extinguishing liquid 69

Antifreezing solutions for automobile radiators 69

Prevention of foul-gas formation in ammonia-absorption refrigerating machines. ."

; 70

Development of automatic analytical apparatus for use in nitrate plants . . 70

Hydrogen detectors for use in submarines 71 Determination of carbon dioxide and oxygen in the air of a submarine 71 Tests of gas masks and oxygen-supply apparatus 71 Miscellaneous 72 Chromatic camouflage and chromatically concealed insignia 72 Coke-oven investigations 73 Preliminary work of the Bureau 73 Fuel situation in early part of 1918 74

Attention focused on Roberts oven 74 Test conducted by the Bureau 75 Results of test at Dover 76

Conference at Pittsburgh -. 77 Further work by the Bureau 77

Interest in the use of midcontinent coals increased 78 Test of Koppers plant at St. Paul 78 Results of test at St. Paul 79 Further work at Dover 79 Blast-furnace test on St. Paul coke 80

Additional work carried on by the Bureau 81 Conclusions 81 Concrete and cement 82 Concrete ships 82

Load tests of concrete floors of Arlington building 82 Laboratory work on cement and concrete 84

Concrete ships 86

The development of a light, strong concrete 86

Corrosion tests of reinforcing steel 87

Bond tests •'•'Hj 88

Repeated reversal of load on reinforced-concrete beams 88

Impact tests on concrete slabs and built-up steel plates 88

Leakage of water through cracks in reinforced-concrete shell 89

Shear and compression in reinforced-concrete beams 89
CONTENTS 5

Concrete ships—Continued Page I Reinforcement of concrete slabs 91

Length of lap required for reinforcing bars 92

Value of brackets and haunches in flanges 92

Shrinkage of concrete in setting as related to ship construction 92

Electric batteries 93

Development of chemical work on batteries 93

Standardization and preparation of specifications for batteries 97

Reports on special subjects 100

Military tests of batteries 101 Electric blasting apparatus 107 Electric generators 108

Primers no

Electric tractors and trucks 112 Object of tests. . .*. 112 Method of testing 112 Results of tests 113 Limitations shown by tests 113

Electrical inductance method for location of metal bodies 114 Gages, precision 116

Testing of munitions gages 116

Manufacture of precision-gage blocks 116

Salvage of obsolete gages 117 School of instruction in gage work 117 Publications on gage work 117 Illuminating engineering 117 Acetylene generators for field service 117 Incandescent electric lamps 120

Protective fence lighting 121 Rockets and illuminating shells 124

Signaling lamps for daylight transmission of messages 126

Inks and ink powders 128

Liquid inks and ink powders 128

Indelible inks 129

Invisible signaling 130

Ultra-violet position marks and ultra-violet signaling 130

Signaling by invisible radiations 133 Thermal-radiophonic devices for secret signaling 135

Invisible writing, means for the detection of 139

Leather 141 Investigation of sole leathers 141 Composition soles 143 Investigation of strap and harness leathers 144

Chrome retan and bark-tanned upper leathers 144 Transmission belting 145 Leather packing for recoil cylinders 145 Waterproofing materials for use on Army shoes 146

Shoe cements 146 Shoe laces 146

Rubber heels 147

Specifications and routine tests 147 Magnetic investigations 148

Magnetic compasses 148 Magnetic analysis of rifle-barrel steel 149
6 WAR WORK OF THE BUREAU OF STANDARDS

Page

Manila rope 151 Medical supplies 153 Dental amalgams 153 Druggists ' rubber supplies 154

Dilution pipettes 154

Metallurgical investigations 154

Aluminum 154

Research in connection with the welding of steel 158

Copper crusher gages 1 58 Machine-gun erosion 159

Identification tags for the Navy and Army 159 Tests of new alloys 159 Gold-palladium alloys as substitutes for platinum 159 Nickel spark-plug electrodes * 160

Cements for spark-plug electrodes 160

Conservation of manganese 160

Oil proofing concrete liners 161 Tin conservation 161 Cadmium solders 161 Bearing metals 162 Metals for aeronautical instruments 162 Test-bar fractures 163 Hardness of brass cartridge cases 163

Centrifugal-steel castings 164

Magnesium-aluminum alloys for mirrors 164

Steel helmets for the United States Army 165 Effect of prolonged annealing high-silicon cast iron 165 Horseshoe nails 165 Deterioration of nichrome castings upon heating 166 Light armor plate 166 The relative cutting properties of ' 'cooperite '

' and ' 'stellite " 166 Miscellaneous investigations of iron and steel 167 Preparation of specifications 169 Foundry research and production of castings 169 Work for the Ordnance Department of the Army 170

Miscellaneous metallurgical investigations for the military departments. ... 170

Military inventions 172 Information furnished by correspondence 172 Membership in war boards and military committees. 172 Physical tests of metals and metal structures - 173 Load tests of 150-ton floating crane for the Navy 173 Strength and efficiency of electric welding 174 Investigation of strength of chains 177 Wheels, investigation of, artillery, truck, and airplane 178 Metal construction for airplanes 178 Natural-gas investigations 179 Beginning of natural-gas work 179 General natural-gas investigation 179

Relation to the United States Fuel Administration 180

Technical results 181 Investigation of town-border, natural-gas meters 1S2 Recovery of helium from natural gas 182
CONTENTS 7

Page

Optical glass and optical instruments 183

The production and testing of optical glass 183 Testing and design of military optical instruments 185 Binocular testing 189

Mil scales 192 Ordnance 193 Hardness of brass cartridge cases 193 Machine-gun erosion 193 Copper crusher gages 193 Defects of shrapnel steel 194

Light armor plate , 194

Synchronizing devices for airplane guns 194

Removing metal fouling from rifle barrels 194

Munitions gages 194

Airplane-gun mount 194

Powder-shipping containers 194

Semisteel shells 195 Copper rotating bands for shells 195 Gun barrel with gored rifling 195 French and American trench mortars 196

Railway mount recoil piston rods 196

Wheels, investigation of artillery, truck, and airplane 196

Magnetic analysis of rifle-barrel steel 196

Paper 196

Wall and plaster board 196

Paper as a substitute for linen in airplane construction 1 98

Paper filters for gas masks 199

Paper containers for axle grease and saddle soap 200

Photography 302

General photography 202

Photography as applied to spectroscopy 203

Photographic spectroscopy at the Bureau of Standards 203 Military problems in photography '. 204

Photographic method for detecting camouflage 207

Protection of motion-picture film from heat of lamp 207

Metallic mirrors for cameras 207

Automatic regulation of diaphragm by intensity of light 207

Production of dense barium crown glass for lenses 207 Tests of photographic lenses and camera shutters 208

Protective coatings 208

Electroplating investigations 208

Bituminous materials 211

Varnishes 214

Enamels 216

Slushing oils 217

Fireproofing of fiber board 218

Fire-retarding paints 218

Paint specifications 219

Paint testing 219

Publications and information : 220

New scientific publications 220

Metric literature '220 Soldiers' Manual of the Metric System 221

Technical information activities 221
8 WAR WORK OF THE BUREAU OF STANDARDS

Page

Radio communication 222

Radio in warfare : 222

Relation of Bureau of Standards radio laboratory to military services 224

Cooperative activities 225

Information and reports to the Army and Navy 226

Radio instruction 226

"Radio Instruments and Measurements" 227

"The Principles Underlying Radio Communication" 228

Radio direction finder 229

Coil aerial as transmitting and receiving device 330

Submarine radio signaling 231

Signaling system for airplane landing 232

Electron tubes 233

Special military researches on electron tubes 235

Radio measurements and tests 237

Cathode-ray oscillograph 239

Insulating materials 240

Permanent crystal detectors 242

Peace-time value of work 243

Radiometry 245

Researches 245

Radiant power life tests of quartz-mercury vapor lamps 245

Optical properties of balloon fabrics 245

Photoelectric sensitivity of molybdenite and various other substances 245

Amplification of bolometer current for signaling purposes 245

Infra-red transmission spectra of various substances 245

Protection of moving-picture film from heat of lamp 245

Glasses for protecting the eyes from injurious radiations 246

Reflecting power of stellite and magnalium 246

Instruments and methods of radiometry 247

Lacquers for protecting tarnishable metallic surfaces 247

Specifications and methods of test 248

Conferences, consultations, etc 249

Publications 251

Thermal-radiophonic devices for secret signaling 251

Radium 251

Information and recommendations 252

Investigation of specific problems 254

Equipment for factory inspection of dials 255

Routine precision measurements 255

Rope, manila 255

Rubber 255

Solid tires 255

Pneumatic tires and tubes 257

Gasoline hose 259

Oil-proof packing 259

Insulated wire 260

Mechanical rubber goods 260

Rubber jar rings for canning 261

Druggists' supplies 261

Safety standards for military industrial establishments 261

Searchlights 263
CONTENTS 9

Page

Sound-ranging apparatus 265

Introduction 265

Preliminary work 268

Brief review of investigations of various phases of the sound-ranging probj'y ti'iein'. ..... '.K-s'K *v/U». /; !•>.'.'. l-'j-'H ......

1

^ 269

Sounds transmitted through the earth 171 Geophone 271 Seismomichrophone 272 Submarine detection 2 73 Means for visual detection 273

Telephone problems 274

Study of the telephone situation in the District of Columbia 274

Testing machines, calibration of 276

Textiles 276

Cotton fabrics 276

Woolen and mixed fabrics and felts 279

Waterproofed canvas 281

Airplane fabrics 282

Cordage , 282

Military textile equipment, uniforms, blankets, etc 283

Dyestuff chemistry 285

Timepieces 286

Information and specifications 286

Chronometers 286

The beginning of a new industry 287

Testing of timepieces 287

Stop watches 287

Airplane clocks 287

Toluol recovery 288

Preliminary work, conferences, etc 288

Report on toluol recovery 290

Additional committee work 290

Publications on toluol recovery and gas standards 291

Previous publications combined in technologic paper 292

Increased production of toluol in the United States 292

Wheels, investigation of artillery, truck, and airplane 293

Wheel-strength requirements 293

Types of laboratory tests 294

Value of tests 294

Artillery wheels 295

Truck wheels 295

Technologic paper on wheels 295

Unique stress analysis of wheel 296

Analysis aids efficient design 296

Airplane wheels 297

Palmer wire-spoke wheel 297

Comparison with early American wheel. 297

X-rays 298

Protective materials 298

Radiography 299
IO WAR WORK OF THE BUREAU OF STANDARDS

INTRODUCTION

It is the object of this report to collect in one pamphlet short

descriptions of some of the more important work carried on by

the Bureau of Standards during the war, and which was of direct

service to our military forces. It may be stated in this connection

that practically all the time and energy of the Bureau's personnel

were devoted to military problems during the period of hostilities,

and therefore a war-work report becomes, in truth, a report of all

the Bureau's activities during that time. Not all the investigations which the Bureau conducted during the war are mentioned

in these pages. Unfortunately, some of the most interesting and

important of them are of such a nature that for military or other

reasons they can not be described. Likewise it has been impossible

to cover in a comparatively short pamphlet all the investigations

in which the Bureau had a part; but the more important ones

(with the exceptions noted above), and those which seem most

likely to result in permanent benefit not only to the military

departments, but also to the industries and public, are believed

to have been touched upon.

Among the most important work which the Bureau performed

during the war was the examination of all sorts of plans and

inventions designed to be used by the Army and Navy. The

Bureau, through its cooperation with numerous governmental

organizations and committees, assisted in selecting from the

great mass of ideas submitted, those which appeared to possess

actual value. Members of the scientific staff served on these

committees, thus maintaining the closest possible contact between

the committee and the Bureau. A few particular cases of this

assistance are described in the subsequent paragraphs, but many

have necessarily been omitted.

A great deal of the assistance which the Bureau, through its

experts in all the fields of science, was able to render to our military

forces came through oral advice and consultations. The value

of this work can not even be estimated, and unfortunately most

of it was not of a nature to become a part of the permanent

records. Without doubt, a great deal of valuable time and money

was often saved by the military service through informal confer- ences with members of the Bureau's staff.

It is hoped that those who read the following pages will find

some material of assistance to them in their work, as it is the

belief of this Bureau that many of the problems^—the solution of
AERONAUTIC INSTRUMENTS 1

which was undertaken as a war measure—are of equal or even

greater importance in the arts of peace. Their solution was one

of the real benefits resulting from the war. AERONAUTIC INSTRUMENTS

Information

From the beginning of the war the Bureau of Standards was

the best-equipped organization in this country for furnishing

information on the subject of aeronautic instruments. Six years

of previous experience in the investigation of altitude instruments, including tests made for the United States Army and

Navy, furnished the basis for a general study of the many instruments used in aviation. Much valuable material had been

gathered abroad and through conferences with foreign officials

who visited this country, and this was augmented by information

obtained by a member of the Bureau's staff during a trip to some

of the principal laboratories, factories, and airdromes in England,

France, and Italy during the war. Through such means as this

the exchange of information with the air services of foreign

countries was facilitated.

Routine testing at the Bureau of a specified portion of the

instrument production of this country was another source of

information. The intimate knowledge thus obtained regarding

the construction and performance of the various instruments

particularly fitted the members of the staff thus engaged for

making suggestions and originating improvements which many

times proved to be important.

Early in the war a critical study was made of British-instrument

specifications which were placed at the disposal of the Bureau of

Standards by the Royal Flying Corps.

Data thus obtained were supplemented by those derived from

careful tests of all suitable types of instruments which could be

collected. Such information, coupled with the results of a survey

of the manufacturing facilities of this country, enabled the Bureau

to render expert assistance in writing specifications and advising

in regard to instrument production. As a result of this preparation, the performance specifications, and in some cases the construction specifications also, for all instruments adopted as standard by the Army and Navy during the war were based

directly on technical information obtained at this Bureau.

The early work of the Bureau of Standards in studying altitude

instruments and in assisting to start the production of aeronautic
1 2 WAR WORK OF THE BUREAU OF STANDARDS

instruments made it natural that the military and naval authorities should turn to the Bureau for information whenever questions

arose in any phase of the instrument work. Much information

and advice was given out in reply to official correspondence and

to verbal requests. A considerable part of this consisted of

examining and reporting on inventions relating to aeronautic

instruments and other appliances submitted by the General Staff of

the Army and by the National Advisory Committee for Aeronautics.

Members of the staff were called on frequently for conferences

with visitors. During the summer of 191 8 production officials

of the Army and Navy visited the Bureau practically every day

to follow the results of investigations or to discuss specifications

in connection with instruments.

To make information more readily accessible and to provide

for a simple means of distribution in the proper channels, a

series of confidential technical information circulars was issued

covering various phases of the instrument work. These met with

immediate and continually increasing demand, as they constituted the first attempt of this nature to satisfy a pressing need.

Distribution abroad created a demand among the foreign air

services for this material. A large number of the circulars have

been furnished British, French, and Italian officials, and it is

understood that in many cases translations have been made. A

number of these circulars contained confidential information from

the allied Governments which, together with the necessary secrecy

surrounding all developments during the war, made it imperative

to limit their circulation to official circles. The close of hostilities

makes it probable, however, that they will be made available for

more general distribution as fast as permission can be obtained

to release the foreign material.

Altitude tables which were used in calibrating the dials of all

altitude instruments were calculated at the Bureau of Standards

and were furnished to the manufacturers. In addition, tables of

temperature corrections for altitude instruments and altitude

corrections for air speed indicators were computed.

Valuable and much-needed information was given to the

various manufacturers regarding suitable testing methods and

apparatus to be used in the testing. Also from time to time

many useful suggestions were made regarding the best methods

of manufacture and the proper materials to use. Another important part of the Bureau's work consisted in

furnishing to the Army and Navy information regarding the
AERONAUTIC INSTRUMENTS 13

proper use and repair of instruments. At the request of the Navy

Department, a school was conducted at the Bureau of Standards

for naval aviators. An intensive course covering the theory,

testing, and use of aeronautic instruments was thus provided.

In addition information was furnished directly to the flying

fields and salvage stations of the American Expeditionary Forces

regarding the testing and proper use of instruments.

Testing and Investigation

The starting of aeronautic instrument production in this

country necessitated immediate preparation for testing the instruments. It was necessary to control the quality of the output by

frequent tests more thorough than the acceptance tests given by

the inspectors at the factories. To this end provision was made

to have the Bureau of Standards give thorough laboratory tests to

4 per cent of the total production. For this purpose the design

and construction of suitable testing apparatus was rapidly carried

out. This apparatus included temperature chambers and vibration stands, so that the instruments might be subjected to the

same conditions as would be encountered in actual use. To facilitate testing at the factory the Bureau developed

modifications of its laboratory tests for acceptance purposes and

instructed the Government inspectors in these methods of testing.

In a number of cases the Bureau calibrated manufacturers' standards and even constructed standards and loaned them to manufacturers.

Investigations were made on different occasions to determine

the causes for the failure of instruments to function properly.

For instance, at one time the Bureau's tests on altimeters showed

consistently poor performance. A careful study showed that

this was due to the rusting of the small, steel chain which

operates the pointer. This discovery led to the rejection of

5,000 instruments which had already been accepted by the Air

Service. Along the same line tests showed that most of the

breakdowns which occurred in a certain type of tachometer were

due to a faulty type of escapement. The latter was changed to

a sturdier type, and the durability of the instrument was much

improved.

The laboratory tests on large quantities of instruments were

naturally very important as a source of information regarding

the average performance of different types. The long-continued

investigation of such instruments as altimeters, airspeed indicators,

oxygen apparatus, and tachometers has furnished statistics
14 WAR WORK OF THE BUREAU OF STANDARDS

which are and will be in the future of considerable value to the

scientific and engineering world.

Although complete laboratory tests indicate quite accurately

the quality of an instrument, the performance of the latter during

flight tests will often reveal defects which would not be indicated

in the laboratory. Consequently, flight tests were made by members of the Bureau's staff with a view to noting peculiarities in

the performance of different instruments. To mention a specific

case, laboratory tests on a certain liquid manometer type of rate-ofclimb indicator gave most satisfactory results. However, when

the instrument was tested in flight the combined effect of acceleration and inclination caused such fluctuations of the liquid column

as to make the readings of no practical value. Improvements

were immediately suggested owing to the discovery of this fact

which might not have been brought out so forcibly had only

laboratory tests been made. In such a manner laboratory data

were supplemented by flight data, and an extensive knowledge of

the performance of the instruments under all conditions was

obtained.

Development

The first aeronautic instruments submitted for test, with the

exception possibly of altimeters, were in a more or less elementary

stage of development. The data gained from these tests suggested improvements which could be made, and thus the instruments were gradually developed.

As aviation progressed, new instruments were needed; for

example, oxygen-control apparatus for furnishing a regulated

supply of oxygen to the aviator at high altitudes, rate-of-climb

indicators for giving the vertical component of the speed, and an

automatic means of taking instrument readings during performance tests.

The Bureau of Standards took an active part in the development of oxygen apparatus in the United States by promoting

cooperation between the foreign experts and American manufacturers in order to get production started. Valuable suggestions

were made looking toward the elimination of defects and improvement in the performance of the instruments after careful tests

had been carried on at the Bureau. A new feature designed to

avoid the main source of temperature error was developed.

The necessity for measuring accurately the speed of ascent in

performance tests created an urgent demand for an instrument
AERONAUTIC INSTRUMENTS 15

which would read this quantity directly. The inherent errors

in the liquid-manometer, rate-of-climb indicator, made it desirable

that a new type of instrument be developed, using some means

other than a liquid column as a pressure measuring device. The

Bureau of Standards consequently undertook the development of

a rate-of-climb indicator whose indications depended on the

deflection of very sensitive diaphragm boxes. This instrument

was nearly completed at the end of the war and gave promise

of being an improvement over former types.

As high-altitude flights became more common the need of

barographs capable of recording such altitudes became more

acute. At the request of the flight-test officers, several 10 000-

foot barographs were remodeled to give a 30 000-foot range,

according to a method developed at this Bureau.

For some purposes it is more convenient to have the pressure

of the atmosphere indicated instead of the altitude. On this

account a number of altimeters were remodeled and fitted with

special dials to meet this need.

Detail drawings of a gyrostabilizer for instruments had been

prepared at the time of the armistice and a working model of

about one-fourth size constructed. A bomb sight and doublepivot compass to go on the stabilizer formed a part of the design.

A new type of inclinometer or banking indicator for use in

determining the position of the aircraft relative to the proper

banking angle was developed. Actual tests showed the instrument to be practical and to possess advantages over those ordinarily in use. The instrument differed from the ordinary bubble-type of

banking indicator in having, instead of a bubble, a carefully

ground glass ball, the inside of which was coated with a selfluminous paint. This ball was mounted inside of a curved glass

tube mounted convex downward on an angularly graduated base.

The position of the ball in the tube indicated the position of the

aircraft relative to the proper banking angle. The instrument

could be easily read without artificial illumination.

The importance of securing accurate records of aircraft performance tests led a member of the Bureau's staff to consider

using the principle of the motion-picture camera to obtain a con- tinuous photographic record of the instrument board during

flight. It was recognized that the development of such a device

would be an improvement in many ways over the use of recording
1 6 WAR WORK OF THE BUREAU OF STANDARDS

instruments. Later a similar suggestion was received from

Maj. R. W. Schroeder, and plans were made for development of

such a "dummy observer," as it was called, and the apparatus

was constructed subsequent to the signing of the armistice.

Instrument Collection

The Bureau of Standards possesses one of the most complete

collections of aeronautic instruments in the world. Not only

samples of practically every kind of airplane instrument made in

this country, but all kinds of foreign instruments, as well, were

obtained during the war. A collection of typical instruments

which the Bureau prepared for exhibition purposes is shown in

Fig. r. The original purpose of the collection was to aid in instrument

production by making available for the manufacturer types of

foreign instruments with which he had had no experience. In

several cases production was facilitated at the beginning of the

war by the copying of instruments thus made available by the

Bureau of Standards. Later, as it grew, the collection became

useful for instruction and investigation purposes. The great

variety of American, British, French, Italian, and German instruments included make it one of the most useful collections for

reference and comparison in existence.

Magnetic Compasses

This subject will be found to be treated under the heading,

"Magnetic Investigations."

AERONAUTIC POWER PLANTS

Description of Altitude Laboratory

The part played by aircraft in the war was of the first importance, and at the time the United States entered the conflict it was

apparent that the victory was likely to go to the side having the

largest number and most efficient types of machines. It therefore

became the duty of the Government to make a thorough study

of the aeronautic situation with a view to improving, wherever

possible, the performance of airplanes and their appurtenances.

Since the success of an airplane depends very largely upon the

operation of the power plant, a study of aeronautic-engine performance on a larger scale than anything before attempted was

decided upon. As a consequence, in cooperation with the National

Advisory Committee for Aeronautics, the Bureau constructed

what has since become known as the altitude laboratory for the
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. i. —Group of typical aeronautic instruments

The bureau has assisted the aviator by supplying him with more reliable indicating devices, the

sense organs of an airplane

Fig. 2.The "Liberty 12" airplane engine mounted in the altitude chamber

WTien the doors (one ol which is shown at the right) are closed this chamber is practically air tight. The air pressure and temperature are then lowered to those corresponding to any desired alti- tude, and the engine tested under actual flying conditions
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 3.The carbureter test plant

This plant is specially designed to test airplane carbureters under altitude conditions. Even

the pulsations in the inlet manifold caused by the pumping action of the engine's cylinders

are duplicated in this apparatus
AERONAUTIC POWER PLANTS 17

testing of aircraft engines as nearly as possible under service

conditions. Since its construction, the laboratory has been in

almost continuous operation and results of the greatest possible

value, not only in the field of aeronautics, but to the automotive

industry in general, have been secured.

It is perhaps not generally known that the laboratory testing

of aircraft engines presents peculiar difficulties not met with in

the case of other types of internal-combustion engines. These

difficulties are due to the fact that the engine of an aircraft performs most of its work not at the earth's surface, but at altitudes

ranging from a few thousand to 30 000 feet. Atmospheric conditions at the higher altitudes are very different from those at

the earth's surface, the pressure of the air at 30 000 feet being

less than one-third that encountered at sea level. The average

temperature at such an altitude is in the neighborhood of — 35 F,

and both the atmospheric density and temperature have a pronounced effect upon the operation of an internal-combustion

engine. The amount of explosive charge which the engine is

capable of drawing into its cylinders varies with the density of

the air, which, of course, is a function of altitude. Temperature

is also a controlling factor, and, besides affecting the quantity of

the charge, produces numerous other variations in the operation

of the engine, such as those brought about by changes in the

temperature of the jacket circulating water, lubricating oil, etc. When it was decided to conduct a thorough investigation of

airplane-engine performance, it was apparent that the laboratory

must be so designed that the entire engine could be surrounded

with conditions existing during an actual flight. Time has shown

that this decision was a correct one, but it meant the construction

of a laboratory unlike anything before attempted. The essential

features of the altitude laboratory consist of a concrete chamber,

the walls of which are of such thickness and so reinforced that

they are capable of withstanding a considerable pressure from

without. Within this chamber, the engine is mounted on a stand

designed to duplicate as nearly as possible the typical airplanefuselage mounting. The chamber is provided with doors on

opposite sides, so that the interior may be easily reached, but

these doors are arranged to close upon rubber gaskets, so that

when shut they form an airtight joint. The exhaust from the

engine and the air within the chamber are withdrawn by means

of a centrifugal exhauster driven by an electric motor so that the

26035°—21 2
1 8 WAR WORK OF THE BUREAU OF STANDARDS

pressure within the chamber may be reduced as low as one-third

of an atmosphere, or that corresponding to an altitude of about

35 ooo feet. Fig. 2 is a view of the liberty 12-cylinder engine

set up in the chamber.

The air supply to the carbureter first passes over a series of

refrigerating coils by which its temperature is lowered to a point

approximating that met with at the altitude of the test. Similar

coils within the chamber keep the air surrounding the engine at

about the same temperature, and electric fans cause a circulation

somewhat similar to that met with during a flight. These coils

for cooling the air form part of an ordinary direct-expansion

ammonia-refrigerating plant. Since the temperature of the air

can not be controlled very readily by means of the refrigerating

plant alone, electric-heating grids are placed within the air passage

to the carbureter so that in practice the temperature of the air

is first lowered by the ammonia coils and then raised slightly by

the electric grids to the exact temperature desired. The engine

is connected by a coupling and shaft, passing through an air-tight

stuffing box in the chamber wall, to an electric dynamometer and

water brake, by means of which its power is absorbed and

measured. Thermocouples are placed at all points at which

temperature measurements are desired, and manometer tubes are connected to the engine and piping systems to measure the

pressures. These are all led to convenient points outside the

chamber. The fuel used is weighed by tanks mounted on scales

on a platform sufficiently high to insure a flow of fuel to the

engine by gravity.

The exhaust from the engine is water cooled, the water entering

the exhaust pipe at some little distance from the engine, so as not

to affect the operation in any way. This water is removed from

the exhaust gas in what may be termed "settling tanks" placed

outside the chamber. From these tanks the gases are removed

by the exhauster, mentioned above, while the water is drained by

gravity, the drop of the pipe being sufficient to prevent any breaking of the vacuum.

The altitude laboratory as originally constructed and operated

during the war consisted of a single chamber placed in a temporary

wooden building. This has now been replaced by an installation of

two chambers in the permanent dynamometer laboratory of

the Bureau. The arrangement is such that the chambers may be

used either separately or together; that is, communicating doors
AERONAUTIC POWER PLANTS 19

may be thrown open and both sets of pumping equipment used

to remove the air and gases from a single engine. In this way

the capacity of the plant will be greatly increased.

Operating Conditions Studied in the Laboratory

The problem first presented by the National Advisory Committee for Aeronautics for solution by the use of the altitude

laboratory was that of the performance of different grades of gasoline at high altitudes in typical aircraft engines. The lubrication

division of the Signal Corps requested also the preservation of

samples of the lubricating oil to determine the effect of fuel

composition and of altitude on the deterioration of such oils.

A staff of two or three men was detailed by the lubrication division

to assist in securing the desired data.

As different grades of fuel (all of comparatively high quality)

affect engine power and performance only to a very slight extent,

the satisfactory solution of this problem required the highest

possible accuracy in obtaining complete data on engine performance as previously outlined. Thus a practice was established by

which all the measurements of power, speed, fuel consumption,

barometric pressure, air and water flow, temperature, and pressure

provided for by the apparatus are customarily made, no matter

what is the immediate purpose of the test in hand. The result

is, in addition to the data directly desired, an accumulation of

valuable supplementary data on engine performance.

Observations have been made to determine specifically the

following relations

1. Horsepower-altitude relation for engines at normal speed.

2. Horsepower-speed relation at a range of altitudes up to

30 000 feet.

3. Horsepower-compression ratio for normal speed, using compression ratios of 4.7, 5.3, and 6.2 to 1 at a range of altitudes up

to 30 000 feet.

4. Horsepower-inlet air temperature at a range of speeds and

altitudes.

5. Effect of variation of intake pressure on horsepower at a

range of altitudes to simulate the effect of supercharging equipment.

6. Effect of exhaust back pressure on horsepower over a limited

range of pressures.

7. Mechanical losses at various speeds, altitudes, and engine

temperatures.
20 WAR WORK OF THE BUREAU OF STANDARDS

8. Metering characteristics of a number of different types of

carbureters with and without altitude compensation or control

for the full range of speeds and altitudes.

9. Optimum mixture ratios for maximum power over the range

of speeds and altitudes with several different carbureters.

10. The performance of a number of automatic and handoperated altitude-compensation devices for different carbureters.

11. The total heat distribution for all speeds and air densities

at full throttle.

12. The performance of special fuels: "Hector," a combination

of cyclo-hexane and benzol; " Alco-gas," a combination of alcohol,

benzol, gasoline, and ether at a compression ratio of 7.2 to 1. Other relations have been investigated from time to time.

Moreover, the detailed records taken for each test include much

information bearing on other characteristics of engine performance, such as, for instance, the behavior of spark plugs and ignition systems under conditions of low-air pressure and temperature.

Carbureter Performance as Affected by Altitude

In addition to the altitude laboratory the Bureau has constructed a complete plant for the testing of aeronautic carbureters, and in cooperation with the National Advisory Committee

for Aeronautics has carried on an extensive investigation of these

devices. The performance of carbureters under the conditions

existing at high altitudes, where air density and temperature are

low, is a matter of great importance and affects markedly the

operation of airplane engines. The carbureter test plant is made

up of a strongly constructed box of wood and metal with a glass

door within which the carbureter is mounted. The opening in the

carbureter which would ordinarily be connected to the inlet manifold is coupled to a pipe leading to a centrifugal exhauster driven

by an electric motor. A shutter is placed in this pipe and con- nected by step pulleys with a small motor, so that it may be

driven at any desired speed end thus simulate the conditions of

pulsating flow encountered in an actual manifold. Air is admitted

to the inclosed chamber through a metering orifice and regulating

valve, and its temperature may be raised above that of the sur- rounding air by means of electric heating grids. Fuel is fed to

the carbureter from a weighing tank and automatic devices are provided for recording the consumption in a given time. The

construction of this plant is clearly shown in Fig. 3. With this

plant complete investigations have been carried out on all the
AERONAUTIC POWER PLANTS 21

ordinary styles of airplane carbureters, and their metering characteristics have been determined over the range of altitudes likely

to be encountered in actual service. The plant was not designed

and has not been used to eliminate the engine testing of carbureters, which will always be the final determining factor, but the

preliminary work may be done on the carbureter-test plant much

more rapidly and cheaply and with far greater accuracy than on

an engine. With the test plant all undesirable variables may be

omitted and only those factors changed which it is desired to

study.

Aircraft Cooling Radiators

In connection with the work on aeronautic power plants, the

Bureau of Standards has conducted for the past four years an

extensive investigation of the performance of airplane radiators.

The efficient functioning of the cooling system is an extremely

important matter in the case of aircraft engines, since any form of

radiator offers some head resistance and must take away a portion of the power of the engine which would otherwise be available

for driving the plane, while at the same time a radiator of high

cooling capacity is needed, owing to the fact that aviation engines

are generally run at their maximum power for long periods of

time. The ideal radiator for airplane use is, therefore, one with

a large cooling capacity and low head resistance (not necessarily

for the radiator alone, but for the combination of plane and radiator) , but these two requirements are in general contradictory.

This subject became of extreme importance when the United

States entered the war, and shortly thereafter the Bureau undertook, in cooperation with the National Advisory Committee for

Aeronautics, a complete investigation of the relative merits of

existing types of airplane radiators. Since that time, tests have

been made on nearly all makes of radiators now in use, and the

results have been correlated and issued for the benefit of those

interested, through the reports of the above-mentioned committee.

Specimens of the various standard radiators were submitted by

the manufacturers. These were all constructed to certain given

dimensions of height and width, but the sizes of the air and water

tubes and the depth of the core were those which would be used

in the actual radiators. In this way, all the tests were reduced

to a common basis, only those peculiarities which were due to

the design and not to the size of the radiator having an effect on

the result.
22 WAR WORK OF THE BUREAU OF STANDARDS

The investigational work carried on in this connection falls

naturally under two heads: (i) The determination of the head

resistance of the radiator core, and (2) the determination of the

efficiency of the radiator as a cooling device. The first property

was investigated by mounting the specimen of radiator core upon

the vertical arm of an aerodynamic balance in one of the Bureau's

wind tunnels. Air streams of various known velocities were

caused to impinge on the specimen, and its head resistance could

therefore be easily determined. In these tests the bare core without water boxes was used. Experiments were likewise conducted to determine the relative head resistances of a model

fuselage with stream-line nose and radiator mounted in an open

position on the plane and that of the same fuselage with a nose

radiator, such as has largely been employed on modern machines.

The results of this investigation were of particular interest as showing the very large amount of power absorbed by nose radiators.

Although this position possesses certain advantages, particularly

in the case of airplanes designed for use in warfare, it would appear

to be a very poor position for the radiator from the point of view

of head resistance.

Two methods were used for determining the efficiency of a

radiator as a cooling device. In the simplest of these, the radiator was mounted in a tunnel through which an air stream was

forced. At the same time superheated steam at atmospheric

pressure was admitted to the water space of the radiator and

the amount of steam condensed in a given time with a given air

flow determined. The radiator which would condense the greatest

amount of steam in a given time was, of course, the most efficient

cooling device. The other method used consisted in mounting

the radiator in a tunnel, the whole of which was inclosed in an

air-tight tank. The pressure within this tank could be reduced to

that corresponding with any desired altitude up to about 35 000

feet, while at the same time the air was circulated through the

radiator by a fan driven by belt from an electric motor. The

same air constantly passed through the radiator, but was cooled

by a honeycomb on the other side of which water was circulated.

In these tests water, and not steam, was used in the radiator.

The tunnel, just now described, was the one originally used in

carrying out the investigation of radiator-cooling capacity, but

owing to the fact that a very long time was required for establishing stable conditions within the tank, the steam tunnel was finally
AERONAUTIC POWER PLANTS 23

used, as it was found that it gave just as satisfactory comparisons

between different types of radiators.

As a result of this work it has been possible to state with accu- racy the percentage of the total available horsepower of an airplane

engine which any given type of radiator will absorb and also the

efficiency of the radiator as a cooling device. Fundamental data

have been collected, and the Bureau has been able to indicate

certain general features which should be observed in the design of

a successful radiator for airplanes.

Airplane-Engine Fuels

From the beginning of the war the work of the Bureau of Mines

on automotive-fuel conservation was actively supported by the

Bureau of Standards through close and constant cooperation. At

the meeting of the Interallied Commission on Specifications for

Petroleum Products of the Interallied Petroleum Conference some

of the foreign delegates urged a very rigid gasoline specification

for fuels for use in combat aircraft, basing their recommendations on their own satisfactory experience with certain gasolines, but without full knowledge of the possible performance of

other gasolines. The adoption of such close specifications would

have materially reduced the available supply of combat aviation

gasoline and introduced unnecessary expense and serious difficulty,

not only in production but in overseas shipment and distribution.

A careful comparison of the power-producing qualities of 10 different gasolines selected through cooperation with the Bureau of

Mines was made by actual engine tests under flight conditions in

the altitude laboratory of the Bureau. A report on these tests

was the only quantitative data presented to the interallied commission on this subject, and it resulted in the adoption of more

liberal gasoline specifications, which were amply justified in service

and which resulted in a saving to the American people of millions of

gallons of oil in their fields and thousands of dollars waste effort

in the refining and distribution in France of aviation gasoline.

In connection with the work on aviation fuels, a thorough study

was made of the best methods for determining the quality of

gasoline. It is generally recognized that the simplest test, that

for gravity, does not give a reliable indication of the value of

gasoline as a fuel. On this account tests were made of the viscosities of various commercial and aviation gasolines, in the hope

that this property might prove to be of value, in connection with

others, in specifying the quality of fuels. It was found that the
24 WAR WORK OF THE BUREAU OF STANDARDS

viscosity has a marked influence on the metering characteristics of

carbureter nozzles, and must be taken into account. A thorough

discussion of this subject will be found in Technologic Paper No.

125, "The Viscosity of Gasoline."

In addition to service tests on common and aviation gasolines,

a number of synthetic fuels were tested at the request of the

Bureau of Mines and the Navy Department, respectively. Reports

were prepared on the performance of " Hector" fuel, a mixture of

70 per cent cyclohexane and 30 per cent benzol developed by the

Bureau of Mines, and "Alcogas," a fuel containing a large percentage of alcohol. The general conclusions from these tests will

be compiled for publication. Five proprietary preparations intended to be used as gasoline substitutes were tested for the

military service. Many of the so-called "gasoline improvers"

were tested for the inventions section of the General Staff of the

Army. Two devices for the convenient use of kerosene instead

of gasoline in the usual gasoline engine have also been tested for

this section.

Ignition Systems

In November, 191 6, the National Advisory Committee for Aeronautics requested the Bureau of Standards to undertake a study of

the causes of failure of spark plugs, and to develop, if possible, a

new insulating material which would be superior to those then

available for use in such devices. This request was the result of

reports from abroad which indicated that spark-plug trouble was

one of the limiting features in the design of the most recent highpower aviation engines. A program was laid out according to

which the Bureau's ceramic laboratory was to prepare a number

of samples of porcelain of widely different composition. These

were to be tested by the electrical laboratories for their relative

merits, and on the basis of these results further porcelains were

to be made up until a satisfactory material was found.

The early experiments indicated a great need for more information as to the conditions under which spark plugs were required

to operate, and when the more general program for the study of

all phases of aeronautic power plants was begun at the Bureau

the ignition investigation was enlarged and fitted in as one of

the principal divisions of the program. The ignition staff was

enlarged, and during the latter part of the work consisted of

seven persons; the work included a study of the conditions in

aviation engines and the measurements of the various constants

of ignition systems, as well as the development of materials.
AERONAUTIC POWER PLANTS 25

Throughout the work intimate contact was maintained with

officers of the National Advisory Committee for Aeronautics and

the Bureau of Aircraft Production, and much of the testing was

at the direct request of the inspection section of this latter bureau.

Owing to the frequent and unavoidable changes in organization

of the branches of the War Department connected with aviation

during the war, it was found difficult to obtain data as to the

actual service performance of the various spark plugs and ignition

systems in use at the flying fields.

The duty of the ignition system is to produce at the proper time

in the interior of the combustion space of gasoline engines a spark

which, by igniting the compressed mixture of gasoline, vapor, and

air, causes it to burn and deliver its energy to the engine. All of

the systems in practical use on high-speed engines are of the

jump-spark type. The essential feature of the system is an

induction coil, which consists of an iron core upon which is wound

a primary coil of few turns of relatively large wire and a secondary

coil having a very large number of turns of fine wire. A current

is established in the primary winding either by means of a battery

connected in series with the coil, as in the case of so-called battery

and coil systems or else by inducing current magnetically in the

primary coil by the relative motion of the coil and of a permanent

magnet, as is done in the case of magnetos. With either type of

system when a spark is desired in the engine, the circuit breaker

is suddenly opened by means of a cam and the magnetic flux produced by the primary current rapidly decreases. This decrease

in flux generates in the many turns of the secondary winding a

high voltage which is conducted from the distributor to the spark

plug in the proper engine cylinder. The current passes across the

spark gap at the plug to the grounded electrode and returns

through the engine frame to the other end of the secondary coil.

There are two essential operating characteristics of this type of

apparatus which must be borne in mind in considering its behavior

under various adverse conditions. First, with the secondary circuit open the voltage will build up to a certain maximum value

(10 000 to 20 000 volts) which is determined by the inductance

and capacity of the circuits, and no spark will be produced unless

the breakdown voltage of the gap between the spark-plug electrodes is less than this value. The length of the spark gap usually

used in aviation engines is such as to break down at about 6000

volts, thus affording in this respect a factor of safety of two or

three. Second, if the spark plug is shunted by a resistance, the
26 WAR *WORK OF THE BUREAU OF STANDARDS

maximum voltage obtained across its terminals is very considerably reduced, the reduction being greater as the shunting resistance becomes less. With most ignition systems, the voltage

reached becomes less than the 6000 volts required to produce a

spark when the shunting resistance is less than 100 000 ohms.

It is, therefore, the duty of the spark plug to perform three functions: (1) To maintain a gap between its electrodes which shall

have a breakdown voltage of approximately 6000 volts; (2) to

maintain an insulation resistance between its terminals of not less

than 100 000 ohms; (3) to be substantially gas-tight in order that

the leakage of heated gas through the plug may not raise it to

such a high temperature as to cause preignition of the engine and

destruction of the plug. These requirements can be met with

comparative ease in spark plugs used in automobile engines, but

the conditions of operation in the modern aviation engine, where

every effort is made to obtain high powers with small space and

weight, are very much more severe. Measurements which have been made at the Bureau in aviation

engines show that the pressures attained may amount to 500 to

600 pounds per square inch, and the difficulty of maintaining gastight joints is very great. Also, experience has shown that the

mechanical vibration of even well-balanced engines is often sufficient to crack the porcelain insulation. During a cycle of operation of the engine the spark plug is alternately exposed to a blast

of cold air which during the intake stroke may be at a temperature

well below zero, and is immediately thereafter exposed to the

flame of compressed and burning gasoline vapor, the temperature

of which may be estimated at 2500 C. These severe temperature

conditions tend to crack the porcelain, and by the expansion of

the parts, to open up cracks for the leakage of the gas. Moreover,

refractory materials of the class used for spark-plug insulators

(mica, porcelain, glass, etc.) become conductors of electricity if heated to a sufficiently high temperature.

In addition to the trouble just mentioned, the flame of burning

gasoline deposits a layer of soot on any cold surface with which it

may come in contact, and, furthermore, the lubricating oil which

is present in the cylinder may be sprayed against the heated portion of the spark plug and, decomposing, also leave a layer of

carbon. These carbon deposits tend to short-circuit the plug

and may reduce its insulation resistance below the limiting value.

Another type of failure is produced if the surface of the electrodes

becomes covered with lubricating oil, or more particularly, if a
AERONAUTIC POWER PLANTS 27

drop of oil bridges the gap, since this oil before being decomposed

has a breakdown strength of from 10 to 15 times that of air. The

voltage required to produce a spark across the gap is much increased and may exceed the value which the ignition system can

deliver.

The aim in spark-plug construction is to satisfy as completely

as possible the three requirements of definite spark voltage, high

insulation resistance, and gas tightness by suitable modification of

design or material, while the aim in ignition-system design is to

reduce as much as possible the stringency of these requirements.

The ignition staff of the Bureau has endeavored to assist the

military departments of the Government in ignition problems:

(1) by making such measurements and tests of commercial apparatus as were requested by the departments concerned, in order

to determine the relative and absolute merits of devices then on

the market; (2) by devising new methods of test to show more

clearly such relative merits, and preparing specifications based on

these tests; (3) by collecting as much information as possible as

to the dimensions, constants, and performance of various types of

systems in order to be able to give more intelligent advice on the

subject: (4) by assisting various manufactures of ignition apparatus, by tests and consultation, in their development of materials

and designs which showed promise of success; (5) by studying

the conditions under which such apparatus operates on aviation

engines and thus securing data otherwise unobtainable by individual manufacturers; and (6) by developing in the Bureau's laboratories improved materials and better arrangements of circuits.

The following paragraphs outline in more detail the results of

these various lines of work.

The program for the development of improved insulating material mentioned above has been carried out with the result that several porcelains have been obtained which show very excellent properties as regards electrical resistance while hot, resistance to cracking when exposed to sudden temperature changes, and mechanical

strength. The composition of these materials has been given to

various porcelain manufacturers requesting it, and it has been put

into production by the largest spark-plug manufacturer in the

country. The method of measuring resistivity used in this development work has been adopted by a number of manufacturers

for their own laboratories, and others have submitted samples of

their product to the Bureau for test. One of these materials,

which had hitherto been used only to a slight extent in spark
28 WAR WORK OF THE BUREAU OF STANDARDS

plugs, showed very satisfactory results when subjected to the

Bureau's tests, and, as a result, has been adopted by several of

the principal spark-plug manufacturers.

It was necessary in the work to devise various methods of testing spark plugs. In addition to the conductivity measurements

developed for the porcelain testing, methods have been devised for

testing the resistance of the insulating material to sudden changes

of temperature and to mechanical shock, and a quantitative

method has been developed for measuring the gas tightness of the

plugs while they are heated as in an engine. Methods have also

been developed for measuring the heat energy in the spark produced by various types of ignition systems and for determining the

ratio of turns and the magnetic leakage between the primary and

secondary coils of such systems. A general view of the sparkplug laboratory showing most of the apparatus used in these

investigations is given in Fig. 4. The performance of ignition systems as to the maximum voltage obtainable and the minimum re- sistance across which they can produce a spark seems to depend

in a very large degree upon the amount of eddy current which may

be produced in the iron core and upon the electrostatic capacity

of the various parts of the circuits. No methods are at present

known for conveniently determining these quantities, but the

Bureau is still engaged in developing a method which, it is hoped,

will provide a satisfactory measurement of these important properties.

At the request of the Bureau of Aircraft Production and of the

Motor Transport Corps, specifications have been prepared on the

basis of which they may purchase their spark plugs, and the tests

developed at the Bureau have been incorporated in these specifications.

A very considerable amount of testing of spark plugs of various

designs and of proposed types of ignition systems has been carried

out at the request of the inspection section of the Bureau of Aircraft Production. (See Fig. 5.) The results have been reported

in detail to this section and to the manufacturers of the particular

products tested. These tests, together with those incident to the

development of the Bureau's methods and the study of spark

plugs obtained from various foreign sources, have brought up

the total number of spark plugs on which records have been kept

to over 3 000, among which over 100 distinctly different types are

represented.
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 4.A comer of the spark-plug laboratory

At the right are the two electric furnaces used in measuring the electrical resistance of various

porcelains, using samples in the form of cups, as shown near the furnaces. The instruments

used in the measurements are shown in the center, while at the left are the pressure tanks and

glass bell jar for measuring gas leakage through plugs. In the rear are sample plugs and porcelain cups submitted for test
Miscellaneous Publications, Bureau of Standards, No. 46

This form of construction permits the use of smaller pieces of high-grade wood as well as inferior woods in the building of airplanes. The strength of these laminated beams is just as great as that

of solid beams
AERONAUTIC POWER PLANTS 29

Measurements have been made of the temperatures existing in

various parts of spark plugs when operating in aviation engines,

and these results have formed the basis for the other testing work

just mentioned. There is still much need for further work to see how these temperatures vary with the type of plug and engine used.

At the request of the Bureau of Aircraft Production, extensive

oscillographic tests were made on 12 different types of ignition

systems. This method of test shows photographically the current

in both the primary and secondary coils at each instant throughout

the operation of the system and can be made to show the shortcircuit current and open-circuit voltage of the magnetos and the

behavior of the circuit breaker. The photographic records obtained give a complete account of the performance of the apparatus

and the values of current, voltage, etc., can be read off at leisure.

Copies of the records were sent to the various branches of the War

Department interested, and the large mass of data contained in

them was correlated by the Bureau as time permitted, and the

results have been published in the Fourth Annual Report of the

National Advisory Committee for Aeronautics.

In connection with the oscillographic test, other electrical constants of the ignition systems, such as the inductance, capacity,

resistance, and the heat energy in the spark, were observed on a

variety of systems, both to detemime their relative merits and to serve as a basis for possible improvements in the design of such

apparatus. It is hoped to continue the testing of a variety of systems in order that the fundamental data may be obtained and

published for the benefit of American manufacturers.

Another distinct part of the ignition work has been the study

of the use of subsidiary spark gaps which frequently have been

proposed as an improvement over the usual types of ignition

systems. These devices have the advantage of enabling a system

to produce a spark even though the plug may be shunted by a

resistance decidedly less than the limiting value of 100 000 ohms

stated above. The manufacturers of these devices, however,

frequently have made exaggerated claims as to their merits,

and the work at the Bureau was undertaken with a view to

determining to what extent these claims are justified and to

obtaining definite information as to the possibilities and true

performance of this type of device. It has been found that the

claims of increased power and efficiency are unwarranted, but

that the device has the very definite merit of causing a fouled plug
30 WAR WORK OF THE BUREAU OE STANDARDS

to fire, since an engine has been made to fire continuously although

the plugs were fouled with a resistance of only 5000 ohms.

The rubber-insulated cables connecting the spark plugs with

the distributer occasionally give trouble as a result of the cracking

of the insulation. This is a progressive deterioration which

occurs where the cable is sharply bent, and after continued ex- posure to the high voltage electric stresses incident to the operation of the system. The Bureau of Aircraft Production asked

that the precise reason for this cracking be determined, and a

series of experiments was carried out which demonstrated conclusively that the cracking was the result of a chemical reaction

between the rubber and the ozone formed by the high-voltage

electrical discharges which occurred at the surfaces of the cable.

This reaction is localized in cracks whenever the rubber is subjected to mechanical tension. The remedies suggested are the use

of a thoroughly impregnated braid, the avoidance of sharp bends

in the wiring, and the use of such rubber compounds as are least

affected by ozone. The results of the various lines of work mentioned above were

issued in a number of separate reports which formed a part of a

series on aeronautic power plants. These reports were distributed

by the Bureau to a limited mailing list made up of those officers

of the War and Navy Departments interested, and, where no data

of a confidential nature from a military or commercial point of

view were involved, to manufacturers and other persons interested.

These reports were all published at a later date in the Annual

Reports of the National Advisory Committee for Aeronautics.

Lubrication of Aircraft Engines

Although the matter of the satisfactory lubrication of aircraft

engines was admitted to be one of great importance, it was not

until several months after the United States entered the war that

a definite investigational program of this subject was commenced.

Before the beginning of actual experimental work, representatives

of the Bureau visited various aviation fields and obtained more or

less complete data on the oils in use. Samples of new and used

oils were obtained and were later analyzed in the laboratory. A

conference was also held with one of the members of the Council

of National Defense, and the subject of lubrication was thoroughly

discussed. The results of this preliminary woik showed that no

one kind of oil was in use at all the fields, and that even at the
AERONAUTIC POWER PLANTS 31

same field contradictory opinions were held respecting the merits

of various brands.

In October, 191 7, the Bureau was asked to cooperate with the

Signal Corps in testing airplane lubricants. By agreement the

Bureau made certain tests of a large number of new oils and of

the same oils after they had been used in engine runs made at the

Navy Yard. This work led directly to a complete investigation of

lubrication problems, which was carried out in cooperation with

the Bureau of Aircraft Production. A program was decided

upon covering the entire complex situation, and a laboratory

fitted up especially for the purpose. Tests in actual engines under

service conditions were made in the altitude laboratory, with

the object of securing data upon which to base satisfactory

specifications for airplane engine oils.

Miscellaneous Investigations

In addition to the investigations already mentioned, a number of

others of fundamental importance have been carried out. Among

these may be mentioned experiments to determine the rate of

flame propagation in the cylinder of an internal-combustion

engine. For this work a special single-cylinder gasoline engine

has been built the cylinder and valves of which are identical with

those used on the Liberty aircraft engine. Very successful preliminary results have been obtained by an electrical method

developed through the cooperation of the aeronautic-powerplants section and the electrical division.

The determination of the pressure cycle in the cylinders of highspeed aircraft engines is an extremely difficult matter; in fact,

until recently no successful indicator for this purpose was on the

market. Indicators entirely suitable for slow-moving stationary

gas engines are not at all successful in indicating the pressure

ranges on light high-speed aircraft engines, due to the inertia of

the indicator's moving parts. The Bureau has been working on

this problem for some time, and a successful indicator has been

developed which is now being manufactured on a commerical

scale. The designing and constructing of a satisfactory indicator

for high-speed gasoline engines will greatly aid the work of

engineers in problems connected with aircraft power plants.

For many years the effect of small amounts of water injected into

the intake manifold of gasoline engines has been discussed, some

engineers maintaining that this practice results in the development of increased power and the removal of a large proportion
32 WAR WORK OF THE BUREAU OF STANDARDS

of the carbon from the cyUnder and the piston. In order to investigate the merits of these claims, the Bureau conducted a set of

tests in which water in varying amounts was used. The results of

these experiments have been made public through one of the

reports of the National Advisory Committee for Aeronautics.

Many special designs of engines and accessories were submitted for

test to the aeronautic-power-plants section during the war. Among these may be mentioned a small direct-injection Marburg

heavy-fuel engine, a "barrel type" of engine, and a special Ford

automobile engine having 16 instead of the usual 8 valves, as well

as two direct-connected gasoline engines and generators designed

for battery charging work for the Signal Corps. Among the gasengine appurtenances may be mentioned the testing of a very

successful mercury-cooled exhaust valve for airplane engines and

the investigation of numerous carbureters with special devices

for altitude compensation.

The materials-testing laboratory of the Bureau conducted a

thorough study of a broken crank shaft from a small-sized Liberty

engine. Tensile, hardness, impact, photomicrographic, and chemical examinations were made on this specimen. The tensile test

covered those portions of the shaft forming the crank pin and

cheek near the break. The only one of these various lines of

study which showed any defect in the crank shaft was that for

impact resistance. The Izod impact results showed an average

of 50 foot-pounds of energy absorbed, while chrome-vanadium

steel corresponding approximately to the analysis of this shaft

usually tests about 72 foot-pounds. This lack of resistance to

shock might have been due to faulty heat treatment, especially in

the final drawing temperature, and those concerned with the construction and use of these engines were cautioned in that regard

AIRCRAFT CONSTRUCTION

Metal Construction for Airplanes

The tremendous increase in the use of airplanes brought about

by the war resulted in an unusually heavy demand for spruce, the

wood considered most suitable for constructing such machines.

Even before this country entered the war in 191 7, however, spruce

of the required grade was becoming scarce, and this, together

with the desirability of rendering the airplane noninflammable,

directed the attention of engineers to the possibility of using

metal for at least a portion of the airplane. Wood has some
AIRCRAFT CONSTRUCTION 33

advantages over metal, particularly where but a few machines

are to be built, as the initial cost of the plant necessary for turning

out the planes is much lower than for any designed to construct

metal parts. Nevertheless, when the last-mentioned plant is

once completed and equipped with suitable dies, tools, jigs, etc.,

the cost per plane is comparatively low. Therefore, metal construction appeared to offer numerous advantages where airplanes

were to be produced in large quantities for military purposes.

The Bureau made a very careful study of the possibility of

substituting metal for spruce for certain parts of airplanes, and

undertook complete computations of the probable strength of

various types of metal beams suggested for this class of construction. Many of the proposed sections were found to be impracticable and were, therefore, discarded. One type of box

beam was worked out which appeared to possess the desired

strength, and test beams of this design were made from sheet

aluminum, and when subjected to transverse loading showed a

strength well above that of Sitka spruce of standard design and

equal weight.

About this time several commercial organizations engaged in

fabricating sheet metal became interested in the possibility of

producing a satisfactory all-metal airplane. The above-mentioned

company actually constructed a complete machine similar to

the Curtiss JN-4, except that it had no engine or wing covering.

This was tested by the Bureau, but the wing under sand load was

shown to have a factor of safety of only 2 as compared with 7 or

8 for standard wood construction. Since this result was considered unsatisfactory, a member of the Bureau's staff went

to the factory of this company and aided them in producing

a better design of all-metal plane. A representative of the

Aircraft Board was also assigned to this work to assist in

securing material, and the results accomplished were largely due

to his skill and energy.

Many attempts showed that sheet metal having the necessary

tensile strength could not be obtained in the nonheat-treated

form, either in a carbon or chrome-vanadium alloy steel. Efforts

to secure added strength by cold-rolling also failed, and for this

reason the use of steel for airplane beams was given up and attention devoted to aluminum alloy. As these aluminum-alloy beams

made a good showing in average strength, two complete sets of

wings using this type of beam and steel ribs were constructed

26035°—21 3
34 WAR WORK OF THE BUREAU OE STANDARDS

by the manufacturer and tested on an airplane at McCook

Field, Dayton, Ohio. During the tests, which covered about

58 hours of flying, this plane behaved in all respects in as satisfactory a manner as those made of wood. Sand-loaded tests of

one of these sets of wings showed that this method of building was

in every way as strong as the best wood construction. The possibility of the successful manufacture of airplanes with metal-wing

frames was thus demonstrated, and the problem of insuring fireproofness of the plane now hinges on the discovery of a satisfactory

noninflammable wing covering to replace the fabric ordinarily

used. Although hostilities ceased before the solution of this

problem was reached, considerable progress had been made and

the investigation is being continued with fair prospects of success.

It is hoped to develop a covering which will be not only fireproof,

but transparent as well.

Many other tests of metal parts besides wing structures were

conducted in this laboratory, such as hydrostatic, tensile, and

compression tests of electric arc-welded longitudinal joints in

steel pipes, and routine physical tests of inventors' models of ribs,

beams, struts, cables, turnbuckles, etc. An investigation was

carried out on triangular girders for dirigibles, and as a result it

was shown that those first constructed were relatively too strong

in the diagonal lattice elements and too weak in the longitudinal

members. A redistribution of metal made as a result of this discovery resulted in a very satisfactory form of girder manufactured either from the French aluminum alloy " Duralumin " or its

American equivalent 17-S.

Design of Variable-Camber Airplane Wing

The problem of increasing the speed range of airplanes is

one of the most important in military aeronautics. The maximum

speed has greatly increased within recent years and doubtless will

continue to do so; but with this increase in maximum speed has

come an equal increase in landing speed, since the latter has been

and still remains about one-half that of the former.

Various devices may be used to increase the speed range.

Among these the most promising from all points of view, including

that of construction, appears to be the variable-camber wing.

Such a wing, designed by a former member of the Royal

Flying Corps, was thoroughly investigated by this Bureau. This

wing is so constructed that at low speeds it assumes a deeply

cambered or lifting form, while at high speeds it takes a stream-
AIRCRAFT CONSTRUCTION 35

line shape. In combination with wings of the usual construction

in triplanes or biplanes, it allows a vastly greater speed range.

The design of the wing hinges on the construction of a satisfactory

variable-camber rib. This was accomplished in the wing constructed at the Bureau, and wind-tunnel tests proved it to be

thoroughly practical.

Laminated Wooden Members for Airplane Construction

As mentioned in the opening paragraph of this article, the

tremendous demand for airplanes during the war resulted in a

scarcity of airplane spruce. Numerous attempts were made to

meet this condition. One of these, that of constructing metal

planes, has already been mentioned. Other possibilities were:

(i) The use of some form of laminated members which would

allow the utilization of spruce with less waste than in the cus- tomary construction, and (2) the discovery of suitable substitutes

for spruce.

The Bureau early undertook an investigation of the firstmentioned solution and has tested many different forms of laminated construction as used in ribs, beams, struts, spars, tailbooms,

and girders, and has also assisted in the development of wood

veneer for wing and fuselage coverings. As a result of this work,

it has been proved that laminated beams made up in a proper

way are just as satisfactory as solid beams, and although the

cost of manufacturing is somewhat greater, the reduced cost of

the raw material utilized results in a saving. Cross-sections of some

of the laminated wooden beams which the Bureau tested are given

in Fig. 6. In addition to the tests conducted on solid and laminated beams of the same kind of wood, this series furnished comparative data on the strengths of such woods as spruce, fir, and

cypress, and the relative advantages of rectangular and oblique

I-sections, and on the strengths of various types of joints and

different brands of glues.

It was shown that beams of fir can be produced which will

have as high a specific strength as those made from spruce,

although such beams will not be quite so stiff. Cypress can not

be considered as a satisfactory wood for this construction. Beams

made up of pieces glued together were proved to be as strong in

shear as the solid wood, and no weakening of the bond with glued

joints was observed even when subjected to moisture and vibration.

In addition to the test on beams, research work was conducted

on many other wood members. An interesting test was that of
36 WAR WORK OF THE BUREAU OF STANDARDS

an experimental three-ply mahogany veneer-covered wing. This

wing was constructed with glued joints throughout, no nails or screws being used. Two different designs of rib were submitted

with the wing, one of which proved to be considerably superior

to the other. When subjected to drifting and sand-load tests,

the wing showed a satisfactory strength; but since its weight was

approximately 30 per cent in excess of the ordinary type of fabriccovered wing, it could not be considered altogether satisfactory.

Other miscellaneous tests included those on so-called "pigeon

hollow" spars, Navy model—T-spars, etc.

In the investigation and development of various types of

airplane struts, the value of the Bureau's work is very forcibly

shown. Tests of veneer struts were under way on the day

America declared war upon Germany. Many different styles were

investigated and certain types of veneer construction were shown

to be satisfactory. The compressive strength of such members

was investigated. Many types of square-end and round-end

struts of various slenderness ratios were tested, and as a conse- quence of this work rational mathematical expressions were

formulated and constants evaluated which give results corre- sponding closely to the values determined experimentally. Prof.

Boyd likewise developed a formula of more general application,

which is suitable for use in connection with the tapered struts

used in airplane wing construction.

Various Wood Species as Spruce Substitutes

As another possible means of assisting in the rapid production

of military airplanes, the Bureau, in cooperation with the Aircraft

Production Board, undertook an investigation of the possibility

of using woods other than spruce. Theinvestigation of the different

types of woods was one of the most complete carried out by this

laboratory. Woods of all promising species were investigated,

and many special tests were developed for use in this connection,

some of which required the use of novel designs of testing apparatus. A special hammer for a beam-impact testing machine and

a rotating bar machine for fatigue testing were designed particularly for this investigation. On the basis of these tests, a

table and data were furnished showing the relative values of

various woods for airplane work.

Artificial Drying Processes for Wood

The successful substitution of other species of wood for spruce

in airplane construction depended very largely upon the discovery
AIRCRAFT MATERIALS 37

of a satisfactory quick-drying process which would not check the

woods. Air drying is, of course, the ideal method for preparing

lumber for the mill, but in the case of certain species of wood it

involves months or even years of delay. The Bureau's participation in the development of suitable artificial drying processes consisted chiefly in the inspection of the plants of operators using

various patented processes, in proposing desirable improvements,

and in testing the products. In nearly all of the plants inspected

it was found that no particular engineering skill had been used in

the kiln or plant construction, and the operators did not appear to

have much knowledge of wood technology. The Bureau's suggestions were thankfully received and promptly put into operation in

the majority of instances with marked gains in plant efficiency.

Some of the processes investigated indicated that it was possible

to produce wood equal in strength to that dried in air by artificial

drying methods with a great saving in time.

Wood Protective Coatings

For certain parts of the airplane structure, such as the propeller,

the protection of a metal coating or a composition impregnation

has proved highly desirable. Initial tests on electrodeposited

sheet copper for such a purpose led to the conclusion that a satisfactory grade of this material could be produced. The covering

of the entire propeller involved too great an increase in weight,

however, to be practical, but the plating of the tip of the blades

has been successfully carried out. Bakelite-impregnated woods

were also investigated with the idea of using them for propeller

construction and also for the manufacture of motor-truck steering

wheels. Bakelite-impregnated maple and walnut specimens

showed increased strength over ordinary wood, but the weight

increases were so great that such wood was not deemed suitable

for aircraft use, although it has been successfully employed in

automobile work.

AIRCRAFT MATERIALS

Airplane Dopes

A complete description of the Bureau's work in this field will be

found in the article under the above heading.

Paper as a Substitute for Linen in Airplane Construction

This work is described in the article on "Paper."

Development of Satisfactory Cotton Fabric for Airplane Wings

This work is treated under the heading "Textiles."
38 WAR WORK OF THE BUREAU OF STANDARDS

Balloon Fabrics

Radiant-power life tests of quartz-mercury vapor lamps: This

work was undertaken in connection with the investigation of the

deterioration of balloon fabrics when exposed to sunlight and ultraviolet light.

The ultra-violet as distinguished from the infra-red rays appear

to have a marked effect in accelerating chemical action; as, for

example, in the fading of dyes. There has arisen among manufacturers of paper, dyes, cloth, rubber goods, paints, etc., a need

for information concerning the sources and their constancy of

emission of ultra-violet radiations, for use in testing the lasting

quality of their products.

It is well known that the intensity of the radiation (especially

the ultra-violet component) from quartz-mercury vapor lamps,

decreases greatly with usage.

In response to the demand for exact data, methods were devised

for determining quantitatively the decrease in intensity of emission with usage, and measurements were made on radiant-power

life tests of a number of quartz-mercury vapor lamps, using the

radiometric instruments devised at this Bureau, and described in

Scientific Papers Nos. 229 and 282.

The data obtained indicate a marked decrease in the total radiation emitted, as well as the ultra-violet component, in the course of

1000 hours' usage of the quartz-mercury vapor lamps now obtainable on the market. See Scientific Papers Nos. 196 and 244.

In connection with the general investigation (chemical, mechanical, etc.) of this subject, the transmissive and reflective properties

of numerous samples of balloon fabrics were determined, using

a hemispherical mirror and thermopile. Measurements were made

also of the rise in temperature when the fabrics were exposed to

solar radiation, using a modification of the fine thermocouples

used in measuring heat from stars.

Investigation of the Thermal Expansion of Materials Used in Aircraft-Engine Construction

The thermal expansion of the materials used in the building of

aircraft engines was determined by the Bureau, to aid in the selection of proper metals and alloys for the various parts.

AIRCRAFT (MISCELLANEOUS)

Instruments for Measuring Tautness of Airplane Wires and Cables

In an attempt to reduce the weight of airplanes to an absolute

minimum the factors of safety employed in the design of many
AIRCRAFT (MISCELLANEOUS) 39

of the members were frequently lowered during the war. Since

in many cases the stresses set up in the members by the initial

tension in the stay wires is a large percentage of the total stress

to which they are subjected, it therefore becomes important to

know the magnitude of these loads. No satisfactory instruments were available to manufacturers or inspectors in the early

stages of the war for determining the initial load on the stay

wires. A "tuning" method was used in some instances with

satisfactory results, but this method required an observer with a

highly trained musical ear. The Bureau attempted the solution of this problem, which was

successfully completed by a member of the Bureau's staff. An

instrument known as a tensiometer was designed and built in

the latter part of 191 7. (See Fig. 7.) The instrument is now

being successfully used by both the Army and Navy in their airplane-manufacturing plants. It requires no special skill or experience in its operation and has been found to give results sufficiently accurate for all practical purposes.

The design is simple and is based on the fundamental principles of mechanics. If any balanced system of forces acts at a

point, the resultant force is equal to zero by definition. If a wire is supported at two points and deflected at the middle of the

span thus formed, we have a system of forces in equilibrium.

Knowing the length of span, the amount of deflection at the

center, and the force required to produce this deflection, it is

possible to calculate the tension in the wire.

The tensiometer provides a convenient method of obtaining

the necessary data for this solution. The wire is supported on

two pins at a known distance apart and loaded at the center of

the span thus formed. Load is applied through a yoke, spring,

and plunger by the closing of hand levers. The required deflection of the wire is indicated by an Ames dial and the corresponding

lateral forces exerted on the wire are shown by another dial. We

know that the tension in the wire is proportional to the load on the

spring for a given amount of deflection and it is therefore possible

to make the second dial indicate the tension directly by always

deflecting the wire a constant distance. The design of the instrument is such that estimated divisions on the second dial indicate

pounds of tension on the wire for the standard deflection of one- tenth inch (or one revolution of the first dial).

The instrument is portable, quick reading, and does not have to

be attached integrally to the wire at any time. The instrument
4Q WAR WORK OF THE BUREAU OF STANDARDS

can be constructed so as to give direct load readings for the type

of wire most commonly encountered in the construction of the

planes on which it is designed to be used. For shapes and sizes

of wires differing materially from those for which the instrument

was designed, it is necessary to apply correction factors. Instruments have been built for use on cables of various sizes and on

wires of circular and stream-line shapes.

The Bureau was subsequently called on to conduct calibrations

of other types of instruments designed for this purpose, but these

were found to be more dependent than the tensiometer on the

skill of manipulation and the position in which the instrument

was applied. They also suffered from unsatisfactory mechanical

construction and in some cases were based on incorrect principles.

Most of them used varying deflections of the wire for different tensions on the wire. This prevented the instruments from being

self-indicating, and calibration curves or tables always had to be

used to enable the observer to determine the tension.

Synchronizing Devices for Airplane Guns

Tests were made upon a hydraulic synchronizing system such

as is used in synchronizing machine-gun fire from airplanes.

These tests were made in order to determine the effect of varying

the size of different parts on the operation of the mechanism.

The operation of the gear may be described as follows: The

necessary pressure in the system is effected by means of oil in a

high-pressure plunger tube and is maintained by a reservoir

plunger spring. A needle valve operated from the airplane control

stock closes the opening to a low-pressure tube and at the same

time opens a ball valve, which in turn releases the pressure to the

auxiliary pipe lines. This pressure forces a hardened steel ball

attached to the end of a generator plunger against a cam which is

mounted on a rotating axle. When the cam is rotated so as to

move the plunger, the oil in the system is forced through two pipe

lines—an auxiliary and a main—against the plunger in the reservoir, and against the base of the trigger motor.

The pressure per unit area exerted by the reservoir plunger is not

sufficient to produce motion of the trigger-motor plunger. Hence,

if the cam is rotated slowly enough to allow the oil to flow through

the auxiliary pipe line, the trigger motor will not operate. However, as the tube connecting the generator and reservoir is very

small, the viscous forces are so large that considerable resistance

is offered to the rapid movement of liquid through this tube.

Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 8.

Two views of the Dover By-Product Coke Co.'s plant at Canal Dover, Ohio

The bureau, in cooperation with the Bureau of Mines, carried on extensive tests on the coking of low-grade midcuutiueut coal in the Roberts ovens installed at this plant
AIRCRAFT (MISCELLANEOUS) 4

Hence, when the cam is rotated rapidly, the resistance in the

auxiliary pipe due to viscosity is so great that the liquid is forced

through the main pipe against the base of the trigger motor with

sufficient force to operate the plunger of the trigger motor.

The minimum speed at which the trigger motor will function

will depend not only on the relative sizes and lengths of the two

pipe lines, but also upon the strength of the plunger spring and the

trigger-motor spring. When the speed is sufficiently high to make

the operation satisfactory, there is comparatively little motion of

oil in the auxiliary pipe line. Attention may then be concentrated

on the main pipe line. The movement of the generator plunger

during the rotation of the cam causes an increase of pressure in the

main pipe line. This pressure is not immediately communicated

to the trigger-motor end of the pipe line, but passes down as a

pressure wave.

The three factors which affect to some extent the velocity with

which this wave is propagated are:

1 . The expansion of the copper tube of the main pipe line under

the increased pressure. Since the copper walls are thick (oneeighth inch) , this expansion relative to the compression of the oil

is small and may be neglected.

2. The compression of the oil in the main pipe line due to its

retardation by viscous forces which are developed when a liquid is

forced at a rapid rate through a small tube. Computations of the

pressure thus developed at the generator plunger by a speed of

1 200 rpm show that the pressure at this end of the main pipe line

for a 6-inch pipe is not in excess of 10 pounds per square inch over

that of the motor end.

3. The compression of the liquid due to its inertia. Computations of the pressure due to the inertia of the liquid show that

at the same speed the pressure at the generator end of the main

pipe line exceeds that of the motor end by 4000 pounds per square

inch for a 6-foot pipe, and 6600 pounds per square inch for a

10-foot pipe.

The inertia effect may then be considered as the important

factor in preventing the instantaneous equalization of pressure in

the main pipe line. This pressure wave is propagated in the same

manner as a sound wave; therefore at approximately the same

velocity. This velocity determines the time lag between the

generator and the motor, but has no relation to the velocity of the

liquid in the pipe.
42 WAR WORK OF THE BUREAU OF STANDARDS

The effect of changing the various elements of the system is as

follows:

1 . Increasing the strength of the spring in the reservoir increases

the pressure in the system, and, therefore, puts a greater initial

pressure on the spring of the trigger motor. It also has the advantage of compressing any small air bubble.

2. Changing the size and length of the auxiliary pipe line. Decreasing the size and increasing the length increases the resistance

offered to the flow of the liquid, hence the slower the speed at

which the apparatus will operate. If the auxiliary pipe line becomes too short, the oil system may have very little damping, so that chattering of the plunger of the trigger motor may occur

3. Size of the main pipe line. Increasing the main pipe lines

does not materially affect the rate of propagation of the wave;

but, since it increases the mass of the liquid, the strength of the

trigger-motor spring must be increased in order that the plunger

of the generator may at all times be in contact with the cam.

4. Length of the main pipe line. Increasing the length of the

main pipe line increases the time for transmission of the pressure

wave and also increases the mass of the liquid. In case the pipe

is too short, chattering of the trigger-motor plunger occurs, due

to the very small amount of damping. In the results obtained

some chattering has occurred in most cases. This, however, is

not excessive, and it is not believed to be sufficient to be the cause

of stray shots, since the extrusions are too small to cause firing of

the gun.

From the discussion above it will be seen that the factors

enumerated will determine a suitable design for a given installation.

The experiments performed from which the above results were

obtained are described below. Two methods of measurement

were used—the rotating drum method and the stroboscopic

method.

In the rotating-drum method the movements of the plunger of

the trigger motor were recorded on a rotating drum operated by

the same motor as the generator cam. A stylus attached to the

trigger motor recorded its movements on a paper carried by the

rotating drum.

In the stroboscopic method two disks were used, one being

mounted on the end of the motor shaft and the other near the

first on a shaft coaxial with the motor shaft, which was rotated by
AIRCRAFT (MISCELLANEOUS) 43

hand. On the latter disk was a scale graduated in degrees and

read by means of a stationary pointer. To make an observation

the position of the pointer was read when the highest part of the

cam was pressing against the ball of the generator plunger. The

motor was started, the speed of the motor determined, and the

fixed disk rotated until the trigger-motor plunger was at its maximum extrusion, when the position of the pointer was again read.

The time required for the rotating disk to turn through the observed angle of rotation of the fixed disk is the time for the transmission of the pressure wave from the generator plunger to the

trigger-motor plunger and for the trigger-motor plunger to act.

Measurements taken in this manner give values for the time

lag of from 0.002 to 0.004 second. The observations taken were

insufficient to determine accurately the velocity of propagation.

However, values ranging from 1500 to 4000 feet per second were

obtained.

The effects of removing the damping valve from the T-piece

upon chattering of the trigger motor were also observed. The

experiments were made with the Constantinesco system set up

in the regular manner. This is the hydraulic system in most

general use and was used in making the preceding tests. It was

found that when strong springs were used in both the trigger

motor and reservoir a little more chattering occurred with the

damping valve removed.

In order to determine the effect of using different lengths of

pipe line, tests were made with lengths of 10, 6, and \ ]/2 feet.

For all lengths of ^% feet or more, no differences were noted in the

trigger-motor plunger. This was the case for various pressures in

the reservoir, various speeds of the generator, and for the removal

of the damping valve. For short lengths of pipe, the system was

found to operate better under low pressures, the extrusions of the

trigger-motor plunger being exceedingly large for high pressures.

With the reservoir plunger spring removed tests were made

upon the pressure required to operate the system. This depends

upon the strength of the trigger-motor spring and is independent

of the length of pipe line. With a 25-pound trigger-motor spring,

70 to 90 pounds pressure was necessary to operate the system,

increasing for a 50-pound spring to 100 to 125 pounds.

The effect upon the trigger-motor action of varying the speed

was also studied. It was found that the initial parts of the impulses were very much alike, also that they occurred at approxi-
44 WAR WORK OF THE BUREAU OF STANDARDS

mately the same place on the drum. However, at 1200 rpm the

plunger remained at its maximum extrusion for a longer time.

This is caused by the fact that the trigger-motor plunger is re- turned by the force of the spring.

Some general observations were made upon the working of the

system as to the number of bursts, effect of air, and kinks in the

system. With the Constantinesco system of gears, the average

of several trials was 24 bursts. No direct effect could be noted

as a result of kinking the pipe. However, kinks in the pipe make

it hard to free the sytem from air. The washers used during the

tests were of English composition and were found to be very

satisfactory. Both English and American made reservoirs were

used. The valve fittings on the English reservoir gave less leakage

trouble. An English generator was used in making the tests.

It worked very satisfactorily and showed no signs of wear. In order to determine something of the behavior of the oil when

the system was being operated, the top half of the pipe line was

cut away for a distance of about 3 inches, and a piece of glass was

slipped over the hole. The motion of a rider placed on a fine

copper wire stretched along the slit was then observed. The

observations showed that in the transmission of the generatorplunger action to the trigger motor, there was a movement of the

oil as well as a compression wave.

The oil used in the system during the experiments consisted of

about 9 parts kerosene and 1 part machine oil. A test was also

made as to the effect of using Liberty-motor oil in the system.

No difference could be noted in the operation when this oil was

used.

A great number of tests were made with the Marlin trigger

motor. For an indicator a small brass strip was soldered directly

to the trigger-motor plunger. For pressure tests, variation of

speed, and lengths of pipe fine, the same results were obtained as with the Constantinesco system. However, the construction of

the trigger motor permitted a greater motion of the trigger-motor

plunger, and for rather great pressures, very great extrusions of

the trigger motor were obtained. The tests made with the system

are not, however, conclusive, due to the fact that the complete

Marlin system was not operated together. The generator used

belonged to the Constantinesco system. The difference in this

generator from the Marlin, quite likely, would influence the

results.
AIRCRAFT (MISCELLANEOUS) 45

On June 17, 191 8, an officer who had had extensive experience in flying on the European battlefields visited the Bureau

and pointed out the need of a synchronizing gear or gun-control

system, which would permit of the gun being fired through the

propeller in any direction at the will of the operator. He was

of the opinion that an electrical type of gear would most easily

meet the requirements imposed by the movable-gun feature.

On July 24 a communication from the office of the director of

military aeronautics requested that the work on this electrical

synchronizing gear be carried to completion.

After several conferences and some preliminary work the

problem was taken up actively about the middle of August, 191 7. At that time, a modification had been made in one of the heavy

Browning guns under the direction of two officers of the Ordnance

Department. The modification replaced the regular sear and

trigger by a sear operated from above and back of the bolt by a

link which moved in a direction parallel with the barrel of the

gun. The purpose of this modification was to get a more direct

action between the sear and an electromagnet or solenoid with

which it was proposed to fire the gun.

If the gun is to be fired through the propeller in any direction

at will, the phase of the control mechanism must be changed as the

position of the gun is changed, otherwise adjustments which are

correct for one position of the gun would not be correct for other

positions, and the propeller blades be struck by projectiles. As the

position of the gun is changed, the control apparatus should change

the phase of firing by the same amount that the line of fire is

changed with respect to the axis of the propeller.

With most synchronizing systems, adjustments are made so that the gun fires only a safe distance back of the propeller blades

with the propeller at rest, or turning with a fairly low speed; then

as the speed is increased the gun fires furtherand further back of

the blades, and at the highest permissible speeds may be firing just

ahead of the next blade. With a propeller speed of 1800 rpm the

blades rotate through an angle of about 11° in 0.001 second and

with the two-blade propeller the safety zone between blades may

be considered to be about 145 . Consequently, if the gun is to

be fired at any speed from o to 1800 rpm it is necessary either to

advance the phase of the control mechanism as the speed increases or make the over-all time lag less than 0.01 3 second. Any arrangement which would automatically change the phase of firing with
46 WAR WORK OF THE BUREAU OF STANDARDS

changes in speed would add to the complication of the apparatus,

and thus should be avoided if possible. We may, therefore, consider that we must keep the over-all time lag less than 0.013 second.

The over-all time lag depends upon the time required for the

separate operations which must occur in succession between the

beginning of the actuation of the control mechanism and the

passage of the projectile through the plane of the propeller. It

includes the time required for the action of the control motor

(the timing apparatus connected directly or indirectly to the

propeller or crank shaft), the time required for this action to be

transferred to the trigger motor (the apparatus which actuates

the trigger, or sear, and releases the firing mechanism of the

gun) ; the operation of the trigger motor and sear ; the operation

of the firing mechanism or firing pin of the gun, and the explosion

of the charge and the passage of the projectile through the barrel

of the gun and through the plane to the propeller. The time

required for the last-mentioned operations depends upon the

ammunition and position of the gun on the plane. With the

regular ammunition and the gun at a distance of 6 feet from the

propeller, it amounts to about 0.0035 second. It can not be

made much less than this, since usually the gun can not con- veniently be placed much closer to the propeller, and it is not

practicable to obtain quicker action ammunition. The time

required for operation of the firing pin of the Browning heavy

field gun is about 0.006 second. With this gun set at a distance

of 6 feet from the plane of the propeller, we would have only

0.004 second as the maximum possible time for the action of the

entire control system, unless the phase of the control apparatus

were to be advanced as the speed of the propeller is increased.

With the Browning aircraft gun, the time required for the operation of the firing pin is probably about 0.0015 second; consequently

the permissible time for the operation of the control system is

about 0.009 second.

A preliminary study of the problem showed that it would not

be practicable to fire the heavy Browning gun as modified with

any type of solenoid or electromagnet. The difficulty with

apparatus of this type is that it would be entirely too slow in

action to meet the conditions of the problem, since the inertia

of the sear and sear trigger together with that of the armature

or plunger would necessarily be large, and the force which could

be produced would be small. This preliminary study showed

further that if an electrical control system were to be considered,
AIRCRAFT (MISCELLANEOUS) 47

it should preferably be one in which the work of accelerating the

sear and the other moving parts of the control system would be

furnished by the recoil of the gun rather than by any type of

electric motor which for each shot would have to start from rest

and perform its function within a few thousandths of a second.

Later a suggestion was made by Maj. Mattel that the recoil of

the gun might be used to set an actuating lever and spring which,

by means of an electromagnet, would be tripped when it was

desired to fire the gun.

The plan adopted for the control gear was to have the recoil

of some part of the gun move the armature, against the action

of a stiff spring, adjacent to the pole pieces of an energized electromagnet. Then when it is desired to fire the gun. it is necessary

only to break the circuit of the electromagnet or otherwise suddenly cause a material reduction in the current. This releases

the armature from the pole pieces and it moves quickly under

the action of the stiff spring into contact with and releases the

firing mechanism of the gun. As actually carried out, the armature is released in about o.ooi second after the propeller reaches

the desired position for firing, and the armature moves the distance

required for firing the gun in about 0.002 second more. Thus

the entire control mechanism performs its functions in about

0.003 second.

With the first apparatus constructed, the target was made with

a burst of 100 shots with a fixed gun, when the propeller was

running at the rate of 850 rpm, and two shots when the propeller

was being turned very slowly by hand. Measurements made

from this target showed that the over-all time lag, including the

action of the control mechanism, the action of the firing pin, the

action of the primer and the charge, and the passage of the projectile to about 4 feet beyond the muzzle of the gun was slightly

less than 0.01 second, and the variation of this time for different

shots was slightly less than o 001 second.

With the second control apparatus the results obtained were

not so good. However, the causes for the inferior action were

definitely located and found to be of a kind which could easily

and certainly be remedied by changes in the proportions of the

parts.

Recovery of Helium from Natural Gas

Paragraphs briefly describing this work will be found under

heading "Natural Gas Investigation."
48 WAR WORK OF THE BUREAU OF STANDARDS

AIRPLANE DOPES

Introduction

The chemistry division of the Bureau of Standards became

interested in the treatment of airplane wings during the six

months preceding a declaration of war by this country. At that

time the value of air strategy in military operations had been

fully demonstrated abroad, and the attention of the War Department was directed to the development of heavier-than-air craft

in this country. The Signal Corps was directed to design and

build types of aircraft suitable for the purpose. The first planes

constructed were doped with nitrate dope prepared from cellulose

nitrate or guncotton. Acetate dopes prepared from cellulose

acetate had been used in this country, and the cellulose acetate

manufactured by the Bayer Co. of Germany and known as " Cellit

was employed. Supplies of the material in this country were

rapidly exhausted, and for a time the nitrate dope only was

available. One of the large makers of photographic supplies, in

the manufacture of a noninflammable moving-picture film, had

accumulated considerable quantities of cuttings and scraps of the

film consisting essentially of cellulose acetate. Subsequently this

material was used in the preparation of acetate dope for a considerable time. It contained in addition to cellulose acetate residues of plastic, including compounds, and as a rule the material

had aged considerably.

In the preparation of dopes additional amounts of plastics were

added, the material was frequently overloaded with these compounds, and the durability of such dopes was not as satisfactory as that of products prepared directly from cellulose acetate. The

amount of raw material available for dopes of this type was

limited.

In the construction of airplanes the question of a suitable dope

properly applied is usually considered of no importance and

receives scant attention. This was the experience of England

and later of America until the necessity of stripping the fabric

from a plane improperly doped, re-covering, and redoping it was

found to involve considerable expense. The airplane program as

originally planned overlooked the subject of dopes entirely in

spite of protests from the War Industries Board and this Bureau.

Owing to the sudden expansion of the Signal Corps, difficulties of

organization, and the greater importance of other problems this

fact is not surprising. Not until seven months after the declaration of war was provision made for insuring an adequate supply
AIRPLANE DOPES 49

of raw material. When action was finally taken, the total supply

of raw material necessary for the preparation of solvents and

cellulose acetate was commandeered by the Government.

Until the War Department was able to provide a personnel

for the consideration of doping problems all questions on the

subject were referred to this Bureau. Samples of dopes submitted by lacquer and varnish companies were examined to

determine their value in the construction of aircraft. Material

of suitable quality was assigned to a "list of approved dopes."

In cooperation with the Society of Automotive Engineers the

Bureau assembled a committee to prepare specifications. Representatives of the Government, dope manufacturers, and constructors of aircraft met on several occasions and suitable specifications were submitted and accepted by the War and Navy

Departments. A decision was also rendered by the committee

in regard to acetate dopes containing tetrachlorethane as solvent.

This compound has marked toxic properties and may be decomposed with the liberation of hydrochloric acid. The committee

on dopes decided that the use of this solvent involved considerable

danger to workmen and that no dopes containing it were to be

used on Government aircraft.

A representative of this Bureau conferred with Signal Corps

officials on numerous occasions before a section and laboratory

were organized by the War Department. Questions relating

to raw materials, cellulose acetate, solvents, plastics, the relative

merits of dopes on the approved list, and the preparation of standard formulas for acetate and nitrate dopes received consideration.

Assistance was also rendered in the preparation of reports on

various topics. Subsequently work was carried out on the

pigmentation of dopes for the Department of Military Aeronautics

and a report submitted on this subject.

The Navy Department consistently conferred with this Bureau

throughout the period of hostilities, and the Bureau represented

the Navy Department in several conferences with representatives

of the War Department. In cooperation with the Bureau of Construction and Repair, specifications were prepared for the compounds entering into the standard dopes, and for solvents intended

for repair work. Work was carried out on fireproofed dopes, solutions proposed as dope substitutes, and on the fireproofing of silkballoon flares. Several trips were taken to aircraft factories for

the solution of problems connected with the practical application

of dope, control of humidity, and the relation of dope to fabrics.

26035°—21 4
50 WAR WORK OF THE BUREAU OF STANDARDS

Function and History of Dopes

A dope is applied to airplane fabric covering wings and fuselage

to shrink it, making it drum tight, and to stabilize it, so that no

changes occur under varying conditions of humidity and temperature. Resiliency in flight and lifting qualities are thus imparted

to the plane. The dope also fills in the interstices of the fabric

and makes it impermeable to wind and moisture. It should afford

a smooth surface so that skin friction or surface resistance to the

wind is reduced to a minimum, and it should be as resistent to

fire as possible.

When heavier-than-air craft were first constructed, the wings

were covered with unproofed cotton stretched as tightly as possible. Flying could be attempted only in fine weather, and the

necessity of some treatment which would make the plane weatherproof was apparent. Various treatments were given a trial, but

for numerous reasons rejected. The treatment was affected by

weather conditions, or added too much weight to the plane, or lacked durability, or the oil from the motor penetrated the coating,

which was softened and lost its original tautness.

Rubberized fabrics were tried, and fabrics were coated with

compositions of glue and casein, as such, or treated with bichromate or formaldehyde to render them insoluble. Mixtures of

paraffin and beeswax were used, linseed oil, shellac, and varnishes.

A French art student, Voisin, who later became an aviator, re- called the use of starch paste to tighten a canvas before painting.

This was tried on an airplane wing and found suitable, but it lacked

durability. The value of shrinkage, however, was demonstrated.

Starch paste is used to-day in experimental wr ork.

Subsequently, solutions of collodion or guncotton were found

to produce excellent shrinkage. Because of the inflammability

of guncotton, the use of thin sheets of cellulose acetate was recommended, and this led to the use of cellulose acetate in solution.

These solutions were exploited chiefly by Eichengriin, a German

chemist. Cellulose-acetate dopes are now in common use, particularly on planes designed for combat purposes. The cellulose

esters belong to the class of colloidal compounds, and shrinkage is

a characteristic property of such compounds when drying from a

solution.

Dopes are also used on balloon fabric to reduce the permeability

of the fabric to gas. The English Government uses Delta dope

for this purpose, a nitrate dope containing sufficient castor oil to
AIRPLANE DOPES 51

make it nonshrinking. The Navy Department has used Delta

dope on certain airships, on which the fabric had become too permeable to gas, and satisfactory results were obtained. Acetate

dopes may also be used for this purpose.

Composition of Dopes

A dope consists of the cellulose ester dissolved in suitable solvents to which diluents are added, with the addition of plastics

and a compound to neutralize the traces of acidity in the solvents or acidity which may develop in the film. The solvent contains

a compound of high-boiling point which allows the cellulose ester

to emerge from the solvent mixture in a transparent condition,

free from precipitated cellulose ester which would appear in the

film in streaks or spots. The development of such whitened

areas is known as "blushing." It results from the application of

dope in a humid atmosphere, or from the rapid evaporation of

low-boiling solvents and diluents, or both. In the presence of a

high-boiling solvent, the moisture has a chance to evaporate

before the film is dry, and the cellulose ester is not precipitated.

The amount of the "high boiler," as it is frequently called, depends upon its boiling point. If the latter is high, less of the compound is needed than when it is low. Solvents with boiling points

between 125 and 200 C are generally used. A high-boiling

diluent may be present in nitrate dopes to assist in the prevention

of blushing.

Diluents generally consist of mixtures of alcohols and hydrocarbons, and frequently denatured ethyl alcohol and benzene are

used.

Plastics are occasionally used in nitrate dopes, but are always

present in acetate dopes. The nitrate film has sufficient inherent

strength and elasticity without further modification, but a small

amount of castor oil or camphor is sometimes incorporated in it. Cellulose acetate, however, is inherently brittle, and certain

softening bodies or plastics must be added to it in order to impart

suppleness and increase its life. A plastic is frequently a solid of

low melting point, sometimes a liquid or a mixture of liquids, and

generally a solvent of the cellulose ester, with which it forms a

solid solution. A small amount of the "high boiler" is always

left in the dope film, and this also plasticizes it. A suitable base

is generally present in the film to neutralize acidity. The base

commonly used is urea.
52 WAR WORK OF THE BUREAU OF STANDARDS

Cellulose Nitrate Dopes

Cellulose nitrate or guncotton is produced by the nitration of

cotton or some form of cellulose approximating the degree of

purity of cotton. For dopes a low-nitrated cotton is desirable.

It must be stable in order that no decomposition with development of acidity may occur. The high boiler in nitrate dopes is

generally amyl acetate or butyl acetate. The former is a product

of fusel oil, and the latter is prepared from butyl alcohol, a byproduct in the production of acetone by fermentation. The

diluent is generally a mixture of denatured alcohol and benzene,

although methyl alcohol, methyl acetone, and xylene are also

employed. A low-boiling solvent, such as ethyl acetate, may also

be present. The solvent and diluent combination used in nitrate

dopes is influenced by the degree and method of nitration, and,

therefore, is subject to considerable variation.

Cellulose-Acetate Dopes

The manufacture of cellulose acetate is a technical art, demanding careful supervision and control. Variations of a few degrees

of temperature during the process have an adverse effect upon the

product. The correct preparation of the material is known to but

a few chemists. It is quite difficult to make two batches of the

ester alike, and frequently there is trouble in spite of efforts to

keep the quality uniform. The material is a white solid, its

appearance depending upon the method employed for its precipitation. A good cellulose acetate has an asbestoslike quality when

rubbed between the fingers.

The commonest "high boiler" used in this country in acetate

dopes is diacetone alcohol, a product of acetone obtained by

condensation in the presence of lime. In Germany, before the

war, ethyl lactate was the "high boiler" in common use. This

substance has a tendency to break up into ethyl alcohol and

lactic acid unless certain compounds are added to it to make it

stable. Methyl ethyl ketone in suitable amount also prevents

blushing, but not as effectively as the preceding compounds, unless

a considerable amount is present. In this connection it may be

pointed out that a suitable proportion of alcohol and benzene,

when present in the dope, removes much of the moisture present.

A certain mixture of alcohol, benzene, and water has a higher

vapor pressure than any of its constituents, and, when this mixture results during evaporation, water is readily removed. No

practical application has been made of this fact. Acetone oils are
AIRPLANE DOPES 53

also used as high boilers, but the composition of these oils varies

greatly, and because they may break up with the development of

acidity unless carefully purified, they have not found as much

favor as compounds of known purity.

Solvents are usually acetone, methyl acetate, methyl acetone,

tetrachlorethane, and ethyl formate. Acetone was not used during the period of hostilities because it was thought to be necessary

in the preparation of cordite and for other purposes. The preparation of methyl acetate involves less consumption of acetate of

lime than the production of acetone, and hence has been preferred

because its use conserves raw material. Methyl acetone is a product of the destructive distillation of wood. It is largely a mixture

of acetone and methyl alcohol, and when the latter is acetylated,

the water removed, and the acid present neutralized, a good

solvent results. The composition of methyl acetone varies considerably, and sometimes it is necessary to increase its solvent

power by the addition of methyl acetate or acetone. Tetrachlorethane was formerly a favorite solvent in acetate dopes. It combines the functions of a solvent and plastic and dissolves cellulose

acetates of a wide degree of hydration. However, its vapor has

been shown to be about four times as toxic as that of chloroform,

and, unless pure, it decomposes and causes deterioration of the

fabric. The vapor of the compound causes jaundice, and in England several fatalities resulted from the application of dopes containing it. The decomposition of tetrachlorethane can be prevented, and the danger attending its application could be nullified

if all the doping rooms were provided with adequate means of

ventilation. Unfortunately, ideal conditions of ventilation do not

exist, and one by one various Governments have all abandoned the

use of tetrachlorethane dopes. France and Italy have even ruled

out dopes containing chlorine in any form.

Ethyl formate has not been used in the United States, but is

allowed by the British Government. It is an excellent solvent.

The diluents commonly used are denatured alcohol and benzene, and sometimes methyl alcohol either added as such or present

in methyl acetone. Cellulose acetate dissolves in a mixture of

alcohol and hydrocarbon when warmed and is reprecipitiated in

the cold, but the solubility persists in the presence of a solvent.

When the ratio of hydrocarbon to alcohol is three to one, an increased amount of diluent may be used.

The plastics which have been proposed for use in acetate dopes

include many compounds, some of which are much superior to
54 WAR WORK OP THE BUREAU OF STANDARDS

others. Benzyl alcohol is used by the British Government.

Mixtures of eugenol and triacetin have found favor in France.

In this country the commonest are phenyl salicylate, which is an

excellent softener, mixtures of benzyl benzoate and benzyl acetate,

benzyl acetate alone, and triacetin. Triacetin is soluble in water,

and may decompose with the liberation of acetic acid. Triphenyl phosphate is in universal use in acetate dopes. It waterproofs and fireproofs the film, and is an excellent softener. When

used in excess, however, triphenyl phosphate softens in warm

weather and makes the acetate film soggy. Urea is used in small

amount to neutralize any free acid which may be present.

Dope Covers

The dope, as has been previously mentioned, protects the fabric,

keeping it taut so that flying is possible under all weather conditions. It is also necessary to protect the dope film by covering it

with some suitable coating containing pigments to exclude light

rays. Either pigmented dopes or varnish enamels are used for

this purpose.

Pigmented dopes are preferable because they dry more quickly

and are more suitable for quick repairs. If varnishes or enamels

are used, the dope must be thoroughly dry, as residues of highboiling compounds may dissolve some of the oil in the varnish

and carry it into the dope film, and thus cause a relaxation of the

fabric.

It has been conclusively proved by the Royal Aircraft Factory

that the deterioration of dopes is practically entirely caused by

sunlight. A prolonged investigation indicates that the curves of

the intensity of sunlight and the curve of deterioration of doped

fabrics are almost identical. It is, therefore, more feasible to use a pigmented dope or a pigmented wood-oil varnish than clear

dope or varnish as a dope cover. Clear varnish has until recently

been used in this country on Army planes, while the Navy has

used a gray pigmented varnish enamel. The Royal Aircraft

Factory has recently demonstrated that doped fabrics covered

with pigmented dope retain their tautness longer than similar

fabrics covered with an enamel. It has also been demonstrated

that a pigmented dope retains its tautness best of all, and that

such a dope effects a considerable saving of cellulose acetate. The

English Government for a long time has used a type of pigmented

dope cover, khaki colored by iron pigments and lampblack, which

is called P. C. 10. It is a nitrate dope containing the above pigments and sufficient castor oil to reduce to a minimum the shrink-
AIRPLANE DOPES 55

age ordinarily effected by a dope. Reports from the front indicated that the use of such a cover has resulted in excellent retention of the tautness and durability over a long period.

Dope covers may be colored black by means of lampblack. A

dull-black surface is produced which is suitable for flying at night.

Similarly, an aluminum finish may be used on planes designed for use in hot, dry climates, because of the highly reflective surface

produced. Other effects are possible by a proper choice of pigments.

Application of Dopes

In the application of dopes to fabrics, it should be remembered

that the fabric does not of itself shrink in the sense that mercerization causes shrinkage. In other words, there is no physical

change occurring in the fabric. The dope film contracts when drying out of solution and diminishes the space between the threads,

the total effect of which is to reduce slightly the area originally cov- ered by the fabric when under a given tension. The British Government at one time used a dilute solution of dope next to the fabric.

This was called a " scratch coat." The dope contained very little

softening agent, and possessed maximum contractibility. The

scratch coat, however, was found to reduce the tear resistance of

the fabric and was, therefore, abandoned. Such a coating penetrates the fabric very thoroughly and locks the fibers and threads.

It is apparent that the viscosity of the dope must permit of some

penetration, so that the dope will not peel off, but the penetration

must not be excessive. The amount of size in the fabric to some

extent influences penetration. The first coat of dope is well

worked into the fabric, and subsequent coats are flowed over it, care being taken not to go over a given area more than once or

twice, or the doping brush will drag over the dope film. Sufficient

dope is applied to produce an increase of weight of 2 to 2.5 ounces

per square yard. The Army specifications require four coats of

dope on all planes, and specify nitrate dope on training planes and

acetate dope on combat planes. Two coats of clear varnish or enamel are applied over the dope.

The Navy Department specifies two coats of acetate dope over

the fabric, followed by three coats of nitrate dope and two coats of

Navy gray enamel. The inflammable nitrate dope is thus laminated between the relatively fire-resistant acetate dope and enamel,

the pigment of which also affords resistance to fire. It has been

contended that the use of one type of dope above the other may

produce two films of different physical properties, but to date no
56 WAR WORK OF THE BUREAU OF STANDARDS

trouble has been experienced by the Navy in the durability of

dopes applied as above.

Fireproofed Dopes

Inasmuch as nitrate dope is comparatively cheap and acetate

dope quite expensive, numerous attempts have been made to re- duce the inflammability of the nitrate film. This has been attempted by fireproofing the fabric or dope or both. Fireproofing is

generally effected in one of three ways: By incasing the material

in a coating of inert mineral salts ; by using compounds which decompose with the liberation of a gas which checks combustion, or by incorporating an organic fireproofing compound in the dope

film.

Any compound used for checking the spread of combustion

should not hydrolyze with an acid or alkaline reaction in the presence of moisture, as acids, particularly mineral acids, attack the

fabric, and alkalis have a saponifying action on cellulose esters and

certain plastics. A great variety of fireproofing solutions for fabrics and fire-resistant dopes has been submitted to the Bureau of

Standards for examination. The best treatment for fabrics has

been found to be a 10 per cent solution of ammonium phosphate

neutralized with ammonia. This has been found to exert no deleterious action on fabric or dope. Soluble chlorides in general have

been found to weaken the fabric.

Several pigmented fireproofed dopes have been examined. The

pigments used consisted of finely ground ammonium phosphate

or magnesium-ammonium phosphate. These were incorporated

in suitable proportion in a state of fine division in a nitrate dope.

The dope is applied alternately with clear dope, one coat of pigmented dope on the fabric, then clear dope, then pigmented, etc.,

five coats in all. A pigmented varnish is applied over the dope.

Several fireproofed dopes resembling an English product called

"titanine dope" have also been submitted. These consist of

nitrate dopes containing chlorides of zinc, calcium, or magnesium

added in alcoholic solution. The hygroscopicity of these salts is

objectionable, and such dopes tend to become slack on the fabric

in humid weather. This can be overcome in part by laminating

the dopes between coats of clear dope.

Nitrate dopes may also be fireproofed by incorporating tricresyl

phosphate or hexachlorethane in the dope film. The former compound is preferable and forms a better solid solution with cellulose

nitrate than triphenyl phosphate. It is necessary to fireproof the

fabric when dopes of this type are applied.
BALLOON GASES 57

Relation of Dopes to Fabrics

It has been previously stated that shrinkage is caused by a film

of cellulose acetate or cellulose nitrate embedded in a fabric and

drying from solution. Silk is a continuous fiber, and linen is characterized by staple, and no trouble is experienced in obtaining

shrinkage with fabrics made of these fibers. When ordinary cotton

fabrics are doped, the shrinkage is poor and may not result at all. Cotton of the longest staple obtainable has a short fiber when

compared with silk or linen. The cotton fibers, under the tension

of the dope film, appear to slip, or since the cotton fiber has the

appearance of an evacuated rubber tube and is twisted rather than

straight, the cotton fiber under tension becomes straightened.

The total effect of the behavior of the individual fibers is a refusal

on the part of the fabric to respond to shrinkage.

The cotton airplane fabric developed by the textile section of the

Bureau of Standards and adopted not only by this country but by

England, was constructed of long-staple cotton, mercerized in the

yarn without tension. Mercerization not only changes the physi- structure of the cotton fiber, but also appears to have a cementing action owing to the decomposition of sodium cellulose by

water. The resulting fabric responded to shrinkage excellently,

and could be manufactured from raw material produced in this

country.

It is necessary that the fabric be made of long-staple cotton.

When short-staple cotton is used, the fibers of the fabric are

slightly untwisted and raised by the doping brush. When the

dope film is dry, these small fibers project through the film or are buried in it, producing hills and hollows on the surface. When

enamel is applied over the dope, the surface of the fabric has the

appearance of "gooseflesh" and is very rough under the hand.

This is objectionable, because skin friction is abnormal when the

plane is flying, and maximum speed is impossible.

BALLOON GASES

Compilation of Information

Even before the beginning of the war and during the entire

time that the United States was engaged in the conflict, the

Bureau was frequently consulted by both the Army and the Navy

regarding a great variety of technical facts connected with the

production, storage, properties, analysis, and use of balloon gases,

particularly hydrogen. Many of these questions required extensive study, and it is possible to mention here only the more important of them.
58 WAR WORK OF THE BUREAU OF STANDARDS

At the request of the Navy Department a critical study was

made and an extensive report rendered on methods of generating

hydrogen practicable for use on shipboard. Later a conference

was held and recommendations were made for the generation of

hydrogen for signal balloons to be carried by seaplanes.

An extensive bibliography of the scientific literature relating to

helium was prepared at the request of the Navy Department as an

aid in the development of this gas for military purposes. This

bibliography has been published by the Bureau as Circular No. 81.

A large part of the "Hydrogen Manual," a general handbook

upon the production, properties, handling, and use of hydrogen,

published by the Navy Department, was prepared or edited by the

Bureau of Standards.

Reports were issued upon the "Influence of Water Vapor in

Hydrogen upon Lifting Power of the Gas," upon "The Effect

of Oxygen in Balloon Gas, " and upon the compressibility of hydrogen, the latter report being used in the purchase of hydrogen from

the manufacturers.

Laboratory and Field Work upon the Generation of Hydrogen

At the request of the War Department, the Bureau undertook

a comprehensive study of the generation of hydrogen by the

reaction between sodium hydroxide and ferrosilicon. This study

included a thorough laboratory investigation of the fundamentals

of the process for the purpose of determining the best materials

and methods to be employed in the process and a less-complete

investigation of the equipment used in the field. This investigation was covered by no less than five reports issued at various

times. The more important results obtained are given in report

No. 40 in the Fourth Annual Report of the National Advisory

Committee for Aeronautics. It was shown by the work of the

Bureau that about 60 per cent of the sodium hydroxide formerly

used in the method could be saved. This represents, in the

aggregate, a large saving of money to the Government. The

present practice of both the Army and Navy in carrying out this

extensively used process is based upon the investigation made

at this Bureau, as are also the specifications for the materials used.

Tests of Hydrogen Plant at Langley Field

The final tests of the purity and quantity of hydrogen produced

by the $200 000 hydrogen plant at Langley Field, Va., were made

by this Bureau, after the contractors and the inspectors for the

Signal Corps had failed to reach agreement. Acceptance of the
CALIBRATION OF TESTING MACHINES 59

plant and the amount of compensation rendered the builders were

based upon this determination.

Inflammability of Mixtures of Hydrogen and Helium and the

Ignition of Balloons by Incendiary Bullets

A laboratory investigation was made to determine the amount

of hydrogen which could be added to helium in balloon practice

without losing the advantage of noninflammability. In order

to have the information ready as soon as helium should become

available as well as to avoid the use of larger quantities than

necessary of so expensive a gas, the inflammability of hydrogen and

nitrogen mixtures was first investigated with especial reference

to the ignition of jets of the gas issuing from an orifice such as would be made in a balloon fabric by an incendiary projectile.

This preliminary study with nitrogen made unnecessary more

than very brief and inexpensive experiments with helium, and

the required data were ready well in advance of any immediate

need for their application.

The Bureau also cooperated with the Air Service in making a

study of the ignition of hydrogen balloons by means of incendiary

bullets. Several hundred experiments were made under various

conditions and with a variety of incendiary bullets upon hydrogen

bags made of balloon fabric. These bags and other facilities were

prepared by this Bureau.

Gas-Leak Detectors

At the request of the Signal Corps a laboratory investigation

was made of instruments for the purpose of detecting leaks in

balloons, and a report was rendered recommending the use of a

particular type of instrument commercially available. The rec- ommendation is understood to have been followed by the Air

Services of both the Army and Navy.

Means for Deterniining the Specific Gravity of Balloon Gas

An apparatus was designed and a model constructed at this

Bureau for determining the specific gravity of balloon gas.

This apparatus has been adopted by both the Army and Navy.

Some of the essential parts of the first 50 instruments placed in

service were also made at this Bureau, but the apparatus is now

supplied by a commercial instrument maker.

CALIBRATION OF TESTING MACHINES

The purchase of immense quantities of war materials under

specifications which prescribed minimum physical requirements
60 WAR WORK OF THE BUREAU OF STANDARDS

necessitated the employment of numerous testing machines at

manufacturing plants for the use of Army and Navy inspectors.

In order to make sure that the results obtained by these machines

should be sufficiently accurate, it was necessary to calibrate them

and check their readings against those of some machine of known

accuracy at a central point. In order best to carry out this work,

the chief of the engineering materials section of the Bureau of

Standards was appointed advisor of physical control for the

Ordnance Department of the Army in 191 7. The Bureau acted

in a like capacity for numerous other Government departments

during the war. Comparison Bars for Calibration

The major part of the Bureau's work in testing machine calibrations consisted in the tensile testing of "comparison bars" for

the purpose of comparing certain loads on manufacturers' machines

with the machines at the Bureau. The accuracy of the latter

has been determined by dead-weight calibrations, but this method

is unsuited for use on machines a long distance away owing to

the difficulty of transporting the necessary weights and levers.

The comparison-bar method depends for its accuracy on the

uniformity of the steel in the bar from which the tensile specimens

are cut and also upon the accuracy of the tests in both machines.

The usual way in which such a test is carried out is as follows:

A bar of steel is cut into sections which are numbered consecutively, tensile specimens are machined from the sections, and

alternate ones are pulled in the standard machine and the others

in the machine which it is desired to calibrate. The method is

not recommended, and the Bureau will give no certificate of

accuracy for a machine calibrated in this manner. It was realized

that this method of calibration was merely a makeshift, but it

was necessary to employ it in the war emergency.

Preferable Calibration Methods

Preferable methods for conducting calibrations of universal or

tensile testing machine are by calibration bars, by proving levers, or by direct dead-weight loading, the last, of course, being the

most accurate, but usually impracticable for large capacity

machines. Calibration bars, as distinguished from comparison

bars, are stressed repeatedly over ranges not exceeding the proportional or elastic limits of the material. An extensometer is

attached, preferably in some permanent manner, and the deformation readings as observed on either machine serve as a basis
CHEMICAL INVESTIGATIONS (MISCELLANEOUS) 6

for comparison. It is clear that this method verifies the accuracy

of the testing machine over a larger portion of its range and it

also possesses marked advantages from a number of other aspects.

The proving levers employ dead weight, but with a multiplying

lever device so that the weights which must be transported with

the machine are not so heavy as to be prohibitive. However,

even this device is too large and expensive to be practicable for

most of the calibration work such as was carried out during the

war. All of these calibration methods were resorted to by the

Bureau on various occasions in response to requests from the

Army and Navy. At the present time experimental work,

which was laid aside during the war due to the pressure of military

investigation, is now in progress; it will provide a calibration

apparatus having a capacity of 100 ooo pounds and an accuracy

sufficient for all commercial requirements.

Hardness Machines and Extensometers

Beside the work outlined above on tensile and universal

testing machines, the Bureau's calibrations also cover a number

of hardness-testing machines of the Brinell and scleroscope types.

A Brinell meter, designed to furnish a portable hardness-measuring

machine, was studied. Experimental data justified its recommendation for all purposes where a variation of ±5 per cent

from the reading which would have been obtained on the ordinary

hydraulic or dead-weight testing is allowable. The Bureau

likewise conducted a rather extensive investigation of the accuracy

of various instruments for measuring the deformation of tensile

specimens under progressive loading. It was decided that a

certain make of extensometer was unsatisfactory for a determination of the elastic Hmit where successive applications and re- leasings of the load are required, or for the determination of the

modulus of elasticity, but would probably be satisfactory for

determining the yield point or for approximate determination of

the proportional limit of the material.

CHEMICAL INVESTIGATIONS (MISCELLANEOUS)

Ferrous Materials

The work on the above subject consisted chiefly in the analysis

of material required by the various branches of the Army and the

Navy, and in supplying information to other divisions of the

Bureau in their investigations, or developing suitable materials for

the various military needs. It was necessary that these results be
62 WAR WORK OF THE BUREAU OF STANDARDS

furnished as accurately as the case required and with the least

possible delay.

Several branches of the military service detailed chemists to the

Bureau for their tests, working under the direction of members of

the Bureau's staff. Naturally this created a delicate situation

requiring much care and thought to maintain proper adjustment,

but it is believed the situation was satisfactorily met. Ultimately

separate laboratories were established by these military branches

at points nearer the source of production, though the Bureau's

laboratories were still called upon for check and control analyses.

Under the stimulus of war needs, many new alloy steels were

produced and submitted for tests; also materials obtained by our

special agents abroad were sent to the Bureau for examination.

It was necessary to make careful analyses of these materials to

determine their composition, not only of the ordinary elements,

but also of unusual alloying elements, and to develop methods of

analysis and to study their influence on the standard determinations ordinarily used.

The regular methods for the determination of molybdenum and

vanadium have been modified so as to apply to many of the alloy

steels. The accuracy of the determination of silica in ferrosilicon

has been tested under varying conditions, and a quick method for

the determination of chromium by persulphate oxidation has been

investigated.

The persulphate method for the determination of manganese

was found not to be applicable to steels containing over one-half

per cent chromium, and the end point was masked by high content

of nickel. Cobalt up to 20 per cent was found not to interfere with

the determination of nickel by the glyoximine method. More con- cordant results were obtained on the determination of carbon in

nichrome by direct combustion than by solution in double chloride

of potassium and copper.

Nonferrous Materials

The work in this laboratory is very similar to that of the ferrous

laboratory, consisting chiefly in the analysis of material required

by the various branches of the military service and in the supplying

of information to the other divisions of the Bureau to aid them in

their investigations to determine the most suitable materials for

the various military needs and to explain causes of failure.

In the study of light-weight alloys for aircraft construction the

effect of small additions of various elements to aluminum required

a special study to develop suitable methods of analysis.
CHEMICAL INVESTIGATIONS (MISCELLANEOUS) 63

While the major part of these investigations were of a physical or metallurgical nature, knowledge of the composition was most

important, not only of unknown alloys, but also of alloys made on

definite formulas to measure segregation and losses.

In many of these alloys unusual elements or combinations of

elements occurred which necessitated a study and adoption of

methods to each particular case. Some of the cases may be mentioned:

It was found that in some cases nickel failed to deposit. Some

experiments were made on known solutions containing chromium,

vanadium, and uranium salts ; in these cases nickel deposited only

partially or not at all. It was found that large amounts of ammonium sulphate had no effect on the deposition of nickel. Iron

and manganese have little or no effect, so it was necessary to re- move chromium, vanadium, and uranium before depositing the

nickel.

When zinc is the only impurity in appreciable quantities in tin,

difficulty is experienced in its separation. The most effective

method found was to add pure lead or copper salts, and then

separate all the sulphides together and in the mixed sulphides re- move lead and copper electrolytically. So far, this plan works

effectively.

It was found that zinc could be removed from aluminum in

0.0 1 iV solutions of sulphuric acid. The same method can be used

effectively for separation of large amounts of zinc from nickel.

Recent experiments indicate that ammonia can be used instead of

Sodium hydroxide, thus eliminating impurities in sodium hydroxide.

Considerable work has been done in aluminum solders. These

vary greatly in composition, and methods must be varied accordingly. In alloys high in tin, the tin was determined electrolytically

from oxalic-acid solutions. Considerable work was required to

determine proper conditions, and further study is required before

all points will have been covered.

The failure of nichrome tubes used in calcining gas-mask carbon

has been studied. No satisfactory method for the analysis of

this alloy was found in the literature and much difficulty was

encountered in the determinations required. Satisfactory methods

show a marked difference in various parts of the tubes, but it is

Still impossible to say if these variations are due to segregation

in the original tube or resulted from their use. The separation of small quantities of cobalt and nickel is

required in the analysis of some of the new alloys, and methods

are being studied to this end.
64 WAR WORK OF THE BUREAU OF STANDARDS

Platinum Metals and Platinum Substitutes

A chemical laboratory for the study of platinum and the metals

associated with it was organized in this Bureau in July, 191 7. In conjunction with other laboratories of the Bureau its purpose

was to prepare the pure platinum metals and their alloys, study

their chemical and physical properties, and develop the analytical

methods for the group.

Opportunities for rendering assistance in the prosecution of

the war soon became apparent. Work for the nitrate division

of the Ordnance Department of the Army came first in order

and soon occupied a position of first importance. Platinum wire

woven into gauze was used in large quantities as a catalyzer in

the oxidation of ammonia to nitric acid. Much experimental

work as to the size of wire, mesh of gauze, and purity of the

platinum necessary to obtain the highest efficiency had to be carried

out. The first two of these items were handled principally by

the nitrate division, but several of the gauzes used were examined

by the division of weights and measures of this Bureau for size

of mesh and regularity of weave.

There was considerable uncertainty as to the effect of small

amounts of rhodium, iridium, palladium, iron, and other metals

alloyed with platinum on the efficiency of the latter for catalytic

purposes. It was claimed by some authorities that the platinum

must be specially free from iridium. As this element, together

with rhodium and iron, is almost always present in commercial

platinum, it was necessary to be able to obtain accurate analyses

of the platinum used. The methods used were based for the

most part upon those employed by Deville and Stas in the analysis

of the platinum-iridium alloy used in the international standard

mete. Their method gave very accurate results for iridium.

The separation of rhodium and platinum by potassium pyrosulphate fusion proved extremely tedious, and a primary separation by distillation in a current of carbon monoxide and chlorine, as recommended by the German Reichsanstalt, was later adopted.

Iron was best determined colorimetrically on a separate sample.

Complete analyses were made on several gauzes the efficiency of

which had been previously determined. Some iridium determinations were made on material refined for the nitrate division

by the New York Assay Office.

An attempt was made by the optical division of the Bureau

to determine small amounts of impurities in some of the samples

submitted by the nitrate division by spectroscopic methods.
CHEMICAL INVESTIGATIONS (MISCELLANEOUS) 65

Owing to the lack of standard alloys this proved unsatisfactory.

Occasionally use was made of a rapid method for an approximate

determination of the total impurities which was developed by

the metallurgical division of the Bureau (Scientific Papers Nos.

254 and 280). This method depends upon the emf developed

at a hot junction of a platinum alloy with pure platinum. Some

of the determinations were made by the metallurgical division.

Another section of the last-named division made metallographic

examinations of some of the gauze before and after being used in

the oxidation of ammonia. The results obtained were helpful in

determining the phenomena which occurred in the catalytic

process.

In addition to the work already described the chief chemist of

the Bureau served the nitrate division of the Ordnance Department in an advisory capacity on numerous questions relating to

the sources and supply of platinum and the assay of platinum

ore received from Russia. The nitrate division in turn cooperated

with the Bureau by detailing a member of their chemical staff

to work in the platinum laboratory and furnishing funds for part

of the necessary equipment.

In the latter part of 191 8 problems of a similar nature to those

already outlined arose in the Bureau of Aircraft Production.

One complete analysis was made on platinum-iridium contact

points for airplane magnetos. Later the electrical division of

the Bureau undertook a study of the relative efficiency in service

of magnetos equipped with contact points of varying iridium

content. This was done in order to determine the possibility of

economizing on iridium, the available supply of which was very

low. Magnetos for several different types of engines were tested.

Determinations of the iridium and iron content were made on all

the types of contact points used. It was found that the iridium

content fell somewhat over 50 per cent short of specifications in

each type. This rendered the results of the whole series of tests

only partially useful. The manufacturer of the contact points

proposed to make up a new set of alloys, but the second series of

service tests was not undertaken owing to the termination of

hostilities.

The shortage of platinum a short time before and during the war

aroused the interest both of commercial organizations and the

public in general. Quite a number of "platinum substitutes"

were developed, and many samples of supposed platinum ore were

26035°—21 5
66 WAR WORK OF THE BUREAU OF STANDARDS

submitted to various Government laboratories. A few of the

latter were examined by this Bureau. None of the samples submitted showed any platinum. The most interesting case was of a

mineral from the Grand Canyon, which was repeatedly brought

forward as a source of platinum in spite of the statement from the

Geological Survey that it contained no precious metal. New samples were taken by the Survey and assayed in their own laboratory,

that of the Mint, and of this Bureau. No platinum could be found.

A more detailed report of this investigation is given in Mining and

Scientific Press (118, p. 185; 1919).

The substitutes proposed for platinum were of two kinds, those

composed of base metals and alloys of the noble metals. Of the

latter, two were examined, known as rhotanium and palau. Both

are alloys of gold with relatively small amounts of palladium.

These were tested in conjunction with the metallurgical division

of the Bureau and were found suitable substitutes for platinum

in numerous operations in the chemical laboratory. A detailed

report of these tests was published in the Journal of Industrial and

Engineering Chemistry.

In the case of the base-metal substitutes none was found which

approached platinum in general usefulness. In one case steps

were taken to suppress extravagant advertising. Two alloys were

examined which were found suitable for the purposes for which

they were designed. One was an alloy very resistant to nitric acid

and the other could be used for electrical contact points under a

limited range of conditions. The former was submitted by the

nitrate division of the Ordnance Department, but the greater part

of the work on platinum substitutes was done for the platinum

section of the War Industries Board.

Prevention of Corrosion

The work of the Bureau has included a study of the corrosion of

metals and its prevention. The tests were generally made by the

salt-spray method, originally described by J. A. Capp (Proceedings of the American Society for Testing Materials, 14, part 2, p.

475) and greatly improved in the Bureau's laboratory, as described

in Proceedings of the American Society for Testing Materials (18,

part 1, p. 237, 1 918). It is thought that this test indicates, in

an accelerated way, the relative resistance to corrosion of metals,

especially when exposed to saline conditions. Tests on corrosion

of aluminum, undertaken chiefly in the interest of aeronautics, were

made on alloys of aluminum with copper, nickel, manganese, and
CHEMICAL INVESTIGATIONS (MISCELLANEOUS) 67

magnesium prepared by the metallurgical division of the Bureau.

The following conclusions were drawn

(1) A decided difference in resistance to corrosion may be produced by quenching some aluminum alloys; (2) a less marked difference is produced by annealing ; (3) with some alloys no apparent

difference is produced; (4) if any change is produced by quenching,

it improves the quality of the metal; (5) the magnesium, nickel,

and nickel-magnesium alloys have about the same resistance to

corrosion regardless of heat treatment; (6) annealing improves

somewhat the quality of the copper-magnesium alloys and reduces

the quality of the manganese-magnesium alloys; (7) quenching

produces the most desirable effects in the copper, copper-magnesium, and manganese alloys; (8) commercial aluminum, as rolled,

does not resist corrosion satisfactorily, and the sample tested was

almost completely disintegrated at the end of the test; annealing

or quenching materially improves it, but it is not equal to some of

the alloys.

In developing the data on which these conclusions were based

and in other tests, it is noteworthy that ordinary sheet aluminum

as rolled frequently exfoliates, showing a laminated structure instead of a homogeneous mass.

The various types of zinc coatings were tested and no evidence

was obtained to indicate superiority of hot galvanizing, sherardizing, or plating. The use of zinc was recommended for protection

of iron or steel against corrosion wherever its application was possible, the value of the coating (or protection afforded) being judged

by its life in the salt spray or amount of zinc applied per unit area,

depending on conditions of exposure anticipated in service. This

report is covered in more detail in the report on " Protective Coatings," appearing elsewhere.

Corrosion produced by the use of soldering fluxes was also considered. For general purposes the use of zinc chloride fluxes seems

to be almost universal, and although they will undoubtedly accelerate corrosion, their use seems to be unavoidable. Rosin was

recommended whenever it could be used, and if zinc chloride was

used, thorough washing with hot water was advised.

Examination of hydroplane radiators indicated that leaks which

develop in storage are caused by corrosion accelerated by the zinc

chloride flux which was left on the metal. Washing inside and out

with hot water and sodium carbonate solution was recommended

as a probable means of correcting this difficulty.
68 WAR WORK OF THE BUREAU OF STANDARDS

Removing Metal Fouling from Rifle Barrels

Prior to the war, a solution made according to the following

formula was used for removing the cupro-nickel fouling from

rifle and machine-gun barrels:

Ammonium persulphate ounces . . i Ammonium carbonate grains. . 200

Water ounces. . 4

Ammonium water (28 per cent) do. . . . 6

In September, 191 7, the office of the Chief of Ordnance of the

Army found that not enough ammonium persulphate was produced in the entire country to supply the needs for cleaning

rifles, and requested this Bureau to recommend a substitute.

At this time there appeared to be only a shortage of ammonium

persulphate, and numerous experiments were made in trying to

find a satisfactory substitute for this chemical. Nothing was

found which at all met the requirements. While these experiments were still in progress it developed that the supply of ammonia water was becoming depleted and that no further supplies of this substance could be relied upon.

At this stage of the investigation, an electrolytic method for

cleaning the barrels was successfully developed. This was quite

simple and consisted in using an electrolyte made of a mixture

of sodium carbonate and ammonium sulphate dissolved in water,

a steel rod being used as the anode and the rifle barrel forming

the cathode. The experiments with this method demonstrated

that in using a current of about 0.5 ampere and from 4 to 5 volts,

cleaning was more rapid by the electrolytic method than by the

use of the old persulphate solution.

It is believed that the ordnance officials developed an apparatus for generating the required electric current for this work,

and it was submitted for approval. The electrolytic method

had the objection of requiring a source of electric current, either

from a central station or from batteries, and hence could not be

satisfactorily used except at base stations. The method would,

however, probably have been introduced had it not developed

middle of December, 191 7—that a sufficient supply of ammonium

persulphate would be available.

The ordnance officers deemed it advisable, however, to eliminate the use of liquids which would have to be transported, thus

necessitating avoiding the use of ammonia water. After making

numerous experiments, it was found in December, 191 7, that a

mixture of 3 grams of ammonium persulphate, 5 grams of am-
CHEMICAL INVESTIGATIONS (MISCELLANEOUS) 69

monium sulphate, and 2 grams of caustic soda dissolved in water

to make 35 cc was quite efficient in dissolving cupro nickel and

had no appreciable injurious effects on the steel. Such a mixture

had distinct advantages; the reagents could all be kept in a

solid form, and it was suggested that the ammonium persulphate

and ammonium sulphate could be prepared in solid tablets which

could be kept in glass, metal, or cardboard containers. The

sodium hydroxide could also be kept in metal or glass containers.

It would then be very simple to make up the solution by dissolving the requisite number of each kind of tablet in water and

mixing the solutions for use. Ordnance officers took up the question of making contracts

for tablets and found that it would be necessary to use a small

amount of binding material, such as sugar, and a lubricant similar

to stearic acid or paraffin, in the manufacture of the tablets. The

amount of these additions was small, and specifications were

finally drawn up for these tablets and have been issued by the

War Department.

Soap

A number of different brands of shaving soaps (including

stick and cream) were examined by the Bureau for the purchase,

storage, and traffic division of- the War Department during May

and June, 191 8. Following this examination, specifications for

stick shaving soap and shaving cream were drawn up by the

Bureau and submitted to the War Department.

Numerous analyses of laundry soap have been made for the

same department during the same period.

Carbon Tetrachloride Fire-Extinguishing Liquid

At the request of the War Industries Board and the Quartermaster General of the Army experiments were made to find a

substitute for chloroform as freezing-point depressant in carbon

tetrachloride to be used as a fire-extinguishing liquid. It was

found that gasoline and turpentine were both efficient freezingpoint depressants of carbon tetrachloride, and that the resulting

mixtures were fire-extinguishing liquids. The signing of the

armistice removed the demand for conserving chloroform, and

hence the mixtures suggested were apparently not used.

Antifreezing Solutions for Automobile Radiators

The question of a satisfactory antifreezing solution for radiators used in connection with gasoline motors was studied. The

chief constituent of all antifreezing compounds tested was cal-
70 WAR WORK OF THE BUREAU OF STANDARDS

cium chloride, and numerous tests showed that the corrosion

produced by their use was decidedly rapid, particularly at soldered

joints in radiators and on all-aluminum parts which are used in

some engines. Whenever solutions of calcium chloride get

on the ignition system, either from leaks or overflow, electrical

leaks or short circuits are produced which interfere with engine

performance, and such electrical leaks are very difficult to correct.

The use of alcohol and water was recommended for trucks,

automobiles, etc., but such solutions have a peculiar limitation

when used on aircraft, that of a low-boiling liquid for high altitudes.

Tests were undertaken and are still in progress to determine if the

addition of glycerin to such a solution will overcome this objectionable feature.

Prevention of Foul-Gas Formation in Ammonia-Absorption Refrigerating Machines

A problem started before the war, but which assumed added

significance shortly after the beginning of hostilities and which was,

therefore, pushed to completion, was the causes and means of

prevention of foul-gas formation in ammonia-absorption refrigerating machines. On account of the scarcity of ammonia during

the war and the large losses necessitated in purging a plant of

foul gas, the solution of this problem was of considerable importance, as it helped toward the conservation of ammonia. It was

found that the main causes of this trouble were leaks of gas into

the system and the gas produced by the corroding of the metal in

the plant by impure aqua ammonia. This latter cause was entirely prevented by the addition of sodium dichromate to the charge

of aqua ammonia. The results of this work have been published

in Technologic Paper No. 180, "Causes and Prevention of the

Formation of Noncondensible Gases in Ammonia Absorption

Refrigeration Machines.''

Development of Automatic Analytical Apparatus for Use in Nitrate

Plants

During the summer and autumn of 191 8 a force of about 15

men was engaged upon the problem of designing and building an

automatic apparatus for the continuous analysis of the gas mixtures of widely different character occurring in the contact process

for the manufacture of ammonia. This apparatus was regarded

as essential to the efficient operating control of the large nitrate

plant projected at Mussel Shoals. At the signing of the armistice

one unit of this apparatus capable of automatically making and
CHEMICAL INVESTIGATIONS (MISCELLANEOUS) 7

recording in series 12 different analyses was nearly ready for

installation. A smaller unit for the same purpose was provided

for the laboratory engaged upon the fixed-nitrogen research.

While this work did not reach the stage of application to the

purpose for which it was intended, the methods developed, which

are largely new, should find extensive application in many

industries.

Hydrogen Detectors for Use in Submarines

The problem of designing a suitable hydrogen detector to prevent

the accumulation of a dangerous amount of gas in submarines was

presented to the Bureau as the result of two serious explosions

prior to the war. Ten or more devices for the same purpose,

designed and constructed outside the Bureau, were submitted to

the Bureau for tests and criticisms. An apparatus believed to be

satisfactory for the purpose was designed at the Bureau and, after

extensive laboratory tests, was submitted to the Navy Department. The tests upon the instrument made in the New York

Navy Yard were reported to be entirely satisfactory, and 60 of

the instruments were constructed and calibrated. The severity

of the mechanical and electrical conditions to which they were to

be subjected was underestimated, however, and they did not

render satisfactory service. Another type of instrument was then

designed especially to meet the most severe conditions of service,

even at a sacrifice of several of the desirable features of the earlier

device. This instrument has been tested by the Navy Department and reported upon favorably, but has not yet been placed

in production for use aboard ship. The earlier work along this

line is reported in Scientific Paper No. 334 of this Bureau.

Determination of Carbon Dioxide and Oxygen in the Air of a

Submarine

Much time was devoted to the problem, initiated by the Navy

and transferred to this Bureau by the Sanitary Corps, of automatically indicating the percentage of carbon dioxide and oxygen

in the air of a submarine. This problem appeared to be well on

the way to solution when the Bureau was informed that it was no

longer regarded as of much importance, and it was abandoned for

more urgent work.

Tests of Gas Masks and Oxygen-Supply Apparatus

Tests were made and recommendations reported regarding the

use of gas-supply apparatus for aviators when more than one man

was to be supplied from the same source. Prior to the organ-
72 WAR WORK OF THE BUREAU OF STANDARDS

ization of the Chemical Warfare Service this Bureau also did the

preliminary work of examining the gas masks used by European

armies. This work included the identification of the materials

used as absorbents and testing the resistance to respiration and

other mechanical features of the masks.

Miscellaneous

A great many gasolines and gasoline substitutes were examined

in connection with the work on airplane engines. Castor oils

were investigated quite frequently for the Signal Corps, and miscellaneous materials, including neat's-foot oil, saddle soap, and

white floating soap, were examined for the Ordnance Department.

CHROMATIC CAMOUFLAGE AND CHROMATICALLY CONCEALED INSIGNIA

Owing to the fact that different spectral distributions of light

may give the same color, it is possible to have samples accurately

color-matched as examined by the unaided eye in daylight, and

still show glaring chromatic contrast when examined through

suitable light filters (colored glasses, etc.) . This circumstance was

a source of danger to the camouflage artist. For example, a fabric

might be dyed green to closely match green foliage, and through

a properly chosen filter it might appear bright red on a dark green

or black background of normally green foliage. Indeed, it might

be about as conspicuous as a fire at night. On the other hand, it

might, through another filter, appear dark on a bright red background of normally green foliage.

At the request of the War Department, the Bureau made

several tests of materials in this respect and was able to recommend dyes and select fabrics to overcome this difficulty.

The Bureau itself did not undertake a comprehensive and

unified investigation of the subject of "camouflage." However,

a great deal of work bearing on it was done at the request and

instigation of others working on these subjects. A great deal of

oral information on ray filters, spectral transmission, and reflection

and chromatic camouflage, often illustrated by experimental

demonstration, was given to officers of the Army and Navy and

representatives of the National Research Council. Ray filters

were lent from stock, and others were made to order of prescribed

properties and supplied to the applicants for them.

The Bureau was also asked to investigate the practical possibilities of chromatically concealed insignia; that is, insignia woven,

painted, or made in such a way that they would be invisible to the
COKE-OVEN INVESTIGATIONS 73

unaided eye in daylight and be rendered visible by examination

through properly selected filters. Many combinations of dyed fabrics were prepared which were nearly or quite indistinguishable to

the unaided eye, but showed remarkable color differences when

examined through suitable filters. These were exhibited and ex- plained to numerous representatives of the War and Navy Departments. An exhibit of some of these was made in connection with

the American Physical Society exhibit at the Bureau, April 25 to

26, 1919.

COKE-OVEN INVESTIGATIONS

During the latter part of 191 7 the attention of the Department

of Commerce was directed to the Roberts coke and gas oven

through the efforts made by the American Coal & By-Products

Coke Co., the owners and operators of the Roberts process, to secure Government support for this enterprise. This matter was

referred to the Bureau of Standards for action.

Preliminary Work of the Bureau

Since there were 24 Roberts ovens in operation in Canal Dover,

Ohio, three representatives of the gas engineering section of the

Bureau were detailed to inspect the plant at this point and carried

on their work on December 12 and 13. Two views of this plant,

showing the general lay-out, are presented in Fig. 8.

The promoters of this process claimed a number of advantages

for this oven which it was said were not embodied in other types.

Among these were the following: (1) Ability to coke so-called

noncoking coals and produce a satisfactory grade of metallurgical

coke from high-volatile, midcontinent coals; (2) larger yields of

by-products recovered than from other types of ovens; (3) more

substantial construction than possible with existing types of ovens

(4) greater degree of flexibility of heat control than with existing

types of ovens; and (5) increased earning power per oven over the

Other types of ovens. At this investigation it appeared that the ovens were operating

in a fairly satisfactory manner, and although the Bureau was not

able to verify these claims to any great extent in such a short

period, the indications were that the oven could be developed into

a commercial success. Therefore, the Bureau of Standards re- ported to the Assistant Secretary of Commerce on December 15, as follows

We do not hesitate to recommend favorably this type of oven for further consideration for we feel sure that benefit to the Government and the people may be expected

from the commercial development of the process.
74 WAR WORK OF THE BUREAU OF STANDARDS

Fuel Situation in Early Part of 1918

Early in this country's participation in the war it was realized

that a successful end would be possible only through the intensive

driving of our industries. This became particularly evident during the early part of 191 8, and a great expansion of the steel

industries of the country resulted. Likewise, it was realized that

high explosives had to form a large part of the equipment of the

American Expeditionary Forces. The rate of production of these

necessary materials was limited to a great extent by the rate of

the recovery of by-products of coal. The output of steel was curtailed because of the lack of iron, which in turn was not produced

in sufficient quantities due largely to the lack of coke. The production of high explosives was not keeping pace with the growth

of the armed forces of the Nation, because of the lack of fundamental materials—toluol, benzol, ammonia, etc.

In addition to the lack of coke-oven plants, climatic conditions

during the winter months of 191 7-1 8 greatly reduced the coal

supplies of the existing plants. Transportation of large quantities of coal became increasingly difficult as the severe winter

weather continued and as the railroads became choked with materials moving toward the seaboard. This particularly interfered

with the maintenance of the production at full capacity on the

part of the coke ovens in the central section of the country, since

most of the existing plants in this section were dependent for

their coal supplies upon so-called eastern coal. Likewise, with

the increase of traffic more and more coal was used by the railroads and the use of raw coal in boiler plants and in other industrial activities, and in the heating of dwellings, factories, etc., due

to the extreme cold and lack of other fuels, depleted the supply of

fuels for these ovens. Accordingly the utilization of much of the undeveloped fuel resources of the country became a question of paramount importance. Attention was forcibly directed to the large quantities

of midcontinental coal available, particularly in Indiana and Illinois, but which was not being used. Inasmuch as the steel production of large plants, such as those at Gary, Ind., and Joliet,

111., was sometimes reduced to 30 per cent through lack of coke,

it was evident that some relief was essential.

Attention Focused on Roberts Oven

Since it was claimed for the Roberts oven that it was able to

produce a first-class grade of metallurgical coke from these midcontinental coals, it was natural that this type of oven should be
COKE-OVEN INVESTIGATIONS 75

looked upon as a proper agency to aid in the forestalling of the

crisis which seemed imminent, as well as to assist in the development of these hitherto unused coal resources of the country.

Therefore, using the Bureau's report of December 1 5, Mr. Roberts

endeavored to interest the Government to aid in the further development of his process and to construct two plants, one at East

St. Louis, 111., and the other at Chicago, 111., which would use

coal from the Illinois (midcontinent) field, thus avoiding the long

railroad haul and accelerating the production of coke, toluol, etc.

Test Conducted by the Bureau

Since the December 15, 191 7, report of the Bureau was only a

recommendation for further consideration, early in March, 1918,

the Secretary of Commerce, acting by direct instructions from the

President, ordered the Bureau to conduct an operating test of the

Roberts oven installation at Canal Dover and to associate with

itself the Bureau of Mines and the Geological Survey in this work.

Accordingly, plans were immediately made for such a test, and

representatives of the Bureau proceeded to Dover on March 18,

but found that it was not feasible to begin the test at the time

specified owing to a lack of boiler capacity.

The ovens at Dover were operating at this time on Cambridge

(Ohio) coal, which, although somewhat similar to the midcontinent

coals, bears a striking resemblance to the eastern coking coals.

It was decided, however, that the test should be condutced with

the same coals which would be used at East St. Louis and Chicago

therefore the Bureau was instructed to assist in obtaining the

necessary coal for this test, together with the required boiler parts.

This the Bureau proceeded to do, but hindered by numerous

construction and transportation delays, it was not until April 26

at 7 a. m. that the test was officially started. Quantitative

observations of all parts of the plant operation were undertaken

and were continued 24 hours each day, including Sundays, until 7

a. m., May 11. During this test 4800 tons of Illinois coal were

used in the ovens and all of the usual by-products, including light

oil, ammonia, and tar, were recovered and either carefully weighed

or measured. The coal used was shipped from the Royalton,

Sesser, and Orient mines in Franklin County, 111., and the Ayrshire

mine, Pike County, Ind. This work was conducted by 22 representatives of the Bureau of Standards and 9 members of the

regular staff of the Bureau of Mines; 5 consulting engineers were

also present at the request of the Bureau of Mines to advise concerning the work.
76 WAR WORK OF THE BUREAU OF STANDARDS

The Bureau's representatives were in charge of the test and

responsible for observations of all work done about the coke oven,

the by-product department, the light-oil department, and other

accessory operations. Exact records were made of the charging

and discharging of the ovens, the quantities of tar, ammonia

liquor, light oil (containing benzol, toluol, etc.) , and gas produced

during the test period. Samples of all these materials were

regularly taken, and analyses or tests of these samples made at

appropriate intervals. Likewise, high-temperature measurements

at various parts of the battery were carried on during the test. The Bureau of Mines was responsible for the sampling of the

coal at the mines, at which time record was made of the car numbers and weights of the coal shipped for the test. The Bureau of

Mines also weighed and sampled for analysis the coal as it was

unloaded in Dover for the test, thus identifying by car numbers

and car weights the origin of the fuel used. The Bureau of Mines

also was responsible for the sampling, weighing, and analysis of

the coke produced from the test coal.

Because of mechanical difficulties the regenerators were not

used during the test; therefore the ovens were not operated upon

preheated air, but upon cold air. This precluded the making of

any surplus gas, as it was necessary to use all that was obtained

in heating the ovens. Difficulty was also experienced in the

uniformity of the heating of the oven walls, the ends particularly

being noticeably cold.

Results of Test at Dover

The coke produced from three of the test coals was satisfactory as to quantity and quality, the yield being substantially the same

as that obtained from other by-product ovens. On the basis of

dry coal, the yield of dry coke was 69.5 per cent, and the percentage

of the sizes of dry coke to total coke were furnace size 75.1, nut

16.8, and breeze 8.1 per cent. A sufficient amount of coke was

not produced by the ovens to operate the 500-ton blast furnace

adjacent to the plant without the use of additional coke from other

sources. Since the furnace was not able to operate at more than

three-fourths capacity, and since the quantity of coke had to be

increased by the addition of outside coke to the extent of from

30 to 50 per cent, it was impossible to determine the real metallurgical value of the coke. However, the opinion of the superintendent of the blast furnace was that when 100 per cent of this Illinois

coke was used it would make a satisfactory blast-furnace fuel, with

the furnace at full capacity.
COKE-OVEN INVESTIGATIONS 77

The yield of toluol both as to quantity and quality was good and

amounted to about 0.43 gallon per ton of dry coal, and the yield

of benzol amounted to 1.55 gallons per ton of dry coal. The

yield of other by-products per ton of dry coal were as follows:

Ammonium sulphate, 26 pounds; tar, 10.7 gallons; and gas about

10 000 cubic feet. However, on the basis of the quantity of these

materials actually in the gas, the yields were somewhat higher

than those quoted.

Conference at Pittsburgh

After the test at Dover was completed, a conference, which was

arranged by the Bureau of Mines, was held in Pittsburgh on May 22,

and the observations and results of the tests were discussed at

length. Substantial agreement was reached as to what had been

demonstrated by the test and what the results signified, and a

report of this conference was made to the Secretary of Commerce

on May 25, which was signed jointly by the Directors of the Bureau

of Standards and the Bureau of Mines. The report was as follows

The Roberts oven produced a satisfactory grade of metallurgical coke from three

of the four coals used. These coals have not heretofore been used to make metallurgical coke in commercial quantities. The gross yield was substantially the same

as that obtained by other by-product ovens. The coke was mixed with about an

equal amount of coke from other sources, because of the limited supply of Dover coke,

and was used in a blast furnace running at about three-fourths capacity. A satis- factory grade of pig iron was produced. The superintendent of the furnace is of the

opinion that he could operate satisfactorily with this coke alone and at full capacity.

The quantity and quality of the gas produced was good. After removing the byproducts all the gas was used in the process of coke making. An excess of gas will be available when regenerators are in successful operation.

The quantity of by-products in the gas was good. The amount of tar, toluol, benzol,

etc., in the gas was about the same as is obtained in other ovens when high-volatile coals are used and was greater than the average yield from low-volatile coal, or the

usual mixture. The amount of ammonia in the gas was very good.

The construction of the ovens is substantial. The heating system of the Dover

plant leaves something to be desired in the matter of uniform heating of walls, and

the regenerators for preheating air have not been in operative condition. Experience

with the plant shows it can be improved in some particulars, and the company believes

successful preheating of air and uniform heating can be demonstrated in a short time.

It was necessary to run the test without regenerators, and, as their use is essential for most efficient operation under usual conditions and in normal times, this further

demonstration is believed to be necessary. The Roberts Co. immediately proceeded to carry out the agreed

program for a further demonstration, but great mechanical difficulty was experienced in putting the ovens into shape for this

purpose, and it was not until the latter part of September that it

was possible to complete the work.

Further Work by the Bureau

The Bureau wished further to study the effect of temperature

distribution in the various types of ovens, so that the feature of
78 WAR WORK OF THE BUREAU OF STANDARDS

greater uniformity and flexibility of heating, which Mr. Roberts

claimed for his oven, could be either verified or disproved. Therefore a separate series of high-temperature measurements were con- ducted at Canal Dover during June, and similar tests were likewise

carried out in the Koppers oven installation of the Laclede Gas

Light Co., St. Louis.

The Bureau has also made an investigation of the existing patent

literature and other literature on the subject of coke ovens, and

prepared a report showing the development of the art of byproduct coking of coal. This report has been given to several

persons for criticism.

Interest in the Use of Midcontinent Coals Increased

During the period from May to October, 191 8, other coke-oven

companies had taken under serious consideration the use of these

midcontinent coals in their particular types of ovens and had car- ried on experimental work. As a result, the Bureau received a

request from the Koppers Co., of Pittsburgh, to conduct an operating test of the Koppers oven installation in the plant of the Minnesota By-Product Coke Co., St. Paul, Minn., which would be

similar to that conducted at Dover in May.

At this time the Bureau was advised that 600 000 tons of Indiana coal had been used in the Gary, Ind., coke-oven plant, and

received a report which referred to this occassion from G. C.

Lowell, of Chicago, who mentioned it in the following manner:

During the latter part of the year 19 12, when there was a serious depression in the

steel business, it was decided to charge a portion of the ovens at the Gary plant with

100 per cent of western coal. This coal was what was known as Clinton coal, coming

from the Universal mines, located near Clinton, Ind. There was also a number of ovens charged with 100 per cent of coal from the Kelly mines located near Westville

and known as Westville coal. This coke, made from 100 per cent of Indiana coal, was first produced with an idea of supplying a cheap coke to the blast furnaces at Gary that were supplying gas to the electric generating station, and no particular

attention was paid to the yield of iron, it being attempted to hold the iron production

to as low a figure as possible and produce a maximum quantity of gas. The coke was used in this manner for a few months, and when the iron production was again increased by the blast furnaces one battery of ovens was kept on the Clin- ton coal, and the coke produced from this battery was mixed with the regular coke

produced at the Gary plant and charged into the blast furnace as mixed coke, using

up to about 15 per cent of the Clinton coke in the blast-furnace charges. Fairly

good results were obtained from the blast furnaces.

Test of Koppers Plant at St. Paul

Since such a long delay was experienced in placing the Roberts

plant at Canal Dover in operating condition, the bureau acted

upon the request of the Koppers Co. and secured permission from

the President, through the Secretary of Commerce, to conduct an
COKE-OVEN INVESTIGATIONS 79

extensive operating test of the plant at St. Paul. The Bureau of

Mines likewise cooperated in this test, which was officially started

at 7 a. m., September 27, 1918, and continued until 7 a. m.,

October 5, 1918.

The test of this plant, consisting of 65 Koppers coke ovens and

all accessory equipment and apparatus for the recovery of all byproducts, was conducted by 37 engineers and chemists, and in

addition a considerable number of expert engineers visited the

plant while the test was under way. The Bureau of Standards

was responsible for the general planning and supervision of the

test work. Its representatives made all observations of battery

operation, high-temperature measurements, by-products recovery,

and chemical laboratory work on gas and by-products. The Bureau of Mines was responsible for the sampling of the coal at the

time it was loaded at the mines and for the weighing, sampling,

and analysis of the coal as used at the plant, and of all sizes of

coke produced. Its representatives also made general observations on the character of the coke and the operation of the ovens. For this test 7600 tons of coal were used from the Orient mine,

Franklin County, 111. The quantity of all products was carefully

weighed or measured at regular intervals, samples of each of the

products were taken, and complete analyses of the coal and these

products have been made.

Results of Test at St. Paul

The yield of dry coke was 68.4 per cent, and the percentage of

the sizes of the coke on the basis of total coke were: Furnace, 56;

domestic, 37.6; and breeze, 6.4 per cent.

The yield of toluol amounted to 0.54 gallon per ton of dry coal,

and the yield of benzol to 2.29 gallons per ton of dry coal.

The yield of other by-products per ton of dry coal were as

follows: Ammonium sulphate, 30.3 pounds; tar, 8.5 gallons; and

gas, about 1 1 000 cubic feet.

Further Work at Dover

Immediately upon the completion of the St. Paul test, the

members of the Bureau's party proceeded to Dover for the final

demonstration of the Roberts process, with the regenerators

operating. Since the War Industries Board had requested that

a complete operating test be made with mid-continental coal, 1500

tons of Orient and 1000 tons of Ayrshire coal were secured for this

test, and arrangements made whereby the coke would be stored

until a sufficient amount had been accumulated, so that the blast
80 WAR WORK OF THE BUREAU OE STANDARDS

furnace could run for several days at full capacity on 100 per cent

Illinois coke.

The test began on October 12, with the same methods pursued

as were carried on in the May test, but before evening on October

14 the representative of the Roberts Co. requested that the

demonstration be stopped, since the quality of the coke and the

condition of the plant showed that it was not possible to make a

successful demonstration at this time. The Bureau acceded to

the request, and after conference with the War Industries Board,

decided that until the company could demonstrate that the

Roberts ovens could coke 480 tons of coal per day, the Bureau

would not consider another test.

Blast-Furnace Test on St. Paul Coke

During the latter part of the work at St. Paul, arrangements

were made to ship 1 500 tons of the furnace coke produced to the

blast-furnace plant of the Mississippi Valley Iron Co., St. Louis,

Mo. Soon after beginning the use of the test coke in the blast

furnace an additional quantity of about 360 tons was ordered.

Of the total tonnage ordered, 1746 tons were actually used in the

blast-furnace test. A representative of the Bureau of Standards

was present during the period of the test, which started with the

first charge of Illinois coke into the blast furnace at 1 p. m., October 19, and continued until 4.30 a. m., October 28.

This furnace was operating at a capacity of about 190 tons

of iron per day and at the beginning of the test was making

malleable iron. However, it was recognized that the most conclusive test of the merits of the coke would be obtained in making

a run on basic iron.

From this test the following general conclusions were drawn by

F. W. Sperr, jr., chief chemist of the Koppers Co., who was present

throughout the test:

1. The coke was first-class blast-furnace fuel, which could be substituted directly

for the regular coke (Laclede-Elkhorn) without creating injurious irregularity in

operation.

2. The coke carried the normal basic burden well, with every indication that it would make any grade of foundry iron with the normal burden.

3. It was indicated that with the Illinois coke the consumption of coke per ton

of pig iron is normal, and possibly even less than normal. This fact can not, however,

be absolutely established in so short a test. Great caution should be used in applying the results of this test

and in predicting what Illinois coke might do if used on an older

blast furnace of larger capacity or of different construction. The

coal from which the coke used in this test was made represented
COKE-OVEN INVESTIGATIONS 8l

the highest grade of Illinois coking coals, and the results should

not be too strictly applied to Illinois coke in general.

Additional Work Carried On by the Bureau

In order to determine the effect of variable temperatures upon

the coking of Orient (111.) coal and upon the quality and quantity

of gas made from this coal, a series of tests were run in an experimental retort of one of the large steel companies. These tests

were five in number; the weight of the charge of coal in each test

was about 4 pounds, and the temperature ranged from 835 C

to 6oo° C.

The results of these tests in general show that the volatile

matter in the coke increases as the temperature of coking decreases, and, correspondingly, with high-volatile matter in the

coal, the yield of coke is high. However, at the lower temperature

the percentage of fine material is much greater and the quality

of coke very much inferior. In this connection, however, it

should be noted that in none of the coking tests was it practicable

to secure temperatures as high as are frequently used in oven

practice with coals that are regarded as specially suited to the

production of metallurgical coke. If high temperatures had been

used another influence noted in connection with the St. Paul test

would probably have appeared, namely, that at the high temperatures there is great tendency for the coke to be brittle, fingery,

and small instead of tough and blocky.

By comparison of the results for the five tests, the very large

influence of temperature of coking upon the quantity and quality

of gas is evident. In this connection it should be noted that the

high-temperature results represent not only a more complete

eHminating of the volatile material from the coal but also a

decomposition of the heavier volatile material into gaseous constituents. Naturally as the vapors leaving the coal are subjected

to this greater decomposition at higher temperature, the average

heating value of the gas is diminished. This diminution of heating

value per cubic foot is, however, by no means enough to offset

the effect of the larger volume, as is shown by the fact that the

British thermal units in the gas per pound of coal carbonized at

840 C is almost double that at 6oo° C.

Conclusions

From the investigation of these subjects by the Bureau of

Standards the following facts have been demonstrated:

1. At least the majority of the coals from Franklin County, 111.,

and some from Pike County, Ind., located in the mid-continent

26035°—21 6
82 WAR WORK OF THE BUREAU OF STANDARDS

field, can be coked in by-product coke ovens, and a fairly satisfactory grade of metallurgical coke can be produced. Likewise

by-products of reasonable quantity and good quality can be

obtained from these coals.

2. The Roberts process at the time of these tests was still in

the development stage, but credit should be given to Mr. Roberts

for his work in connection with the coking of these coals. His

efforts along these lines undoubtedly did much toward arousing

interest among other coke-oven operators looking toward the use

of midcontinent coals.

3. The Bureau believes that at least some of the coal from the

midcontinent field should be used in the coke-oven plants in

the central section of the country. Even though the coke, on the

whole, proved not to be uniformly as satisfactory as that from

the so-called coking coals, the advantage due to the elimination

from the coke-oven plants in the eastern section will go far in

overcoming any lack of quality of the coke. There can be no

doubt that where domestic coke is wanted these coals can fulfill

all requirements. Such uses will materially aid in the proper

development of the fuel resources of the country.

The results of the investigations conducted at the Koppers

plant are embodied in Technologic Paper, No. 137.

CONCRETE AND CEMENT

Concrete Ships

This subject is treated separately, under the above title in an- other part of this report.

Load Tests of Concrete Floors of Arlington Building

On account of the vast amount of work connected with insurance

carried by our soldiers during the recent war with Germany, it

became necessary to increase the personnel of the Bureau of War

Risk Insurance. In order to do this more room was required, and

it was decided to use the new Arlington Building which was not

yet completed.

This building is constructed with System "M" steel framing

and with a well-known type of hollow-tile floors. In order to

determine its degree of safety and also the desirability of erecting other Government buildings on this system, the Treasury

Department requested the Bureau of Standards to conduct a

loading test upon various portions of the structure. No prior

loading test on this type of construction is known in which straingage measurements were taken.
CONCRETE AND CEMENT 83

The load tests were planned to determine the maximum live

load which could be applied to individual panels and to determine

the stress of the beams and columns of the System " M " construction.

The original plans of this building were changed so as to make

the structure, which was intended for a hotel, suitable for a Government office building. The design was modified so as to provide

for a live load of 100 instead of 74 pounds per square foot.

The specifications were changed to require a 2 -inch layer of

concrete above the tile to care for this additional live load, and

the amount of steel was also increased.

The investigation comprised strain-gage readings of deformations and corresponding deflection readings when loads were applied by piling bags of cement on the panels tested. Deformation

readings were taken with Berry strain gages on the embedded

structural steel and also on the concrete and tile. The reduction of the experimental data involved the making

of temperature corrections and the changing of observed strains to

corresponding stresses by the employment of the proper modulus

of elasticity, as determined from laboratory tests on sample

materials. Curves were plotted showing the relations between the

load on the panels and (1) the steel stress, (2) the concrete deformation, and (3) the panel deflection; also between the magnitude of

the stress or deformation and its position on the panel. The

elastic curves of sections of the panels, as determined from the

deflection readings, were also drawn.

Numerous fallacies in this system of construction were disclosed.

The mathematical development was found to be in error in several

places. For a square panel simply supported on four sides, the

formula used by the designers gives a value for the bending moment

along the diagonal, which is one-third that obtained by the use of

the formula in the report of the Joint Committee on Concrete and

Reinforced Concrete. The latter is logically developed from the

laws of statics, and the illogical steps in the development used for

this construction were pointed out by the Bureau.

The test results disclosed continuity of the beams in the Arlington building which had been designed to function as simple

beams. In another case a maximum concrete stress of 1909

pounds per square inch, at twice the designed live load, was found

due to the misplacement of continuity bars. In still other cases compressive stresses as high as 13 10 pounds per square inch, at

twice the designed live load, were found in the concrete. Con-
84 WAR WORK OF THE BUREAU OF STANDARDS

crete stresses were computed by the use of a value of 2 500 000

pounds per square inch for the modulus of elasticity. Tile

stresses as high as 1600 pounds per square inch at three times the

designed live load, were found by using 3 500 000 pounds per

square inch as the modulus of elasticity of the tile. Maximum

stresses of about 25 000 pounds per square inch were found in

the steel in the center of the panel and also in bars in the beams,

at twice the designed live loads.

While not indicating a dangerous condition in the building as now being used by the Bureau of War Risk Insurance, these test

results and the examination of the above-mentioned formulas

indicate that radical modifications should be made in that system

before further Government buildings are so designed. It is demonstrated in the Bureau's report that this method of deducing the

allowable working stress on a floor consisting of tile and concrete

leads to an erroneous factor of safety.

Laboratory Work on Cement and Concrete

The importance of concrete in building construction was recognized as a war measure, not only on account of its structural

advantages, but also on account of its release of less-readily re- placeable materials. To meet the greatly increased use of cement

and to prevent delay in testing, the Bureau's facilities were

enlarged in the Lehigh district by the addition of a chemical

laboratory to the physical laboratory and inspector's central office

at Northampton, Pa. The construction of a $40 000 000 concrete

pier and warehouse at Staten Island for overseas transportation

required nearly a million barrels of cement. This cement was

shipped in bulk by water from the Hudson district in New York.

Very satisfactory laboratory space was obtained at these points,

permanent laboratory fixtures installed, and equipment and personnel provided so that the laboratories were functioning in less

than a month after the site was selected. This relieved the con- gested condition in the Washington laboratory, made shipment of

samples unnecessary, and materially shortened the time required

to report results.

It also seemed desirable to increase the Bureau's testing and

investigating facilities on the Pacific coast. After considering the

needs of the Army, Navy, and the Emergency Fleet Corporation

at San Francisco, Los Angeles, and San Diego, a very convenient

laboratory for chemical and physical work was installed in one of

the more permanent exposition buildings at San Diego. This
CONCRETE AND CEMENT 85

laboratory was especially helpful in the construction of concrete

ships, and to both the Army and Navy in their construction of

aviation fields on North Island. ft The facilities of the laboratory at San Francisco were also increased by enlarging and readjustment of space. The large testing machines of the engineering division of the University of California, at Berkeley, were also made available for the Bureau's use,

which was extremely fortunate, since manufacturers of testing

machines could not make deliveries in less than a year and all the

machines in the country were being worked overtime.

In addition to the routine testing carried on in the Washington

laboratory, investigations were made on concrete surface hardeners. From the many commercial products examined, magnesium fluosilicate was found to be the most effective and was

recommended and adopted by the concrete-ship section of the

Emergency Fleet Corporation for use on the concrete ships.

The light-weight aggregates also required for the concrete ships

were examined to determine their composition and resistance to

salt water. While this phase of the Bureau's work will be described in detail in another part of this report, it is interesting to

state that satisfactory concrete which weighed only 105 pounds

per cubic foot was obtained in the laboratory from cellular, hard,

burnt clay, while normal concrete weighs from 135 to 140 pounds.

Another investigation which is still in progress was probably

caused by trade conditions resulting from the war. In the effort

to obtain potash in the cement industry and as this by-product was

at times more valuable than the cement, the established procedure

was modified to increase the potash yield. As a result, some

erratic cements were put on the market.

Some of this cement was passed by the Bureau for important

Government work, but after it had been delivered on the job was

found to be unsound. This was very disquieting, as it was not

believed that the Bureau's method of testing had been faulty, but

that the sample tested had not been representative or that satisfactory cement becomes unsatisfactory. To determine these

points, runs have been made at the plant where this cement was

made, reproducing as far as possible all the conditions under which

the cement was produced. No cement has been found to become

unsound and apparently the samples originally tested and passed

were not representative.
86 WAR WORK OF THE BUREAU OF STANDARDS

CONCRETE SHIPS

During the war a large portion of the investigational work in

reinforced concrete was carried out for the concrete-ship section of

the Emergency Fleet Corporation under the direction of a member

of the Bureau's scientific staff. Details of this investigational

work are given in the following paragraphs. A paper giving a summary of the most important of this work was presented at the

annual meeting of the American Concrete Institute, June, 191 9. The Development of a Light, Strong Concrete

In connection with the building of concrete ships a demand at

once arose for a concrete having the least possible weight and yet

with sufficient strength for this unusually severe work.

This meant that a concrete as fight in weight as possible, yet

stronger than any used in ordinary building construction, would be

needed. The cost was not an important factor, as every pound

per cubic foot deducted from the weight of the concrete meant an

important saving in the dead-weight of the vessel and a gain in

the cargo-carrying capacity.

When it became known that the Government wanted such a

material, suggestions and samples were sent to the U. S. Shipping

Board from all parts of the country.

It was the function of the Bureau of Standards to test these

samples and aid in the development of the ideas and suggestions

that were submitted.

Two ways of lightening the concrete were suggested: (1) The

use of a light-weight aggregate; (2) the use of a light-weight

cement. The use of a light-weight cement, which was usually

a mixture or blend of Portland cement and a light-weight adulterant, such as diatomaceous earth, gave a concrete only a few

pounds lighter than ordinary concrete and caused a marked reduction in strength and an increase in absorption.

It was by the use of a light-weight aggregate that a satisfactory

light and a strong concrete was finally obtained. This was a

burnt clay or shale, puffed during burning to about double size,

and which is light in weight because it contains many small, closed

cavities throughout its mass. It is produced commercially both

in a stationary brick kiln and in a rotary cement kiln and crushed

to proper size after burning.

Many other light-weight aggregates, particularly volcanic rocks,

were submitted and were tested in concrete. In general they were

tested in two classes of concrete: Class A, 1 part cement, two-
CONCRETE SHIPS 87

thirds part of fine aggregate passing a sieve (No. 8) having an

opening of 0.093 inches, imparts of coarse aggregate smaller than

one-fourth inch, but retained on the No. 8 sieve, or a 1 : 1 : 1 mix

of the same materials; Class B, 1 part cement, 1 part of fine aggregate smaller than one-fourth inch on a No. 8 sieve, and 2 parts of coarse aggregate, one-half to one-fourth inch in size.

It was planned to use Class A concrete in the major portion of

the ships, and it was assumed that Class A concrete, which is

really 1 : 2 mortar with twice as many coarse particles as fine,

would give a compressive strength of 4000 pounds per square inch

in 28 days under working conditions. Because of the small amount

of space between reinforcing bars and forms, the maximum size of

aggregate was one-fourth inch.

Class B concrete was designed for use in the larger sectioned

areas of the ships ; it is a 1 : 3 mix with one-half inch as the maximum size of aggregate.

As a result of these investigations it may be stated that the old

idea that an aggregate must be heavy and dense to produce strong

concrete or that a heavy and dense aggregate will produce a better concrete than a light one is not true.

For mixtures rich in cement, such as were included in these tests,

a concrete stronger than the aggregate it contains can be made.

As an example, the average compressive strength of salmon underburned bricks is 1765 pounds per square inch (with a range of

1380 pounds to 2240 pounds), while the 28-day strength of concrete made using these bricks crushed as aggregate was as high as 3800 pounds per square inch in a rich mix.

Based upon these tests, the Shipping Board manufactured and

used on a commercial scale a burnt clay or shale aggregate in

the concrete ships which it constructed.

A description of this material, its method of manufacture, and

tests of concrete made from it and used in the ships may be found

in the Engineering News-Record for April 24, 1919 (28, No. 17,

p. 802).

Corrosion Tests of Reinforcing Steel

The corrosion tests were made to obtain information relative to

the importance of corrosion of the reinforcement in concrete ships

and to methods of preventing or mitigating corrosion of the reinforcement. About 20 proprietary coatings, including paints and

asphalts, were used as protective coatings, and salt-spray tests

were made to determine their effectiveness. Many of the coatings

were found to be effective in preventing corrosion, but to have
88 WAR WORK OF THE BUREAU OE STANDARDS

serious effect in reducing the bond strength of steel when embedded

in concrete. (See section on "Protective Coatings.")

Bond Tests

Pull-out tests of specimens, consisting of steel bars coated with

the protective coatings previously referred to, were made on about

400 specimens. These tests showed that practically all coatings,

even including metallic coatings such as zinc, had a deleterious

effect on the bond strength (the resistance to slipping through the

concrete) of bars embedded in concrete.

Repeated Reversal of Load on Reinforced-Concrete Beams

An investigation of double-reinforced concrete beams loaded

in alternate directions was carried out, using special machines

designed for this work by the Bureau. One of these is illustrated

in Fig. 9. Four beams were tested to failure, and in all cases

failure was by tension in the steel. One beam, which was subjected to 2 000 000 applications of the design load, showed no

indication of the approach of failure at the time the test was

discontinued. In one beam there was a large amount of slip of a

reinforcing bar before failure occurred. Within the limit of these

tests there is no indication that the strength of a doubly reinforcedconcrete beam (reinforced for bending in opposite directions) is

determined by the properties of concrete, if the ordinary requirements of design are met, unless it be that of the bond stress.

The abrasion of the concrete at the edges of cracks in reinforcedconcrete ships was considered as a possible danger, and the tests

were initiated to obtain information on this subject. There is no

indication that this is a real danger. Not all the tests originally

planned have been completed. The danger of slipping of bars

either where they are lapped at the center of the span or where at

the end of the beam they do not have anchorage by hooking of

the bars is one which should be investigated. This investigation

is fully described in Technologic Paper No. 182.

Impact Tests on Concrete Slabs and Built-up Steel Plates

In an effort to secure a basis for comparison of resistance of

concrete slabs and steel slabs to impact, tests were made in which

the impact was furnished by dropping a 1 -ton ball upon the center

of the slab. Eight reinforced-concrete slabs and one steel slab,

designed to represent conditions on reinforced-concrete ships and

steel ships, respectively, were tested. Six of the reinforcedconcrete slabs were 6 feet 6 inches by 7 feet in size, and two of

them were 10 by 10 feet. The steel slab was 12 by 10 feet 2 inches

in size.
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 9.

Special machines for producing alternating stresses on concrete beams

of the type used in concrete ship construction

These machines cause stresses similar to those which would be produced by waves acting on the completed ship. The number of repetitions of stress necessary to cause failure of the beams is automatically recorded
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. io. —The nine sizes of dry cells recommended as standard by the Bureau as the result of its investigations

Before this work was started the military services were using over 40 different sizes of cells, result- ing in a great deal of useless expense and trouble
CONCRETE SHIPS 89

Leakage of Water Through Cracks in Reinforced-Concrete Shell

Early in the investigation of shearing strength of reinforcedconcrete beams it was found that cracks were likely to form when

shearing stresses were considerably lower than those which it

seemed necessary to use in the design of concrete ships; yet it

was not known whether these cracks were such as would permit

leakage of water through them or not. Tests were made in which

hollow beams were loaded in such a way as to cause diagonal

tension cracks in the side walls at the same time that the beam was

filled with water, which was maintained under pressure varying

in head from 1 5 to 30 feet. These tests indicated that the smallest

crack which could be detected—say 0.001 inch or less in width

would permit the passage of enough water to cause a moist surface

on the outside around the crack. As the crack width increased

the leakage increased rapidly, provided that time was not given

for the closing up of cracks by the deposit of sediment of any kind.

When the crack was 0.01 inch wide, water spurted clear of the

outer surface of the beam. When the beam was allowed to stand

overnight with the pressure head and the load maintained, the

leakage was decreased markedly. This was probably due to the

deposit of a substance which helped to fill up the cracks. Further

indication of this was shown by the appearance of efflorescence on

the surface of the beam in the neighborhood of the cracks. If

the cracks had been very small at the time of their formation and

had developed very slowly, it is possible that the silting would

have kept up with the opening of the cracks and that leakage

would not have occurred. Apparantly this is what happened

with some of the concrete ships and barges which are afloat. An

inspection made on a concrete ship which had been in the water

about a year showed the presence of cracks which were large enough

to cause leakage under the conditions to which these test beams

were subjected. However, there was no leakage, although the

cracks were below the water line, and apparently there had been

none. There was efflorescence apparent at cracks on the inside

of the hull, indicating that the process of silting had been taking

place.

Shear and Compression in Reinforced-Concrete Beams

These tests were begun as a part of the study of reinforced concrete in adapting it to use for the construction of concrete ships.

One of the first serious difficulties in the designing of concrete

ships was that of getting sufficient strength to prevent cracks

forming diagonally in the vertical sides of a ship of practicable
90 WAR WORK OF THE BUREAU OF STANDARDS

weight. Using the methods ordinarily employed in reinforcedconcrete design, a shell thickness of at least 15 inches would have

been required instead of the 4 inches used in the 3 500-ton cargo

ship. Tests of large reinforced-concrete beams were started to

make certain that no mistake was being made in using a 4-inch

shell. These first tests were made on (1) beams of 4 feet 4 inches

deep and 18 feet 6 inches long; (2) one beam 10 feet deep and 22

feet long; and (3) specimen ship frames of full-sized cross section

and 20-foot span. The frames were cut off at a point corresponding to the point of inflection, or 4 feet 6 inches above the top of

the keel. The tests were made in the 10 000 000-pound testing

machine at the Pittsburgh laboratory of the Bureau of Standards.

For the beams the load was applied at the center of the span

upon the upper flange. The beams were supported at each end

of a steel-plate girder. The beam, 10 feet deep, was first loaded

40 times with 640 000 pounds, which was four times as much as the maximum which the standards of the joint committee on concrete and reinforced concrete would have allowed as its working

load. The widest crack at the first application of this load was

0.013 inch, and with 40 repetitions of the load there was no appreciable increase in the widths of the cracks. The beam was then

inverted and load was applied in the opposite direction, causing

failure at 1 363 000 pounds, or nine times as much as the joint

committee standards for reinforced-concrete design would have

allowed as a working load.

The ship frames were tested by applying first only a vertical load

and adding later a horizontal load at the sides corresponding to

the horizontal water pressure on the sides of the ship. It was

found that the strength here was about eight times as great as the

joint committee recommendations allowed for the working load,

also that the shear due to the horizontal forces reduced the stresses

set up by the shear due to the vertical forces; in other words, that

the horizontal water pressure would reduce the stresses caused by

the vertical shearing forces on the frame.

These tests made it possible to design with confidence for shear

in reinforced-concrete ships, using working stresses much higher

than those which are recognized by the final report of the joint

committee. In effect, the joint committee report limits the

amount of web reinforcement to about three-fourths of 1 per

cent, while these tests show that for deep beams a much larger

amount of reinforcement would be effective. Apparently, the main

reason for the higher shearing strengths found in these tests is
CONCRETE SHIPS 91

the larger percentage of web reinforcement which may be used

effectively in deep beams where the web bars have much better

chance for anchorage than in shallow beams.

After these preliminary tests were completed, a more nearly

exhaustive investigation was initiated at Lehigh University,

Bethlehem, Pa., for the concrete-ship section of the Emergency

Fleet Corporation.

In the economical use of building materials, the importance of

using higher shearing stresses in reinforced-concrete beams has

been recognized by many. The results of the tests made for the

concrete-ship section were so significant in this direction that the

Bureau continued the investigation after the program of tests as related to concrete ships was completed. In all, 172 beams have

been tested, and the results have been quite fully worked up,

giving data for a technologic paper which should be of much importance to the reinforced-concrete industry.

The conclusion from these tests is that not only working stresses

in shear may properly be increased, but that they may be increased to such an extent that other features of the design become

the controlling features. In order to make use of the high shearing stresses permitted, compressive stresses would be increased

beyond all present reasonable values. This led to the making of

tests to determine if an increase in compressive stresses was permissible. These tests were only four in number and not sufficient

to afford a basis for a general conclusion, but, so far as they go,

they indicate that higher working stresses in compression than

are now generally recognized could be used with safety. It is

important that further tests of this kind be made.

Reinforcement of Concrete Slabs

There has been much uncertainty as to the relative economies

of reinforcing slabs with (1) bars in the direction of the span, (2)

bars making some angle with the span, and (3) expanded metal.

Twenty-six slabs, 4 inches .thick, were tested, in each of which one

of the three methods of reinforcing described above was used.

The results as they stand indicate that the largest amount of steel

is required in the case in which the bars are placed diagonally

with the span, and that as regards quantity of steel required there

is a slight advantage for expanded metal over the use of bars in

the direction of the span. However, certain conditions of the

tests make it important that more tests be made before this

question is considered to be settled.
92 WAR WORK OF THE BUREAU OF STANDARDS

Length of Lap Required for Reinforcing Bars

Tests were made to determine how great a length of lap is neces- sary for cases in which the reinforcing bars used are shorter than

the span and are applied by lapping them in the center of the span.

Four beams were made in this series, and the indications from

the test results is that with this size of bar (one-half inch round)

a lap of about 50 diameters is required. The concrete used in

these beams had a strength of about 5000 pounds per square

inch, and it is to be expected that with a leaner concrete a larger

lap would be necessary. Some information from tests in which

expanded-metal reinforcement was lapped in the same way is

available. As to quantity of steel required for the lap, this indicates a slight advantage in favor of expanded metal.

Value of Brackets and Haunches in Flanges

For purposes of architectural effect or for increasing the strength,

connections between columns and beams are frequently provided

with brackets. This development sometimes takes the form of

an arch construction. However, in the design little attempt is

usually made to determine how much strength is added by the

presence of the haunch, and usually advantage is taken of only a

portion of the value of the haunch or bracket. In the design of

reinforced-concrete ships the strength value of such brackets is of

much importance. To obtain information on this subject, a series

of tests was made, including as test specimens eight reinforcedconcrete frames having a span of 14 feet, a height of 7 feet, and

brackets ranging from no bracket to one so large as to give the

appearance of an arch. These tests indicated that the brackets

had much more value in strengthening the frames than that for

which allowance is usually made in the design. The results are

of much importance, since the weight of the frames in a concrete

ship can be reduced materially by taking full account of the

strength added by the brackets in the frames. If the results are adapted to general design in reinforced concrete, they will have

an important bearing on the reinforced-concrete industries where

such structures are involved.

Shrinkage of Concrete in Setting as Related to Ship Construction

It is recognized that shrinkage of concrete occurs during setting.

In many constructions this is manifested through cracks which

appear in the concrete surface, but the laws which govern this

shrinkage have not been very thoroughly determined. This subject becomes important in connection with the concrete ship, since,
ELECTRIC BATTERIES 93

as pointed out in a previous paragraph, the smallest cracks will

permit a slight leakage unless silting prevents it. In one of the

barges constructed by the Emergency Fleet Corporation for the

Inland Waterways Commission a series of careful measurements

was made in the effort to determine why more frequent and

larger cracks occurred in this barge than occurred in the others.

While the effort was not entirely successful, the measurements did

show that there was an elongation and shortening of the barge

which corresponded closely to even the slightest rise and fall of

temperature. With any rise in temperature the cracks began to

close, while with a decrease in temperature the cracks opened.

The largest crack present was less than o.oi inch, and although

the barge was not loaded the results of examinations of concrete

ships which have been in service indicate that a deposit of silt or

efflorescence will prevent leakage through cracks of this size.

ELECTRIC BATTERIES

Development of Chemical Work on Batteries

In connection with the testing of electric batteries for the various branches of the War Department, the chemical work has been

carried out for the purpose of checking up the data obtained from

the electrical tests and for the purpose of obtaining information

which might suggest improvements in certain types of batteries.

At the request of the Signal Corps chemical analyses of batteries

and materials entering into their construction were made.

This work included tests upon both dry-cell and storage-battery

materials.

The chemical work on dry cells has consisted in (i) the chemical

examination of the component parts of finished dry cells; (2) the

examination of raw materials which enter into the construction

of dry cells; and (3) the development and improvement of special

types of dry cells.

The chemical examination of the finished dry cell had for its

object primarily to determine whether it contained the quantity

and quality of materials necessary to give the service expected.

In competitive tests of batteries of different brands, the results

of chemical analyses of these batteries placed them in the same

order of quality as did the results of the electrical tests. The

chemical tests have the advantage of greater speed than the electrical tests, which require the battery to be discharged for a period

of time. It must be understood that the chemical tests, at the
94 WAR WORK OP THE BUREAU OF STANDARDS

present stage, indicate only the capacity or output of the dry cell

and not its shelf-life qualities. The shelf life of a dry cell depends

upon factors which at the present time it is impossible to determine by chemical analysis. Since, however, these factors are dependent upon the physical and chemical properties of materials

composing the cell, it seems entirely possible to devise tests which

will indicate the shelf characteristics.

When the chemical work upon dry cells was begun, there were

no methods of analysis for the examination of dry cells given in

the treatises on batteries, and the laboratories of some of the manufacturers hesitated to make known to the Bureau even such chemical information as they possessed on the subject. It was neces- sary therefore to start at the beginning and devise a routine method

of analysis to furnish the information desired. This work consisted not so much in the development of new methods as in the

application of the usual analytical methods to this particular

problem. As a result a procedure has been developed for the

chemical examination of dry cells which seems superior to the

methods used by the manufacturers, which now have been made

known to the Bureau.

It was found that a determination of only two constituents

ammonium chloride and manganese dioxide—was sufficient to

indicate the capacity of the dry cell. The other principal constituents—namely, carbon, zinc chloride, and water—were determined ; but it has not yet been possible to draw valid conclusions

from the results, except that the content of zinc chloride and water,

as well as the starch paste, are some of the factors which determine

shelf life. Certain impurities, deleterious to dry cells in the manganese ore, such as copper, antimony, cobalt, nickel, etc., were

determined, and in some cases failures of the cells were attributed

to these.

In order to obtain data that may suggest methods of analysis

for determining whether a dry cell has good shelf life, an investigation has been started upon a large number of cells of a certain

brand. This study consists simply in analyzing at intervals of

several months cells from this lot, and, at the same time, determining the electrical output of cells from the same lot. By comparing the results of chemical analysis with the results of the electrical tests, it is hoped that the causes of deterioration may be

found. When this information is obtained, it should be possible

to determine by chemical examination whether a dry cell will have

a good shelf life.
ELECTRIC BATTERIES 95

The examination of the raw materials entering into the construction of dry cells is a much simpler problem than the examination

of the finished dry cell, since the difficulty of analysis increases

with the number of constituents present.

The manganese ore situation was critical when the supply of

Caucasian ore was cut off by war conditions. This made it neces- sary for the manufacturers to conserve their supplies of Caucasian

ore and experiment upon the use of ore from other sources ; namely,

Japan, Cuba, Brazil, and domestic sources. The lack of information about the proper use and suitability of these ores for dry-cell

manufacture produced an uncertainty in the industry which caused

hesitancy on the part of the manufacturers in guaranteeing their

product to be equal to that of prewar times. For this reason,

complete analyses of manganese ores were requested by the Signal

Corps.

In connection with the foreign assembly of batteries by the

Signal Corps, some of the raw materials were examined to determine their suitability and uniformity of quality. This work

involved no difficulty except in the examination of manganese

ores. Incidentally, some of these ores were being purchased by the

Signal Corps for French manufacturers, whose methods of manufacture are somewhat different from American practice. The

difficulty in the examination of the manganese ores is the determination of impurities, very small amounts of which are so deleterious that in some cases only a few hundredths of i per cent

of certain metals will cause destruction of the dry cell within a

few days.

The analyses conducted by the Bureau included both samples

of natural ores of unknown sources and artificially prepared manganese dioxide. The methods for determining the small amounts

of impurities in the presence of large amounts of manganese had

to be worked up, as no published methods for such determinations

were to be found. A method of procedure was devised for determining arsenic, antimony, copper, cobalt, nickel, and iron.

In addition to the difficulty of accurately determining these small

percentages, it is still more difficult to interpret the results because

of the lack of definite information about the limits of impurities

permissible. From a chemical analysis alone it is not possible, for

instance, to state whether 0.05 per cent of copper will be deleterious, because the deleterious action of the copper depends upon the

particular physical or chemical state in which it exists. Neither

does the Mn02 content as determined by chemical analysis give a
96 WAR WORK OF THE BUREAU OF STANDARDS

reliable indication of the suitability of the ore. In factory practice

the question of suitability of the ore is determined by actually

making a cell from the material and then observing its electrical

characteristics. This kind of a test requires considerable time,

since it is necessary to wait several days or even months for results.

It was on account of this inconvenient expenditure of time for

making such a test that the largest manufacturer of dry cells re- quested the Bureau to undertake the study of manganese ores,

with the object of devising some quick method for determining the

suitability of ores. This company furnished the Bureau with

samples of ores, some of which were known to be satisfactory and

some unsatisfactory for dry cells. This study was undertaken by

the Bureau but has not been completed.

In connection with the tests of the Ba-2 battery for radio sets

for the Signal Corps, it was found that the specifications did not

require a sufficiently long shelf life for foreign service. As a result,

many thousands of these batteries were scrapped before they had

opportunity to give any service. In an effort to devise a battery

which would have a long shelf life, several types of reserve batteries

were tried. These batteries were made up from the same mixture

of materials as are used in ordinary dry cells, except that no water

was added to the mixture. In the dry state the cell will keep indefinitely, provision being made in the construction of the cell for

the addition of water, which is all that is necessary to make the

cell active whenever it is desired to use it. Failures in this type of battery were usually due to leakage of

the electrolyte between the cells of the battery, which was due

principally to the difficulty in providing satisfactory insulation.

It was suggested that a construction similar to the voltaic pile

might be designed to give a voltage and capacity sufficient for

the service required. After numerous trials, a simple type of

construction was designed which met the requirements. The

Signal Corps considered the design of sufficient importance to

request that the matter of obtaining a patent be undertaken.

At the suggestion of the Signal Corps a visit was made to the

factories of the leading manufacturers to obtain data upon the

shelf life of cells (H by i %) used in the Ba-2 batteries, and samples

of cells of various ages were obtained for test. Also, results of

shelf tests on all cells made during one year by a certain

manufacturer were summarized, and showed this make of battery

to be superior in shelf characteristics to other brands. On the
ELECTRIC BATTERIES 97

basis of the results obtained on this trip, the Bureau recommended

the use of this make of cell in Ba-2 batteries, provided that they

were shipped unassembled to France to be assembled into batteries

when desired.

The chemical work on storage batteries for the WarDepartment

was devoted principally to the study of methods of tests and comparison of specifications for sulphuric acid used in storage batteries.

The need for this information was emphasized when the Signal

Corps requested such data for making specifications to be used by

a large number of manufacturers and users of batteries, and it

was found that the specified amounts of impurities varied as much

as iooo per cent.

Some of the methods in common use for testing battery acid

were found to be unreliable, this being particularly true in the

methods for determining the amounts of nitrates and nitrites.

Much labor has been spent upon the comparison of methods of

testing preliminary to the main problem of determining the limiting amounts of impurities permissible, and eventually of drawing

up reasonable specifications for battery acid.

In connection with the comparative testing of truck storage

batteries for the construction division of the Army, the electrolytes of the batteries were analyzed. The results of analyses

showed that the batteries giving the best electrical performance

contained the purest electrolyte, while the batteries giving the

poorest electrical performance contained the most impure acid.

These chemical tests were, therefore, confirmatory of the quality

of the different brands of batteries tested.

In addition to the work upon battery acid some analyses were

made upon special storage-battery plates and fillers for dry storage batteries.

At the request of the Signal Corps analyses were made upon a

large number of alkaline electrolytes taken from storage batteries supplied by the Edison Co. to determine whether they con- tained the specified amounts of potassium and lithium hydroxides.

Standardization and Preparation of Specifications for Batteries

Before the United States entered the war, questions relating to

dry cells were brought to the attention of this Bureau by several

of the military departments. The first problem presented was to

find a suitable cell of American manufacture which could be used

to replace cells purchased by the British Navy from manufacturers

in Scandinavian countries. This and other problems emphasized

2G035 —21 7
98 WAR WORK OF THE BUREAU OE STANDARDS

the need for the Bureau undertaking a systematic study of battery

problems. Information has been secured on the performance

and specifications of dry cells from publications on the subject, by

consulation with the manufacturers wherever possible and by

experiments in the laboratory. The collection of information

with regard to storage batteries has been undertaken in a similar

way. The information which the Bureau has gathered has been

made available to military departments (1) in the form of special

reports when these have been asked for; (2) in reports of tests on

batteries which have been submitted; (3) in a circular of information about dry cells; (4) by cooperation with the Standardization

Committee of the War Department.

The Bureau has prepared and published a circular of information

on dry cells (Circular No. 79) which contains a brief historical re- view of the development of the dry cell and the theory of the

reactions which take place in it. The various kinds of construction are described in detail, since this has an important bearing on

the utilization of the cells. The two most common types are the

so-called "paper-lined " cell and the " bag-type " cell. The paperlined cell is the one most commonly made in this country, and it

is well adapted to some purposes, besides being easily and cheaply

manufactured. It does not possess, however, as desirable characteristics as the bag-type cell for many of the uses which resulted

from the war. This is because the cells deteriorate when standing

on open circuit. If long periods of time must elapse between the

manufacture of the cell and its use in a distant field of operation,

the deterioration which takes place greatly reduces the service

which the cell can render. The bag-type cells of the larger sizes are less subject to this deterioration and are more commonly used

in Europe than in this country. However, the small flashlight

cells which are made in the United States in very large numbers

are nearly all of the bag-type construction, this being necessary

since the deterioration of these small cells is more rapid than in

the larger sizes.

The circular describes sizes and kinds of cells which are available on the American market and the uses to which they are best

adapted. The electrical characteristics are discussed with a view

to showing how the best service may be obtained from the cell, an

important matter, since it often happens that dry cells are used in

such a way that only a small part of the service which they might

perform is obtained.
ELECTRIC BATTERIES 99

The tests which are commonly made on dry cells have grown up

with the industry; many are not considered to be entirely satisfactory, and some are not easily carried out. Nevertheless, these

tests are discussed in detail, since in the absence of simpler and

more reliable tests, they are the only ones that can give relative

information as to the performance of the various brands now on

the market.

Specifications covering all of the various sizes and kinds of dry

cells in common use have been prepared by the Bureau and incorporated in the circular as an appendix. These specifications

were prepared as a possible guide for the various Government

departments in the purchase of dry cells, and they have been

formally adopted by the War Department.

Before the circular on dry cells was published, the War Department undertook the standardization of electrical supplies in general, and a subcommittee on batteries, consisting of officers representing a number of different bureaus of the War Department and

two representatives of the Bureau of Standards, was appointed.

When this committee began its work, the question of specifications

for dry cells was immediately taken up. The specifications which

the Bureau had already prepared served as a basis for the discussion which took place in the committee, with the War Industries

Board, and with the War Service Committee of the Manufacturers.

Only minor changes in these specifications were made, and an

agreement was reached with all the parties concerned. The Standardization Committee then adopted these specifications.

Two important results of these specifications were, first, the

limiting of the number of sizes which are considered as standard,

and, second, the specification of the minimum service required of

the different sizes. In limiting the number of sizes, the Bureau had

the cordial cooperation of the manufacturers who had been more or

less compelled in the past, for trade reasons, to manufacture a

large variety of shapes and sizes for which there was comparatively little use. The number of the large-size cells was cut from

10 to 3, and of the small or flashlight cells from an indefinite number, about 40, to 6. (See Fig. 10.) The Bureau also had the

cordial cooperation of the War Industries Board in thus limiting

the number of standard sizes, since part of their conservation work

was directed toward the elimination of useless sizes. It is probable

that the Bureau's recommendation for limiting the number of sizes

would have been made mandatory by the War Industries Board
IOO "WAR WORK OF THE BUREAU OF STANDARDS

but for the signing of the armistice. It is anticipated, however,

that the Bureau's recognition of these as standard sizes will lead

the manufacturers to eliminate gradually those which are less

desirable.

This subcommittee on batteries also considered the question of

storage batteries. The Bureau cooperated by gathering information from various sources about the characteristics and performance of different types of storage batteries. The Bureau also

carried out extensive tests on these batteries as described elsewhere.

Specifications covering storage batteries were prepared jointly by

representatives of the construction division of the War Department and by the Bureau of Standards in consultation with the

engineering committee of the Manufacturers' Association. These

specifications were formally adopted by the standardization

committee.

Reports on Special Subjects

The Bureau has been called on in a number of instances for

information dealing with battery problems by different bureaus

of the Government departments. Only three of the more important of these will be mentioned here.

A controversy arose between the Food Administration and a

large manufacturer of batteries concerning the use of wheat flour

in the manufacture of dry cells. This flour is used for making

the electrolytic paste which separates the zinc container from the

depolarizing mixture in the cloth bag. A few manufacturers in

this country have been using cornstarch instead of the wheat flour,

but this process of manufacture of the cell is so entirely different

from the more common or wheat flour process that a manufacturer using one process could not change to the other without

alteration of the methods and machines employed. For this

reason the proposal of the Food Administration to prohibit the

use of wheat flour in the manufacture of dry cells was a serious

one to the industry, and particularly so in the case of the abovementioned company, whose product was largely for the War

Department. At the suggestion of this company the Food Administration referred the matter to the Bureau of Standards, and

conferences were held with both the manufacturer and the Food

Administration. A satisfactory basis of agreement was found,

since it is possible to manufacture dry cells with wheat flour which

is unfit for human consumption. Accordingly, the Bureau recommended to the Food Administration that the battery maker be
ELECTRIC BATTERIES IOI

permitted to use such flour, and apparently this recommendation

was entirely satisfactory to both parties.

A request was received from the Bureau of Ordnance of the

Navy Department for information on silver chloride cells with a

view to their use in submarine mines. In addition to reporting

on the structure and electrical characteristics of these cells, the

Bureau made tests on sample batteries which were submitted by

the Navy Department.

In connection with the testing of storage batteries for industrial trucks and tractors, it was requested that additional information be furnished on the relative characteristics of acid and

alkaline storage batteries as applied to tractor work. The Bureau

gathered information on this subject from various reliable sources,

and the report was made as a lecture before the truck and tractor

committee of the War Department and other officers whom they

invited to be present.

Military Tests of Batteries

About 50 tests on batteries of various kinds have been made

for the military departments, many of which have involved an

extended series of measurements. The purpose of some of these

tests has been to determine the fitness of various kinds and makes

of batteries for particular purposes, while in other cases the object

was to determine the quality of material submitted by manufacturers. In still other cases the work has taken the form of

experimental development of new types and kinds of batteries

to meet unusual service conditions. A brief description of some

of the more interesting tests is given below.

A test of over six hundred 15-cell batteries of the type Ba-2 has

been made for the Signal Corps. These batteries were intended

for use in the amplifiers of radio sets such as are used in airplane

service, but had not given satisfactory service, due to deterioration

when standing idle, as in storage or in transit. This had been so

large that many of the batteries had been found unfit for use when

wanted. The Bureau was asked to make a study and test of these

batteries to find what could be expected of them and what improvements could be made. Nearly 700 of these batteries, representing

the product of several manufacturers, have been sent to the

Bureau for test. In addition to testing these batteries at the

Bureau, measurements were also made on much greater numbers

in the military storehouses during June and October of 1918,

the results of the latter measurements showing that very large
102 WAR WORK OF* THE BUREAU OE STANDARDS

percentages of the batteries in storage were unfit for service. The

deterioration of dry cells is more rapid in the smaller than in the

larger sizes, and for this reason it was suggested to the Bureau of

Steam Engineering of the Navy Department that similar batteries

for Navy use should be made from larger cells. This recommendation was adopted and shortly afterward the Navy bought batteries

containing cells of the recommended size, which they designated

as CBG-3535. The Signal Corps, however, preferred not to use

batteries of a larger size, since they would not fit in the compartments of their apparatus. The Bureau suggested that batteries

might be made in such form that water could be added to the

individual cells at the time they were required for use, thus making

them similar to the so-called "reserve" or "desiccated" cells

which are common in the larger sizes. It was also suggested that

these batteries might be assembled in France, since in this way

those for use abroad could be obtained without the delay which

otherwise occurred between the time of manufacture and their

utilization. This work was undertaken by the Signal Corps in

the latter part of the year.

Tests which the Bureau made showed that, of the batteries

manufactured in this country, some were distinctly superior to

others, and it was therefore suggested that a large number of individual cells of the best makes, complete but not assembled into

batteries, should be shipped abroad so that each cell might be

tested individually at the time they were to be assembled. In this

way those which were defective might be discarded. Most of the

batteries manufactured in this country were assembled without

any such tests being made on the individual cells, and the Bureau

considers that this is partly the reason for the large number of

failures which were experienced. As the failure of any one cell

is sufficient to cause the failure of the entire battery, it is apparent

that the chances of the battery failing are 15 times as great as that of the failure of any one cell. In a number of cases the Bureau

was able to show conclusively that the failure of the battery was

of this type.

One result of the Bureau's experiments was to show that a very

simple empirical test of these batteries could be made in the

military storehouses or in the field, which would give reliable

information as to whether they were fit for service. This test

consisted in measuring the voltage of the batteries with an ordinary

voltmeter and discarding any batteries showing less than 20 volts.

This test depends on the fact that the ordinary voltmeter of 100
ELECTRIC BATTERIES 103

ohms per volt of the scale draws enough current from the battery

to indicate whether the latter is in fit condition, in addition to

indicating what may be termed its semiopen circuit voltage.

The batteries tested at the Bureau were discharged under many

different conditions. In one of these experiments it was found

that when they were discharged at temperatures below o° C

or 32 F the service rendered was very small even though the

batteries were in good condition. This is a matter of importance,

since the service in airplanes, for which they were intended, may

expose them to very low temperatures.

In addition to the electrical tests a careful chemical examination

of the contents of some of the batteries was made. The results

indicate clearly that those giving the most satisfactory service

were the most uniform in their chemical composition and contained sufficient manganese dioxide and other ingredients.

Batteries similar to the above, but designated by the Signal

Corps as type Ba-5, have also been tested in large numbers.

These batteries are of the so-called " reserve " type; that is to say,

the battery is made up dry and is made active by adding water

at the time it is required for service. Numerous mechanical

difficulties developed in connection with these batteries owing to

the difficulty of providing sufficiently large vents for adding water.

Since these batteries were assembled dry, there was no means of

testing them until such time as the water was added when they

were required for use. For this reason, large numbers failed

almost immediately after being filled with water because of the

leakage of electrolyte from the cells into the battery, causing short

circuits. It was found that batteries which did not show this

initial defect gave reasonably good service. The results of the

Bureau's tests on these batteries indicated that the percentage of

failures due to leakage was rather too high to consider them

satisfactory.

Another type of battery intended for the same purpose, and

designated by the Signal Corps as the type Bb-12, is made up of

1 2 small storage cells. They were made as an experiment by two

different manufacturers and were of the so-called " dry " or nonspillable type, in one case the battery electrolyte being thickened

with gelatin. The service which these batteries gave was unsatisfactory, and it also developed that when they were placed in

a closed compartment containing other apparatus the metal parts

of the latter became corroded. The Bureau's experiments

indicated that these batteries should not be used.
104 WAR WORK OF THE BUREAU OF STANDARDS

The Bureau undertook, at the request of the Signal Corps, a study

of the galvanic pile to ascertain its suitability for furnishing the

small currents required of the batteries mentioned above. In the

course of this investigation a form of disk battery was developed

which is rugged and can be made active by the addition of water

as in the case of the reserve cells. They are now being made at

the Bureau and assembled for further tests. These batteries have

certain advantages over those of the Ba-2 and Ba-5 type, although

the actual service which they will render is slightly less than the

others when the latter are in the best condition. The units of

this disk battery are usually small dry cells, but the Bureau has

also made experiments on a similar construction, in which the

elements were to be those of a storage battery. In the case of the

disks assembled as a battery the cells are assembled in a glass

tube, so that the battery can be watched during the time it is in

use. Such an arrangement reduces the maximum difference of

potential between adjacent cells to 1 % volts, a distinct advantage

in diminishing leakage trouble. Experiments on this form of

battery are being continued.

An unusual test of dry cells intended for use with a trench

signal projector was made at the request of the Bureau of Aircraft

Production. Its object was to ascertain how long the batteries

would operate the signal lamp satisfactorily. In imitation of the

service anticipated, the lamp was caused to flash twice in each

second with a duration of one-fourth second for each flash, and

measurements were made on the batteries until the light given by

the lamp was no longer serviceable. On this test various types

and sizes of dry cells were used, some of them being ordinary cells,

while others were of the bag-type construction.

Competitive tests of various brands of flash-light batteries

were made for the Depot Quartermaster, the Field Medical Supply

Depot, the General Engineer Depot, and the Ordnance Department, to show the relative merits of the different brands submitted,

as a basis for large purchases. The experiments showed conclusively that in the case of a few brands, on which an unusually low

price had been quoted, the cells were of very inferior quality.

After these tests were completed and contracts awarded, the

General Engineer Depot asked the Bureau to test samples of the

batteries furnished by the manufacturer, to determine whether

they conformed with the samples which he had submitted. A

large number of batteries of various kinds were submitted for
ELECTRIC BATTERIES

test by the Signal Corps, in addition to those which have been

previously mentioned.

At the request of the Bureau of Ordnance a long-duration test

was conducted on the shelf life of special batteries designed for use

in submarine mines. Part of this test consisted in keeping the

batteries under temperature conditions comparable to those of sea water with the idea that this Bureau should notify the Navy

Department when they might expect failures of the batteries in

planted mines. They also requested information and tests on silver

chloride batteries, and a number of experiments were made.

This cell differs materially from the ordinary dry cell, as the depolarizing agent is chloride of silver instead of manganese dioxide,

and the cells are less subject to deterioration on open circuit than

the ordinary dry cells. An examination was made for the Navy

Department of six small dry cells which had been taken from a

German submarine mine.

The extensive use which has been made of the dry battery in

the present war has been emphasized by the number of different

military organizations which have requested tests by this Bureau

and by the number of different kinds of batteries which they have

submitted for test. Altogether, more than 1600 dry cells or batteries have been delivered to the Bureau in connection with purely

military tests. In many cases these tests have been of a special

character because of the use for which the batteries were intended.

The results of the Bureau's experiments and tests have been not

only to benefit those requesting the information, but in several cases have led to important changes on the part of manufacturers.

This is particularly true in one case where a manufacturer has

carried out a partial reorganization as a result of the Bureau's

work in showing the poor quality of the cells which were being

supplied.

The Bureau has carried out a test of large storage batteries

such as are used for the propulsion of electric trucks and tractors.

These batteries were representative of seven different manufacturers, and they were tested for capacity, efficiency, and ability

to maintain their voltage over widely varying conditions. Likewise, some measurements were made at low temperatures, and a

number of experiments were carried out to determine the velocity

and acceleration of an electric tractor when equipped with different

types of batteries. The request for this test came from the

chairman of the Committee on Standardization of Electrical

Equipment and Supplies.
106 WAR WORK OF THE BUREAU OF STANDARDS

The results showed that some of these batteries gave a very

satisfactory performance in the laboratory. Others, however,

failed to equal their rated capacities, and these for the most part

gave a relatively poor performance on the other tests to which

they were subjected. . The batteries may be divided into two main

classes: (i) The lead-acid type of storage batteries, including the

ordinary flat-plate type of 1 5 or 1 7 plates per cell and some similar

styles with thinner plates, and the so-called "ironclad" or pencilplate batteries; and (2) the nickel-iron storage batteries, containing alkaline electrolyte.

Measurements of the ampere-hour capacity of these batteries

for continuous and intermittent discharge were made, and their

efficiencies were determined at the normal rate of 45 amperes and

at 90 amperes discharge. There was no great difference between

the various makes of lead-acid batteries, but both the amperehour efficiency and the watt-hour efficiency of the alkaline batteries were distinctly lower than in those of the lead type. The

watt-hour efficiency of the different types of batteries has an important influence on the cost of charging them. The average voltage of the different batteries at the normal rate of discharge was

approximately the same for all the different types tested, the

differences being less than 2 per cent, but at the highest rate of

discharge—that is, 350 amperes—the average voltage of the

alkaline batteries was found to be only 60 per cent of the average

for the lead batteries. Measurements on these different types of

batteries at low temperatures indicated that the lead-acid batteries

gradually decrease in capacity as the temperature of the cell is

lowered, but a different phenomenon was observed in the case of

the alkaline batteries. It was found that for these a certain

critical temperature, dependent on the rate of discharge, exists,

below which the battery can give but a very small output.

The experiments made with the electric tractor equipped with

the lead-acid batteries and the alkaline batteries consisted in

making exact measurements of the velocity and acceleration of

the tractor operating under different load conditions. For this

purpose a series of 39 electrical contacts was prepared, spaced at

definite intervals along the path of the truck and arranged to be

broken as the truck passed along. The time at which each contact

was broken was recorded on a smoked paper record which also

bore a time scale. This latter apparatus was developed by the

section of the Bureau devoted to work on sound ranging. From

the records obtained the time at which each contact was broken
ELECTRIC BLASTING APPARATUS

was determined to within o.oi second, and from the time observed

and the spacing of the contacts it was possible to calculate the

time-distance diagram from which the curves of velocity and acceleration were plotted. The results of this test showed that when

the truck was running without load or with^only a light load, its

speed after the attaining of a unifrom velocity was greater when

the truck was equipped with the alkaline batteries, but when the

load was increased beyond 2 tons a greater velocity was obtained

with the lead-acid batteries. This observation confirms the laboratory tests which showed that, at the higher rates of discharge, the

alkaline batteries could not maintain as high an average voltage

as the lead type, due to their higher internal resistance. It was

also found in testing these alkaline batteries that when the tractor

was heavily loaded and running up a grade of 3 per cent, the acceleration of the tractor at the end of the run was negative; that is

to say, the tractor had attained a maximum velocity which the

alkaline batteries were unable to maintain.

A number of other tests of storage batteries have been made,

but these will not be described in detail. The Signal Corps submitted to the Bureau some military batteries of French manufacture, which were constructed with celluloid containers. A considerable fire hazard is encountered when celluloid is used, as a

bad contact between two cells may ignite the celluloid. In one

case examined the complete destruction of the battery was prevented by an outer container also of celluloid which inclosed the

individual cells. This did not burn through before the oxygen

within was exhausted and the fire extinguished.

For testing portable storage batteries submitted by the Signal

Corps a rack was constructed and installed at the Bureau. The

Bureau provided facilities and cooperated in the supervision of this

test, but the personnel for carrying it out was provided entirely

by the Signal Corps.

An interesting test of small storage batteries was made for the

Chemical Warfare Service. These were intended for use with individual smoke precipitators to prevent the clogging of gas masks.

ELECTRIC BLASTING APPARATUS

About June 1, 191 8, the Bureau of Standards was requested to

undertake an investigation of equipment used by the American

Expeditionary Forces in the electrical ignition of explosives.

Two branches of the Army were concerned with this apparatus

the Ordnance Department, the officers of which were developing
108 WAR WORK OF THE BUREAU OE STANDARDS

equipment for firing Livens gas projectors, and the Engineer

Corps, which was charged with the problems of demolition.

The Livens gas projectors are designed to be hurled into the

enemy's territory from points near the front-line trenches. Short

shafts are sunk in the ground and the projector placed therein

above a charge of powder. A small primer (or squib) , made of a

capsule containing fulminate of mercury and guncotton surrounding a fine metal wire, is placed in the mass of powder. This is so connected to external wires that it can be fused by sending through

it an electric current of the proper intensity. This fusion ignites

the material of the primer, which in turn fires the entire charge

under the projector. A similar primer was used by the Engineers

to fire charges of dynamite in demolishing bridges and other

structures of value to the enemy.

Electric Generators

The apparatus used to generate electric current for this purpose

should have at least three characteristics, especially when used

for military service. First, it should be reliable; second, it

should be portable; and, third, it should have ability to supply a

sufficient amount of energy to insure firing the primers connected

to it. It is important that the operator shall be absolutely cer- tain that when his generator and circuits are properly arranged

he can depend upon them to fire, for most of this work involves

life hazard for the men detailed to it. Closely allied with this is the ability to supply sufficient energy.

The complete demolition of a bridge often requires from 30 to 60

separate charges of dynamite, each sometimes containing two

primers. The electric generator should then be capable of firing

all of these simultaneously, which means that it should generate

sufficient voltage to force through all the primers in series a current

of the proper intensity.

The necessity for compactness scarcely needs any comment.

The conditions under which these generators are used prohibit an

elaborate arrangement of permanent apparatus. The source of

power should be capable of being carried about by one man with

ease. At the beginning of the war there were available in this country

several small generators which partly met the above requirements.

They were being built for use in mines and quarries, and were

called by the trade name "electric blasting machines." A typical

machine of this sort, with the number of primers which it would
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. ii. —The old type of blasting

machine used for firing primers

when the United States entered

the war

The total number of primers which this machine is capable ol firing are piled

at its base

Fig. 12.The improved blasting

machine developed for the use of our overseas forces by the Bureau

It is interesting to compare the number of primers which this machine will lire (shown at its base) with those shown at the base of the old machine in Fig. n. The machine likewise proved to be much

more reliable, and a great deal easier to manufacture
Miscellaneous Publications, Bureau of Standards, No. 46

Fjq. j., —Set of gage blocks constructed at the Bureau

Prior to the war all such blocks were made in Europe. As these are used as reference standards

in munitions Plants, large numbers were required during the war. The Bureau aided by pro- during many sets in its own shops

Fig. 14.—Electric lampsfor daylight transmission of messages

The type of lamp used, means for causing flashing signals, and other phases of the problem were

studied
ELECTRIC BLASTING APPARATUS IO9

ordinarily fire, is shown in Fig. 11. They were small, portable,

series-wound, two-pole, direct-current generators, in appearance

somewhat like the early Edison dynamos. The armatures were of

the Siemens type, and both armature and field were of solid iron.

A long rack with a handle is meshed with a pinion on the shaft of

the generator. In operation the external circuit of primers was

connected in parallel with a switch, short-circuiting the generator.

As the rack was pressed down, current flowed through the generator and short-circuiting switch. At the end of the stroke, this

switch was opened by the rack, thereby making available a comparatively high voltage to force current through the circuit of

primers.

These machines were portable and were probably reliable

enough for the purposes for which they had been used. However,

soon after the American Army began using them, it became clear

that their capacity was very limited, and that even with only a

few primers connected to their circuits, they often failed to

function. Upon examination of the constructional details, some

members of the Bureau's staff recognized that they were precisely

similar to generators designed for the same purpose more than 25

years ago. In view of the great development in the electrical

field during that time, the Bureau was asked to undertake an

investigation to determine whether a generator could be designed

of approximately the same size and weight, but of greater reliability and capacity.

It was apparent that with solid-iron construction the output of

these generators was much below that of machines of similar size

constructed along modern lines. Accordingly, the experimental

work was begun by securing several standard direct-current

motors, such as are used for driving electric fans, and arranging

them to be driven as generators. After testing the capacities of

several such machines and making a number of changes in the

electrical design (such as size of wire and number of turns on

armature and field), it appeared that a machine could be built

with considerably greater capacity and with practically no

increase in weight. Moreover, iron castings and stampings, which

were being used in large quantities in electrical factories in the

manufacture of small motors were suitable for this purpose. As

the Army had immediate need for these generators, this was a

decided advantage.

Some trouble developed in these experimental machines in the

form of armature breakdowns. The new generators, wound with
IIO WAR WORK OF THE BUREAU OF STANDARDS

fine wire, generated voltages which were too high for the insulation

of the wire. Using heavier insulation, however, at the expense of

a smaller number of turns, solved this difficulty without seriouslydetracting from the capacity.

These results were communicated to the General Engineer

Depot about one month after the investigation began. Meanwhile, urgent messages had been received from the commander

of the American Expeditionary Forces in France, telling of numerous failures of the blasting machines and setting forth the necessity for a more reliable source of current. With the results of

these tests, the General Engineer Depot took up with two of the

large manufacturers of electrical apparatus the question of adapting stock material to the building of a new generator. By October i, 1 91 8, the details had all been worked out, contracts had

been let (with these two companies) for 10 000 generators, and

the machines were already in production. Since the unreliable

blasting machines in use constituted a real life hazard, arrangements were made by which large orders for them already placed

were canceled.

As a result of this work there was made available for the Army

a portable generator which was capable of supplying sufficient

energy to fire 100 blasting primers connected in series without

danger of failure. Its weight was no greater than that of the

early blasting machine, which was rated at 20 primers and accomplished this only occasionally. The improved machine developed

by the Bureau is shown in Fig. 12. The large number of primers

which it will fire should be contrasted with Fig. 1 1

.

Incidentally, the cost of the new machine was only about 90

per cent of that of the earlier one, due to the fact that its construction was similar to that of other machines already being manufactured in large quantities, so that while far greater reliability

and capacity were secured, several hundred thousands of dollars

were saved to the Army in the machines then contracted for.

Primers

In order to determine the electrical output required of the blasting generators, a study was made of the current required to fire

the primers and of the time between the application of the current

and the explosion of the primer. This latter information is of

importance in cases where a number of caps are connected in series, as it is essential that the slowest cap be heated to the ignition

point before the explosion of the fastest cap interrupts the circuit.
ELECTRIC BLASTING APPARATUS III

The tests were made on both the Ordnance Department's gasdefense squibs, in which the body of the primer is filled with black

powder, and on the caps used by the Engineer Corps, which contain

a charge of the high explosive known as "tetryl." A fine copper

wire was tied around each cap to be tested in such a way as to be

broken by the explosion of the cap. A weak electric current

passing through this copper wire was recorded on an oscillograph, as was also the actual firing current which passed through the fuse

wire in the interior of the primer. From the photographic record

obtained the instants at which (i) the firing circuit was closed,

(2) the fuse wire was melted by the current, and (3) the outer wire

was broken by the explosion of the cap, could all be determined

to 0.0001 second.

Three different arrangements of circuit were tried and found to

give concordant results at each of the different values of firing cur- rents used.

The conclusions drawn from the results are as follows

1 . Both types of cap tested have substantially the same currenttime characteristics.

2. A current of at least 0.4 ampere is required to insure certain

firing of a single cap.

3. At small currents, the explosion occurs before the resistance

wire is fused by the current. In the case of the tetryl caps this

explosion invariably breaks the bridge wire, but in the case of the

black-powder squibs the wire sometimes survives the explosion

undamaged and is later fused by the current. This can not be

depended upon, however, to maintain the circuit when several

squibs are connected in series.

4. At the large currents (above 3 amperes) the wire is fused by

the current before the explosion occurs.

5. The measurements at the large currents indicate a fairly constant time interval of 0.004 second between the heating of the wire

to the ignition point and the explosion of the charge.

6. At currents of 2 amperes and below, the maximum variation

in firing time among different primers is greater than this 0.004

second, and consequently there is some danger that the circuit

may be interrupted by the explosion of the quicker caps before the

slower ones reach ignition temperature.

7. In the tests with three caps in series, all three caps fired in all .

trials at 1 ampere or above. It appeared from these tests that the

small current (only 0.9 ampere) which was delivered by the oldstyle machines would explain the reason for their unsatisfactory
112 WAR WORK OF THE BUREAU OF STANDARDS

service, and that a machine of considerably greater current ca- pacity was required. The new design of generator chosen by the

Engineer Corps delivers 1.5 amperes at 300 volts when connected

to a circuit of 100 caps in series, and the current is correspondingly

greater when fewer caps are used. Under these conditions the caps

are fired in about 0.01 second with practical certainty.

ELECTRIC TRACTORS AND TRUCKS

This investigation was planned and executed by members of

the staff of the Bureau of Standards, assisted by representatives

of the construction division, Engineer Corps, and Ordnance Department of the Army.

The object of the work was to obtain complete information

relative to the mechanical and electrical details of construction

and operation of electric tractors and trucks for the use of the

Government departments when purchasing and using such equipment.

The tests were conducted at the Union Station, Washington,

D. C. The electrical and mechanical inspections were made by

engineers of the War Department, and during the inspection of

each vehicle representatives of the makers were present. The

scope of the work included the following: Performance tests to

determine operating characteristics; electrical inspection of wiring,

motors, and control apparatus; and mechanical inspection of

framework, gearing, brakes, and safety features.

Object of Tests

The object of the performance test was to determine the comparative operating characteristics of the tractors and trucks. The

following data were obtained : •

(1) Energy consumption in watt hours per ton-mile; (2) loadcarrying capacity in ton-miles per hour; (3) operating speeds;

(4) power taken from the battery.

In general, each of the above characteristics was determined for

two (or more) loads under two conditions: (1) On an approximately level surface of smooth concrete; (2) on an asphalt-block

surface having a grade of 6.5 per cent.

Method of Testing

Each run was made over a measured course. The truck or tractor was brought up to speed before reaching the starting point.

The current taken from the battery, the voltage at the battery

terminals, and the time to traverse the course were observed, each
ELECTRIC TRACTORS AND TRUCKS 1

1

by a separate observer. Readings were taken at intervals of 10

to 20 seconds, depending on the speed of the vehicle. Each vehicle

was operated by a representative of the maker.

In the case of the tractors the load consisted of trailers on which

were placed bags of sand, the loaded trailers having been weighed

on a platform scale. In the case of the trucks the platforms were

loaded to their rated capacity, and where additional load was

required it was obtained by coupling trailers to the truck.

On account of the limited time allotted to the work, only two

loads, in general, were applied to each vehicle. For the tractors

the loads used were approximately 4000 and 25 000 pounds on the

nearly level surface and 4000 and 8800 pounds on the 6.5 per cent

grade. For the trucks the corresponding figures were 4000 and

12 000 on the level and 4000 on the 6.5 per cent grade. In a few

cases intermediate loads were used, and this would have been done

for all vehicles if time had been available.

In all, 13 tractors and 14 trucks were tested, representing 12

manufacturers. In accordance with an agreement with the

makers, the results were reported in full only to Government

departments for their confidential use. Each maker was supplied

with all the results, but only the data on his own products were

identified, the remaining data being marked with arbitrary

numbers.

Results of Tests

The results were reported in the form of curve sheets. They

included transportation capacity in ton-miles per hour and the

energy consumption in watt hours per ton-mile, both as functions

of the load, the speed, and the power taken from the battery, these

being likewise expressed as functions of the load.

Limitations Shown by Tests

Three of the tractors stalled when part way up the 6.5 per cent

grade with a load of 8800 pounds. One of them was tried at an

intermediate load—namely, 5000 pounds—but its transportation

capacity fell off noticeably as compared with the 4000-pound load.

The fact that the tractor was probably much over-loaded when

pulling 5000 pounds is indicated by the steep rise in the corre- sponding curve of watt hours per ton-mile. Another one of the

trucks required an excessive value of watt hours per ton-mile at

the 4000-pound load.

Using the results of these tests, a committee of the War Department on which the Bureau of Standards was represented prepared

26035°—21——8
114 WAR WORK OF THE BUREAU OF STANDARDS

specifications for standardized trucks and tractors for warehouse

and other Government use. In drawing these specifications,

special attention was given to the dimensions of battery compartments, in order to adapt them for use with the different types of

battery required for various service conditions.

As an important by-product, it is believed that this test, which

was the first thorough comparative test of its kind, had an important influence on the improvement of trucks and tractors as supplied later for commercial purposes.

ELECTRICAL INDUCTANCE METHOD FOR LOCATION OF

METAL BODIES

At the beginning of the war a number of devices, which depended

upon the effect of iron on the inductance of a coil brought into the

neighborhood of the iron, were submitted to the Bureau for

criticism. In order to properly criticise these devices, it was

necessary to make experiments and accumulate data so that the

Bureau could readily determine by an examination of the drawings

whether the proposed devices would operate. Accordingly, a

number of coils were constructed and experiments performed to

determine the effect of a mass of iron on the inductance of the coils.

Incidentally, it was found that a nonmagnetic metal had nearly as great an effect as a magnetic one on account of the eddy currents

which were set up in the metallic mass.

Several different coils were constructed. These differed both

in shape and in the number of turns of wire. The largest constructed had a diameter of 1.5 m. There were four coils of this

size, each having a winding of 125 turns of No. 18 wire. They

were wound in pairs, each pair being on a frame. The distance

between the inside edges of the two coils was 1 cm. Other coils of

various sizes were used in the course of the investigation.

Two different methods of detecting the change in inductance

were employed. In the first, the two coils of a pair were con- nected in series so that their magnetic fields aided each other.

The coils were then connected in an Anderson bridge balanced

with a frequency of approximately 1000 cycles per second. When

a piece of metal was brought into the neighborhood of the coils,

it would change the inductance of the coils and cause an unbalancing of the bridge which would be detected by the current

through the telephone.

In the second method, a coil of one pair was connected in series

with a coil of another pair. Through these an alternating cur-
ELECTRICAL, INDUCTANCE METHOD 115

rent was sent. The other two coils were connected so that the

induced electromotive forces were in opposite directions. Normally the induced electromotive forces were equal, so that no

current flowed through a telephone receiver in the circuit. However, if one coil was brought near a mass of metal the induced

electromotive forces were no longer equal, causing a flow of cur- rent through the telephone. To make this sensitive on alternating current, a frequency of 500 to 1000 cycles was required.

This method may also be used on direct current employing a

galvanometer instead of a telephone. In this case, however, it is

necessary that the coils be so arranged that the variations in the

earth's magnetic field do not produce a current through the

galvanometer.

The two methods were approximately of the same sensitive- ness when used with alternating current. If the coils near the

mass of metal are moving, then the direct-current method becomes

more sensitive than the alternating-current one. Of course, there

is no effect whatsoever when the coils near the mass of metal are

stationary. The results given below apply only to the use of

alternating current.

By using one pair of the large coils described above in the Anderson-bridge method and applying 175 volts at 500 cycles to the

bridge, a sheet of iron 120 cm square was detected. Sheets of

zinc and copper were tried and their presence was detected quite as well as pieces of iron. In fact, a thin sheet of copper containing

6000 sq. cm could be detected at the same distance as a sheet of

iron containing 1 1 000 sq. cm.

In using the second method indicated above and applying 500

cycles and 0.5 ampere alternating current to the coils, the same

sensitiveness was obtained as indicated above for the Andersonbridge method. However, when used with direct current, which

is interrupted twice per second, the same piece of iron was detected

at a distance of 4 m.

By means of a small coil connected to a telephone the field of

one of the coils was explored. The field could be readily detected

at a distance of 30 m from the coils.

The theory would indicate that for a given piece of metal the

effect on inductance would vary approximately inversely as the

4th power of the distance from the coils. The experiments indicate that the theory agrees with practice. It is also to be ex- pected that the distance at which iron can be detected will depend

on the area of the iron.
1 1 6 WAR WORK OF THE BUREAU OF STANDARDS

GAGES, PRECISION

Testing of Munitions Gages

The entrance of the United States into the World War resulted

in the manufacturing of guns, ammunition, and other ordnance

material on a strictly interchangeable basis on a scale never before

attempted in this country. By interchangeable manufacture is

meant the practice of manufacturing in different factories and different parts of the country the various parts entering into a completed

mechanism, and then assembling these parts at some central

point. One of the prime requisites of such a manufacturing

practice is an adequate gaging system. Only such a system will

insure that the various parts or components, wherever made,

will, when brought to the point of assembly, go together and function properly.

It was early realized that in order to put an adequate gaging

system into effect, it would be necessary for all master gages to be

tested by some central organization provided with suitable equipment and trained personnel. The Bureau of Standards was

selected as the proper and logical organization to perform this

important function, and the gage section was organized and

equipped for that purpose.

At the gage laboratory in Washington and the branch laboratories in New York; Bridgeport, Conn.; and Cleveland, Ohio,

more than 60 000 munitions gages were tested.

Manufacture of Precision-Gage Blocks

In the manufacture and inspection of accurate machine products,

a series of standards of comparison is absolutely essential. The

need for such standards is usually met by the use of precision-gage

blocks. Prior to the war, Sweden was the source of the only

satisfactory precision-gage blocks, and during the progress of the

war the demand for these blocks far exceeded the supply, and as a result prices became excessive and an adequate supply was not

available at any price.

In 191 7, there was brought to the Bureau of Standards an idea

of a method by which the inventor believed that precision-gage

blocks could be manufactured commercially that would be equal

in every respect to the Swedish blocks.

The Bureau was of the opinion that the idea was susceptible of

successful development and, after presentation to the War Department, an allotment of funds was made by that department for the

purpose. Apparatus was designed and either purchased or built as speedily as possible, and the idea developed and put into opera-
ILLUMINATING ENGINEERING 117

tion. After a certain experimental period satisfactory blocks

were turned out, and in the course of the following months 50

complete sets of blocks ranging from 0.05 inch to 4 inches were

completed. Fig. 13 shows a set of gage blocks made by the

Bureau.

Salvage of Obsolete Gages

Of the thousands of gages used by the Ordnance Department of

the Army in the inspection of munitions, large numbers were

continually becoming obsolete by reason of changes in design or because they had been worn out in use. Of these obsolete and

worn-out gages a considerable number could be so rebuilt as to

again become useful. A gage shop was established at the Bureau

of Standards, and nearly a thousand gages were salvaged and about

500 new gages built for the Ordnance Department.

School of Instruction in Gage Work

For inspecting the immense quantities of munitions produced

during the period of the war, a large corps of trained inspectors

was necessary. The available supply of properly trained men

being entirely inadequate, it was necessary to train many new men

for this work. As an aid in this training work, a school of instruction was established at the Bureau, and in this school 50 persons

were given courses of from one to two weeks of intensive training

in the work of gage inspection. Among those to whom this

training was furnished may be mentioned representatives from

13 district ordnance offices, 2 navy yards, 2 arsenals, the Motor

Transport Corps, and 2 large manufacturers.

Publications on Gage Work

Much of the useful information and experience gained by the

gage section has been collected in the form of communications

and distributed to those in position to use it most advantageously.

A list of these communications will be supplied on request to those

interested.

ILLUMINATING ENGINEERING

Acetylene Generators for Field Service

For some time the Bureau of Standards was asked to make tests

of acetylene generators by four branches of the War Department.

In all, 9 reports on the subject have been issued, aggregating about

85 pages, exclusive of performance curve sheets, etc. The requests

have come from the General Engineer Depot, the Signal Corps,

the Field Medical Supply Depot and the Military Intelligence

Service of the General Staff.
Il8 WAR WORK OF THE BUREAU OF STANDARDS

A test for the General Engineer Depot was made on acetylene

generators designed for isolated or field construction work, etc.

The purpose of the test was the selection of the best generator for

the use of the Expeditionary Forces of the United States. A supplementary report dealt with smaller generators intended for use

with small burners for the interior illumination of dugouts, barracks, etc. Another test was performed for the science and research division

of the Signal Corps (later the Bureau of Aircraft Production).

For this test two types of generators were submitted by one manufacturer. The generators were to be used for supplying gas at

low pressure for use in photographic work in portable laboratories.

Still other work, carried out for the Field Medical Supply Depot,

was to determine the most satisfactory types of generators for use

in supplying gas for low-pressure lights and instrument sterilization stoves in field hospitals.

The various generators tested were divided into four classes as regards the methods of bringing the water and carbide into contact

to cause the generation of the gas. They were as follows:

1. Recessional Type, Water in Excess.—In this type the

fuel is supported in suitable racks inside a gas bell open at the

bottom. When the gas cock is opened, the water rises in the gas

bell until it comes into contact with the fuel. Gas is then generated, increasing the pressure inside the bell and forcing the water

down out of contact with the fuel until the pressure drops sufficiently to again raise the water to the fuel level. If the amount

of gas generated exceeds the surplus storage space in the gas bell,

overgeneration occurs.

2. Recessional Plus Flooded-Compartment Type.—In this

type the fuel is contained in trays or compartments without drainage, they being in turn contained in water-tight buckets. When

the water rises to a certain level, it is sprayed through holes in the

side of the bucket onto the fuel. Unless this type is carefully designed to prevent the admission of an excessive amount of water,

large fluctuations of gas pressure and excessive overgeneration

will occur.

3. Carbide to Water, Water in Excess.—Only one generator

of this type was tested. A clockwork attachment was designed

to drop small grains of carbide into water when the pressure fell below a certain value.

4. Water to Carbide, Carbide in Excess.—A few of the

small generators, for indoor use, were of this type. The water is
f

ILLUMINATING ENGINEERING 119

placed in a tank over the carbide container, and is admitted drop

by drop through a needle valve.

In order to determine the suitability and relative merits of the

various generators for the particular service required, very extensive laboratory tests were carried out. Some of the main features

investigated were as follows: (1) mechanical features-—ruggedness,

weight, design, etc.; (2) simplicity and safety of operation; (3) gas

generation characteristics—regularity , pressure fluctuation, amount

per pound of fuel, cost, etc.; (4) light distribution with reflectors

supplied; and (5) illumination characteristics—candlepower, fluctuation, drift with time, total light output, efficiency, etc. ; and (6)

effect of low temperature on operation.

The ususal method of making a test to determine the total light

output, gas yield, etc., was as follows: A number of generators

were given full charges and Operated continuously until exhausted.

A portable photometer was set up so that the candlepower normal

to the bare flame of any one of the flares could be measured.

Some or all of the burners were connected to the generators through

gas meters, so that the gas yield could be measured. In a number

of cases recording pressure gages were connected to record the gas

pressure in the generators. Candlepower measurements were

made at regular intervals of about 10 or 15 minutes throughout

the life of a charge. The total light output, expressed in candle

hours, was obtained by taking the product of the average candlepower and the time of burning.

Other tests were made to determine the reliability of the generators at low temperatures. For this purpose several generators

were charged and put outdoors when the temperature was about

12 to 1F. Only one make of generator was free from trouble,

due to the low temperatures. In all cases where failure occurred

by reason of the low temperature it was brought about by collection of frost in some part of the gas-supply system.

The Bureau's tests for the General Engineer Depot resulted in a

recommendation for the purchase of a certain make and size of generator. For satisfactory operation under all conditions, another

make was found to be superior to all the other generators tested,

but it required a special fuel costing 50 per cent more than commercial carbide, and yielding only about 80 per cent as much gas

for the equal weight of fuel.

For photographic enlargements, reproductions, etc., in the field,

photographic laboratories were installed in motor lorries. In

some of these acetylene generators were used. The Signal Corps,
120 WAR WORK OF THE BUREAU OF STANDARDS

science and research division, submitted two types of generators

manufactured by the same firm for this type of service, with a

request for tests. One of those, known as the "Aviation" type,

was understood to be of English origin. It was a complex apparatus and was not found to be at all satisfactory. The second

type was a special generator combining two gas bells and carbide

racks in one water tank. The two were connected in parallel so that either could be used alone, thus making it possible to remove

and recharge one while the other was in use. As originally submitted, this generator had no provision for pressure reduction or

regulation. Since the generator was to be used for photographic

work, it was evidently very necessary to have a constant gas

pressure at the burner. The Bureau suggested the use of a cer- tain type of pressure regulator which had been tested and found

to give excellent service, but for some reason this suggestion was

not adopted. The generator was revised several times in accordance with the Bureau's criticisms, and finally a satisfactory product was obtained. The pressure regulation in the final type of

generator was not as good as that obtained with the regulators

recommended, but was probably sufficient for all practical purposes.

Generators were tested and inspected which were to be used to

supply gas for lights and for stoves used to heat water for sterilization of instruments for field medical hospitals. The tests performed were not very extensive, as previous work enabled the

Bureau to select the proper generator without much trouble.

Incandescent Electric Lamps

Fully 95 per cent of the inspections and tests of incandescent

electric lamps made during the war were for the Military and

Naval Establishments of the Government. For the fiscal year

1 91 8 the enormous total of approximately 10000000 lamps

was reached on these orders. When the factories reached their

full war output, three inspectors were kept in the field, and it was

found necessary also to considerably abridge the usual inspection

procedure to handle the requisite quantity per day. Even then,

the inspection facilities at the factories were inadequate to permit

the immediate inspection of all lamps ordered, so that the emergency called for immediate shipment of many lamps, which were,

however, usually guaranteed to be of as good quality as the inspected lamps.

During the fiscal year 191 9, up to the time of the armistice about

2 000 000 lamps were ordered.
ILLUMINATING ENGINEERING 121

Life tests were operated to the full capacity of the Bureau, and

as a result of these tests the manufacturers of tungsten lamps

maintained an allowable adjustment of rated efficiencies such that

the average quality of the lamps supplied was kept up to the specified standard.

Protective Fence Lighting

In September, 191 8, the War Department, through the construction division of the Engineering Department, requested the Bureau

of Standards to conduct competitive tests of flood-lighting units, in

order that they might standardize their practice in the use of

flood lights for protective lighting of ordnance depots, etc. The Curtis Bay Ordnance Depot, near Baltimore, Md., was said

to be typical of the areas to be guarded. Its area was several

square miles, and the fence line was irregular. The fence was

composed of heavy woven wire and was about 6 feet high, sur- mounted by three strands of barbed wire, making the total height

approximately 7 feet. The fence passed through fairly rough

country, with weeds, bushes, and trees outside it. The floodlights, equipped with semicylindrical hoods about 2 feet long,

were attached to posts placed just inside the fence and were so supported that they were about 20 inches outside the fence, with

the axis of the beam approximately parallel to the fence. The

path of the guard was from 10 to 100 feet inside the fence, parallel

to it, and was of a fixed length.

The general question of protective lighting received a great

deal of attention during the war period. Several articles dealing with this subject were published during that time, some

of which are as follows: Electrical World, June 15, 191 8, page

1268; General Electric Review, October, 1917, page 816; Journal

of Electricity, December 15, 191 7, page 540; War Department

Document No. 800, "Protective Lighting;" Bulletin No. 30 of

the Engineering Department, National Lamp Works, Cleveland,

Ohio.

In none of the above articles had a satisfactory system been

outlined for the service conditions that existed in the ordnance

depots. A satisfactory system for these conditions had to possess

the following features

1. No Light on or Inside of the Fence.—If any light

falls on the fence, it is very difficult to see through, as the fence

presents the appearance of an illuminated grating. If any light

falls well within the fence, it illuminates the patrol route of the

guard, which makes him visible to anyone outside the fence.
122 WAR WORK OF THE BUREAU OF STANDARDS

2. Bright Foreground.—The foreground outside the fence

should be lighted to an intensity sufficiently high to reveal the

approach of any person at a distance of 50 to 75 feet, either by

silhouette or by direct illumination.

3. Penetration.—The light outside the fence should come

from such a direction or directions that there will be no serious

shadows due to uneven ground or bushes. Hence, in order to

give the proper penetration, there should be an appreciable angle

between the light beam and the ground.

4. Uniformity of Illumination.—The illumination should

be of such uniformity as to form no dark spaces which would

interfere with the vision of the guard.

5. Spacing.—Units should be spaced sufficiently close so that

long, dark spaces would not be created by the failure of one light.

Short spacing is also necessary to give good lighting in foggy

or stormy weather.

6. Glare.—Protective lighting units should create a dazzling

glare in the eyes of anyone outside the fence and a minimum glare

to the guard. The ideal conditions would be to have a blmding

glare to the prowler and at the same time have the lighting units

totally dark to anyone inside the fence. Since it is impossible to

have the protected area dark on moonlight nights, the most

effective way to decrease the vision of the prowler is by the use of

glaring lights projected in his direction.

Nearly all of the units submitted were equipped with "spill

rings" or "baffles" over half of the front glass. These spill rings

were designed to let through all the light projected approximately

parallel to the axis of the floodlight, but to deflect or absorb all

light which would normally be projected to one side of the axis.

In order to test the effectiveness of the various flood lights submitted, a tower was built beside the fence around the Bureau.

This fence is of woven wire, similar to that described above. The

flood lights were mounted on this tower and the beams projected

beside the fence. Observations were made from both inside and

outside the fence to determine how closely the various units fulfilled the above conditions. A number of such tests were made,

the final conclusion being that none of the units was satisfactory

for this purpose. It is evident that if the flood-light projects any

light within the fence it would be necessary to entirely obliterate

one-half of the beam or else deflect it to the outside, if the lighting

is to be satisfactory. This would mean that the beam must change

from a maximum value to zero within i° or 2°. It is apparently
ILLUMINATING ENGINEERING 123

impossible to accomplish this. Even a small amount of light inside the fence causes a glare in the eyes of the guard if he has to

face it at any time, and the amount of light necessary to reveal

his presence was found to be surprisingly low. Where the fence

is not straight and the area to be protected is very large, it is

practically impossible for guarding to be successfully accomplished by a guard making a complete circuit of the fence. Hence,

when he is traveling back and forth over a definite route, he must

at some time face one or more units, and, as has been observed,

these may seriously interfere with his vision, even at distances as great as half a mile.

The principal faults of flood lights for this type of protective

lighting when used in a manner similar to that at Curtis Bay, may

be summarized as follows:

1. Light on and Inside the Fence.—Even the best units

tested were open to this objection.

2. Nonuniform Light Along Fence.

3. Dark Spaces for 25 to 50 Feet on Either Side of Each

Flood Light.

4. Lack of Downward Penetration.—Since the light strikes

the ground almost at grazing incidence for a good part of the way,

it will not penetrate hollows at appreciable distances from a unit,

and weeds or bushes may make long shadows, thus creating hiding

places for prowlers.

5. Lack of Distance Penetration in Bad Weather.—If

the weather is foggy or rainy, the flood-light beam may not penetrate sufficiently to be effective over distances greater than 200

feet, thus leaving long spaces insufficiently illuminated.

6. Glare in the Eyes of the Guard.—At Curtis Bay this

condition was found to exist even at distances of one-half mile or more.

7. Lack of Glare Opposing the Prowler—Since any person

approaching the fence receives the light from one side, it has

practically no glaring light in his eyes.

8. Serious Effects of Failure of One Unit.—If one lamp

burns out, a long space is left dark, this space being approximately

the spacing distance.

Consideration of the disadvantages of flood-lighting units led to

the conclusion that much more satisfactory results could be

obtained by the use of local units with short spacing; these units

to be of such a nature as to project the maximum intensity in a

direction out from the fence, and give fairly uniform illumination
124 WAR WORK OF THE BUREAU OF STANDARDS

along the fence. Several types of reflectors were obtained for

these tests.

The Bureau's tests and demonstrations apparently show that

for protective fence lighting a system composed of elliptical reflectors, equipped with ioo-candlepower Mazda C street series lamps,

or ioo-watt Mazda C multiple lamps, mounted about 10 feet high,

spaced about 40 to 50 feet, and inclined outward about 45 from

the vertical, would be quite satisfactory and far superior to any

other system investigated, and would apparently be better than

any other units now on the market.

The reflectors recommended are enameled metal reflectors with

an elliptical cross section, and are inclined outward when the lamp

axis is vertical. When the lamp axis is inclined outward about 45 , the units being suspended about 1 to 2 feet outside the fence,

practically all the required conditions as outlined above are fulfilled. The reflectors are cheap and durable, and are easily

cleaned.

Small units with short spacing are superior to large units with

longer spacing, for the following reasons

:

1 . More uniform illumination along the fence.

2. Greater glare in the eyes of the person outside the fence.

3. Shorter dark space if one lamp fails.

4. Lower wattage lamps are less likely to be exploded by rain or snow than larger wattage lamps.

In order to prevent darkness along a long stretch of fence in case the circuit is broken, it is advisable to have two separate circuits,

series or multiple, with alternate lamps on the different circuits.

Under these conditions, a single dark space will not exceed 50 feet

in case one circuit fails.

This test was made to determine the best units for lighting

fences of the type above described, but apparently it would be

equally good for solid fences; in that case, however, it would be

desirable to set the units at such an angle that some light would be

thrown on the inside of the fence.

Rockets and IUuminating Shells

In modern warfare rockets and illuminating shells are extensively used for Ughting up the battle field, revealing enemy movements, making light barrages to obstruct and defeat enemy

attacks, indicate the trajectory of projectiles, etc. The types and

uses have been described by A. Bergman in the Transactions of

the Illuminating Engineering Society (13, Xo. 4, p. 219; 1918).
ILLUMINATING ENGINEERING 125

Previous to the fall of 191 7 rockets and shells for these purposes

were bought without specifications as to their performance, as regards illuminating value and smoke produced. Since their function is to furnish a high illumination for a short time, and since

some of them are suspended from parachutes while burning, it is

very important that there shall be as little smoke produced as

possible. Immense quantities of these materials were being purchased by the War Department, and there was available no quantitative information about their performance. Four things had to

be done: (1) To make measurements on samples obtained from

different sources in order to find out what might reasonably be

expected of each type of light; (2) to try to improve the performance by modifying the composition and construction; (3) to draw

up specifications stating the performance required ; and (4) to test

samples of material purchased under the specifications. In the

fall of 191 7 the Trench Warfare Section of the Ordnance Department of the Army requested the Bureau to assist them in this work

by making candlepower tests of materials then available and of

samples submitted by manufacturers, and to develop methods of

determining the amount of smoke produced.

The determination of the candlepower of illuminating shells, etc.,

is fairly simple. For this purpose, the shells were burned upright,

and the candlepower was measured as many times as possible

during the period of burning, a Sharp-Millar portable photometer

being used for the purpose. In order to get an arbitrary measurement of the amount of smoke produced, they were burned under

a hood. The smoke was passed through a vertical cylindrical

chamber about 15 inches in diameter and 30 inches high, an ex- haust fan being used to stimulate the circulation of the smoke.

Two small holes were made in opposite sides of the chamber, at

its center. A lamp was placed outside the chamber, opposite one

hole, and a photometer was placed at the other hole. Photometer

readings were taken when the cylinder was clear of smoke and

when smoke was passing through the cylinder. The ratio of the

photometer reading with and without smoke gave a value for the

light transmission through the smoke under the particular conditions of the test. This enabled the Bureau to obtain relative

values for different samples, but at no time was it claimed that,

the conditions were exactly definable or reproducible.

Measurements of candlepower and smoke transmission, as defined above, were made for a large number of samples of shells and
126 WAR WORK OE THE BUREAU OE STANDARDS

rockets, and the methods were found to be sufficiently satisfactory to make it desirable to refine them and build new equipment.

Accordingly, plans for such equipment were drawn up for the

Ordnance Department, and a laboratory was equipped for the

tests at the American University, Washington, D. C.

In order to tie up the results at the new laboratory with those

obtained under the test conditions at the Bureau, samples from a

single lot were tested at both laboratories. Fortunately, it was

found that smoke transmission tests conducted in the laboratory

built according to the plans drawn up here were in practically

exact agreement with the smoke tests made under purely arbitrary conditions at the Bureau of Standards.

In the latter part of 191 7 the member of the Bureau's staff who

had been connected with the tests was given a commission and

took charge of the testing at the new laboratory. Since the new

laboratory was then prepared to make its own tests, the Bureau's

apparatus was dismantled, after making the check measurements

referred to above.

Signaling Lamps for Daylight Transmission of Messages

On numerous occasions from September, 191 8, to February,

1 91 9, the Bureau was requested to make tests of various lamps and

signaling devices for the science and research division of the Bureau of Aircraft Production. The purposes of the tests were (1)

to determine the light-distribution characteristics of regular and

special types of signaling devices; (2) determination of the intensities necessary for perception of light signals over various distances in daylight; (3) tests of the effect of partially silvering the

bulbs used in various units. For the last-named work the lamps

were silvered in the laboratory. One of the signaling equipments

tested is shown in Fig. 14.

The various devices and lamps tested were used for several

types of service, among which may be mentioned the following:

(1) Daylight signaling over land, such as that from one trench to

another; (2) signaling between airplanes; (3) night signals from

an airplane to the ground, indicating that illumination of the

landing field is desired.

Three of the units tested may be described as follows : The first

is known as the Evans "gyrolite." It usually consists of a small

metal reflector and a type C lamp. The lamp is first silvered all

over and copperplated, then the silver is removed from the bulb

in a band about 1 centimeter wide, so that all the light given off
ILLUMINATING ENGINEERING 127

by the lamp is redirected by the reflector. A special adaptation

of the Evans "gyrolite" was used as a signaling unit. A shutter

operated by the trigger at the top of the handle furnished the

means for flashing the signal. The second type of apparatus is

the type EE-10 trench signal unit. Hydrogen-filled lamps with

special types of filaments are used in it. The gas is used to produce rapid cooling of the filament, so that flashing signals can be

sent by means of an exterior sending key. The cooling is very

rapid, and distinct flashes can be sent faster than the eye can

interpret them. The Aldis signal lamp, the third type of device,

is somewhat similar to the trench-signal unit, but produces flashing

signals by tilting the reflector rather than by covering or extinguishing the light.

In September, 1918, the trench-signal unit was mounted on the

roof of the electrical building of the Bureau and directed toward

an observer stationed about 2 miles away. The sky was slightly

overcast. Flashing signals were sent and were acknowledged

when received . This test apparently indicated that the minimum

intensity visible at that distance to the naked eye was about

1000 candlepower.

In October a signaling test was carried out over a 3-mile range.

For this purpose two 1000-watt lamps were used without reflectors.

The day was quite dark, the illumination on a horizontal plane

being only 500 foot-candles, but the atmosphere over the range

was clear. The results showed that intensities below 500 candlepower were invisible at all times, and that an intensity of 1000 or greater would be necessary for certainty of signaling under those

conditions.

In the case of lamps to be used for signaling from airplanes to

the ground at night, they should be visible over a fairly wide area and should employ an extensive type of distribution.

In order to determine the degree of improvement in the beam

intensity and spread which might be obtained with the trenchsignal unit EE-10 by partially silvering the lamp bulb, a large

number of tests were made. In each case the bulbs were wholly

silvered, then silver was removed until all the light which would

normally be incident on the reflector was unaffected, while that

which would normally fall outside the zone of the reflector was

redirected onto it. Since it is very difficult to direct the axis of the beam toward

the point receiving the signals, it is desirable to have a fairly high

intensity over a solid angle of 5 or more. It was found that a
128 WAR WORK OF THE BUREAU OF STANDARDS

ribbon filament gave the best results in this respect. The use of

a ribbon-filament lamp in the Evans gyrolite unit achieves the

object desired, namely, a fairly uniform distribution through a

wide angle.

The Aldis lamp, an English design, uses a special type C lamp

of about 25 watts. It has two parallel coil filaments and is operated with the axis of the lamp at right angles to the axis of the

reflector, the axis of the reflector being in the plane of the filament

coils. The result is an enlarged image of the filament on a screen placed in the beam. Silvering one-half of the bulb results in an

increased efficiency, but a comparison with the type EE-10 unit

shows the latter to be superior as regards light distribution and

efficiency.

INKS AND INK POWDERS

The Bureau of Standards was called upon to do considerable

investigation and inspection work on inks for the various offices

of the War and Navy Departments. Although much work had

been done along this line during the past 10 years for the various

civil branches of the Government, many new manufacturers had

started up and new products placed upon the market, thereby

requiring considerable testing work to determine the merits of

this material. For convenience, this discussion will be divided

as follows: (1) Ink and ink powder, (2) indelible ink.

Liquid Inks and Ink Powders

Writing ink is a solution or fine suspension of some colored substance in water which will leave a permanent mark upon paper

after drying. It is judged by its permanence, durability, and

writing qualities. By permanence is meant the resistance which

the writing will show to the agents of time, such as light, moisture,

and moderate heat. The durability is judged by the freedom

from the formation of scum, sediment, and mold. The writing

quality is a factor that must also be taken into consideration,

inasmuch as some fluids, in spite of excellent durability and

permanence, are unsuited for pen work because of improper

consistency.

Ordinary writing ink consists essentially of an aqueous solution

of iron gallotannate, although Prussian blue, chrome-logwood,

copper-logwood, finely divided carbon (India ink), and dye solutions are sometimes used. The various types of fluids were compared with one another in regard to the properties above mentioned

and for most ordinary work the iron gallotannate was found to be
INKS AND INK POWDERS 129

the most satisfactory. This type of ink had already been adopted

as official by the Government several years previously.

For overseas shipments it seemed desirable to use ink in powder

form, if possible, and to dissolve it in water as required. Such a

system would greatly reduce shipping space, eliminate breakage,

and prove very convenient in the field, where small amounts of

ink could be made up at one time. The idea of preparing ink in

the form of a powder or tablet was not a new one, as many concerns had been making this material for some time. However,

most of these powders were essentially nothing but organic dyes

which would dissolve in water to form a colored liquid. The writing produced by such a solution was found to be very fugitive to

light and water, and could not be relied upon to produce a permanent record. It was natural, therefore, to try to produce the gallotannate (which was known to be satisfactory) in the powder form.

A few manufacturers had done this, but the product was in many

respects inferior. The amount of insoluble matter was very high,

in some cases equal to 50 per cent of the weight of the powder,

Furthermore, the ink did not keep well. In some instances it

formed such a thick deposit in less than a week as to render it unfit for use. This will be better understood when it is stated that

the gallotannate of iron ink which is purchased in the liquid form

contains hydrochloric acid, which is necessary to keep the iron in

solution. The hydrochloric acid, which is a gas readily soluble

in water, can of course not be produced in the form of a powder.

Experiments were carried out using various solid organic acids in

place of the hydrochloric. Most of these were found to be unsuitable in that they did not prevent precipitation. Oxalic acid,

however, was found to suit the purpose very well and seemed to

possess no other disadvantage than that of retarding slightly the

rate of blackening of the record.

Indelible Inks

A considerable quantity of indelible ink was required by the

various military organizations for labeling garments, blankets,

bales, etc. Although this did not require very much investigational work, it was necessary to try a great many of the brands

which were upon the market in order to determine their suitability.

The composition of these inks varied widely and included solutions of dyes in oils, aniline, and cresol ; silver salts ; combinations

of metallic salts with logwood; suspensions of carbon; and mixtures of copper salts with aniline and some oxidizing agent de26035°—21 9
1 30 WAR WORK OF TftE BUREAU OF STANDARDS

signed for the production of aniline black upon the fiber. The

commission from the French Government reported that they

had been using suspensions of lampblack in various vegetable oils,

especially peanut oil, for marking uniforms. The West Point

laundry had been using a mixture of unsulphonated nigrosine with

cresol, which was very successful upon certain fabrics. It was

necessary to subject these various materials to practical tests.

With the cooperation of the Quartermaster Corps, fabrics were

marked with the different inks and carried through the process

of laundering. The results obtained were at first very misleading,

inasmuch as inks of the same type varied so greatly among

themselves as to indelibility. In general, the copper-aniline

combinations were found to be very permanent, although it was

difficult to produce legible marks with these upon the fabric.

Some of the cresol dye mixtures were excellent and would withstand 10 or 15 laundry operations, whereas others were so poor

as to be almost eliminated by a single washing. This was at first

difficult of explanation, but it was finally concluded that improper

dye had been used in the inferior grades. The carbon suspensions,

although showing great resistance when soaked in laboratory

reagents, were largely rubbed out after a few laundry operations,

and the silver inks, although much more expensive, were found to

be inferior to the cresol-dye mixtures.

INVISIBLE SIGNALING

Ultra-Violet Position Marks and Ultra-Violet Signaling

Several months before the entry of the United States into the

war the Bureau of Standards was requested to advise the Navy

as to the selection and specification of a lamp to be used as a stern

light, so designed that it would be visible to other ships of the

same squadron at 1000 yards (914 m.) astern while not visible at

greater distances and not easily picked up by enemy ships.

This request suggested the possibility of screening the source with a filter transparent to ultra-violet, while opaque to the visible,

and observing it with a fluorescent detector. Experiments made

at the Bureau, February to May, 191 7, showed in general the

feasibility of this idea; and a letter to this effect was delivered to

the Navy Department, June 1, 191 7. A detailed technical report

was made to the above Department March 6, 19 19. Most of the

following information is taken from this report, and has also been

published in the Physical Review (August and September, 19 19).
INVISIBLE SIGNALING 131

The experiments were made under the following conditions:

1. Sources.—A right-angled carbon arc with current up to 25

amperes and a vertical iron arc with current up to 15 amperes were

used. (A mercury arc would perhaps be more favorable than

either of these, but was not used because of the a priori conclusion

that such a lamp would not be rugged enough for actual service at

sea.) No condensing, collimating, or directing mirrors or lenses

were used in these trials, although they were recommended for use

in service.

2. Screens.—Corning glass G-55-A-62, the suitability of

which was known for this purpose from tests made in another

connection in 19 16, and similar glasses made by the Corning Glass

Works at the Bureau's request; aqueous solution of nickel sulphate; aqueous solution of p-nitrosodimethylaniline. The wave

lengths actually used were in a narrow band centered at about

340-350 fi.

3. Range.—Experiments were made in an open range of about

654 m. Rotating sectors were employed to give effect of greater

distance. To facilitate the experiments, the sending and receiving stations were in direct telephonic communication.

4. Receiver.—The receiver consisted of a short-focus quartz

lens forming an image on the fluorescent screen, which was

observed by a low-power positive ocular from the opposite side.

The observer's eyes were completely shaded by a close-fitting

shade, and a thin piece of "purple-ultra" glass (Corning G-55-A62) was inserted between the objective and the screen. This cuts

out extraneous illumination, showing the fluorescent image on a

dark background, and is essential to sensitiveness.

5. External Conditions.—All tests were made at night, but

under various conditions of light from sky, moon, etc.

The conclusions may be stated as follows:

1. General Conclusions.—Working on the above range and

with the apparatus mentioned, clearly visible fluorescent images

have been observed when the source was nearly or quite invisible

to the unaided eye, and the fluorescent image still remained

visible when a 4 per cent rotating sectored disk was interposed

before the source. However, the following qualifications of this

general conclusion must be noted.

It is very difficult to reach any definite conclusions as to the

absolute invisibility of such a source to the unaided eye. The
132 WAR WORK OF THE BUREAU OF STANDARDS

circumstances of the visibility or quasi visibility of the source with filters used in these experiments were as follows

:

Even with the best ultra-violet filters, the source was always

visible when near it. At the receiving station, when the source was nearly invisible, it could never be focused as a blue or violet

point source by the unaided eye, although the same source with a

red filter could easily be seen as a red-point source. However,

when carefully looked for, an indefinite blue-gray haze, covering

a large area of sky, could be seen. This phenomenon is apparently

due to fluorescence of the eye media rather than to true visibility

of the light transmitted by the ultra-violet filter. The personal

equation in the visibility of this blue haze is considerable ; it may

be invisible to some and quite visible to others. This visibility

is a function of age, the source of light being more easily seen by

a younger than an older observer. This is due to the senile yellowing of the crystalline lens. Its appearance in the sky is of such

an elusive nature that its presence can only be determined by the

method of right and wrong answers. The darkness or lack of

darkness of the night, of course, affect this visibility to the unaided

eye, while not affecting the detector as it was here used. The

advantage of this detector over the unaided eye is thus greatest

on moonlight nights or with other lights in the neighborhood of

the sending station.

The source may, of course, be found and sharply focused by

"night glasses " when it is invisible to the unaided eye. However,

the fluorescent image may be seen in the detector when the source can not be seen using this same optical system simply as a telescope

(fluorescent screen removed)

.

2. SpEciaIv Conclusions.—(a) An absolutely dark (or invisible

in perfectly dark surroundings) ultra-violet source for practical

signaling through the earth's atmosphere is not possible, because

the source is disclosed by the fluorescence of the eye itself, although

the appearance is very vague and ill defined.

(b) As position and identification lights designed to be inconspicuous (if not quite invisible) and capable of having their visibility increased to one provided with the fluorescent detector,

the ultra-violet screened sources may be recommended as worthy

of trial in practice.

(c) The method could be used very efficiently at night and the

source be made entirely invisible to the unaided eye (probably also

to ordinary telescopic examination) if the sending station were
INVISIBLE SIGNALING 133

"camouflaged" by bright yellowish lights (carbon filament lamps

of arcs screened with "no-glare" glass) placed close to it. The

glare from such sources would obliterate the faint blue haze. It

seems probable that this procedure would be quite practicable in

certain military and naval circumstances.

Regular lighthouses along our coast might send ultra-violet

signals which could be picked up by our own ships and never be

suspected by any one not equipped with the fluorescent detector.

(d) Although we have made no trials by daylight, it would

appear that day conditions might be more favorable than night

for obtaining the desired result.

(e) The best practical signaling apparatus is apparently the

iron arc with the Corning glasses and nickel sulphate. The p-nitrosodimethylaniline is not necessary. Silver films have been tried as ultra-violet screens without practical success. The uranyl

sulphate was the most sensitive detector tried by the Bureau.

Signaling by Invisible Radiations

In connection with the development of radiometric instruments for secret signaling by means of invisible radiations (whether

ultra-violet or infra-red rays), an investigation was made of the

photo-electric properties of various substances. The object in

view was to find a substance which is expecially sensitive to infrared radiations. The results were published in Scientific Paper

No. 322.

One substance (molybdenite, MoS2) was found suitable for signaling purposes and was given a thorough investigation as to the

effects of temperature, light intensity, humidity, etc., upon its

photo-electrical sensitivity. The applications and actual tests of

the efficiency of this substance in a thermal radiodynamic signaling

device are described elsewhere in this report.

In view of the numerous inquiries received as to the applicability

of a bolometer for secret signaling, for detecting the presence

of hot objects (for example, the smokestack of a battleship) in a

fog, etc., experiments were made in increasing the efficiency of the

bolometer.

It is evident that for military purposes the auxiliary apparatus

must be robust, so that the use of a sensitive galvanometer is

precluded. Hence the bolometer was used in connection with a

telephone and an audion amplifier, simply as receiver of thermal

radiations. Thus the response of a bolometer was increased by

amplifying the electric current which would ordinarily pass
1 34 WAR WORK OF THE BUREAU OF STANDARDS

through the galvanometer by passing it through an audion amplifier. In the present experiments the receiver consisted simply of a

thin blackened strip of platinum or gold leaf and a storage battery,

which were connected to the primary circuit of a suitable transformer. The secondary winding of this transformer was con- nected to the grid circuit of a three-stage audion amplifier. A

telephone receiver was connected in the usual manner to the

amplifier.

The source of radiation was an acetylene flame. The receiver

was exposed to this flame through a rotating sectored disk having

15 openings. This combination formed a radiophone.

When a sensitive platinum-bolometer receiver was used as a

radiophone, the sound produced in the telephone was not very

audible. This is, no doubt, attributable to the great heat capacity

of the material, which made the rapid changes in resistance, and

hence in electric current, of insufficient magnitude to affect the

telephone receiver. Fig. 15 shows a field outfit for signaling of

this sort.

Using a lightly smoked strip (6 by 2.5 mm) of gold leaf, the ends

of which were clamped between thin (0.02 mm) strips of tin, the

sound produced in the telephone receiver was as loud as was

observed in a photophone made of selenium. This device was

mounted in a glass bulb which could be evacuated. As was to be

expected, there was no marked difference in the intensity of the

sound produced when operated in air and in a vacuum.

In the gold-leaf radiophone, as used, the limit of audibility was

attained for a light (radiant power) intensity of 4.8 X io"5 watts.

Using a larger receiver and amplifier and a larger current (which

was 0.2 ampere in the present tests) through the receiver, the

sensitivity could be greatly increased.

The results obtained indicated that this bolometric receiver

device forms a feasible means of secret communication by means

of infra-red rays, which can not be detected by the enemy.

From laboratory tests and from data on the energy radiation by

a powerful searchlight, it was computed that the range of communication would be 5 miles or perhaps even 15 to 20 miles, depending upon the intensity of the source of radiation and the complexity of the auxiliary receiving apparatus.

Some of the data obtained in these experiments were published

in Scientific Paper No. 319.
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 15.Field outfit used in signaling by infra-red rays

This system is the most secret of all means of conveying messages and has been developed to a

practical point. It is impossible for the enemy to detect and intercept such messages
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 16.

Machinefor testing the wearing quality of sole leather

Samples of leather are secured to the rim of the wheel, which is rotated by a small electric motor. This wheel conveys motion, through the leather samples, to a horizontal disk made of an abrasive substance. A brake retards the motion of this disk. Dust is removed by the small vacuum

blower. Thus the resistance to wear ol each of the samples is determined
INVISIBLE SIGNALING 135

Thermal-Radiophonic Devices for Secret Signaling

In secret signaling—the secret transmission of intelligence bymeans of invisible thermal radiations—radiometry attained its

greatest triumphs and its most far-reaching applications.

It is a method of signaling par excellence which, unlike electricwave signaling, can be directed, which practically can not be

detected, and which can be operated without interference.

In the sense that no methods are known for detecting its use

(unless one were in direct line of sight), it is a two-edged sword,

and it is a moot question whether or not it should be developed

further.

The submarine can be combated with depth bombs. Radiotelegraphy and telephony can be detected and interfered with,

but the device for the secret transmission of intelligence by means

of invisible thermal radiations, while still in its infancy, stands

unique as capable of being operated without disclosing its position.

Several writers (Ruhmer in Germany and Miessner in the

United States) have written books discussing secret signaling

devices. Selenium was practically the only substance which was

known at that time (191 3) to be photo-electrically sensitive and

which was discussed as a means of signaling.

The Bureau of Standards became interested in this subject

in 1 91 5, but no extensive researches were begun until early in 191 7,

when a search was made for a substance which should have a marked electric sensitivity for infra-red rays.

The unusually high photo-electric sensitivity, as well as the

quickness of response of molybdenite to infra-red rays, renders

this substance far superior to selenium as a radiophonic signaling

device.

Data have already been given on the thermal-radiation sensitivity of a radiophone in which the (nonselective) receiver consisted of a strip of gold leaf which was smoked on one side. This

receiver was connected in series with a battery and the low-voltage

side of a small transformer. The high-voltage side of the transformer was connected to the input side of a three-stage audion

amplifier of French construction. A Baldwin telephone was

used as a receiver of the audible signal. A pulsating electric cur- rent was produced by rotating a sectored disk placed in front of

the gold leaf so as to interrupt the incident radiations. The heat

capacity being small, the variation in temperature, and hence

the resistance of and current through the strip, caused by the
I36 WAR WORK OF THE BUREAU OF STANDARDS

intermittent exposure to radiation were of sufficient magnitude to

cause the telephone receiver to emit a fairly loud sound. In this

radiophone, using a gold-leaf receiver, the limit of audibility was

attained for a radiant power intensity of 4.8 X io-5 watt. The

receiver was small, and it was evident that by using a larger

receiver the sensitivity could be increased at least four times, or to a limit of 1 X io-5 watt.

Most of the present radiophonic experiments were made on

molybdenite sample No. 1, though good results were obtained

with samples Nos. 8, 9, and 12.

The radiophonic tests, using molybdenite as a receiver, differed

from those just described employing gold leaf in that no auxiliary

transformer was used. The crystal MoS2 and a battery or dry

cells, giving 40 to 60 volts, were connected directly to the input

terminals of a French three-stage amplifier. A concave silveron-glass mirror, 16 cm in diameter and of 50 cm focal length, was

used to concentrate the radiations upon the molybdenite receiver.

For a field outfit the mirror, sectored disk (operated on a 6-volt

battery), and molybdenite receiver were mounted upon a camera

tripod.

The radiation sensitivity of molybdenite sample No. 1 was compared with the gold-leaf receiver by exposing it directly to a

standard of radiation, using minimum audibility as a criterion for

making the comparison. The results showed that molybdenite

(sample No. 1) was 160 to 200 times as sensitive as the gold-leaf

radiophone.

An interesting test was made of the radiation sensitivity of the

field outfit, using the full moon as a source of radiation. A

thermopile having the same receiving surface as the molybdenite

was used in place of the latter to measure the lunar radiation in

absolute value. The molybdenite receiver was covered with

colored glasses which absorbed all the visible rays, but which had

a high transmission for infra-red rays. Using a single absorption

glass, the effect of the transmitted lunar radiations caused a

rather loud sound in the telephone. Using two absorption glasses,

the sound was still easily detected, so that signals could have been

recognized. Under these conditions the energy value of these

infra-red lunar radiations was 3 X io-7 gram-calories per second.

It is, of course, understood that the radiation sensitivity (as

determined by ordinary radiation standards) is too low, owing to

the fact that much of the incident energy is of wave lengths which

do not affect these selective receivers.
INVISIBLE SIGNALING 137

A practical test of the field outfit was made, the source of radiation being a 300-candlepower tungsten lamp in a 2 8 -cm searchlight

reflector at a distance of 3 miles. The signal stations were the

roof of the Bureau's electrical building and the clock tower of the

United States Soldiers' Home, respectively. The intervening space

was partly occupied by city houses and streets, with attendant

dust, etc. The signals transmitted by the aforementioned absorption glasses were loud and easily detected, in spite of a high wind

and other disturbances.

Using an automobile headlight consisting of a 20-candlepower

tungsten lamp in a 15-cm metal reflector, the signal through the

absorption glass was not always heard, showing that this was

about the limit of audibility. When this field outfit was sighted

upon a street lamp (tungsten filament in a clear bulb, 80 candlepower) at a distance of one-half mile, a clear audible note was

heard in the telephone when no absorption glass intervened; but

the signal was uncertain when using only infra-red rays.

It is of interest to note that, when using the sectored disk, the

molybdenite is exposed to radiation for only about -5-017 of a

second. Nevertheless, in this short interval of time, the electrical

conductivity undergoes a change sufficient to produce the effects

just described. Hence it may be useful for lecture-room demonstration. Good results may be obtained by simply joining the

molybdenite receiver in series with a telephone and a battery of

dry cells of from 40 to 80 volts. However, for a really successful

demonstration it is desirable to connect the crystal and a battery

of dry cells of 30 to 60 volts directly to the input terminals of an

amplifier. Using a rotating sectored disk before the molybdenite

receiver upon which is concentrated the light of an acetylene

flame, the telephone emits a musical note of sufficient loudness to

be audible in a remote part of the building.

The method of producing a pulsating current in the telephone

by interrupting the light which is incident upon the molybdenite

by interposing a rotating sectored wheel is inefficient in view of

the fact that (1) only one-half of the incident light is utilized and

(2) the exposure time is only about 1/500 of a second, which is

not sufficient to permit a great change in the photo-electrical

conductivity. A signaling system which can utilize longer ex- posure of the receiver to the incident light will produce a greater

change in the electrical conductivity.

When using the sectored-wheel radiophone, the signal is re- cognized by the musical note emitted by the telephone receiver.
1 38 WAR WORK OF THE BUREAU OF STANDARDS

the loudness of which is determined by the intensity of the incident radiations. The signal could be recognized also by a change

in pitch of the sound in the telephone receiver, provided apparatus

can be devised to function by changing the pitch of the sound.

This change in pitch was frequently observed in the French

amplifier used in these experiments, but it was found to be inefficient (insensitive) and not reproducible. However, such a

method is feasible. It is based upon the observation of T. W.

Case that an audion bulb can be made to transmit a pulsating

current. A change in current in the grid, or input, circuit causes a change in frequency of the pulsating current, and hence a change

in pitch of the sound produced in the telephone receiver. The

time of exposure of the signal light can be made quite long, so as to utilize the full change in conductivity of the crystal receiver.

This method of signaling seemed so attractive that an attempt

was made to obtain a test of its efficiency as compared with the

sectored-disk radiophone, using, in both devices, molybdenite for

the receiver of the thermal radiations which were used in transmitting the signal.

Being unable to obtain the requisite apparatus and working

solely upon the report that a suitably evacuated audion bulb can

be made to function so as to change the pitch of the sound emitted

by the telephone, the following apparatus was devised. An audion

amplifier bulb, consisting of a grid, plate, and heating filament,

was attached to an oil pump and evacuated to the pressure of

mercury, which was found to produce the desired result. The

wiring connection used was practically the De Forest audion connections with the grid potential positive. A resistance of 5 to 10

megohms is inserted in view of the fact that molybdenite has a

comparatively low resistance, whereas it was found that the circuit must contain a high resistance in order to cause the audion

bulb to function properly. The result of this test showed that

owing to this high resistance, which was in series with the single

receiver of molybdenite, but which did not function photo-electrically when exposed to light, the method of signaling by change

in pitch was not so sensitive as the rotating-sectored disk radiophone. Using several molybdenite receivers joined in series so

as to obtain the required high resistance when exposed to light,

the sensitivity of this device was improved. As already mentioned,

it is proposed to make artificial sensitive material.

A photo-electric cell of the gas-ionic type—for example, the

potassium hydride photo-electric cell—is well adapted for use
INVISIBLE WRITING, MEANS FOR THE DETECTION OF 1 39

with this change-in-pitch method of signaling. The high resistance

is used as ballast to the photo-electric cell. This combination was

found to be the most sensitive of the radiophonic type of receivers

yet tested. The applied voltage can be adjusted so that the telephone receiver emits a sound only when the photo-electric cell is

exposed to light.

Very instructive experiments can be performed with such a

device. For example, the rate of charge and discharge can be

adjusted so that the sound in the telephone is a series of clicks

which increase in rapidity with increase in intensity of the exciting light. It is a simple task in glass blowing to arrange two

electrodes and a heating strip (of platinum) to produce ionization.

INVISIBLE WRITING, MEANS FOR THE DETECTION OF

Early in the war it was suspected with more or less plausibility

that enemy agents were using so-called "invisible inks" in their

communications. The secret-service agents of the Government

had intercepted and held on suspicion vast quantities of corre- spondence, and the Bureau of Standards was asked for advice as

to methods of examining this for the suspected invisible inscriptions, which, if existent, could doubtless be developed and read

by suitable means. Development and supervision of chemical

tests was assumed by other agencies, and this Bureau undertook

only the matter of optical and photographic tests. Special apparatus was designed and constructed at the Bureau and used by

the offices of the Naval and Military Intelligence. The purpose

of this apparatus was to provide convenient and rapid means for

the routine examination of a great number of pieces. The methods for regular routine examination were the following: (1) Examination in intense light at grazing incidence; (2) examination of

regular reflection; (3) examination by transmitted light; (4) ex- amination in extreme violet and ultra-violet light; (5) examination by ultra-violet photography.

The first three tests mentioned above involved essentially nothing more than specific control of the direction of illumination and

the fine of sight in the examination of the paper. It is a matter

of common observation that faint marks, erasures, indentations,

etc., on a sheet of paper can be seen much better at certain angles

than at others. The apparatus for tests (1) and (2) merely provides convenient and comfortable means for the critical examination under two specific conditions, both of which greatly accentuate the appearance of irregularities in the paper surface. For
I40 WAR WORK OF THE BUREAU OF STANDARDS

test (3) the paper was laid on a ground glass illuminated from

below. No special apparatus had to be constructed, as an Edison

mimeoscope served this purpose very well.

Methods (4) and (5) are somewhat further removed from ordinary experience, and so require more explanation.

Method (4) depends upon fluorescence; that is, the property

which many substances possess of emitting light when excited by

ultra-violet rays which themselves do not cause vision.

Inscriptions made with such substances, dissolved and used as

inks, may be quite invisible in ordinary light under any kind of

illumination, but show up in bright characters on the darker

background of the paper when excited by ultra-violet rays.

Paper itself, in common with many materials, is fluorescent in

varying degree. If the ink is composed of a substance less fluorescent than the paper, or if the solvent dissolves the surface glaze,

the writing will show dark on a light background. Inscriptions

written with pure water may be detected in this manner on some

kinds of paper.

The test is performed by allowing ultra-violet rays to fall on the

paper in a dark room. The ultra-violet is obtained from a CooperHewitt glass mercury lamp screened by a glass which absorbs

nearly all of the light from this lamp, while it transmits very

freely the ultra-violet and a small amount of violet light.

Method (5) depends upon the fact that some substances may

be so nearly the color of white paper as to produce little or no

contrast when inscribed on it, while they may differ from it sufficiently in their absorption for ultra-violet as to give noticeable

contrast in an ultra-violet photograph. For this purpose ultraviolet rays of wave length considerably shorter than used in the

fluorescence test were employed. The quartz-mercury arc and

the iron arc are suitable sources for such rays. The blue and

violet light and the longer wave length ultra-violet are absorbed

by an aqueous solution of nickel sulphate and gaseous chlorine in

quartz cells. Since these rays are absorbed by glass, the lenses

used must be made of quartz, fluorite, or other material which will

transmit them.

Five illustrated technical reports on this subject were issued to

the Office of Naval Intelligence during the war. Information on

this subject was also given to the division of Military Intelligence.

An exhibit of the apparatus used was included in the American

Physical Society exhibit at the Bureau, April 25 to 26, 1919.
LEATHER 141

The methods developed are also of use generally in the critical

examination of paper and documents. Last April the Bureau was

able to decipher the name and address on a military registration

card sufficiently well to establish certain identification of the

bearer after the card had been immersed in sea water with the

dead body of the drowned registrant so long that it was quite

illegible to ordinary observation and the body itself was completely

unrecognizable.

LEATHER

The demands caused by the war resulted in a considerable

shortage of leather for certain lines of work, and for this reason

the study of methods for conserving this material and the development of possible substitutes assumed great importance. The

work of the Bureau on this subject was largely composed of routine

tests, but at the same time a number of complete investigations

were carried out.

Investigation of Sole Leathers

During the early part of 191 7 the Bureau was requested to

assist in developing a suitable specification for sole leather to be

used by the War Department, the object in view being along the

lines outlined in the above paragraph. Radically different

opinions were held by competent authorities as to just what limit

should be accepted for certain of the ingredients found in the

many brands and tannages of commercial sole leather. Honest

differences of opinion were expressed regarding the effects of added

glucose and salts on the wearing quality of the leather.

In cooperation with the National Association of Tanners and

with the War Department investigations were started in an effort

to determine the effect of these two substances on the wearing

quality of sole leather. Four typical tannages were selected for

the test, one a long-time tannage with a minimum loading of epsom

salts and glucose, one a tannage produced by drumming extract

into a half-tanned leather, one produced by loading a half-tanned

leather with glucose, and the fourth a medium-tanned leather with

a moderate amount of loading. The various leathers were placed

on shoes worn by soldiers at Camp Meade, Md., and the wear data

were obtained in terms of a day's wear per unit of thickness and per

unit of weight. Each type of leather filled with glucose and salts

was tested against two types of unfilled leather and vice versa. Each pair of shoes used in tests was soled with two types of leather,

one sole of filled and one of unfilled leather. In this manner,
142 WAR WORK OF THE BUREAU OF STANDARDS

actual wearing tests were made with 500 pairs of shoes, and during

the test the soles were inspected weekly by representatives of the

Bureau. The data obtained showed that the tannages tested were

not materially different in wearing qualities and the leathers

tanned to the belting stage and then filled gave about 8 per cent

more wear per unit of thickness, and the one stuffed with glucose

the best per unit of weight. The analysis of the worn soles

showed that almost all of the glucose had leached out of the

leather during wear. Besides the actual service tests on sole leather above outlined

a special machine was designed (Fig. 16) for determining the comparative durability of samples of different leathers.

There was found to be a wide variation in the wearing qualities

of leather from different portions of the hide. The portions over

the kidney showed the best wear, and the wear of the other parts

of the bend dropped off so that the leather from the belly edge of

the bend gave an average of 73 per cent of the wear obtained from

leather about 8 inches from the backbone edge of the bend. That

from the extreme shoulder end near the backbone edge also seemed

to be inferior in wearing quality. It is thus evident that it is very

necessary to specify from what portion of the bend soles shall be

cut if the best service is to be obtained. Complete data have been

obtained as to the relative waterproofness of the different tannages

and the leather from the different locations of the bend. These

data showed that the more open and spongy portions of the hide

absorbed more water than the more compact portions, although

there were several exceptions to this general rule. Considerable

water-soluble material was leached out during the immersion in

water, and a correction was applied accordingly. The apparent

water absorption is always considerably less than the actual absorption, because of the loss of soluble material, and the correction

must also be made when the test pieces are immersed for more than

an hour. In an immersion of not longer than an hour the amount

of material leached out does not appreciably affect the results for

water absorption, while in the 24-hour test as much as 1 1 per cent

of water-soluble material was leached out of the leather. This

result was found in the case of a leather containing about 9 per

cent of glucose. The loss in the other tannages was considerably

less, but amounted to 6 or 7 per cent, making a considerable correction, as the total absorption amounts to but 40 per cent.

The complete data obtained from the above tests have been

published as a technologic paper of the Bureau, and added details
LEATHER 143

of the work may be obtained therefrom. The success of this work

was largely due to the hearty cooperation of the National Association of Tanners, the American Leather Research Laboratory,

and the military authorities at Camp Meade, Md.

Another test showed that a leather tanned to the belting stage

and containing 8 per cent of grease will outwear the same leather

fully tanned and containing less grease. This test was made on

double backs, one side of each back being taken out of the layers at

90 days and finished with a heavy oiling, while the other was left

in the layers for 70 days more and finished with the regular oiling

with about 2 per cent grease. This method of test eliminates any

difference in the quality of the hides and makes a given amount of

the data more reliable than where different hides are used. The

full tanned leather contained an average of 23.7 per cent watersoluble material and 1.9 per cent grease, Avhile the light tanned

leather contained only 13.9 per cent water-soluble material and

9.1 per cent grease.

Composition Soles

As mentioned previously, at the time the United States entered

the war the European countries had already used a vast quantity

of leather for military purposes; therefore it was apparent that

the greatly increased consumption which would be brought about

through the participation of the United States in the conflict

would result in an acute shortage of leather within a comparative

short time. Realizing this possibility, the Council of National

Defense requested the Bureau to compare the serviceability and

wear of various kinds of composition and leather soles, with a view

to the possible use of the former material instead of leather, should

this become necessary. Many wearing tests were conducted by

supplying soldiers at Camp Meade with pairs of shoes, one soled

with composition and the other with ordinary leather. The results

of these tests showed that there was little difference in actual wear

among the composition soles, and that so far as wearing quality

was concerned, the composition compared favorably with highgrade leather, but that the composition was not so serviceable

as the leather and that wearing out at the toes, pulling out of the

stitches, and cracking were common causes of failure of the

composition soles.

Other experiments were made to determine* the possibility of

using half-soles of composition material instead of leather in repair

work. It was shown that composition half-soles could be either
144 WAR WORK OF THE BUREAU OF STANDARDS

sewed or nailed to the shoes and that they would wear as well as

leather, but as in the case of whole soles they would not be as

serviceable, owing to the fact that they often became loose.

Investigation of Strap and Harness Leathers

Investigations along similar lines were conducted with strap and

harness leathers, though in this case actual wear tests were impossible on account of the long life of the materials under the ordinary

conditions of use. The preliminary investigations covered merely

the immediate effect of different amounts and types of stuffing on

the tensile strength of the leather. The data were insufficient to

warrant any broad conclusions, as long-time effects should always

be the criterion of value. As far as the immediate effect is concerned, the data show that the addition of stuffing to degreased

leathers produces an increase in tensile strength as high as 20 per

cent, and this increase depends more upon the viscosity of the

stuffing mixture than upon the chemical nature of the constituents.

This was strikingly illustrated by the fact that the two stuffings

causing the highest increase in tensile strength were entirely different in nature, one being a mixture of petrolatum and paraffin,

while the other was composed of wool grease, tallow, and cod oil.

Their viscosities at room temperature were approximately the

same. The addition of stuffing to leathers already containing

some grease did not produce any appreciable increase in tensile

strength when there was over 14 per cent of grease in the original.

The amount of grease necessary to give maximum tensile strength

varies with the leather and the nature of the stuffing used. Some

tannages containing a small amount of stuffing (5 per cent) were

strengthened by the addition of more stuffing, while others containing similar amounts were but slightly benefited by the addition

of grease.

Chrome Retan and Bark Tanned Upper Leathers

A difference of opinion developed between our overseas and

home departments regarding the proper upper leather to be used

in Army shoes. The experts in this country were of the opinion

that chrome-retan leather was more suitable, while the overseas supply office favored the use of bark-tanned leather. The Bureau

was requested by the Hide and Leather Control Board and the

shoe committee of the War Department to investigate the relative durability and waterproofness of these leathers in actual

service. Accordingly, several pairs of shoes were made, one shoe

having bark-tanned and the other chrome-retanned upper leather.
LEATHER 145

These shoes were placed on workmen whose duties alternately

subjected the shoes to service under wet and dry conditions. The

chrome-retanned remained more pliable, soft, and also more

resistant to moisture. The results were reported to the War

Department, which afterwards sent a special representative to

Europe to investigate this problem. The result was that the

chrome-retan leather was adopted as being more suitable.

The relative resistance of these two types of leathers to fermentation caused by mixtures of animal products was likewise investigated. This work was carried out in order to determine the relative fitness of the two types of leather for use in the trenches.

The data indicated that the chrome-retan leather was much more

resistant than the straight vegetable-tanned leather. The difference was greatest where the leathers were lightly stuffed, allowing

the samples to be acted upon more strongly by the mixtures in

which they were immersed. As considerable stuffing was removed

from the leather by saponification, the use of unsaponifiable grease

was recommended.

Transmission Belting

At the request of the standardization committee of the General

Staff, the strength, amount of horsepower transmitted, water

absorption, and resistivity to heat and stretch were determined

for several types of belting made from rubber, leather, cotton,

balata, and hair. The results were used in selecting the most

suitable belting for field use.

Leather Packing for Recoil Cylinders

A leather capable of withstanding a high degree of heat is needed

for packing in the recoil cylinders of large guns. A number of

tests were made to determine the heat resistance of different

leathers as affected by the character of the stuffing mixture. The

most desirable sample proved to be chrome-tanned, and it appeared that the most resistant leather was the one having the highest degree of chroming. The test consisted of heating in oil at

2 2

C for a maximum period of two hours, though it is very

doubtful if so high a temperature is ever attained in the cylinder.

Various stuffing mixtures were tried for their effect on the leathers

at this temperature. Samples stuffed with wool grease and petrolatum showed somewhat better resistance than pieces stuffed with

other mixtures, but the difference in heat resistance was small

compared with the differences observed between the various

types of leather.

26035°—21 10
146 WAR WORK OF THE BUREAU OE STANDARDS

Waterproofing Materials for Use on Army Shoes

As a result of investigation on this subject it would appear that

the waterproofing effect of a stuffing is approximately proportional

to the amount of stuffing present up to a point where the pores of

the leather are completely filled. Any water-soluble materials

that can be introduced into the pores of the leather will increase

its resistance to water, but there are many other things to take

into consideration. About 40 per cent of grease will fill the pores

of the cowhide upper leather used on field and trench soles, but

the stuffing must have a rather high viscosity or it will be worked

out of the leather and will require frequent replacement. The

ideal stuffing should possess the following characteristics:

1. Not detrimental to the leather.

(a) Free from detrimental impurities, such as acid.

(b) Chemically inactive itself.

(c) Not easily decomposed.

2. Should remain in the leather.

(a) Nonvolatile.

(b) High viscosity.

(c) Not easily emulsified.

3. Insoluble in water.

4. Not stiffen the leather unduly, and make it more flexible if possible.

5. Not dry out hard or separate into its constituents on standing.

On account of the large variety of materials which will conform

to requirement No. 1 , there is an almost unlimited number of possible mixtures which should prove satisfactory. A number of

these have been approved by the Bureau and several more have

been suggested for use. Shoe Cements

A satisfactory method developed at the Bureau for testing ce- ments used in shoe manufacture is to stick two pieces of leather

together with the cement to be tested and then to note the pounds

pull required to separate the joints thus obtained. Although this

was a comparative test, the results obtained check with what were

considered commercially as the best materials, and thus aided the

War Department in their purchases.

Shoe Laces

A comparative test of shoe laces was developed. It consisted

merely of comparing standard Army laces and any new ones presented for adoption. The standard laces were of fabric construction with metal tips. Laces with cellulose tips and impregnated

fabric were tested, but were found to be inferior to the standard

lace. In conjunction with laboratory tests, actual service tests
LEATHER 147

were made on soldiers' shoes which gave conclusive results as to

the best wearing lace.

Rubber Heels

A comparative test was made between leather heels with heel

plates attached and rubber heels with metal plates vulcanized into

them. The latter proved unsatisfactory and would not stand the

rough wear, the heel plate gradually becoming loose and finally

coming off.

Specifications and Routine Tests

At the request of the Signal Corps of the Army, specifications

were prepared for the leather used in the construction of aviators'

safety belts.

Representatives of the Bureau assisted the Committee on

Leather and Leather Goods in developing standard specifications

for all classes of leather. Many physical and chemical tests were

conducted for the information of this committee. The Bureau

offered the facilities of its laboratories for the testing of all lots

of equipment leather purchased. Tests were made for the inspection division of the Ordnance Department of the Army to determine

whether the samples submitted conformed to the standard set by

the War Department. The work served to check the quality of

the materials being delivered to the Government. The data obtained were of value to the Government, as they showed what

variation could be expected in a single type of leather and how

closely a leather could be expected to conform to specifications.

They likewise helped the tanner to control his product and showed

him where he was not getting the results desired. One hundred

thousand dollars may be estimated as the amount saved the Government through this work. The Bureau examined a total of

2 355 samples of leather and related materials, such as stuffing or waterproofing compounds, which consisted of a great variety of

oils, greases, tars, rosins, and insoluble soaps. Waterproofing

compounds were tested for their effect upon the leather and for

their efficiency for the purpose desired. The routine test work

may be tabulated as follows

Number of samples

examined

Tests requested by

Leather Other

materials

War Industries Board Ordnance Department, U. S. Army

Quartermaster Corps, XJ. S. Army.

47

1390

900 6

12
148 WAR WORK OF THE BUREAU OF STANDARDS

The materials examined for the War Industries Board consisted

of sole leather and shoes, while the work done for the Ordnance

department was largely on harness, strap, back, and other equipment leather, as well as a few analyses of the stuffing materials

used by the tanners supplying leather for the above purposes.

For the Quartermaster Corps routine tests were made on harness

leather and on upper stock, waterproofing, stuffing for Army

shoes, leather soles, composition soles, laces, shoes, and rubber

heels. Representatives of the Bureau were constantly in conference with officials of the Hide and Leather Control Board, the

Shoe Committee and Supply Section of the Quartermaster Corps,

the Committee on the Standardization of Leather and Leather

Goods, the inspection division of the Ordnance Department of the

Army, and the War Industries Board concerning the quality and

testing of various leathers.

MAGNETIC INVESTIGATIONS

Magnetic Compasses

The Bureau cooperated with the Signal Corps and later with the

inspection division of the Bureau of Aircraft Production in the

development of testing methods for inspectors at the factories.

These methods were established in the light of a preliminary

investigation and test of 60 compasses submitted by the Signal

Corps. Later, changes in the design of the instruments made

necessary certain modifications of test methods and apparatus.

The tests for performance included determinations of period,

damping, magnetic moment, axis error, eccentricity, pivot friction,

and effect of tilt. Specifications were prepared for apparatus

suitable for the determination of these quantities and a set

constructed.

The cooperation with the inspection division was continued by

testing a certain small number of instruments selected by

inspectors at the factory and sent to the Bureau for test. The Bureau cooperated with the science and research and the

engineering divisions of the Bureau of Aircraft Production in

the development of instruments for American production by

investigations covering certain specific points in the construction

of the compasses. These points included the suitability of kero- sene for use as a damping liquid, the possible strength of magnets

obtainable with commercially available steel, the aging of magnets,

and a suitable test for aging. The results of these investigations
MAGNETIC INVESTIGATIONS 149

were reported to the military authorities and utilized by them in

the preparation of final designs and specifications. During the

earlier stages of the work the facilities of the laboratory were

made use of by members of the science and research division

under the direction of officers of that organization. This work

was later continued in other quarters furnished by the Bureau.

In addition to the work on the construction and testing of

airplane compasses the Bureau gathered information and data

on their compensation and behavior under service conditions.

This was done by means of personal conferences with various

pilots and other officers in the Air Sendee, by experimental flights,

from official reports from various sources, and by laboratory

experiments. The points covered had to do mainly with the

so-called northerly turning error, the effect of liquid drag, vibration, etc. The information thus gained has been furnished to

authorized parties by correspondence and conferences. A small

collection of various types of instruments has been made which

have been very useful for purposes of test and comparison.

The Bureau has cooperated with the engineering division of the

Ordnance Department of the Army in the development of a

lensatic compass for use as a marching compass and for artillery

and machine-gun fire control. A sample compass of British

manufacture was examined, and, as it had proved satisfactory

in service, it was decided to use it as the basis of a design adapted

to American manufacturing methods. Tests were made of the

various performance characteristics, and a set of performance

specifications were drawn up which were accepted by the Ordnance

Department. Some problems which arose in the course of the

manufacturing development were referred to the Bureau for

solution. These points included the hardening and magnetizing

of the magnetic needles, a satisfactory shop method for testing

the strength of the needles, and the substitution of stellite for

iridium in the construction of the pivots. These points were all

satisfactorily settled and a good compass was produced. In

addition to the development of the compass a test was made to

determine the effect of the proximity of a machine gun on the

indications of the compass.

Magnetic Analysis of Rifle-Barrel Steel

The investigation of rifle-barrel steel was undertaken in response

to the request of the Ordnance Department of the Army. Due

to unusual conditions of production as a result of the war the raw
150 WAR WORK OF THE BUREAU OF STANDARDS

stock for rifle barrels was found to contain a relatively large percentage of faulty material. The faults, in general, consisted of

pipes or slag inclusions located at the center of the cross section

of the bars. These faults were usually short, rarely extending

more than 8 or 10 inches, and generally could not be detected

until the barrel reached the drilling shop. The effect of these

faults was to destroy the cutting edge of the drill, and thus make

drilling of the faulty material impossible, sometimes even breaking

the drill. The usual method of inspection consisted of selecting

samples at random from a shipment of steel and making up from

these samples a number of barrels. If more than a certain percentage of these barrels failed to drill properly, the whole shipment

of steel was rejected. If it happened that the shipment was

accepted as a result of these drilling tests, it was quite often found

that a large number of barrels would get as far as the drilling shop

and then be found to contain faults and this material was scrapped.

It was thought that magnetic analysis offered promise as a nondestructive method of test by which portions of the material

containing faults could be located and rejected before further

work had been done. This would make possible not only the

rejection of faulty material, but the acceptance of all the bars in

a given shipment which were satisfactory, and thus effect a great

saving of material and labor.

This investigation was carried out with the very hearty cooperation of the Winchester Repeating Arms Co., at whose plant final

tests were made. The apparatus was designed, constructed, and

tried out at the Bureau and then taken to the Winchester plant

for final trial. The apparatus is constructed as follows: The

bar under test is encircled by a magnetizing coil, which also carries

what are known as test coils. The return magnetic circuit is

composed of triangular cast-iron end plates and three iron pipes,

which also constitute the frame of the apparatus. The test coils are connected to a recording apparatus, the operation of which is

based upon the theory that if the bar is uniform mechanically

along its length, it must also be magnetically homogeneous. If

the bar is uniform magnetically along its length, the magnetic

permeability at each point is constant for a given magnetizing

force. In the test the magnetizing coil is energized by a constant

direct current, thereby producing a constant magnetizing force

at its center, and moved along the bar by means of a motor and

cords at uniform speed. If the bar is magnetically uniform along
MANILA ROPE

its length, the test coil will have induced in it no electromotive

force, since the magnetic flux which it encircles will remain constant, while any variation from uniformity will be evidenced

by a corresponding variation in the permeability. The flux will

then vary at this point and an electromotive force will be induced

in the coil which will be indicated by the recorder. Permanent

records of these variations are made photographically. If instead

of using a single test coil in the manner just described, two test

coils are used, connected in series opposition, the record shows the

variation of magnetic leakage along the bar instead of the variation of flux. The leakage is the rate of change of flux along the

bar and is "equal to zero if the bar is uniform.

Before taking the apparatus to New Haven it was set up in the

laboratory and the effects of various types of flaws which were

produced in various ways, such as by drilling holes, bending, and

adding material of higher magnetic permeability, were studied.

The apparatus was then set up at the Winchester plant in New

Haven, Conn., and a large quantity of steel was tested. Practically no faulty material was found up to the time of the signing

of the armistice, but some time later a lot of steel which showed

magnetic nonuniformity failed to drill properly.

MANILA ROPE

No very pronounced demand for standardization among the

specifications of the different Government departments for various

materials had existed prior to the war. Large as the orders for

such materials had been in normal times, the necessity for complete standardization was not very evident. When, however, as a result of the war many Government bureaus were buying goods

of about the same kind at the same time, it soon became necessary

to have some sort of standard specifications ; otherwise many complications were bound to arise in ordering the same general class

of goods for the different departments. As a matter of fact, in

the early part of the war, such complications did arise and caused a

great deal of confusion and loss. Even more serious than this

situation was the necessity for the purchasing of large quantities of

goods without adequate specifications of any sort. One of the

items ordered in vast quantity by the Government, and which

illustrates this last point, was manila rope. The situation in

regard to the purchasing of this material in 191 7 was an extremely

serious one.
152 WAR WORK OF THE BUREAU Of STANDARDS

During that year, at the request of the Bureau of Construction

and Repair of the Navy, a conference was called at which nearly

all the reputable rope manufacturers and representatives of the

Government bureaus were present. The object of the conference

was to draft suitable standard specifications for manila rope, so that all the Government bureaus buying this material might be

reasonably sure of what would be supplied to fill their orders.

Prior to this time one of the common methods of specifying the

requisite quality of rope was to state that it must be equal to the

product of some reputable manufacturer. It is obvious that

purchasing on such a basis is bound to result in dissatisfaction.

No mention was ordinarily made of other elements of equality

than tensile strength, and the requirements for strength of the

various size ropes were as numerous as the bureaus using the

material. The Bureau of Standards, which was represented at

the before-mentioned conference, attempted to codify Government procedure in conformity with the manufacturers' standards,

and as a result formulated the first draft of a set of rigorous specifications covering manila rope. This first draft was carefully

considered, modified, and revised by the joint conference, with the

result that the Government departments and the general public

were provided for the first time with a comprehensive specification

for good commercial quality manila rope. All important points

are covered by these specifications, including the permissible

grades of fiber, certified by the Government inspectors in accordance with designations of the Bureau of Agriculture of the Philippines (see the General Order of this Bureau No. 54, Nov. 15, 191 7),

maximum weight and minimum breaking strength requirements

for various (circumference) sizes, permissible variations in circumference from rated sizes, the minimum and maximum allowable quantity of lubricant, the permissible tare weight in shipment,

size of coils, and character of labeling of the shipment. In

addition, the specifications give clear, concise methods for making

inspection and tests and directions for imposing penalties or

rejecting unsatisfactory rope.

The formulation of these specifications involved a great deal

of work, since it necessitated the obtaining of both laboratory

data and authoritative general information on manila and other

fibers in the raw state and in the fabricated condition. The test

for the detection of nonmanila fiber is in part a new chemical

development used for the first time in connection with these

specifications. It is a process which is quantitatively accurate.
MEDICAL SUPPLIES 153

MEDICAL SUPPLIES

Dental Amalgams

The increased demand for dental amalgams to be used in the

Army, together with the question of quality of material submitted, resulted in the Bureau's being requested to make tests on

the physical properties of a number of alloys.

The alloys supplied for making amalgams are usually composed

of silver, tin, copper, and zinc in a ratio approximating 67:27:5:1.

Variations of 25 to 30 per cent or the entire elimination of some

one or more of the above metals is not uncommon. These alloy

filings or shavings when mixed with an approximately equal weight

of mercury will crystallize and form a mass of indefinite stability,

depending upon the numerous conditions of composition, manufacture, and manipulation.

The resulting amalgam is sometimes slow in crystallizing and

may never become rigid enough to withstand the stresses of

mastication or to maintain proper contact forms with adjacent

teeth. Some amalgams will expand markedly during the crystallization period, whereas others will contract excessively, either of

which destroys the form and adaptation of the restoration. This

change in form on the part of the amalgam causes seepage cavities

to appear at the enamel-amalgam margin and is quite sure to

result in the discoloration of the tooth tubuli, this discoloration

being a good evidence of recurrent decay. Claims of disturbing

electromotive forces are made against certain ratios of the elements as combined in the alloy. Further claims are based on the

methods of cutting and annealing. With these conditions fully

in mind, the Bureau undertook a systematic investigation of the

field.

Dental literature is prolific in articles on the subject, and practically all of the manufacturers maintain testing staffs. (The latter

proved very helpful to the Bureau during the progress of the

work.)

The lack of concordant data on the subject, together with the

absence of details of tests or instruments used in making these

tests, made it necessary to repeat practically all previous work and

to select instruments of greater precision, such that there could be

no question about the results obtained.

After selecting and calibrating the instruments, tests were made

on all alloys submitted under competitive bid to the Surgeon

General. A few additional commercial advertised alloys and many

special alloys were included. These tests included chemical
154 WAR WORK OF THE BUREAU OF STANDARDS

composition, chemical or crystallization changes (dimensional),

crushing strength, tendency to flow under pressure, electromotive-force values, heat treatment of alloy, thermal expansion

of amalgam and tooth materials, and other similar properties.

The results were submitted to the Surgeon General and awards

were made on the basis of this Bureau's findings.

The details of this work, too lengthy to be included in this

article, are given in Technologic Paper of the Bureau of Standards No. 157.

Briefly, it may be stated that no alloy has been found which

could be considered as absolutely perfect, and that in many cases the specific claims made for alloys were found to be quite the opposite to those revealed in the tests. Probably the most significant discovery is the large value of thermal expansion of amalgams

(about 25 millionths per degree centigrade) as compared to the

much smaller value for tooth substance (about 8 millionths per

degree centigrade)

.

Druggists' Rubber Supplies

A short description of the work in this field will be found in the

article on "Rubber."

Dilution Pipettes

The Field Medical Supply Depot at Washington submitted a

large number of dilution pipettes, which were examined and tested

for accuracy. The apparatus received in the early shipments

had a much higher percentage of rejections than that submitted

at a later period. These pipettes were used in making up the

proper solution for making the blood count in the hemacytometer

outfit. Various manufacturers sold pipettes to the Field Medical

Supply Depot, and a large variation in the percentage of rejections

was found, according to the party making the apparatus. About

the time the armistice was signed a special lot of pipettes was submitted for test, and the percentage rejected exceeded any that

had been tested previously. The Bureau requested that some

other pipettes from the same manufacturer be submitted for test,

and these were found to have errors of the same magnitude. As

a result, an order for 3000 of these pipettes was canceled by the

Field Medical Supply Depot, thus preventing the medical service

from being furnished with inferior apparatus.

METALLURGICAL INVESTIGATIONS

Aluminum

One of the most important investigations taken up because of

its military necessity and urgency was that of the technical phases
METALLURGICAL, INVESTIGATIONS 155

of the manufacture and properties of the light alloys of aluminum,

both wrought and cast. Such alloys are of particular importance

in connection with the design and construction of aircraft, since

their lightness and strength well fit them for such service.

In order that the work of the Bureau might constantly best

serve the needs of the military departments, close contact has at

all times been maintained with them, both through the Light Alloys Committee of the National Advisory Committee for Aeronautics, by personal conferences, and through confidential

reports.

One of the interesting results of this work has been the demonstration of the necessity for thorough investigation of fundamental facts and phenomena as the only satisfactory basis for

technical progress in the art of manufacture. Thus at the outset

}he interpretation of test results was rendered extremely difficult

by an almost total ignorance on the part of present-day metallurgists of some of the most fundamental physicochemical data on

aluminum and its alloys. As the technical phases of the work

have proceeded, it has been necessary to give increasing attention

to its theoretical aspects, such as the problems connected with

constitution, until now it appears that further progress depends

upon the solution of several of these fundamental questions.

The investigational work has been carried out along several

different lines, among them being the following

An investigation of aluminum-rich alloys of three ternary alloy

systems has been conducted with the object of developing better

commercial rolling alloys for use in structural construction. A

survey was made of the mechanical properties of the rolled aluminum-rich alloys of magnesium with copper, nickel, and manganese. From 8 to 1 2 compositions of each system were cast and

rolled into sheet at the New Kensington plant of the Aluminum

Co. of America, a representative of the Bureau directing both the

preparation and subsequent testing of the samples. The copper

series proved so superior in respect to mechanical properties in

these tests that the other two series have been practically eliminated from further consideration for purposes for which high

strength is desired. Likewise it is the only series particularly

adapted to heat treatment. The results of this investigation are described in Technologic Paper No. 132.

Heat treatment of the alloy known commercially as "Duralumin" has been practiced for several years, but apparently little

improvement has been made in the actual heat-treatment practice
1 56 WAR WORK OF THE BUREAU OF STANDARDS

since the initial discovery of this property of the alloy by Wilm.

The Bureau's investigation of this question has led to some very

interesting discoveries bearing on the theory of the effect of this

treatment. Important alterations in existing practice of commercial heat treatment have been brought about, resulting in

improved physical properties and reduced wastage from cracking

during treatment. These alterations have been adopted commercially, and the results of this work are being published in

Scientific Paper No. 347.

Researches of a military character at the Bureau showed the

existence of remarkable properties in the metal and its alloys

when aluminum purer than that commercially supplied was employed. Accordingly, special apparatus was devised and materials assembled at the Bureau for carrying on an investigation of

this subject. The apparatus used for the electrolytic production

of aluminum consists of a steel crucible having a pure Acheson

graphite liner for holding the electrolyte and a gas furnace for

keeping the contents of the crucible molten. A movable Acheson

graphite rod, set axially in the crucible, serves as the anode, and

the crucible is arranged so that the aluminum can be tapped off as desired.

Tests have been made of different casting alloy compositions

from the Bureau's foundry (1) to discover alloys which will give

better mechanical properties than those in use at present, (2) to

study the effect of heat treatment on these alloys, (3) to ascertain

the effect of the impurities, iron and silicon, on the properties of

the alloys in the cast form, and (4) to study the effect of melting

and casting temperatures on those properties. The results indicate the possibility of obtaining alloys which are both harder and

at the same time more ductile, hence tougher, than those in use

to-day. This is accomplished both by the choice of a more suitable composition and the application of heat treatment.

The necessity for clearing up a number of questions relating

to the structure and constitution of aluminum and its light alloys

has become increasingly apparent. The fact that further progress

in the art of the manufacture of the alloys depends upon the cor- rect solution of fundamental problems is now well understood and

has led to the undertaking of the determination of (1) the structural identity of the constituents of the alloys of aluminum with

iron, silicon, copper, magnesium, manganese, and nickel, and (2)

the solubility at different temperatures of these constituents in

aluminum in solid solution. These results, together with the
METALLURGICAL INVESTIGATIONS 157

data of previous investigators, practically complete our knowledge

of the constitution of the aluminum-rich alloys of these metals,

and will serve to direct further work in the choice and development of commercial alloys.

The work to date has shown the superiority in strength of both

casting and rolling alloys containing either zinc-copper or magnesium-copper as an addition to aluminum. Since, when this

investigation was undertaken, the National Physical Laboratory

was studying the zinc-copper combination as applied to rolling

alloys, the Bureau's efforts were directed to the improvement of

the Duralumin type of alloy, either by slight alteration of composition or by alteration of heat treatment.

The study of entirely new rolling alloy compositions is considered unnecessary for the present. The results of the above investigation are included in Scientific Paper No. 337.

Another problem that will be undertaken is the possibility of

spot welding duralumin. At present beams and other structural

members of duralumin for aircraft construction are assembled by

riveting. It would be desirable to expedite the production of

such members by spot welding of the component parts, if this

process could be shown to produce reliable joints.

In addition to the work above outlined the behavior of duralumin and commercial light aluminum casting alloys, of great

importance in aircraft construction, received some attention.

One of the problems in which the National Advisory Committee

for Aeronautics and also the Navy Department were greatly interested was the effect of corrosion, particularly under sea-water

conditions, on aluminum alloys such as those used in airplane

manufacture. A systematic program of experiments and exposure tests was started and is still under way. A number of the

alloys covered with various protective coatings, together with

unprotected sheets, are being exposed to the action of the atmosphere and sea water at three widely differing latitudes to determine

the best alloy and coating to be used in seaplane construction.

The Morris engineering process for the liquid forging of light

aluminum alloys was investigated in cooperation with the Naval

Gun Factory, Washington, D. C. This process gives a highly

satisfactory alloy for aeronautic purposes and one which is greatly

superior to cast or die-cast metal, being of increased strength and

ductility and free from blowholes and other inperfections.

The Bureau of Aircraft Production was very much interested

in the problem of the corrosion of aluminum carbureters. Its
1 58 WAR WORK OF THE BUREAU OF STANDARDS

importance lies in the fact that particles of sludge resulting from

the corrosion which takes place in the float chambers of aluminum

carbureters are apt to lodge in the nozzles, thus stopping the flow

of gasoline. The relation of the composition of cast aluminum to

corrosion is being studied, and various protective coatings are being investigated.

For the information of the military departments there were prepared the following circulars: No. 76, "Aluminum and Its Light

Alloys"; No. 78, "Solders for Aluminum"; "Circular Letter on

Proprietary Aluminum Alloys."

Research in Connection with the Welding of Steel

Several national bodies have been interested in furthering our

knowledge of means for improving welding methods, and in this

connection the Bureau has worked in cooperation with the electricwelding committee of the American Welding Association. The

metallurgical division has been concerned with such questions as the outlining of specifications for metallographic examination

and with the experimental study of the relations of structure to

brittleness in welds. This work is being carried out both on material of American manufacture and material furnished by the British Admiralty. The resistance to corrosion of different types of

welds, including their solubility in acids, has also been investigated.

It appears that a welded joint of the usual type will corrode no

faster than a riveted one. It is planned to include in this investigation a study of the effects of the presence of gases entrained in

welds; the identification and role of certain constituents considered harmful, such as the nitrides of iron, and the development of

nondestructive tests for welds. Incidentally, a considerable

number of welds of various types have been prepared for physical

tests.

Copper Crusher Gages

At the request of the Society of Manufacturers of Small Arms

and of the Ordnance Department, the Bureau prepared specifications for copper crusher gages for testing ammunition and aided

in standardizing the methods of use. A considerable amount of

experimental work was also carried out on the characteristics of

copper crusher cylinders, particularly as related to their properties under various conditions of annealing and as dependent upon

precompression, and included a study of the resulting errors. A

publication on this subject is in press.
METALLURGICAL INVESTIGATIONS 159

Machine-Gun Erosion

At the request of and in cooperation with the Ordnance Department of the Army, a systematic study was undertaken of the

problem of gun erosion from the metallurgical point of view, and

particularly as applied to the design, material, and operation of

machine guns. A series of special steels was made up into gun

barrels and subjected to various physical and ballistic tests. The details of the erosion phenomena have also been investigated along several new lines of attack.

Identification Tags for the Navy and Army

Early in 1917 an investigation was commenced at the request of

the Bureau of Identification, Navy Department, to determine the

types of metal suitable for individual identification tags. As a

result of this work monel metal was recommended for this purpose,

and a method was also devised of obtaining a permanent fingerprint record on monel metal. The Navy Department adopted

the Bureau's recommendations and similar action was later taken

by the Army.

Tests of New Alloys

As a result of the war a number of new alloys, or modifications

and processes with new names, were brought out. Some of these

have been submitted for examination, usually with a view to

their military utility. Among them may be mentioned : " Liberty

metal," palau, rhotanium, various aluminum solders, acerial,

magnalium, magnalite, McAdamite, cooperite, al-calcium, magnolia metal, ulco-bearing metal, various metal coating processes,

the alloys dirigo, bario, cosmic, zelco, stellite, tinol, aterite, sperlite, Silliman bronze, etc.

Gold-Palladium Alloys as Substitutes for Platinum

The high cost and scarcity of platinum greatly stimulated,

especially during the war, the production of "platinum substitutes "

for various purposes. Of those intended for use as chemicallaboratory ware no alloy of base metal so far tested has been

found suitable. Two alloys of gold and palladium have been

placed on the market and have come into more or less general use. These are known as "palau" and "rhotanium."

A series of tests has been carried out to determine the suitability

of these alloys as substitutes for platinum in laboratory ware. The behavior of crucibles made from the above alloys on heating

to uoo°and i2oo°C in an oxidizing atmosphere was determined,
l6o WAR WORK OF THE BUREAU OF STANDARDS

and the effect of the various chemical reagents was studied. The

results indicated that in many instances these alloys could replace

platinum very satisfactorily, thus releasing a large quantity of this

metal for other purposes. A preliminary article on this subject

appeared in the Journal of Industrial and Chemical Engineering

(II, p. 570; 1919).

Nickel Spark-Plug Electrodes

A study of the deterioration of the nickel terminals of a certain

make of spark plugs used in internal-combustion engines was

made at the request of the manufacturer, and was later extended

to include other types of plugs. The brittleness which results in

the electrodes upon usage was shown to be a characteristic property

of nickel wire and must be expected to occur to some extent in all

types of plugs. Deterioration is much more rapid in some types

than in others, due to the stresses to which the wires are subjected

while hot. These stresses, in turn, depend upon the arrangement

and shape of the electrodes. The results of the study are given in

Technologic Paper No. 143.

Cements for Spark-Plug Electrodes

The use of cements for welding electrodes to spark-plug porcelains has been found to be attended by various difficulties in hightemperature engines such as are used in airplanes. Among these

difficulties are the promotion of oxidation and destruction of

electrode wires by reactions taking place in the cements and

between the cement and electrode wires; the breaking of porcelain caused by difference in coefficients of thermal expansion of

electrode wires and porcelain; and the cracking of cement with

consequent gas leakage, due to the same cause. A cement composed of silicate of soda and raw kaolin has been found to give

little trouble from chemical action. In order to avoid the difficulties attending the use of any form of cement, the employment

of a mechanical seal at the top of the porcelain has been tried with

promising results.

Conservation of Manganese

Two lines of research which were initiated during the war with a

view to economizing in the use of manganese in steel manufacture

are still being carried on. These investigations include: (1) The

making of a series of alloys of iron, carbon, and manganese, using

pure materials, and the testing of alloys for physical properties in the

heat-treated and annealed condition, with the object of revising
METALLURGICAL INVESTIGATIONS 161

the specifications for certain steels whereby their residual manganese content can be much decreased, and (2) an investigation

in cooperation with the National Research Council and others

whereby substitute deoxidizers, such as various combinations of

the deoxidizing elements of silicon, aluminum, titanium, and manganese, will be tried for making steel. The steel so made will be

rolled and forged in the Bureau's plant and then tested for physical

and other properties. A small open-hearth furnace of 500 pounds

capacity was designed and built for this purpose.

Oil Proofing Concrete Liners

At the request of the Emergency Fleet Corporation, work was

undertaken to find a means for rendering concrete ships impervious

to light mineral oils. The methods suggested were to cover that

portion of the interior of the hull in which the oil is carried with

lead sheets, cast lead, sprayed lead, shellac, neat cement shot from

a gun, barium sulphate, or sodium silicate. Experimental investigations, started on what seemed to be promising lines, were eventually discontinued as impracticable, due either to porosity or

excessive weight of the covering material.

Tin Conservation

All the tin used in the United States is imported, and during

the war a shortage of this material appeared very probable. The

Bureau, in cooperation with the War Industries Board, held numerous conferences and carried on extended correspondence with manufacturers and consumers of articles containing tin, as a result of

which a program was drawn up limiting its use and encouraging

the development of substitutes. The experimental work has

included the finding of suitable solders, the reduction of tin in

bearing metals, modifying bronzes with respect to tin contents,

and recovering tin scrap. Suggestions to the Government departments concerning modification of specifications with the object of

conserving tin were likewise made.

Cadmium Solders

From this investigation it was found that cadmium solders of

the four compositions shown in the accompanying table may be

Metals I n m rv

Pb 90

10

80

1010

85

10

5

7510

15

Cd

Sn

26035°—21 11
1 62 WAR WORK OF THE BUREAU OF STANDARDS

used to solder tin plate, terneplate, brass, and copper as successfully as the ordinary tin-lead soft solders. The manufacture and

use of the 90-10 mixture is rather difficult, due to the extreme

ease with which it oxidizes in the molten condition. The preferred

composition is 80 per cent Pb, 10 per cent Cd, and 10 per cent Sn,

and it has been tried out with success on roofing materials and tin

cans, while tests on fire extinguishers and automobile radiators are now in progress. A patent dedicated to the public was taken

out on this solder.

Bearing Metals

Service tests of different compositions of bearing metals, especially those not containing tin, were made to determine the adaptability of certain lead-base babbitts hardened with alkali or alkaliearth metals. It was found that in some respects they were superior to genuine babbitt, and their use is being recommended in

certain cases. The information assembled on this topic ana the results of these

few tests which have been made on special bearing metals indicate

a need for a systematization of our ideas concerning bearing metals

in general and the advantages and disadvantages of different types,

as well as of more extended study of the behavior of different compositions of both babbitts and bronzes in service. A circular is

in preparation dealing with bearing metals, and Technologic Paper

No. 109 gives an account of the work of the Bureau on conservation of tin in bearing metals, bronzes, and solders.

Metals for Aeronautical Instruments

A study was made of the composition and thermal treatment of

metals suitable for certain aeronautical instruments, such as

recording barometers, altimeters, etc., with the object of diminishing the elastic after effects which are usually so troublesome.

In this connection the behavior of cold-worked nickel-brass,

which is used largely for the diaphragms of these instruments,

was examined. In the cold-worked sheets the "work lines" to

which the hardness is due are very pronounced. Upon annealing

these "work lines" are gradually erased; heating for 20 minutes

at 500 C. is sufficient to remove them entirely. The disappearance of these lines or bands may be taken as an indication of the

rate at which the hardness due to mechanical working is removed.

Above 500 C. the nickel-brass increases rather rapidly in grain

size and becomes soft and ductile.

A suitable spring for altimeters was developed, using a highsilicon nickel steel having an elastic limit well above 100 000
METALLURGICAL INVESTIGATIONS 163

pounds per square inch. This spring when tested in an instrument under conditions duplicating an ascent to an altitude of

25 000 feet, showed an absolutely constant zero and no elastic

after effects.

Diaphragms and springs of various metals and alloys which

had been given different thermal treatments have been and are being subjected to various types of loading in order to obtain a

comparison of their elastic properties, and also to determine the

best metal for such conditions of service, thereby improving

the precision of the instruments in which they are used.

Of the numerous nonferrous alloys investigated the most

promising for the construction of diaphragms is aluminumbronze with 7 per cent aluminum content. A study is also being

made of the hysteresis of steel springs and of its elimination.

The work done to date on elastic hysteresis leads to the probable

conclusion that it is caused by overstrain. The theory has been

developed in detail.

Test-Bar Fractures

During the war the Ordnance Department of the Army accu- mulated a very considerable number of fractured test bars as the

result of examination of many thousands of samples of steel.

The Bureau undertook, in cooperation with the technical staff

of the above department, a statistical and systematic study of

the fractures produced in tension and of the methods of photographing, in order to furnish an explanation and description of

the various characteristic features and to relate them with the

structure of the tension bars. The aim was to embody the

results of this work in the form of a manual which could be furnished to inspectors.

Hardness of Brass Cartridge Cases

An investigation of the hardness of brass cartridge cases by

means of the micro-Brinell hardness machine developed by the

Ordnance Department during the war was carried out by the

Bureau. The hardness investigation was supplemented by

studies of the microstructure of the material, its mechanical

properties, mainly in tension, and its behavior as regards corrosion cracking. A considerable amount of work was also done

by the Bureau in the examination of cartridge cases to determine

the effects of various methods of manufacturing upon the properties of the finished material and with a view to aiding the Ordnance Department in its inspection and specification service.
1 64 WAR WORK OF THE BUREAU OF STANDARDS

Centrifugal-Steel Castings

As a possible means for securing superior steel castings, it was

considered desirable to study the properties of ingots cast by

the Millspaugh centrifugal method. This method produces an

ingot of hollow cylindrical form, and it was thought that there

would be a considerable saving of material, labor, and time in the

manufacture of cylindrical steel appliances. If the method

warranted, it was hoped that cast or heat-treated cast material

made by this centrifugal process could be substituted for forged

pieces. The castings submitted for examination were a miscellaneous assortment of four, having several chemical compositions and cast under various conditions, none of them being cast

strictly in accordance with specification requirements for ordnance material. Very interesting and promising results were

obtained, among them the following:

Segregation of the elements—carbon, sulphur, and phosphorus

appears to exist only radially and is confined mainly to a very

thin layer of the inner zone, but exists also slightly in the outer

zone. Nickel also appears to segregate somewhat, following the

carbon. The maximum carbon segregation found amounted to

0.09 per cent in a steel containing 0.66 per cent carbon and nickel

2.2 per cent. Blowholes appear only in the inner segregative

zone. The density across a section is practically constant;

tensile and shock tests show in general greater strength and

elasticity, but less ductility in tangential than in longitudinal

directions. This method of casting develops very slight internal

stresses. By suitable heat treatment the physicial properties of

steel cast by this method compare very favorably with forged

material of the same composition. The metal of the casting is

clean and sound, and its microstructure better than in ordinary

types of steel casting.

Magnesium-Aluminum Alloys for Mirrors

The Signal Corps and the Corps of Engineers of the Army

were much interested in the development of a light metallic

mirror material of high-reflecting power, and it was desired, if possible, to realize mirrors as large as 6 feet in diameter. The

Bureau undertook the investigation of aluminum-magnesium

alloys for mirrors, and, although it was found impracticable to

build such large mirrors, it was found that the compound Al3Mg4 , containing 50 per cent magnesium, gave a reflection of 85 per

cent in the blue and 93 in the red portions of the spectrum, and

could be made mechanically satisfactory by a vacuum melting
METALLURGICAL INVESTIGATIONS 165

and heat treatment. Although this alloy is much more resistant

to the action of dilute acids and alkalis than any other AlMg

alloy known to the Bureau, it is not recommended where permanency is of prime importance, as some of the samples showed

evidences of slight contamination after standing several months

in the laboratory. (See Scientific Paper No. 363.)

Steel Helmets for the United States Army

Two questions which were presented for solution by the National

Research Council in connection with certain problems arising in

the manufacture of steel helmets were investigated by the Bureau

and may be described as follows:

1 . It was desired to determine whether heating up to quenching

temperature in the treatment of helmets following the pressing

operations was sufficient to remove the stresses set up during the

pressing. The average results of tests showed that the heating

of test pieces of helmet steel to 82 5 C, followed by rapid cooling

in a furnace, reduced the amount of stresses by about 60 per cent,

while those test pieces heated to a like temperature and cooled

slowly in a furnace showed a reduction of some 73 per cent as compared with the amount of stresses found present in the test

pieces which were not heat treated; that is, in the original or pressed condition.

2. The length of time needed to hold helmet steels at the quenching temperature to get full hardening on quenching was also

determined. Helmet steels of 1 1 compositions were examined to

find their critical ranges in connection with the development of

tests for determining their resistance to deformation and penetration.

Effect of Prolonged Annealing High-Silicon Cast Iron

The inspection division of the Ordnance Department of the

Army, which was interested in the use of noncorrodible iron of

the type of "duriron" (cast iron of the approximate composition—total carbon, 1.18 per cent; graphite, 1.09 per cent; silicon,

13 per cent, requested the Bureau to determine the possibility of

any changes in composition upon continued heating. The examination showed that continued heating for as long as 50 hours at

1000 C produced no essential change either in structure or composition.

Horseshoe Nails

At the request of the General Engineer Depot of the Army, an

examination was made of horseshoe nails, representing most of
1 66 WAR WORK OF THE BUREAU OF STANDARDS

the manufacturers of this class of material, with the aim of drawing up specifications. The examination showed a rather wide

variance in the type of steel used (0.07 to 0.20 per cent carbon),

and in the process of manufacture, some being hot-forged while

others were cold-stamped. A simple type of impact tests, using

a notched specimen, was recommended for determining the relative merits of different types of nails.

Deterioration of Nichrome Castings upon Heating

The attention of the Bureau was called to this problem by the

Chemical Warfare Service. The large nichrome castings in the

form of tubes used for the production of charcoal for gas masks

deteriorated rather rapidly in service, becoming weak and brittle.

The examination made of the material showed that, contrary to

the opinion expressed by other investigators of this problem, the

deterioration does not consist in the formation of a carbide by

interaction with the charcoal. On the other hand, the carbide

normally present in the nichrome is removed. An intercrystalline

brittleness apparently identical with that found in nichrome wires

after continued heating is produced, the exact nature and cause

of which have not yet been determined.

Light Armor Plate

In cooperation with the Bureau of Mines and the Navy Department, the properties of special alloy steels suitable for the development of light armor are being studied. The majority of these

steels contain zirconium, while others contain molybdenum, boron,

cerium, etc. About 1 50 ingots have been made by the Bureau of

Mines experiment station at Ithaca, N. Y., and have been rolled

into plates of three-eights or one-half inch thickness at the Bureau

of Standards. These materials are being thoroughly examined to

determine their mechanical, chemical, and thermal properties,

effects of heat treatment and annealing, hardness, resistance to

impact, and microstructure. In conjunction with the ballistic

tests to be made by the Navy Department, valuable and useful

data will be obtained for the design of light armor plate.

The Relative Cutting Properties of "Cooperite" and "Stellite"

At the request of the Bureau of Ordnance, Navy Department,

a test was undertaken to show the relative cutting properties

of the alloys "stellite" and "cooperite." These two alloys,

though quite different in chemical composition, have very similar mechanical properties—they are very hard and able to "keep

an edge" at a rather high temperature. Stellite in particular is
METALLURGICAL INVESTIGATIONS I6 7

used quite extensively to replace and supplement high-speed

steel tools for cutting. Cooperite is essentially an alloy of nickel

and zirconium, with appreciable amounts of iron and silicon.

Stellite, which is manufactured in several different grades, is a

rather complex alloy, the essential elements of which are cobalt,

chromium, tungsten, and molybdenum.

The series of service tests made showed that cooperite is but

slightly inferior to the better grades of stellite. Lathe tools

made of cooperite failed after a cut of 4-inch length made on a 5-

inch round of nickel-chromium steel.

Miscellaneous Investigations of Iron and Steel

At the request of the inspection division of the Ordnance Department of the Army, an extensive and detailed study of the

defects in steel slugs intended for the manufacture of shrapnel

cases, as revealed in the fracture caused by the " nick-and-break "

test, was made. This was supplemented by a study of slugs which

had been sheared as well as broken by the "nick-and-break"

test, the aim being to show whether shearing could be substituted

for the latter method in the work of inspection. The results of

the examination, however, did not appear to warrant a recommendation from the Bureau in favor of the proposed change in

the method of inspection of this class of materials.

An investigation with the object of determining the harmful

effects of pickling, cleaning, and plating on wires, thin rods, and

sheets of various grades of steel submitted to several heat treatments was originally undertaken in connection with the preparation of specifications for aircraft parts. Experiments dependent

upon the tensile tests as a criterion failed to measure properly

the embrittling effect produced by pickling, and although the

impact test on notched bars was also investigated, it was found

that no constant results could be obtained. Alternating-stress

tests of 0.30 per cent carbon steel showed that pickling in sulphuric

acid reduces the resistance to fatigue by more than 30 per cent

for rods ranging in diameter from one-eighth to three-eighths

of an inch. Steel rods three-sixteenths of an inch in diameter

and with a carbon content varying from 0.09 to 0.87 per cent

showed similar reductions in resistance to fatigue. Analogous

results were obtained by the Erichsen test on sheet steel of various

thicknesses and hardness. Brittleness gradually decreases at

room temperature, but recovery is not complete although hastened by heating. Brittleness caused by pickling appears to
1 68 WAR WORK OF THE BUREAU OF STANDARDS

be the result of two effects combined: (i) A temporary effect

supposedly dependent on hydrogen; (2) a permanent effect

caused by the roughening or etching action of the acid. The

effect of plating upon material which has been cleaned, pickled, or sand-blasted has also been studied.

An investigation of the most suitable steels and treatments

for the manufacture of precision gages, resulting from work

originally carried out for the War Department, is in progress.

The work includes the determination and comparison of resistance

to wear, permanence, resistance to corrosion, soundness, expansibility, and economy of different steels under varying thermal

treatments.

Examinations were made of numerous specimens of defective

gun steel and airplane crank-shaft stock which exhibited the

type of defect known as "flakiness." This defect takes the form

of a shining, coarse, crystalline area in the midst of otherwise

sound material. The flake, which may be as large as 1 cm in

diameter, has the appearance of an inter-crystalline discontinuity

in the steel and is very often (if not always) associated with

steel which is badly contaminated with slag and similar inclusions.

"Flakes" reduce the ductility of steel, although the ultimate

strength of the material (in tension) is not affected to the same

extent, and are particularly injurious in material exposed to

repeated stresses. The study of this material is being continued,

and particular attention will be given to the effect of forging

and heat treatment upon such material. A preliminary publication was made from the American Institute of Mining and

Metallurgical Engineers in February, 1919.

As it has been found that a prolonged acid attack may reveal

imperfections in steel, a study of the deep etching of iron and

steel designed for various uses has been undertaken. It is hoped

to show the influence of the various possible factors, such as chemical heterogeneity (segregation), physical heterogeneity

(variations in crystal size, presence of intercrystalline discontinuities, etc.), and mechanical heterogeneity (internal stresses,

etc.). The study of the maerostructure of metals has in general

received much less attention from metallographists than the

microstructure. "The Metallographic Features Revealed by

the Deep Etching of Steel" has been published as Technologic

Paper No. 156.

Laboratory and service tests were made on several types of

high-speed tool steel and their substitutes including cooperite,
METALLURGICAL INVESTIGATIONS 1 69

stellite, and " cobalt chrom. '

' These tests showed that the various

modifications and substitutes, although possibly possessing advantages for special uses, are in general not to be preferred to the

more familiar types of " tungsten-chrom " steels for cutting purposes. An interesting advance in the manufacture of high-speed

tools was the perfection of a method by which such tools are produced direct as castings, thus eliminating the costly and timeconsuming grinding processes hitherto required for shaping them.

Tests of cast tools showed that they give service equally as good

as those made in the usual way.

Preparation of Specifications

In the formulation of specifications for all kinds of metal articles,

the Bureau was frequently called on for advice by the military

departments interested in the work. The preparation of such

specifications often necessitated experimental investigation.

Among the numerous cases of such assistance, the following

may be mentioned: Specifications for shells, cartridge cases,

pressure plugs, metals for aircraft parts, welding electrodes,

coated metals, metals for tanks, horseshoe nails, rotating bands,

bearing metals, surgical instruments, instrument metals, Army

hardware, etc. Foundry Research and Production of Castings

The Bureau's experimental foundry (Fig. 17) was extremely useful during the war, as it produced many special castings for instruments and other devices, which were used in numerous lines of

research both at the Bureau and in the laboratories of other Government departments where military development work was being

conducted.

Thus, for the fiscal year ended June 30, 191 8, the foundry

made the following castings for experimental and special technical

uses, mainly military : *

Metal Castings Patterns Weight

Aluminum alloy 255

241

1701

1

6

10

1

21

13

76

84 334

1

45

13

8

Kg

138. 63

420. 75

1244. 50 12.00

132. 00 33.70

6. 66

39. 50

424. 53

Cu-Mn-Nl alloy

Tin

Total 2249 516 2452. 27
170 WAR WORK OF1 THE BUREAU OF STANDARDS

In addition, investigations of certain new types and modifications of old alloys were carried out on an extensive scale for the

military departments. Work was also undertaken on the reclamation of burnt steel foundry sands, with the object of saving

transportation costs. This investigation, however, was not

pushed to a conclusion.

Work for the Ordnance Department of the Army

As an illustration of the type of work which was carried out in

detail for several of the military establishments during the war,

that performed for and in cooperation with the Ordnance Department may be cited as an example. The several experimental

researches and investigations are described elsewhere, and only

the very considerable amount of testing which the Bureau con- ducted will be considered in this paragraph. The gun section of

the Ordnance Department provided considerable equipment for

carrying out routine tests of gun steel. These were made to

supplement and explain results obtained in the tensile tests of

samples taken from gun forgings, and to show the heat treatment

suitable for controlling the microstructure of large guns during the

forging operation. Examinations showed that the heat treatment

of the gun forging had been, on the whole, satisfactorily carried

out, and that the inferior properties encountered were generally

due to the nonmetallic impurities. Similarly, a systematic series

of tests (including several different methods) was made on 3-inch

brass cartridge cases, representing the product of several manufacturers. Other work included a general study of the defects in

slugs intended for the manufacture of shrapnel cases, examinations of copper rotating bands for shells, and studies of a great

many samples of failed metals for ordnance purposes.

Miscellaneous Metallurgical Investigations for the Military Departments * The more elaborate investigative tests for the military departments included an examination of the characteristics of centrifugally cast steel, which gives promise of possibilities of advantageous use in replacing several lines of steel forging, in cutting

down discards, in reducing machining and segregation, and in

eliminating piping, blowholes, and forging; a study of strains

in cartridge cases, as dependent on manufacturing methods, and

the adaptability of accelerated stress-corrosion tests for predicting failure; the relation of grain size to distortion in cartridge

cases; an exhaustive comparison of the relative merits of cold
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 17.The experimentalfoundry

Gas and oil heated furnaces for nonterrous alloys are shown at the left. The Bureau investigated the properties of nearly all the metals and alloys used in military construction work
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 18.

The specially designed rolling mill used in studying the behavior of metals

under working conditions

The complete process as carried out in the mill can be studied under easily controlled conditions, something which is not possible in a commercial plant

Fig.. 19.

One-hundred-and-fifty-ton floating crane at the Norfolk Navy Yard

Strain-gage measurements on this crane were made by representatives of the Bureau to determine

the stresses in the various members
METALLURGICAL INVESTIGATIONS 171

shearing and nick-and-break method of test for shell slugs; methods for distinguishing between hard and soft rotating bands for

shells ; several tests of. armor plate, and numerous other materials

for Ordnance, Aircraft, Quartermaster, and Engineering Departments of the Army, and for the various branches of the Navy;

tests of fusible tin boiler plugs for steam vessels; a study of

methods for the recovery of tin ; and examination of a very large

variety of coatings for rust-proofing. Interesting features of

these investigations were the nonuniformity in electroplated

coatings, uniformity of sherardized coatings; information con- cerning brass plating, the relations among the metals showing the

superiority of zinc; and a study of the "copper-clad" process;

microexamination of large (12-inch) chain links forged, welded,

and cast, and tarnishing tests on Benedict nickel and German

silver. Among some of the special problems were the heat treatment of very small compass needles, large (30-inch) U bars, long,

slender rods, and very large sheets; service tests of the lead-base

bearing metal "Ulco;" service tests of a special lead-base babbitt; investigation of the cause of failure by cracking of brass

locomotive steam-gage tubes; cause of cracking of casehardened

aeroplane engine-cam followers; failures of aeroplane crank

shafts; service tests of rhotanium and palau (substitute for

platinum) crucibles; corrosion tests on several acid-resisting

alloys; tests of numerous commercial light aluminum alloys; causes of cracking of welded Army aluminum canteens; determination of working temperatures of machine-gun barrels; and

tests of magnalium alloys of high optical reflectivity for mirrors,

including the preparation of a series of such alloys. A large

number of steels and alloys were examined by thermal analysis

to locate their critical points; the processes for the casting of

numerous metals and alloys for instrument parts were studied,

and samples of meteoric iron were examined to determine their

structural characteristics. Numerous samples of platinum were

tested to determine purity and causes of deterioration; a very

serious type of failure known as "flaky" steel occurring in nickelchromium and nickel-steel was investigated in great detail,

while semisteel, cast iron, and steel shells, failed gun forgings,

and other ordnance material were studied to determine the cause

of failure, suitability for use, or special characteristics. Other

work was carried out on valves for aircraft motors, machine-gun

barrels, German rifle bullets, cartridge clips, samples of Duralumin alloy used in Zeppelin construction, zinc coatings on
172 WAR WORK OF THE BUREAU OF STANDARDS

shrapnel timing leads, causes of cracking of steel rivets, and

identification tags of Monel metal for seamen. In all this work

the unusually complete equipment of the Bureau's laboratories

(Fig. 1 8) was of great assistance.

Military Inventions

The metallurgical division has assisted the various Information bureaus of the military departments, as well as the Patent

Office, in the examination and development of military inventions

relating to metals, manufacturing processes, and various devices

made of metal.

Information Furnished by Correspondence

In addition to information furnished in personal interviews on

military and technical subjects, a very heavy correspondence

was maintained on questions relating to metals, some of the advice

given in this way being of considerable importance.

Membership in War Boards and Military Committees

The metallurgical division rendered valuable service in problems of national defense through membership on numerous boards

and committees.

Among the activities of importance may be mentioned particularly that of the chief of the metallurgical division as the representative of the Department of Commerce on the requirements

division of the War Industries Board. This enabled the Department to take an active interest in and to secure valuable assistance

on many exceedingly important matters coming before the Government. Four months were spent abroad by this member of the

committee in the spring and summer of 191 7, while serving on the

scientific mission sent to obtain information concerning applications of science to warfare and the part to be played by scientific

men in the war. The information thus gained proved of inestimable value in planning investigations in the United States.

Another member of the staff was very helpful as adviser in

ceramics to the War Industries Board and assisted in framing

specifications for enameled ware as a member of the Army committee on standardization. Another rendered valuable service as a member of the Interdepartmental Committee on Minerals and

Their Derivatives, and also aided in the manganese-conservation

program. The committee on light alloys of the National Advisory

Committee for Aeronautics carried out most of its experimental

work through the Bureau of Standards, and the results of this have

appeared in a series of publications. The National Research
PHYSICAL TESTS OP METALS AND METAL STRUCTURES 1 73

Council has actively cooperated with the Bureau in several military

problems, and the Bureau's representatives have been active on

1 1 of its committees, among these one of the most important being

a committee to make a survey and recommend practice as to the

ingot and finishing practices of American steel mills. This work

originated in the Ordnance Department of the Army in connection

with the works practice as influencing the output of steel.

Various members of the metallurgical division were called in as

technical advisers by the several branches of the War Industries

Board, particularly on questions relating to tin, steel, and platinum,

and the Bureau of Standards in consequence has undertaken considerable experimental investigation, especially on tin conservation

and substitutes.

In addition to formal committees with regular programs there

have been held a great many conferences at which the Bureau of

Standards' representatives have been present, called by the various

military departments to discuss with manufacturers technical

questions bearing on military materials and specifications.

PHYSICAL TESTS OF METALS AND METAL STRUCTURES

Load Tests of 150-Ton Floating Crane for the Navy

At the request of the Bureau of Yards and Docks of the Navy

Department, engineers of the Bureau of Standards conducted a

loading test and strain-gage analysis of the 150-ton (336 000 pound)

revolving floating crane built for use in the navy yard at Norfolk,

Va. (Fig. 19.) The test was made to determine the stress distribution in the various members of the structure while under load

and to obtain a more complete knowledge of the actual amount

of the stresses in some of the members of such a statically

indeterminate structure.

This Norfolk crane represents the most advanced type of re- volving floating crane of large capacity. The jib is a tapering Pratt

truss, and the balance of the superstructure consists of two subdivided triangular trusses rigidly connected by cross-bracing. The

entire revolving load is carried on a pintle which transmits the load

to a thrust bearing on the deck of the pontoon. The pintle is supported laterally by a hexagonal tower which is constructed integrally with the framework of the pontoon.

The method of stress analysis used in this investigation parallels

that used in the load tests of the Arlington building (described in

the article on cement and concrete) and is the same method which

has been so successfully used in the study of bridges, steel frame-
174 WAR WORK OF THE BUREAU OE STANDARDS

work of buildings, and similar engineering structures. A Berry

strain gage was employed to determine changes of length of established gage lines by comparison with standard reference bars.

With known moduli of elasticity for the materials in question, the

unit deformations may be converted to the corresponding stresses.

In the hands of trained observers such an investigation yields

results of great value for future designing work.

Readings were taken at various points of the deck to determine

the magnitude, and, if possible, the position of maximum stress in

the upper deck plate ; on the tower members to determine whether

the tower acted as a unit; around the manhole in the tower legs

to find the effect of such an opening; on the pintle to determine

the magnitude of the stresses in these members; and on various

members of the superstructure to determine the manner in which

the loads were carried down into the pintle.

The strain gage measurements on this structure showed that

all stresses in the various members were within safe limits. Such

knowledge is an important factor in the design of structures such

as this, which are statically indeterminate. This determination

was of especial importance at the time of conducting the investigation, inasmuch as another large floating crane of somewhat like

construction had only recently collapsed under load while in use on the Panama Canal.

Strength and Efficiency of Electric Welding

The urgent need for ships to transport our men and materials

to Europe during the war made it necessary to adopt every

means of securing maximum output from the shipyards of this

country. The "fabricated" ship, constructed from plate material

on which all cutting and drilling had been completed at remote

mills before shipment to the yard, saved time at the shipyard

under the conditions existing during the war. A radical suggestion which was never used to the extent which

its merits appeared to warrant was the electric welding of the

frames and plates of the hull instead of riveting. Autogenous, or

fusion, welding has been in use for many years. Most of this work

has been done by the use of the gas torch to which oxygen and

acetylene are supplied. The weld is formed by fusing together

the adjoining edges of the pieces of metal. Material is sometimes

added at the same time from a metal rod.

Due to the prohibitive cost of the gases required for oxyacetylene

welding and to nonacceptance of welding for certain work by the
PHYSICAL TESTS OF METALS AND METAL STRUCTURES 1 75

insurance companies, the use of welding ship hulls was greatly

restricted.

The possibility of so developing electric welding as to permit its

being accepted to replace riveting was carefully considered.

In the electric-arc welding process the fusion of the metal is

effected by an electric arc formed between a metal rod (or electrode) and the pieces to be joined. Metal from the rod is deposited in the weld.

The welding committee of the Emergency Fleet Corporation

was formed to study the matter carefully and to conduct any

needed investigations. This Bureau had representatives on the

committee and performed much of the laboratory work for determining the properties of the welds, particularly the strength.

In order to obtain definite information upon welds which were

being made commercially, a large number of pieces of one-half

inch steel plate were welded at different shops using all available

types of apparatus. These were known as the " Wirt-Jones

tests and attracted a great deal of attention from engineers and

shipbuilders.

The welding data included for each test weld, besides the

identification of the operator, the position in which the weld was

made, the type of weld, the rate of welding, the type of electrode

used (with its diameter and manufacturer), the arc and opencircuit voltage, and the amperage. These data were obtained

in the shops where the welds were made. The specimens were

machined there and elsewhere. The physical tests were all made

at the Bureau of Standards and consisted of tensile, torsional,

fatigue, and cold-bending tests.

It was found that all of these except the fatigue tests were

consistent. A specimen showing high strength in the tensile

test showed high strength in the torsional also. The specimens

showing relatively high ductility in the tensile tests showed equivalent ductility in the cold-bend tests.

The fatigue tests were made in three Upton-Ivewis machines and

by three different engineers. Unfortunately, the results do not

appear as consistent as could be wished. Many fatigue experiments should be conducted if reliable data are to be obtained

upon this important property of welds. It is believed by many

engineers that the failure of welds in service is usually by fatigue

and that this property of welds is relatively more important than

the fatigue resistance of the material in which the weld is made.
1 76 WAR WORK OF THE BUREAU OF STANDARDS

The total number of specimens in this series was over two

hundred, and the testing work required most of the time of two

engineers for nearly a week.

In addition to the Wirt-Jones tests, this Bureau was at one

time making progress reports to the welding committee on 14

investigations planned to give information upon some of the

many problems constantly arising in connection with welding

work. The number of specimens involved in these investigations

varied from 5 to 42.

Due to the satisfactory results obtained from these tests, it

was decided that the electric-arc welding process was suitable for

ship construction, and the committee formally recommended to

the Emergency Fleet Corporation that a merchant ship be designed to utilize welding wherever it could be employed to advantage and that the ship be completed as soon as possible.

The signing of the armistice took place before much progress

was made, but some commercial shipyards are now energetically

preparing to construct ships in which nearly all the frames and

plates for the hull are to be welded into place.

It is estimated that the cost of welding will approximately

equal the cost of riveting plates and frames after they have been

"laid off" and the rivet holes punched. For welding, however,

all this preliminary work is unnecessary, and the plates and angles

do not need to be as accurately cut to dimensions. The saving

if welding is used is therefore very large, and it is chiefly a saving

in labor cost, which under present conditions constitutes a large

portion of the total cost.

One result of these extensive investigations was the important

conclusion drawn from the results of the Wirt-Jones tests by

the chairman of the research subcommittee of the welding committee, that the best physical properties were obtained from those

specimens welded with the highest current density in the electrode.

Apparently, under this condition, thorough fusion occurred in the

weld.

The importance of this discovery, which is generally accepted

at present, is very great. The fact that little properly conducted

investigational work has been done upon welding processes, and

that there are many possible lines for improvement, leads to the

conclusion that such work offers great possibilities if properly

carried out.

The American Welding Society, an outgrowth of the welding

committee, has been formed to encourage welding research work
PHYSICAL TESTS OE METALS AND METAL STRUCTURES 1 77

by coordinating the efforts of industrial, educational, and governmental laboratories. This Bureau is assisting the work of this

society in so far as possible.

In an extension of the experimental work to determine the

fatigue resistance of welded joints such as would be actually used

in ship construction large specimens were made from plates onehalf inch thick, 8 inches wide, and 40 inches long.

A fatigue machine driven by a 1 5 -horsepower electric motor

was designed and built to subject these specimens to repeated

bending stresses, with provision not only for recording the number

of cycles of stress required to cause failure, but also for making

an autographic record of the stress produced in the welded material for each application.

Investigation of Strength of Chains

The Bureau was called on to make two extensive series of tests

of chains in connection with its war activities. The earlier series

comprised numerous samples of links for anchor chains and was

carried out in cooperation with the chain committee of the Emergency Fleet Corporation. The research was intended especially

to determine the value of electric welding in chain manufacturing

and the relative efficiencies of cast and forged links.

The anchor-chain links tested included wrought-iron, machinesteel, rolled-shafting steel, and electric-cast steel specimens.

Some were cast integral, others were drop-forged, and still others

were welded. Certain of the links were prepared with studs and

others without. The tests were not extensive enough to warrant

general conclusions on the relative values of these different types

of links, but they sufficed to furnish considerable comparative

data.

Six electric-welded basic open-hearth steel links of

bars showed an average strength of 350 000 pounds. Three

links, each drop-forged from 2-inch bars of steels of various manufacture, averaged as follows: Rolled shafting steel, 212000

pounds; machine steel, 345 000 pounds; and electric steel,

380000 pounds. Electric-welded links of 2>£-inch stock aver- aged 260 000 pounds strength for chain iron and 280 000 pounds

(one test only) for steel. Fracture occurred in all cases at the

welds.

An interesting comparison is afforded by the study of the

results of tests of six links of cast steel, all of 2 -inch diameter

stock. Three of these links which had been heat-treated after

26035°—21 12
1 78 WAR WORK OF THE BUREAU OF STANDARDS

casting failed at loads of 326 000, 400 000, and 365 000 pounds,

respectively. A microscopic study of the fractures showed the

steel to possess a very good structure. Two cast electric-steel

links averaged 440 000 pounds strength, and an accompanying

link made from basic open-hearth steel failed at 370 000 pounds.

This last open-hearth had also been heat-treated after casting,

and showed six times as great elongation as did the two electricsteel links. All anchor-chain links tested were about 12 inches

long over all. This series of static laboratory tests demonstrated the relative

superiority of cast-steel links. Dynamic tests made elsewhere

with the cooperation of the Bureau also served to establish the

relatively greater desirability of a steel link than of a wroughtiron link. Service tests by the Navy Department also contributed

to the establishing of the efficiency of cast chain which received

the approval of Lloyd's Register of Shipping.

In the process of reorganization of the Army, by which the

purchase of various supplies was concentrated in suitable Army

branches under the general direction of the Purchase, Storage,

and Traffic Division the procurement of chain was assigned to

the Engineer Corps. The Bureau was represented, together with

other Government departments on the committee on chain.

The Bureau made extensive tests of harness, vehicle, towing,

sash, anchor, and other types of chain with straight links, twisted

links, plain stud, and other links in its cooperation with the War

Department standardization committee. It also tested harness,

clip-grab, box, and barrel hooks in the course of this investigation.

The test data obtained here, combined with that obtained in commercial tests, furnished the basis for the formulation of chain

specifications. Standard War Department specifications for

chain, together with much other data, including a list of manufacturers, have been published in the War Department Catalogue

No. 5.

Wheels, Investigation of, Artillery, Truck, and Airplane

This subject will be found under the above heading in another

part of this report.

Metal Construction for Airplanes

A description of the work carried out on this subject will be found

under "Aircraft Construction."
NATURAL-GAS INVESTIGATIONS 179

NATURAL-GAS INVESTIGATIONS

Among the war activities of the Bureau may be mentioned the

work on the various problems presented by the natural-gas

industry. The increased demands upon all industries brought

about through the war and the unusually severe winter of 191 7-18

combined to cause a complete breakdown of this industry in particular localities. Calls for assistance came from several such

places and were given the attention of the gas engineering section

of the Bureau.

Beginning of Natural-Gas Work

The first of these calls came in the early winter from Cleveland,

Ohio, where a shortage of natural gas was threatening to cause

considerable suffering. The Bureau had in 1916 made a study of

the city's testing facilities, and in October, 191 7, was asked for

further assistance along that line, and also for help in dealing with

the natural-gas problem in that locality. The survey of local

conditions made by the Bureau's representative in January, 1918,

showed that the situation was being handled as well as could be

expected locally, but that the problem demanded more than

merely local treatment. Recognition of this fact led the Bureau

to consider an extensive investigation of the needs of the industry.

On December 31, 191 7, Louisville, Ky., requested the assistance of the Bureau in dealing with its shortage of natural gas,

since the Bureau in 1913 had assisted in framing the Louisville

gas ordinance. As a result of this request a representative of the

Bureau was sent to Louisville in the latter part of January, 1918,

and a brief preliminary report on the situation was rendered on

January 28 with the recommendation, similar to that made in the

Cleveland report, that the available supply of gas be rationed so

as to secure its most equitable distribution. The need for an extensive study of the natural-gas situation was reemphasized by the

Bureau's experience in Louisville.

General Natural-Gas Investigation

Late in February, 191 8, the Bureau definitely decided to make

the extensive investigation that was so urgently needed. It was

proposed to make a survey of the production, transmission, and

consumption of natural gas with a view to eliminating waste in

its production and consumption, to securing a fairer distribution

between communities of the available supplies, and to securing a

more equitable division of the supply between members of the same
l8o WAR WORK OF THE BUREAU OF STANDARDS

community. The wasteful consumption of natural gas in the

manufacture of carbon black, brick, etc., has shortened the life

of the industry by many years, and the use of natural gas for

other industrial purposes, such as the manufacture of steel, is

undoubtedly a case of putting a natural resource to one of its least

important uses. The interstate transportation of natural gas

gives rise to many complications, not the least of which is the instinctive desire of a producing State to keep its gas at home. Thus

West Virginia dislikes to see two-thirds of its production transported to Pennsylvania, Ohio, Kentucky, even to Indiana, while its

own citizens experience a shortage. In one locality 8 per cent of

the consumers use half of the available gas, and thereby cause

others who need it to go without. These are some of the problems

to the solution of which the Bureau was intended to contribute.

Particular attention was to be given to the Louisville situation

as presenting in concentrated form the various aspects of the

natural-gas problem, with the expectation of later applying to

other localities the principles developed here. The Bureau was

interested principally in the public utility or service aspects of the

work, while it asked for and secured the cooperation of the United

States Geological Survey and of the Bureau of Mines in working

up the scientific and engineering aspects of the problem. One

of the Bureau's consulting engineers was placed in charge of the

field investigation.

An elaborate report entitled "Fundamental Principles of

Natural-Gas Production, Service, and Conservation, with Special

Reference to the Natural-Gas Situation at Louisville, Ky.," was

prepared and presented on August 20. As indicated by the title,

this report explained the methods of natural-gas production,

transmission, and local distribution and utilization, with a useful

discussion of the vital problem of conservation. A fifth part contained much useful information on the Louisville situation. The

Bureau recognized the considerable merit of this work, but did not

think it advisable to publish it without certain modifications of

the treatment. It later appeared as No. 7 of the " Mineral Industries of the United States" series of the National Museum, and no

doubt is finding a wide circulation among those interested in the

natural-gas industry and in the conservation of our natural

resources.

Relation to the United States Fuel Administration

However, the Louisville case still remained unsettled and demanded attention. In September, 191 8, a representative of the
NATURAL-GAS INVESTIGATIONS 181

Bureau went to Kentucky and, with the assistance of an expert,

made a field study of certain gas territory in eastern Kentucky

which might be used to add to Louisville's supply. The report

rendered by this expert has been much in demand. The Bureau's

representative then visited Louisville in hopes of effecting a solution of the problem, which was becoming daily more aggravated.

The local situation rendered the Bureau's recommendations

as to rationing and the manufacture of gas impracticable.

Appeal was made by the local company to the United States Fuel

Administration, and a rationing order similar to those issued for

several other localities was issued. Although the Bureau did not

actively participate in the hearing of this case before the Fuel

Administration, it nevertheless is a source of gratification to know

that the action of the Fuel Administration was exactly in line with

the Bureau's recommendations to the city.

The increasing activity of the natural-gas division of the Fuel

Administration rendered it unnecessary for the Bureau to carry

its investigation further. With the lapse in power of this war

bureau, it is not unlikely that the Bureau will again render such

assistance as is within its power to any localities which may have

natural-gas utility problems to solve.

Technical Results

Certain features stand out clearly as the result of the Bureau's

study of the natural-gas industry. The principal one is that

there can be no adequate solution of the natural-gas problem on

anything less than a national scale. The industry has developed

and spread out in an entirely aimless fashion until now there

exists an overdeveloped demand on what is, after all, a strictly

limited natural resource. Local selfishness results in mad scrambling to secure all the gas possible, regardless of the rights or needs

of other communities. To reconcile these conflicting interests

and to formulate some principles which shall control the future use of natural gas calls for treatment by some national body with

power to compel observance of its orders. Unfortunately, no

such body exists during peace times.

Aside from rationing between communities and States, there

is need for continued rationing within each locality. This has

been accomplished quite generally in some States during the war

and should be extended and rendered a permanent part of our

national program. Industrial use of natural gas should be

severely limited or largely eliminated, and its use for househeating purposes should be actively discouraged.
1 82 WAR WORK OF THE BUREAU OF STANDARDS

In view of the fact that the wisest possible treatment of this

natural resource can only delay for a few years (in most localities) the time when the supply will be so nearly exhausted as to

make it unprofitable to continue either to carry the gas long

distances or to sell it at the present relatively low rates, it is not

unlikely that the Bureau will be called upon by numerous cities

to assist them in framing ordinances governing the manufacture

of gas and its sale, either straight or mixed in some degree with

natural gas. The Bureau has rendered some such assistance to

Sandusky, Ohio. Mention might also be made in closing of the

assistance which the Bureau rendered the State of Oklahoma in

framing its natural-gas service standards. The natural gas problem is by no means solved; in fact, as the years go on, it is certain

to become much more acute. The experience which the Bureau

has accumulated during the period of the war will prove of great

future value.

While by no means the most important work of the gas engineering section during the war, this work on natural gas has afforded a measure of relief to afflicted communities and was of assistance

in forwarding the Nation's war program.

Investigation of Town-Border Natural-Gas Meters

In connection with the above-described efforts of the Bureau

to aid in the conservation of the natural-gas resources of this

country, the United States Fuel Administration requested the

Bureau to determine the accuracy with which gas was being

measured through the meters established at the town borders of a

large number of cities and towns in Kansas and Missouri. Accordingly, the Bureau sent into these States members of its staff

who, during the months of November and December, 191 8, and

January, 191 9, tested 103 of these large meters. Of these 56

were positive meters, 33 orifice meters, 2 pilot-tube meters, and

12 proportional meters. In addition to the actual testing of the

meters, the average conditions of temperature and pressure at

which the gas was measured were investigated.

On the basis of the Bureau's work it has been estimated that

during 191 8 several million dollars' worth of gas was lost by

leakage in the distributing plants receiving gas through the

meters tested.

Recovery of Helium from Natural Gas

Another line of research conducted by the Bureau on natural

gas was the production of pure methane for the determination
OPTICAL GLASS AND OPTICAL INSTRUMENTS 1 83

of its physical constants. Helium was needed for the inflation

of balloons, and the only commercial source of helium was the

natural gas found in certain localities. By far the largest constituent of natural gas is methane, and in order to obtain the

helium, it was necessary to remove the methane. It was decided

that the best method of accomphshing this was by cooling the

natural gas until the methane was liquefied and the helium alone

remained gaseous. It was necesssry to accurately determine the

physical constants of methane in order to properly design the

necessary refrigerating machinery. Methane was produced in

large amounts by three different methods. The first method

consisted in the production of the gas by the Grignard reaction;

methyl magnesium iodide was produced by the reaction between

magnesium and methyl iodide, and this was then decomposed

with water, liberating the methane; the methane was purified

by chemical means, liquefied, and then further purified by

fractional distillation. Considerable methane was also prepared

by the separation and purification of the methane contained in a

sample of natural gas rich in methane; and a third sample was

prepared from aluminum carbide. The samples thus prepared

were turned over to the heat division of the Bureau for the determination of the physical constants of methane. These values

were communicated to the Bureau of Mines and were used in the

designing of machinery and also in checking up the operation of

the plant used for the production of methane.

OPTICAL GLASS AND OPTICAL INSTRUMENTS

The Production and Testing of Optical Glass

Work on the production of optical glass was begun during the

year 191 4-1 5. The first difficulty experienced was in securing

satisfactory pot material able to resist the corrosive effect of these

glasses. This was found in a kaolin-clay mixture which proved

very satisfactory, and the composition of which was communicated

to several glass plants.

The early experiments in the manufacture of optical glass were

conducted with pots holding about 30 pounds of glass. The

quality of the glass produced under various conditions of heating

and cooling the melts was investigated, and the effect of stirring

studied in pots of this size until the winter of 191 6-1 7, when a

larger furnace, holding a 1000-pound pot, was built and operated.

A furnace of this type is shown in Fig. 20. In this furnace the

first large melt of commercial borosilicate glass was produced. At
1 84 WAR WORK OF THE BUREAU OF STANDARDS

the same time the composition of the different glasses was studied

by means of small melts, and the results of this work were continually compared with such information from foreign sources as was available.

The subject of the chemical compositions of the optical glasses

had been practically mastered when war was declared. At this

time a conference was held with representatives of the geophysical

laboratory of the Carnegie Institution, and the information

collected by the Bureau was made available to them. Three

representatives of the geophysical laboratory were then stationed

at the Pittsburgh branch of the Bureau of Standards and were

given an opportunity of observing the operations of glass making

as there carried on. The same information was made available

to three glass manufacturers. There was at all times close

cooperation between the technical men of these plants and the

scientific staff of this Bureau, in connection with both the obtaining of suitable pots and the making of optical glass.

Simultaneously with the work of producing optical glass of high

quality improved pots were developed, and the final product,

the porcelain pot, has given excellent satisfaction. In the construction of this type of pot use is made of the waste bisque of

white-ware potteries, thus affording a cheap and reliable source of

calcine, accompanied by the saving of material heretofore wasted.

Furthermore, a procedure for casting pots was developed in every

detail, a process which does away with the usual laborious hand

building, and results in pots of a superior structure at a considerably lower cost. This process is an original contribution to the

technique of glass manufacture and is bound to result in farreaching changes in the production of glass-house refractories.

Five such pot-making equipments have been designed and the

drawings furnished to glass plants.

At one of the optical glass plants a system of rapid inspection

of optical glass was initiated by a representative of the Bureau,

employing the immersion of the glass in carbon bisulphide and

gasoline. This testing system has been developed by the

Bureau's staff and was used for some time in testing the output of the Pittsburgh plant. The system is likewise being used

at a number of factories. There is a large saving in labor, as the

work of polishing the slabs for examination is thereby eliminated. In addition, accessory tests have been devised which have

proved very useful, and the polishing process has been developed

from an unsatisfactory state to a high degree of perfection. The
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 20.Furnace for making optical glass

The pot in which the various ingredients are melted is shown on the truck and is partially broken away to show the solidified glass. Before the war all the optical glass used in this country was

produced by a few firms in Europe. Through the Bureau's investigations improved manufacturing processes have been developed, and the industry securely established in the United

States
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 2i.—Experimental paper machine

Paper entered into a great deal of the construction work carried on during the war. To 1 gate new manufacturing processes, a complete paper mill is operated by the Bureau. T

chinery is identical, except in size, with that employed in commercial plants

t
OPTICAL, GLASS AND OPTICAL INSTRUMENTS 1 85

testing methods worked out by the Bureau have given general

satisfaction.

The Pittsburgh laboratory of the Bureau, operating eight

single-pot furnaces, worked out in complete detail the melting

operations involved in the production of the principal optical

glasses, the most suitable compositions, the processes of pressing

blanks and of annealing. The yields of good glass produced

at this plant were very satisfactory, and were probably higher

than those obtained at commercial plants. In this manner the

Government secured authentic and accurate information concerning the whole problem of optical-glass making, which is

available to the authorities concerned and to the general public.

More recently the Bureau experimented with the production

of dense barium crown glass of the type used for certain photographic lenses. This glass is more difficult to produce than the

Ordinary types, and the results were not entirely satisfactory.

However, glass of this type of a fair grade was produced and

submitted to the leading photographic lens manufacturers of

the country for trial. These trials have shown that lenses made

of the glass gave satisfactory performance. Demands for the

glass necessitate further production, which will undoubtedly give

larger yields of improved quality as well as proper control of the

optical constants.

Testing and Design of Military Optical Instruments

All the melts of optica,! glass made at the Pittsburgh laboratory

of the Bureau, about 300 in number, were submitted in samples

to the optical instruments section for the determination of the

refractive indices, dispersion, and transmission factor of the

glass composing the melt.

The refractive indices and dispersion were at first determined

on a spectrometer. This method involved the expense and delay

incident to the making of a small and accurately finished prism of

the glass under examination. It was subsequently found far

easier to determine these values on a Pulfrich refractometer,

which requires only a small slip of glass, about 10 by 20 by 2 mm

in size, polished on one face and one end. The indices were determined for three or four spectral lines in the fourth decimal

place. The dispersions, using a differential method, were found

to five decimal places.

The transmission factors were determined on a Martens photometer. By the use of an auxiliary table the loss of light in transmission can be quickly computed in per cent per centimeter.
WAR WORK OF THE BUREAU OP STANDARDS

In addition to performing this work on all Bureau melts, assistance of the same sort was given to a number of manufacturers

of optical glass. One of these companies did not supply anyconsiderable amount of glass to the American Government, but

entered into a contract with the Italian Government to supplyoptical glass of which that country was in urgent need.

A very important point in the inspection and utilization of

optical glass is found in the subject of striae. The best optical

glass should be entirely free from strise; under the stress of war

needs, glass of slightly lower quality was occasionally used in

certain parts of binoculars and other military instruments. The

Bureau has conducted an extended investigation on the subject

of strise and their effect on the performance of the completed

instrument. In some cases it has been found that where the two

barrels are affected to unequal extents by strise, the performance

of the striated barrel is at least as good as the unstriated one. Many other factors than the existence of strise enter into the satisfactory performance of an instrument of this type. In general,

it may be said that strise, if faint or few in number, are not very

injurious in the objective of binoculars, but are considerably more

so in the prisms and eye lenses.

The Bureau has also frequently conferred and advised with

military and naval authorities on the subject of specifications

for optical glass.

While many special types of military instruments were subjected to test by the Bureau, to be mentioned in detail later,

the major portion of the work was centered upon the testing

of binoculars. The Bureau was requested to perform check inspection on one out of every hundred binoculars produced for the

Signal Corps. Special apparatus was designed for the rapid testing of field glasses (to be described in greater detail under the title

"Devices Perfected"), and these methods were adopted by the

Signal Corps, the work being under the supervision of a member

of the optical-instrument section of the Bureau. Occasional

tests were also conducted on instruments of this type for other

branches of the military forces. The table below shows the number of binoculars tested at the Bureau, by months, and serves

also to indicate the rise in production:

Tested before July i, 1918 315

Tested during July, 1918 78

Tested during August, 1918 51 Tested during September, 1918 97
OPTICAL GLASS AND OPTICAL INSTRUMENTS 1 87

Tested during October, 1918 113 Tested during November, 1918 174

Tested during December, 1918 80

Total to Jan. 1, 1919 908

Tested for Navy Department; Crown Optical Co. glasses rejected by British

Government, tested thoroughly for striae 120

Tested for Shipping Board, Emergency Fleet Corporation, acceptance tests only;

Galilean type 1001

The Bureau was called upon by the various branches of the

service to make special tests of photographic lenses, although most

of the testing of such lenses has been carried out under Armysupervision at the experimental laboratory of the manufacturer.

The General Engineer Depot of the War Department, and the Geological Survey in particular, made use of the Bureau's facilities

for such testing.

The facilities of the Bureau were also used by the Signal Corps

to test the speed of their camera shutters. The actual work, however, was done by enlisted men detailed to the Bureau by this

branch of the service.

The Bureau was called upon to make tests of various sorts on a

wide variety of optical instruments for military purposes. Periscopes, small range finders, gun sights for both Army and Navy,

bomb sights, aviators' goggles, and other instruments were

brought to the Bureau for test and for conference. In some cases the work done by the Bureau has been comprehensive, in others the

assistance rendered has been mainly in the nature of advice following a short discussion of the construction of the instrument. In

the first class may be mentioned the tank-gun sight, the 37 mm

gun sight, the panoramic machine-gun sight, a periscopic alidade,

and binoculars from companies who were commencing to manufacture these instruments. In the case of the tank-gun sight, the

inspection division of the Ordnance Department was in almost

constant consultation with the Bureau, and the laboratory facilities were used freely for making the tests necessary for putting the

instrument on a production basis. The range scale for this instrument was computed at the Bureau, and a representative of the

optical-instrument section made a special trip to Boston in connection with the production of this instrument.

A representative of the inspection division of the Ordnance

Department was detailed to the Bureau and made use of the

laboratory facilities for building the apparatus necessary to test

the optics of the 37 mm gun sight.
1 88 WAR WORK OF THE BUREAU OF STANDARDS

A conference on the specification for the panoramic sight for

machine guns was held at the Bureau on July 15, 19 18, and from

then up to the time of the signing of the armistice the engineering

division of the Ordnance Department was in frequent consultation with the Bureau with reference to the specifications and

performance of this instrument.

A periscopic alidade was sent by the Expeditionary Forces to

the General Engineer Depot with the request that the instrument

be copied and supplied to the American Army. The sample was

turned over to the Bureau, and the instrument taken apart and

various parts measured. The General Engineer Depot was then

furnished with all the data necessary for the construction of a

similar instrument. From the data supplied to the Engineer

Depot a blue print of the optical parts was prepared and turned

over to an instrument manufacturer. A sample American-made

instrument was returned to the Bureau of Standards, and this

instrument, after a few minor changes, was approved.

A certain company undertook for the Signal Corps the manufacture of binoculars and worked in connection with this Bureau.

They had some difficulty at first in getting the optical parts of

the binocular properly placed in the instruments and referred

some of their troubles to the Bureau, which was able to be of

assistance in getting this company on a production basis.

In consultation with the Bureau another firm embarked on the

manufacture of a new type of binocular in which the machine

work is largely replaced by pressed metal parts. This company

did not reach the production stage during the war, but there is

promise in their work, and there is a more than fair indication that

they will be able to produce in the very near future a good binocular at a much lower labor cost than is usual at the present time.

The supply of sextant mirrors of a satisfactory degree of parallelism between the two surfaces was inadequate, and great difficulty was experienced in getting workmen to turn out such plates.

A member of the Bureau's staff, detailed to one of the glass-making plants worked out a satisfactory method of polishing these

mirrors, and they are now being produced in quantities and are apparently of a satisfactory grade.

In connection with the work of inspecting binoculars for the

Signal Corps, and in addition to the detail of a man to assist the

Signal Corps in this work, there was held at the Bureau during

the month of October, 1918, a short course for the instruction of

inspectors of binoculars. The inspectors so trained were sent
OPTICAL GLASS AND OPTICAL INSTRUMENTS 1 89

out to the various factories and were engaged in the work of performing the acceptance tests on binoculars. There were nine

inspectors detailed for this work.

For the Ordnance Department of the Army a modification was

made in the Aldis unit sight by the insertion of a lens-shaped

bubble glass to adapt the instrument for use as a bomb sight.

The device has proved very efficient for the purpose.

For the same department a projection-aiming device was

constructed for nightwork with machine guns.

Binocular Testing

Aside from the assistance given by the Bureau in design or construction of optical instruments, described earlier in this report,

the devices perfected and procedure followed in binocular testing

merit further description.

Tests on the following elements of performance or construction

were called for: (1) Resolution; (2) field of view; (3) parallelism

of axes; (4) magnification; (5) exit pupil; (6) transmission; (7)

correctness of mil scale ; and (8) star test. To make all these tests on a large number of binoculars would

be a very onerous task. A set of appliances was accordingly

developed at the Bureau by which these various tests can be

readily made. In fact, this testing has been brought to the stage

where the time consumed in making the actual tests is considerably less than the clerical labor of recording and reporting the

tests and the manual labor of packing and shipping the tested

binoculars. The apparatus is not elaborate, does not require a

great amount of machine work, and the results are obtained well

within the accuracy required. The methods of making these

tests, the tolerances to which the tests were made, and the

apparatus used will be taken up in order.

The resolving power of the human eye is slightly less than one

minute of arc. An instrument of magnification M should be

capable of resolving or separating two objects separated by xjM

X i'. In the case of a 6-power binocular the limit of resolution

should be less than 1/6 X i' = io". A resolution of 6" will be

very good, 10" passing. Greater than 10" not acceptable.

This value was determined by means of a resolution chart. The

resolution screen was drawn on drawing paper on a large scale,

and reduced photographically so that the distances between the

lines would have values of from 3" to 10" when viewed at the

chosen distance, which in this case was 60 feet. A small auxiliary

telescope was placed so as to look through the binocular at the
190 WAR WORK OF THE BUREAU OE STANDARDS

resolution screen. The screen itself was lighted up by a frosted

light bulb in an ordinary projection lantern with lens removed; a

ground-glass diffusing screen was placed where the slide would

normally come, and the resolution screen was placed about 3

inches from the ground-glass screen. This furnished a satisfactory source, sufficiently bright for the purpose. By making

readings on both the vertical and horizontal lines of the screen,

the effects of astigmatism were observed.

The auxiliary small telescope was found advantageous on a

number of counts, although some opposition developed among

manufacturers to its use in testing, their contention being, in

effect, that its use showed defects in binoculars which could not be

detected by ordinary visual and service tests. Common sense must, of course, be employed in collating much more rigorous

tests with service requirements. The use of the small telescope

has the great advantage that it enables resolution tests to be made

without fatigue and strain. In direct tests of resolution without

the aid or the extra magnification furnished by the telescope,

the eye must work at nearly the limit of its resolving power,

soon producing fatigue and rendering the results less trustworthy.

The field of view was tested by means of a scale at a distance

of 15 feet. The scale was so drawn as to allow for the slight cor- rection necessary because of the focusing of the binocular on an

object close at hand, so that the angular field of view could be

read directly from the scale. The binoculars tested had a field

of 8°, which occasionally ran as low as 7 40'; no definite tolerance

was required in these tests.

An important test is that for parallelism of the axes. If the

axes of the barrels of an instrument of binocular type are not

parallel, the eye will be put to undue accommodation strain,

and, if the error is large, it will be impossible to accommodate

sufficiently to prevent the seeing of two images. The amount by

which the axes may depart from perfect parallelism depends

upon the magnification of the instrument. It can be shown that

the angle to which the eye has to accommodate itself to allow for

such lack of parallelism is (ra-i) times the actual angle between

the axes, where m is the magnification. For the six-power binoculars tested the tolerances set by the Signal Corps have been six

minutes in the horizontal plane and three minutes in the vertical

plane. The results of these tests would seem to indicate that

manufacturers have no difficulty in keeping well within these

limits.
OPTICAL GLASS AND OPTICAL INSTRUMENTS 191

The apparatus used for the parallelism tests was modeled from

a description of similar apparatus used by the French Government, and an apparatus working on the same principle has been

described by Drysdale in the 1905 report of the Optical Convention. It consists of two reticles mounted side by side, the distance between them being that between the two barrels of the

binocular, a ground-glass bulb for illuminating the reticles, a

means for holding the binocular in position, and a suitable arrangement of lenses and mirrors with a screen on which the images of

the reticles are projected. The operation is as follows: The

ground-glass bulb gives a diffuse illumination on the reticles,

and the light then passes through two collimator lenses. From

these the light enters the barrels of the binocular. A 7-inch collecting lens takes the light from both barrels and projects the

images of the reticles upon a screen through the medium of two

mirrors. The superposed reticles, with no binocular in position

will produce an image upon the screen. The same is true with

the binocular in place, except that the image will be of smaller

size. Lack of parallelism will show in a displacement of the

image of one reticle in reference to the other. The reticle oblong

is made of such size that its image on the screen will be 6 feet

long by 3 feet high, when a 6-power binocular is under test, thus

enabling the variation from parallelism to be estimated directly

from an inspection of the reticle image.

The apparatus used for testing the magnification is practically

the same as that used for testing the parallelism, except that but

one collimator is necessary and the large 7 -inch lens can be re- placed by a smaller one. A pair of fine lines is ruled on a strip

of ground glass, which is placed at the focus of the collimating

lens. Introducing the binocular, an image of these two lines is

formed on a ground-glass screen, as magnified by the binocular.

The magnification may thus be read off directly to 0.1, which is

sufficient for the purpose and is the tolerance as set by the Signal

Corps.

The exit pupil, or Ramsden circle, should be as large as the eye

pupil of the observer if full advantage is to be taken of the illumination of the object observed through the telescope. For the

quick measurement of the exit pupil a projection system is used

at the Bureau. An electric lamp illuminates the telescope objective and a short-focus lens, I, projects the image of the pupil upon

the screen at s. On the screen there is a movable scale calibrated

to read the pupilary diameter directly in millimeters. The lens
192 WAR WORK OF THE BUREAU OP STANDARDS

/ and the screen s remain fixed to maintain a constant magnification, the telescope being shifted to get the pupil in sharp focus

on the screen. The transmission is defined as the percentage of light which

passes through the apparatus in terms of that incident upon the

objective. This percentage will vary in different instruments in

accordance with the number of separate surfaces in the optical

system, thickness of lenses and prisms, and transparency of the

glass used. In a Galilean type binocular the transmission should

reach 80 per cent. A good prism type binocular should reach 50

per cent in the barrel which has no mil scale and 40 per cent in

the one with the scale; but these values are not often attained.

The transmissions were measured on a Martens photometer.

A set of prisms was arranged to do away with the necessity of

using a comparison light. This was found to be a very satisfactory arrangement, as it obviates the necessity of continually

checking the zero reading of the instrument and avoids the effect

due to fluctuations in the potential of the current used in the

lighting system.

A great saving of time was achieved by providing the photometer with a special divided head by which the percentage of

light transmitted could be read off directly. This procedure,

together with the prisms mentioned above, made the determination of the transmission factors a very simple matter.

In order to make what is known as the "star test," two small

apertures of about 0.7 and 1 mm diameter were provided in the

resolution screen. The appearance of these "star images" as observed through the small telescope and the binocular in the

resolution test frequently affords data of value as to the general

performance of the instrument. The faults thus determined

come generally under the head of "flare," "color," and "scattered light." No definite rules can be laid down for acceptance

or rejection under this test. Decision as to the performance of

the instrument must be based on judgment and experience and a

thorough comprehension of service conditions.

Mil Scales

The mil scale consists of an auxiliary range-finding reticle

which is placed in the eyepiece of the military binocular.

Fine vertical and horizontal lines are ruled on the glass reticle

at definite intervals so that it is possible to make comparisons

and range determinations at the same instant one may happen to
ORDNANCE 193

discover an object or target. The scale posesses the further

advantage of enabling the artillery to point at an invisible or

indefinite target by aiming at some conspicuous object which

may be taken as a reference point on the mil scale.

The Signal Corps requested the Navy Department to construct

in its optical shop large quantities of binoculars equipped with

these scales. Difficulty was experienced in producing them, and

the Bureau was called upon to assist, and in a few days succeeded

in correcting the apparatus so that quantity production became

possible.

Early in 1918 the Bureau discovered that the scales supplied by

one of the largest commercial manufacturers contained serious

errors. This discovery was promptly communicated to the Signal Corps and to the manufacturer. The Bureau was authorized

by the Signal Corps to confer with the manufacturer on this point

and to see that proper corrections were made. After the matter

had been gone over thoroughly, the corrections Were made and

no further troubles were experienced.

ORDNANCE

Hardness of Brass Cartridge Cases

This subject is treated under the heading "Metallurgical

Investigations. '

Machine-Gun Erosion

A systematic study of this subject is being made from the

metallurgical point of view, including the preparation of a considerable number of special tests, determination of the interesting

physical properties, and the ballistic tests, which last are being

conducted by the Ordnance Department itself.

Copper Crusher Gages

At the request of the Society of American Manufacturers of

Small Arms and Ammunition and of the Ordnance Department

of the Army, the Bureau has been actively engaged in the preparation of specifications for copper crusher gages for testing

ammunition and standardizing the method of use. A considerable

amount of work has also been done on the characteristics of the

copper crusher cylinders, particularly as related to their properties

under various conditions of annealing and as dependent upon their

conditions of precompression, and includes a study of the resulting

errors. Several conferences have been held, and it is expected

shortly to close this subject.

26035°—21 13
194 WAR WORK OF THE BUREAU OF STANDARDS

Defects of Shrapnel Steel

This subject is treated under "Metallurgical Investigations."

Light Armor Plate

This subject is treated under the heading "Metallurgical

Investigations."

Synchronizing Devices for Airplane Guns

This subject is treated under "Aircraft, Miscellaneous."

Removing Metal Fouling from Rifle Barrels

This subject is treated under "Chemical Investigations,

Miscellaneous."

Munitions Gages

A complete description of this work is found under the heading

" Precision Gages."

Airplane-Gun Mount

Airplanes designed for fighting were provided with flexible

mounts for the machine guns and a safety belt for the gunner. It

was important to determine whether both the mount and belt

were sufficiently strong for the purpose intended. In order to

subject these to tests approximating actual conditions, special

equipment had to be provided for attachment to one of the

Bureau's testing machines. Through the use of this special equipment the mount could be tested in an inclined position, thus

approximating the probable average flying condition. The

Bureau carried out quite extensive development work along this

line and after a satisfactory form of construction was established

performed a number of acceptance tests.

Powder-Shipping Containers

Some of the powder containers tested were of fiber and others

were of sheet metal. The fiber containers were subjected to the

following tests: Internal air pressure, submergence, Mullen or bursting strength, and tensible strength tests of the cardboard of

the wall. The load required to pull off the crimped-on container

ends was also determined in several instances, as well as the effect

of the submergence test on the metal of the ends. All metal

containers were tested by submergence, air pressure, and in impact

by tipping over a container loaded with sand onto the floor and

also by dropping a weight on it from increasing heights until

failure occurred. As was the case very frequently with all materials, the Bureau was here called on to pass judgment upon
ORDNANCE 195

radical modifications of current design in powder containers.

Such advice, Avhich was more frequently furnished orally than by

correspondence, served as the basis for the Ordnance Department's

action in the standardization of their powder-container design.

Semisteel Shells

Extensive tests were made in an investigation of the possibility

of using semisteel or processed cast iron in lieu of steel for shells.

Initial experiments of American manufacturers with the use of

semisteel were unsuccessful, although French factories were then

turning out satisfactory shells of this material. Careful comparative studies were made of samples of American and French

manufacture, respectively, which included physical, chemical, and

microscopic examinations. The physical tests conducted included

tensile, compressive, and transverse strengths, hardness and impact

determinations. Suitable criterions were established which served

as acceptance bases for the purchase of shells. Quality production

of satisfactory semisteel shells had been begun before the signing

of the armistice.

Copper Rotating Bands for Shells

Considerable trouble was experienced by the Ordnance Department with the copper rotating bands on shells. It was found that

some of the bands when formed to the required size and shape

were so brittle that they failed in service by breaking. Other

bands were so soft that they filled the rifling on the inside of the

gun barrel with copper and caused jamming of the shells. The

possibilities for the use of arsenical copper in the manufacture of

rotating bands were investigated, and numerous suggestions for

improving their quality were furnished the Army.

Gun Barrel with Gored Rifling

One of the special problems investigated was the cause of failure

of a 75 mm gun in which a gash had been torn in the rifling when

the gun was fired. It was important to discover whether this

failure had been due to some imperfection in the metal out of which

the gun had been constructed or because of an imperfect shell.

In order to do this the gun was tested coincidentally with a 155

mm howitzer which had proved satisfactory in service. The gun

with the flaw performed as satisfactorily in the physical tests and

microscopic examination as did the other, which appeared to

indicate that the flaw resulted from a faulty shell and not from

any defect in the manufacture of the gun itself.

1
196 WAR WORK OF THE BUREAU OF STANDARDS

French and American Trench Mortars

An extensive comparative investigation was conducted of the

relative properties of 240 mm trench mortars of French and American manufacture. The study included physical, chemical, and

metallographic examinations. The French steel was found to

have a finer and more uniform texture with over 10 per cent

greater strength than the American material. This superiority

of the French material appeared to be the result of better heat

treatment, as the foreign steel had a lower carbon and manganese

content, which would normally indicate lower strength.

Railway Mount Recoil Piston Rods

A number of 6 and 8 inch diameter recoil piston rods for railwaymount howitzers were prooftested by the Bureau to loads twice

those brought upon them in firing. These rods necessitated the use of approximately the maximum load which can be applied

with the large Emery hydraulic machine, namely, 1 150 000 pounds

in tension. The elongations in a 5 or 6 foot gage length were

obtained as successive loads were applied and stress strain curves

were plotted for the rods.

This is one of the few laboratories in the country which is

equipped for applying large tensile loads to specimens of great

length.

Wheels, Investigation of Artillery, Truck, and Airplane

This subject is described under the above heading in another

part of the report.

Magnetic Analysis of Rifle-Barrel Steel

This is treated in the section on " Magnetic Investigations."

PAPER

Wall and Plaster Board

The use of wall board and plaster board as a building material

for the construction of military cantonments, Government warehouses, office buildings, and similar structures was developed to a

great extent during the war. Wall board is a general term covering those types of building material which are used as a substitute for wood lath and plaster in partitions and for sheathing

on the inside walls of buildings. The construction of the vast

number of Government buildings demanded in the prosecution of

the war required the use of a material that could be quickly

erected, having a low cost as well as adequate supply. This

necessity was met by the use of over 1 00 000 000 square feet of wall

board.
PAPER 197

Wall boards are made of paper, built up of one or more layers or plies that are cemented together with a binding agent such as

silicate of soda (water glass) or other adhesive. Plaster board is

made of three-ply material. The inner ply is made of hydrated

plaster of paris or gypsum, while the two outer plies are made of

a special paper. The finished boards are of thicknesses of threesixteenths, one-fourth, and three-eighths of an inch.

The term "plaster board" is applied to that type of wall covering that is made of two layers of a special paper with fire-retarding

properties superior to ordinary wood lath and plaster and far

superior to the all-paper wall board. The strength of this material

together with its fire-retarding properties and other qualities,

makes it an excellent building material and one that will undoubtedly come into more extended use as its properties and usefulness

become more generally known.

The term "wall board" applies to only that type of wall covering that is made entirely of old-paper stock, ground wood pulp, or other paper-making fibers.

Through the War Department the Bureau was requested to

assist in the preparation of specifications and methods of testing

to determine those qualities desired. Special methods for testing

this wall board had to be devised in order to duplicate as nearly

as possible service conditions. Samples of all the commercial

grades were secured and tested and their relative suitability determined. As the War Department had already used great

quantities of this material and was contemplating using much

more of it, the need of complete data of the service of this type

of building material could not be overestimated. The actual

service rendered by this wall board was investigated at various

cantonments and in buildings lined with wall board ajid plaster

board which had been erected over a year. The result of this general investigational work has been to greatly improve the quality

of the wall and plaster boards used by the Government. These

good results have been made possible largely by the hearty cooperation of several of the large manufacturers.

In order that further information might be obtained as to

the behavior of these boards under service conditions, a questionnaire was sent to most of the military cantonments. For temporary structures fiber wall board was preferred merely because it

was considered quicker and cheaper to erect and because of its

greater salvage possibilities. Plaster board was preferred for

permanent construction (that is, over five years) because it was
198 WAR WORK OF THE BUREAU OF STANDARDS

considered less subject to changes in temperature and because it

makes a warmer building. For hospital use plaster board was

preferred because of its greater resistivity to fire and moisture.

In general, it may be said that wherever quality and performance

were considered, the plaster board was to be preferred.

Paper as a Substitute for Linen in Airplane Construction

An original investigation was undertaken in the summer of

1 91 7 to determine what materials were necessary to produce an

exceedingly strong paper which could be substituted for woven

fabrics in airplane coverings. In preUminary tests a mixture of

jute and manila rope was found as most promising and had the

advantage of being a material which could be purchased in reas- onably large supplies throughout the United States. The investigation was divided into two distinct classes: first, the production

of a sheet of strong paper, and, second, the investigation of methods

for making it waterproof and fire resistant.

A series of runs made on the Bureau's experimental paper

machine, shown in Fig. 21, indicated that a paper from the rope

stock, comparing favorably in strength with textiles, could be

produced. The preliminary experiments demonstrated the limiting factors in cooking, beating, and machine treatment, and made

possible definite standard methods which were adaptable to practice anywhere, making reproduction of the sheet possible. The

result of the preliminary investigation was the production by the

paper section of a paper of quality equal to the samples submitted and of such character that it could be manufactured in widths

up to 144 inches continuously on a commercial-paper machine.

The survey also showed that there was a reasonable supply of the

necessary material available in this country. The method of treatment was 'long and the cost of the paper would be high, but presumably it could be procured at a price lower than woven cotton

or linen fabric. The economic conditions were not investigated

further than to determine that a supply was easily available.

After having made the paper, attempts were made to develop

a method of laminating two or more sheets together to produce a

single sheet, having a weight of 6 ounces to a square yard, since, as manufactured, the sheets weigh about 1 '% ounces per square yard.

It was the idea of the paper section that a glue or adhesive could

be developed which would not only securely fasten the sheets

together, but would also render them waterproof and to a certain

extent fireproof.
PAPER 199

The idea of discovering a material of this type was worked on,

and experiments were made with the following agents: Switzer's

reagent, glue, casein and blood mixed, sodium silicate, formaldehyde glue, bichromate glue, common glue, oil emulsion, zinc

chloride, sani dry, and halowax. No satisfactory results were

obtained in any instance, with the possible exception of the

Switzer's reagent. This agent, however, was abandoned because

of difficulty in manipulation and lack of uniform results.

However, the Bureau is not at all discouraged over the proposition and believes further investigation might develop a product

which would be satisfactory for laminating purposes.

In July, 191 7, the Bureau was formally requested to produce

1000 square yards of rope paper to be forwarded to the DaytonWright Airplane Co. This paper was prepared on exigency order

and forwarded at the earliest possible moment to its proper

destination.

Paper Filters for Gas Masks

In February, 191 8, there was started an investigation to

develop a paper suitable for filtering "sneeze gas," to be used in

connection with gas masks. This work was requested by the war

gas-investigation division of the Bureau of Mines and was later

continued with the cooperation of the Chemical Warfare Service

of the Army.

The first problem which was assigned was to duplicate in this

country a thin, craped, tissue paper which was at that time being

manufactured in England and used by the Allied armies.

Development work was at once begun at a paper mill in

Pennsylvania, and shortly thereafter a paper was successfully

made which duplicated that being used abroad. Further work

was done at this mill, and later development work was carried on

at a mill in Wisconsin, producing a paper of very much the same

kind. Both these attempts were highly successful, but in each

case the plans of the Chemical Warfare Service were changed so that this paper was never produced in any great quantity for use by the American Expeditionary Forces. However, data were

collected so that this material can be made at either of these mills

on very short notice, and it is to be remarked that the organizations controlling these two mills practically permitted their

equipment to be used as an experimental laboratory, although

this necessarily interfered with routine work.

In order to meet certain changes in the shape of the canister

desired by the Chemical Warfare Service, a paper which was very
200 WAR WORK OF THE BUREAU OF STANDARDS

satisfactory as a protection against "sneeze gas" was developed

on the paper machine of this Bureau, and sufficient data were

collected so that this paper can be developed here when needed.

However, it would probably take some time to duplicate this

paper on a commercial scale, although there is no doubt that it

could be done in the course of a comparatively short time under

the stress of war requirements.

In order to assist in the efficiency of this investigation, apparatus

was set up at the Bureau with the help of the Chemical Warfare

Service by means of which the paper developed was constantly

tested so as to incorporate in its production any improvements

which appeared desirable.

In this connection a gas house was built for the purpose ol con- ducting actual service tests of gas-filter paper as well as for

determining the concentration of the gas by means of the nucleation apparatus.

While this work was in progress a large number of commercial

papers were studied to determine whether any grades of paper were

being manufactured which would be suitable for the purpose. It

was felt, however, that a very special paper was necessary and that

there was no paper on the market sufficiently porous to permit a

man to breathe through it, and at the same time sufficiently

compact to retain the small particles of "sneeze gas" which were

injurious to the lungs.

As a result of these investigation it would appear that two

distinct types of paper can be made in the United States on a

commercial scale, both of which would be satisfactory as a protection against " sneeze gas " in the gas-mask canister. One is a very

thin creped tissue, about 70 thicknesses of which are used, while

the other is a relatively thin porous paper, about 10 thicknesses

being needed. In both cases the chief obstacle in the use of paper

is the mechanical difficulty of attaching it to the gas-mask

canister.

Paper Containers for Axle Grease and Saddle Soap

In the interest of the conservation of tin the paper section of

the Bureau was requested to investigate the suitability of paper

containers for materials such as axle grease and saddle soap.

With the aid of the war-service committee of the paper industry

a line of samples representative of all the cartons now on the market

and at all suitable for this purpose was secured. These ranged in

size from a small box capable of holding about 4 ounces to a barrel

of 30 gallons' capacity.
PAPER 20

In general, the packages submitted could be divided into seven

different classes: (1) ordinary cardboard boxes with slip-on

covers; (2) cardboard boxes made from a heavily sized stock;

(3) boxes lined with paraffin or oiled papers ; (4) boxes lined with

parchment papers; (5) boxes impregnated with paraffin; (6)

boxes carefully treated with a suitable grade of varnish; and (7)

boxes composed of three-ply board, the middle one being an asphaltimpreganted ply.

Classes 2, 4, 6, and 7 were found to be the most suitable for the

axle grease. Any box seems to be possible for saddle soap, but

the paraffin-impregnated boxes were less desirable because in

some cases the heat caused by pouring in the melted soap was

enough to cause the paraffin to run. Where a plain unsized or

slack-sized cardboard box was used, the soap stuck to the fiber

of the box, and thus there was some waste in removing the soap.

The very liquid nature of the soap tended to soak off any parchment fining on the boxes, so that a box of this kind does not have

the advantage for saddle soap that it has for axle grease.

Asphalt as a coating material was found to be distinctly unsatisfactory, both because it had little effect in lessening the moisture

resistance and because it had a decided tendency to peel off and

contaminate the contents of the box. An asphalt-impregnated

paper used as a middle ply was reasonably satisfactory, and was

free from the disadvantages mentioned above.

The varnished box (No. 6) was decidedly the preferred type.

The varnish coating used was of such a type as to be very flexible.

Some boxes coated with sodium silicate were received, but these

were too brittle.

The tests were made on the assumption that the boxes of grease

would be carried in a warm place, as, for example, under the hood

of an automobile truck, or exposed to storage conditions in warm

places, as in a steamer's hold. The boxes for soap were tested

on the assumption that they would be filled by pouring in the soap

in the melted form and allowing it to harden.

It is thought that class No. 2 boxes made from heavily sized

stock would be sufficiently good for both purposes except under

extreme conditions, and they are considerably cheaper than some

of the more elaborate forms.

Round containers with slip-on covers are considered most suitable except where economy of shipping space is required. The

covers should be of such a nature as to slip on and off very easily
202 WAR WORK OF THE BUREAU OF STANDARDS

and without injury to themselves or the box. This fact renders

the complicated folding and locking covers open to criticism.

A very interesting field has been opened by the paper barrels

which were received in this connection. In general, these were of

two types: One is a barrel intended for the shipment of pitch or asphalt and as such has a comparatively low strength when empty.

It is made entirely of pulp and is in one piece. The other is made

of paper wound upon a mandrel under tension and is designed to

cover a wide range of use. Paper-board heads are put in after

the sides are completed. This barrel has considerable strength and

will bear the weight of a man standing upon its side, even when

empty.

PHOTOGRAPHY

General Photography

It is well known that the ordinary photographic plate when

exposed in a camera does not reproduce exactly what the eye sees. This is because the ordinary plate is affected by only blue and

violet light, for which the eye is relatively insensitive, and is

scarcely at all affected by the green and yellow, for which the eye

has its maximum sensitivity. These ordinary photographic

plates are practically insensitive to red light, and are, therefore,

handled with safety in light from a ruby lamp. It has long been

known, however, that photographic plates may be made sensitive

to green, yellow, and red light by the admixture of suitable dyes

to the emulsions coated on the plates, but the incorporation of

such dyes in the emulsion generally reduces the sensitivity of the

plate to blue and violet light, so that until very recently the commercial orthochromatic and panchromatic plates have been

slower than the ordinary plates. Their use was, therefore, limited

by the relatively long exposure required, until recent developments along the general lines to be described in the following

paragraphs resulted in remarkable increases in the sensitiveness

to yellow and red light.

A plate sensitive to these longer waves possesses some marked

advantages over the blue and violet sensitive plate. A panchromatic plate reproduces more faithfully what the eye sees, and

when exposed behind a ray filter or color screen it portrays objects

which, on account of haze, smoke, etc., would be hidden from an

ordinary plate, and also gives different contrasts depending on

the nature of the light transmitted to the plate through the filter.

The phenomenon of haze penetration by the longer waves is

known to most outdoor photographers. Not only haze due to

water vapor, but smoke haze, which looks bluish to the eye, is
PHOTOGRAPHY 203

largely eliminated by using light of longer wave length than

that which is most effective in case an ordinary unscreened plate

is used. Objects completely obscured by haze or smoke on an

ordinary unscreened plate may be shown in good detail by using

a panchromatic plate and a red filter. Such red sensitive plates,

of course, can not be handled in the presence of the well-known

dark-room ruby lamp, but must be developed in complete darkness or in a very week green light. To obtain the long-wave

advantages of haze penetration and contrast mentioned above,

the photographic plates must have the greatest possible sensitiveness to yellow, orange, and red light if the exposure times are

necessarily short on account of rapidly moving objects or if the

camera itself is in rapid motion, as is the case in aerial photography. When corrected camera lenses giving very bright

images are not to be had, there is another argument for using

photographic plates of the highest possible sensitiveness.

Photography as Applied to Spectroscopy

It is common knowledge that white light consists of a mixture

of colors of different wave lengths of light, and most colors in

nature are also compounds of several colors. These facts are observed when such sources of light are dispersed or spread out

into spectra by suitable apparatus such as prisms or defraction

gratings, and the analysis of such composite light is the domain

of spectroscopy. The regular observations in spectroscopy in

all spectral colors are now nearly always made by the use of photography; hence every modern spectroscopist is a photographer,

and to photograph the entire range of spectral colors from the

shortest ultra-violet to the long-wave infra-red requires a much

broader knowledge of the numerous complex underlying elements

of photography than that possessed by the average professional

photographer. The names of Huggins, Draper, Vogel, Eder,

Abney, and Schuman call to mind some remarkable applications

of photography which were inspired by spectrocsopic researches.

Photographic Spectroscopy at the Bureau of Standards

The spectroscopy section of the Bureau of Standards began in

1 91 4 an extensive program of measuring standard wave lengths

throughout the entire range of the spectrum which can be observed photographically, and some of this work Avas published in

the following scientific papers of the Bureau:

S 251. Interference measurements of wave lengths in the iron spectrum (2851A3701A) with notes on comparisons of lengths of light waves by interference methods,

and some wave lengths in the spectrum of neon gas.
204 WAR WORK OF THE BUREAU OE STANDARDS

S 274. Interference measurements of wave lengths in the iron spectrum (3233A6750A).

S 302. Wave lengths of stronger lines in helium spectrum.

S 329. Measurements of wave lengths in the spectrum of neon. Then it was observed that although observations of spectra

were extensive in the so-called chemical regions—that is, in the

short-wave lengths from ultra-violet to blue—and were fairly

numerous in the green and yellow, there existed a great scarcity

of data for the red and infra-red, these latter being the regions

for which highly sensitive photographic plates could not be purchased. Accordingly, the Bureau of Standards decided to pay

special attention to spectroscopic observations in the neglected

regions of long waves. This involved the preparation and use of

photographic plates specially treated to make them sensitive to

red and infra-red light. Such sensitized plates have been successfully used at the Bureau since 1914m a systematic study of the

spectra of about 50 of the chemical elements. Some of the results

of these studies have appeared as scientific papers, among which

may be mentioned No. 312, "Wave-Length Measurements in

Spectra from 5600A to 9600A;" No. 324, "Wave-Length Measurements in the Red and Infra-Red Spectra of Iron, Cobalt, and

Nickel Arcs;" and No. 345 "Measurements of Wave-Lengths in

the Spectra of Krypton and Xenon." Applications of such sensitized photographic plates were also made in connection with

other scientific problems, as, for example, Scientific Paper No.

327, "Measurements on the Index of Refraction of Air from

2218A to 9000A," and especially to astrophysical problems.

These later include Scientific Paper No. 318, "Application of

Dicyanin to the Photography of Stellar Spectra," and "Photography of the Solar Spectrum from 6800A to 9600A," Astrophysical Journal (47, p. 1, 191 8); "Solar and Terrestrial Absorption

in the Sun's Spectrum from 6500A to 9000A," publications of the

Allegheny Observatory, and an attempt at Baker City, Oreg.,

to photograph the red and infra-red flash spectrum of the sun at

the time of its total eclipse on June 8, 191 8.

Military Problems in Photography

During the war aerial observation early came to play a prominent part, and it became a matter of great importance to have a

suitable panchromatic plate for aerial photography. Laboratories and research organizations in the allied countries were

busily engaged in trying to produce plates of extreme sensitive- ness or speed. The best commercial orthochromatic (sensitive
PHOTOGRAPHY 205

to blue, green, and yellow) and panchromatic (sensitive to all

colors) plates were too slow for most purposes. For many years,

however, physicists had used yellow and red-sensitive plates

which greatly exceed in speed any of the commercial plates.

These plates are prepared by bathing an ordinary photographic

plate (sensitive to violet and blue) in certain solutions of aniline

dyes, and at the expense of keeping qualities such plates may

be made much more sensitive to red light than any plate known

to commerce. After several years of experience with such plates

in spectroscopic investigations by the Bureau, it seemed worth

while to make an application of them to landscape photography

when the United States declared war upon Germany. Accordingly, experiments were made in 191 7 to determine the practicability of using the bathed plates for landscape photography

with the hope that either this method might be a useful addition

to the photographic methods of our military forces or that the

experiments would lead to improved commercial plates which

would incorporate sensitizing dyes in the photographic emulsions.

With apparatus that was inadequate to test the real merit of

the bathed plate, a number of photographs of various objects

were made which were encouraging enough to warrant a con- tinuation of the investigation, using better apparatus (more

suitable cameras and ray filters) and applying to the staining

bath new dyes of British manufacture.

The attention of the science and research division of the Signal

Corps was directed to these early results, and the Bureau was

given the opportunity of comparing the stained plates with

various plates used by the military forces. Among these were

several types of British-made panchromatic plates which were

then in use on the western front for aerial photography. A

series of experiments soon showed that pinacyanol stained plates

were at least four times as fast as the best commercial panchromatic plates then in use. In particular, plates stained with

some new dyes of British manufacture were found to be much

superior to any commercial panchromatic plates, not only in

speed but also in the range of color sensitiveness.

These encouraging results led to the offer of the Bureau to

supplement the photographic work of our military Air Service

by adding to it a new method which would probably be of great

military importance in special photographic work, such as the

penetration of haze and smoke, detection of camouflage, etc.,

where the ordinary commercial plates could not be satisfactorily
206 WAR WORK OF THE BUREAU OF STANDARDS

used. The Bureau received the assurance of cooperation from

the War Department and was invited by the Signal Corps to test

the bathed plates in aerial photography as soon as facilities permitted. Extensive experiments were made at Langley Field

during the spring and summer of 191 8 under the generous auspices

of the science and research division of the Signal Corps, and after

the armistice was signed the flying facilities of Boiling Field were

used to a limited extent to complete the experiments.

Early in 191 8 a representative of the spectroscopic section of

the Bureau, who was in France, was requested by the French

military authorities to assist the French photographic section in

making fast color-sensitive plates. A temporary laboratory was

installed similar to the ones at the Bureau of Standards with the

exception that the plate-drying cabinet was arranged so as to use air heated by a gasoline stove. This was necessary on account

of the low temperature and high humidity prevailing in northern

France in winter. The following experiments with bathed plates

were conducted by this laboratory. Ordinary fast plates were

stained with pinaverdol and pinacyanol with ammonia, orthochromatic plates were bathed in pinacyanol with ammonia, panchromatic plates were bathed in ammonia. Each type of plate

was used in three ways: Unscreened, with a deep yellow screen,

and with a red screen. The bathed plates were found to be

somewhat faster unscreened than any plate actually used by the

French. Using screens, the bathed plates were shown to be much

faster, particularly for red photography. This matter was also

considered of very great importance by the American Aviation

Section, and Col. Dunwoody requested that one of the Bureau's

physicists cooperate with them on experiments of this kind. This

cooperation was offered, but was not strongly supported by the

military authorities in America, largely on account of the fixed

idea that bathed plates had only reached the experimental stage.

Considering the special equipment and technique required by such

plates, their use at the battle front was held in abeyance with

the hope that commercial panchromatic plates of sufficient speed

would be forthcoming.

The success with which dye-sensitized photographic plates had

been used in the Bureau's laboratories, however, convinced those

engaged in this work that such plates had possibilities of extreme

importance in special military applications and impelled the

Bureau to demonstrate their value by careful measurements in

the laboratory and tests in the field. In addition to the problems
PHOTOGRAPHY 207

of ordinary photography, the use of bathed plates with light filters

involved (1) a study of photosensitizing dyes and of the spectral

sensitivity which they imparted to ordinary photographic plates,

(2) experiments to increase still further the speed of color-sensitive

plates, (3) investigations of the spectral distribution of energy

reflected from landscape, etc., (4) design and construction of new

photographic lenses for use with red light, and other similar

problems. These problems have been investigated by the Bureau

with such success that the importance of dye-sensitized plates in

military photography is now admitted by all, and the practicability of their use has been thoroughly demonstrated. The

great advantage of these special plates in the taking of photographs from an airplane under adverse conditions is illustrated

by Fig. 22.

Photographic Method of Detecting Camouflage

The Bureau, in cooperation with the United States Signal Corps

and the United States Air Service, utilized a photographic method

of detecting camouflage. The method consists of making two

photographic negatives of the group of objects, one before the

change and the other afterwards. A positive is made from one

of the negatives, and this is superposed upon the other negative.

If no change had occurred between exposures, the combination

would form a field of practically uniform photographic density;

but changes are plainly indicated by discontinuities of density.

It is believed that the method has considerable commercial value

for engineering and detective work, etc.

Protection of Moving-Picture Film from Heat of Lamp

A short description of the work done by the Bureau on this

problem will be found in the article on " Radiometry."

Metallic Mirrors for Cameras

This subject is likewise treated in the article on " Radiometry."

Automatic Regulation of Diaphragm by Intensity of Light

A paragraph dealing with some work done by the Bureau on the

practicability of a device for this purpose is described in the

article on " Radiometry."

Production of Dense Barium Crown Glass for Lenses

The experiments which have been conducted in the Bureau's

glass-making plant on the production of glass for photographic

lenses will be found in the article on "Optical Glass and Optical

Instruments."
208 WAR WORK OF THE BUREAU OF STANDARDS

Tests of Photographic Lenses and Camera Shutters

The experimental work performed in connection with the

testing of photographic lenses and shutters is treated in the

article on "Optical Glass."

PROTECTIVE COATINGS

Electroplating Investigations

Even before this country entered the war, numerous inquiries

for information upon plating of military supplies were received

by the Bureau, and a few preh'minary investigations were made

upon special applications of plating; for example, the production

of copper propeller tips by electroplating. Soon after the beginning of the war it became evident that electroplating was being

extensively required upon military supplies of most varied description, and that there were almost no specifications or methods

of inspection relating to such work. Owing to the fact that in

almost every case the plating was considered as an incidental and

minor part of the manufacturing process, very little consideration

was given to this subject by military officials in the early part of

the war. In consequence, confusion and misunderstanding often arose in connection with the plating operations. There was held

at the Bureau of Standards on March 27, 191 8, a conference of

military officials and manufacturers interested in electroplating.

After a detailed discussion of the methods and requirements of

the plating operations certain definite recommendations were

made which were incorporated in a report of the conference,

copies of which have been widely distributed. Among the recommendations of this conference was that one or more experienced

platers should be engaged as plating advisors on military supplies.

In accordance with this suggestion two experienced electroplaters

were engaged by the Bureau and devoted most of their time to

visiting various plants engaged in the manufacture of supplies,

to assist them in producing satisfactory plating.

To a great extent the function of plating upon military supplies was to protect metals, especially steel, from corrosion.

Therefore it was necessary to devise and adopt methods of testing

by which the relative value of plating as compared with other

protective coatings could be determined. This section therefore

cooperated actively with other sections of the Bureau in the

preparation of specimens to be used in comparative corrosion

tests. The principal test used for this purpose was the salt-spray

test, by means of which it was readily shown that zinc coatings
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 22.Views from an airplane taken with an ordinary

photographic plate, and one specially prepared at the Bureau's laboratory

The penetration of haze by these special plates is clearly illustrated in the two pictures, taken at the same time of the same objects. Such plates were oritdnally develuped for use in spectroscopic

work, thus illustrating the practical application of a scientific achievement
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 23.

Radio direction finder or coil aerial used in measuring the distortion of

radio waves in the vicinity of trees, towers, wires, buildings, etc.

Fig. 24.Model set-up in the radio laboratory to illustrate the use of the radio direc- tionfinder

Radio signals are sent out from the two lighthouses and the direction from which they come is determined by the apparatus on the ship. The latter can therefore determine its position even

in fog and under other conditions which render the lighthouse lamp invisible
PROTECTIVE COATINGS 209

exert the best protection against corrosion of steel, and that

satisfactory zinc coatings may be produced by either hot dipping,

sherardizing, or zinc plating (so-called electro galvanizing).

Accordingly, in various specifications the Bureau urged the use

of zinc coatings, not specifying the method of producing these

coatings, but requiring a certain resistance in the salt-spray test.

In connection with the cooperative work with the Ordnance

Department of the Army and with the committees on standardization of supplies for the War Department, it became evident that

there was a lack of coordination between the various protective

coatings required for different articles and for different kinds of

service. A suggested classification of finish for metal parts was

therefore proposed for use by the Ordnance Department and other

branches of the War Department. The basis of this classification

was the use or degree of exposure to which the articles would

subsequently be subjected. While the proposed plan was never

formally adopted by the military officials, it served in numerous

cases as a guide in the specification of metal finish. This classification, together with a review of military applications of electroplating, was presented at a meeting of the Electro-Chemical

Society and was also published in Metal Industry for November,

1918.

The three kinds of plating which were of most importance from

the military standpoint were zinc, lead, and black nickel, upon

all of which investigations were conducted at the Bureau, and

information was furnished to manufacturers and to military

officials.

When the value of zinc coatings for protection of steel against

corrosion was fully realized, its use was extended to a wide variety

of articles. For example, naval airplane parts, material used in

shipbuilding, hardware for ammunition boxes, and parts of the

fuze mechanism for high-explosive shells. It was found that

satisfactory deposits could be produced from both cyanide and

sulphate solutions, but that the cyanide solutions were usually

more satisfactory for irregular shapes or parts with deep recesses. Except for a few plants engaged in the manufacture of storagebattery fittings, lead plating was until recently almost a scientific

curiosity. It was used very satisfactorily, however, on an extensive scale for plating boosters and adapters for gas shells and for

lining certain of these shells. Another important application of

lead plating was on the inside of underweight shells, whereby

thousands of otherwise rejected shells were salvaged. A pre26035°—21 14
2IO WAR WORK OF THE BUREAU OF STANDARDS

liminary circular giving detailed information upon the applications of lead plating was prepared by the Bureau and extensively

circulated. In connection with this work the application of lead

plating for lining chemical apparatus was investigated, and in

cooperation with the officials of the Kdgewood Arsenal a large

tank was plated with lead to a thickness of 0.07 inch. Unfortunately, this experiment was finished too late to permit the general

application of the process on the equipment at Edgewood before

the signing of the armistice.

A large amount of hardware and equipment used by the Government is required to have a black or gray-black finish, the

so-called "Government bronze." This is usually produced by

the process known as black nickel plating. It may be applied to

brass directly or after copper plating and to steel which has been

previously plated with copper or with zinc. Great difficulty was

experienced by the manufacturers in furnishing a satisfactory

finish, but after a great deal of work the Bureau was able to

throw considerable light upon the behavior of such solutions

and to devise simple methods of operation and testing.

There were many demands for information on copper, nickel,

and tin plating which frequently required visits to the plants in

order to determine and remove the cause of the difficulties

experienced.

In addition to the normal applications of plating many unusual

problems arose in connection with which the Bureau was able to

furnish some assistance. Among such problems may be mentioned the following:

In cooperation with the Bureau of Mines the Bureau assisted

in the development of a process by which it was found possible

to produce heavy nickel articles, such as seamless tubes, etc., for

which there was a considerable demand in the nitrate manufacture

and the separation of helium. It was arranged that the Government was to have the use of this process during the war and for

six months thereafter. So far as is known this method has never

been operated upon a manufacturing scale.

It was found that by a simple electrotyping process it was

possible to reproduce at a very slight cost the master range finder

scales used for producing the lines upon range finders.

The Bureau cooperated with the New York Navy Yard and

assisted them in securing the equipment and personnel for producing various plates by electrodeposition.
PROTECTIVE COATINGS 211

The Bureau was requested to investigate the possibility of

relining worn-out guns with a sufficiently heavy coating of nickel,

iron, or cobalt to permit the rerifling of the guns. The limited

force available prevented any exhaustive research upon this

problem, the solution of which on a large scale does not seem to

be very promising. More recently a similar problem has been

submitted, namely, of relining defective recuperator cylinders

used on 75-mm. or larger guns. In the preparation of these

cylinders it is necessary to have an absolutely smooth surface,

which is obtained by "lapping." In the process of manufacture

many defective cylinders have been rejected, and it is desired, if possible, to salvage these cylinders by plating a sufficient coating

of nickel or copper to permit relapping to a true surface. The

possibilities of this process are now being investigated.

The Bureau was called upon on numerous occasions to assist

in the design of plating equipment to be used for military supplies both in privately owned and Government plants. Among

the latter may be mentioned the New York Navy Yard, Marine

Depot in Philadelphia, and the Naval Aircraft instruction schools.

In addition visits were made to the principal arsenals and navy

yards and recommendations were made regarding the equipment

and processes for such work.

Bituminous Materials

The bituminous products are remarkably resistant to acid and

alkaline attack, their physical properties vary from liquid

asphaltic oils and tars to hard and brittle asphalts and pitches,

and they are susceptible to modification through this range by

blending and fluxing.

These physical characteristics have given them a wide and

general application in building construction, and they were called

into important uses by the military authorities not only for such

recognized purposes as prepared and built-up roofing, preservation of timber and waterproofing, but specifically as a coating for

steel and concrete ships, a coating for hand and rifle grenades, for

marine glues used in the construction of pontoons for naval aircraft, etc.

In the preparation of specifications for prepared roofing it was

realized that war conditions had seriously interfered with the

normal production and quality of the raw material used in its

manufacture, and it was necessary therefore to make the specification less exacting than usual so as to obtain the essential produc-
212 WAR WORK OF THE BUREAU OF STANDARDS

tion. The present specification was developed in cooperation with

the War Industries Board and manufacturers producing prepared

roofing and includes instructions to inspectors as well as methods

of inspection and test. Large quantities of material were obtained under this specification which were used on cantonments,

hospitals, and warehouses built in various sections of the country.

The inspection and testing of this material required a great

deal of laboratory work, some thousand samples having been

examined, representing a million squares of roofing. As might

be expected many leaks developed in these roofs, but from such

information as could be obtained they appeared to be due to

faults or carelessness in laying rather than defective material.

Several cases were investigated by members of the Bureau in

cooperation with officers of the construction division of the Army

and recommendations for repairs were made which did not

necessitate relaying. The recommended method of repairs includes a specification for a roofing cement to patch holes or

larger areas in which the exact position of the leak can not be

located. This practice is now being followed and results in

satisfactory repairs at minimum expenditure of time and money

and with maximum convenience.

A specification for built-up roofing is still in process of development. This type was not so urgenty required during the war,

and with the signing of the armistice the immediate need passed.

There is a normal demand for a specification for this type of

roofing by the Government, and it is expected that those interested in the subject will be called together to consider the development of a uniform specification as soon as other more urgent

demands permit.

For covering the interior of steel ships, including the coal

bunkers, it was necessary to produce a coating which would

protect the metal effectually against corrosion in places which

were not readily accessible for inspection and which were always

wet with salt or bilge water. Likewise the coating must adhere

without cracking or flowing when the vessel is laid up during cold

winter months and must not be injured by the severe conditions

encountered in the engine and boiler rooms. Such investigations

required a study of the service conditions, the development of

tests which would duplicate these conditions, the production of

material in the laboratory to meet these tests, and finally the

preparation of specifications to insure the quality of the material

accepted.
PROTECTIVE COATINGS 213

Considerable work has also been done in connection with concrete ships. Such vessels had never before been used to any

extent, and required special treatment. A ship is subjected to

great and various strains and can not be made perfectly rigid, so

that, although concrete is usually considered a rigid material,

it was called upon in this case to act as an elastic substance, and

with proper reinforcement was found to stand much distortion

without failure.

Small hair cracks may develop in the concrete, and one of the

problems presented was to cover the outside of the structure with

an elastic waterproof membrane which would bridge such small

cracks. The coating must not be affected by water, must not

flow when subjected to the pressure of the water when the vessel

runs at maximum speed, and must present a suitable surface for

the application of antifouling, boot-topping, and camouflage

paints over it. All of these conditions were considered and a

number of products tested in an effort to obtain one which seemed

to meet conditions of service best.

Another problem in connection with concrete ships was the

production of a satisfactory inside coating for oil tanks. Many

of these ships were to be used as tankers for the transportation

of a variety of crude and refined oils. The problem was complicated by the presence of water in the oil and also by the fact that

these tanks might frequently be filled with water as ballast on

return trips. This, of course, made necessary a coating resistant

to both water and oil.

After an extended investigation it was recommended that a

long oil varnish, commonly called spar varnish, be adopted for

the inside coating, and a bituminous coating for the outside. It

was also found that treating the concrete surface with a solution

of magnesium fluosilicate was an advantage, as it had a hardening

effect and gave a better bond.

A satisfactory marine glue was required both by the Army and

Navy to cement canvas to light pontoon construction, as the

foreign product was no longer available. The material must be

adherent and elastic after frequent wetting and drying, must

remain tacky and pliable and be waterproof and durable. Many

commercial products were tested and analyzed so as to know

what materials could be used in producing a satisfactory product.

As a result, a specification was developed in which the requirements were based on performance so as to insure a satisfactory

material with the minimum restriction on composition.
214 WAR WORK OF THE BUREAU OF STANDARDS

Hand and rifle grenades required a coating which would dry

hard on a greasy surface, as it was not practicable to clean them

after machining. A hot coal-tar pitch of relatively low penetration

and high melting point was applied to both the inside and outside

of the grenades and excess drained off.

The coating for the inside of high-explosive shells required

different characteristics. It had to be free from any lead or manganese compounds, should not dry hard, but remain tacky,

so as to bond with the molten T.N.T. with which the shells were

charged, and should not have any effect on the efficiency of the

explosive. A Gilsonite fluxed with a soft Bermudez asphalt and

thinned with a slight volatile petroleum product appeared to give

a satisfactory coating.

A war-time specification was also prepared for the construction

division of the Army for creosote oil for wood preservation. This

specification was not put in general use, as contracts had been

placed prior to issuing of the specification, and much inferior

material has been used on that account.

Varnishes

Karly in 1 9 1 7 the Bureau rendered a report to the Aviation Section

of the Signal Corps showing the relative waterproofing qualities of

different treatments on wood. This information, which was re- quested by the chief signal officer, showed that a high grade of spar

varnish wasthe mostsatisfactory transparent coatingfor waterproofing the wooden parts of airplanes and for protecting the dopedfabric

of the wings. The varnish which seemed to answer the requirements most satisfactorily consisted of a china-wood, oil-resin

varnish, and at this officer's request a specification, based entirely

on physical requirements of the film, was drawn up, which appears

to have been the first specification for spar varnish the basis for

which was performance rather than composition. In October,

1 91 7, there was a meeting at the Bureau of representatives of the

various varnish companies and of the Bureau of Standards. This

committee constituted the varnish subcommittee of the standard

committee of the Society of Automotive Engineers, and the committee adopted a specification very similar to the one furnished

by the Bureau's laboratory to the Signal Corps.

About this time the various branches of the Aviation Section

began calling for lists of varnishes that had been approved under

this specification. The Bureau had made examinations of many

samples of varnish under this specification and had complete
PROTECTIVE COATINGS 215

data on exposure tests, so that a small list of approved varnishes

was immediately available. A very large number of samples to

be examined continued to be submitted, and after exposure tests

were completed, those which proved satisfactory were added to

the approved list. As a result there was always available for the

chief signal officer a continually growing list of approved varnishes

that could be ordered by any of the airplane manufacturers on

brand.

In December, 191 7, a chemist from the Signal Corps laboratory,

part of which was then located at the Bureau, was detailed to help

in carrying out the very great amount of experimental work and

testing which Avas required by the more than 200 samples of varnish which were submitted for test. In May, 191 8, when the

Signal Corps laboratory was moved to Pittsburgh, all the work

which had been carried on at the Bureau was transferred to the

new laboratory.

At a conference with representatives of the allied nations, the

Specification for spar varnish for airplanes, with practically no

changes from that originally prepared, was approved and adopted

by the International Aircraft Board. The same specification has

since then been adopted by practically all branches of the Government, including the Bureau of Construction and Repair, Navy

Department ; the United States Shipping Board ; the United States

Railroad Administration; the General Supply Committee; and

the War Department. This specification has proved to be one of

the most generally applicable to all classes of high-grade varnish

for all purposes, although the specification finally adopted by the

Signal Corps of the Army contained several slight modifications,

which were made after the removal of its laboratory to Pittsburgh.

In order to prevent the explosive charge in high-explosive

shells from acting on the metal and to prevent rotation of the

charge independently of the shell, it is necessary that the interior

cavity of the shell be coated with a varnish. Such a varnish should

be free from lead and other heavy metals, so that no reaction will

set in between the explosive charge and the coating. The specification to cover a satisfactory varnish of this type was furnished in

April, 1918, to the explosives section, Engineering Division,

Ordnance Department of the Army, for a shellac-resin mixture cut

in denatured alcohol. Such a varnish had previously proved satisfactory. Another specification covering material for this purpose, but which did not limit the manufacturer to any specific
2 1 6 WAR WORK OF THE BUREAU OF STANDARDS

composition and which would have the proper softening point to

form a good bond between the shell and the explosive in hot

loading, was also furnished to the Ordnance Department.

For coating the metal ends of powder containers the Ordnance

Department had specified an acid-proof lacquer. This caused

considerable confusion, since all oily resinous materials contain

a certain amount of organic acidity, and the Bureau was called

upon to settle this question of dispute between the manufacturers

furnishing the lacquer and the War Department inspectors, who

were guided by the existing specification. As a result the Bureau

recommended spar varnish conforming to the airplane spar var- nish specifications as the most suitable coating for the metal ends

as well as for the fiber container where it is crimped into the ends.

The coating of the interior of rifle and hand grenades presented

a somewhat different problem from the coating of the high-explosive shells. In the process of manufacture the grenades are sent

to the loading plant in a very greasy, dirty condition. In order

to expedite production it was not feasible to clean the grenades,

and a coating material was therefore desired that would adhere

to the greasy interior surface. For this purpose certain loading

stations had been using a varnish which consisted of a solution

of resin in a certain type of gasoline which resulted as a by-product

in a manufacturing process. This gasoline was available only in

limited quantities, and in order to overcome this difficulty samples

of the gasoline were submitted to the Bureau. It was found that

it was nothing but ordinary automobile gasoline containing a considerable quantity of sulphur, free and in solution. In experiments with the varnish made from this gasoline and resin it was

found that the varnish had no particular virtues in adhering to

greasy surfaces and that good continuous films on the interior of

grenades were not always obtained. However, when a solution

of resin in solvent naphtha was used, a much better film was

obtained. A recommendation to this effect was made to the

trench-warfare section of the Ordnance Department. It later

developed that the manufacturing process allowed heating of the

grenades, and this enabled them to use a bituminous varnish

which appeared to be more durable.

Enamels

Soon after extensive varnish testing was under way, it was

realized that the use of an enamel would much better protect the

doped fabric of airplane wings, and such an enamel should be
PROTECTIVE COATINGS 21

light in weight, opaque, and very durable; so experiments on

various types of enamels were begun. As a result of the preliminary information obtained the Bureau of Construction and Repair,

Navy Department, drew up a specification for airplane-wing

enamel which required the necessary physical qualifications of

a satisfactory enamel and limited the manufacturer to a specific

composition of pigment. It developed that it was impossible to use certain types of pigments with airplane spar varnish, which

had been proved to be the most satisfactory vehicle. Further

experiments were made to determine which pigments worked

most satisfactorily in a vehicle of spar varnish, and in cooperation

with the Bureau of Construction and Repair, which made similar

experiments, the airplane-wing enamel specification was finally

changed so as to retain the physical requirements of the original

specification, but eliminated the composition requirements of the

pigment.

Specifications for high-grade air-drying and baking enamels

were also drawn up for various branches of the War Department.

These had for their basis the spar-varnish specification and in

general called for suitable pigments in a vehicle for spar varnish

conforming to the airplane spar-varnish specification. The airdrying enamels, especially the low visibility gray, were used

exclusively on the hydroplanes manufactured by the Navy

Department, and black enamels, both air-drying and baking,

were used for finishing the metal fittings on hydroplanes as well as for giving a black finish on military hardware parts. A blue

air-drying enamel consisting of a pigment in airplane spar varnish

is used for coating the wires and cables of airplanes.

Several samples of baking Japan that were to be used for coating

the cases of submarine mines were examined for the Bureau of

Ordnance of the Navy Department. These Japans were backed

on at very high temperatures (between 250 and 300 C) and had

to resist the severe action of being submerged in salt water.

Slushing Oils

Shortly after the armistice was signed, the Bureau received

many requests on rustproofing compounds which could be used

in storing large quantities of equipment of all types. Examination of some of the samples of rust preventives which had been

submitted to the Bureau showed that they varied greatly in composition and in quality. After many practical tests specifications

were drawn up to cover transparent slushing oils of brushing con-
2X8 WAR WORK OF THE BUREAU OP STANDARDS

sistency and dipping consistency, and opaque slushing oils of

brushing consistency. These specifications did not limit manufacturers in any way as to the composition, but were based entirely

on practical tests. A small mimeograph pamphlet on "Notes on

the Protection of Metal in Storage" was prepared. This dealt

in a general way with the question and included the specifications.

Technologic Paper No. 176 has been issued recently and deals

more fully with slushing oils.

Fireproofmg of Fiber Board

Some of the Army hospitals were constructed from a waterproofed wood-fiber board. This construction proved to be a very

great fire hazard and resulted in the complete destruction by fire

of one or more of the hospitals. The problem of fireproofing the

material was given to the Bureau, and experiments showed that

when treated with a solution of sodium silicate and water the

combustibility was very much reduced. It was recommended

that as far as possible the buildings constructed of this board

be discarded and further use of this building material be discontinued, but that where the buildings could not be vacated,

all the interior walls be treated with a spray coat of a fireproofing solution of water glass.

Fire-Retarding Paints

In the summer of 191 7, at the request of the Bureau of Yards

and Docks, Navy Department, work was commenced on a number

of samples recommended as fire-retarding paints. On November

1, 1 91 7, a report was made to the above Bureau, and since that

time a number of other fire-retarding paints have been tested for

various blanches of the War and Navy Departments. The subsequent work has only tended to confirm the original conclusions,

which are as follows:

Since this investigation was intended to give information regarding fire-retarding treatments for interior surfaces, the tests were not designed to give information as to the durability of the coatings on exposure out of doors; but since any interior surface

may be subject to an occasional wetting, it is believed that the relative behavior

before and after soaking in water is of importance. It should be noted that the per

cents of efficiency in fire retarding, from the arbitrary methods necessary in making

the calculations, are relative only, those having the higher ratings showing the greater

resistance; but the difference between the best and the poorest is actually small. The value of any particular treatment can best be judged by reference to its relation to well-known common methods of coating wood. Thus, whitewash ranks among

the most resistant materials, indian red in linseed oil among the least resistant, and

white lead and zinc oxide in linseed oil are intermediate.

The general conclusions from this investigation are that while practically all paint

coatings have some fire-retarding action, none of the materials examined afford very

great protection. All the samples tested were materially damaged by application
PROTECTIVE COATINGS 219

of the flame for a few seconds. It is noted that both sodium silicate and whitewash

rank relatively high. Both of these have the advantage of cheapness, and there is no reason why both can not be used on the same surface. It is believed that for interior wood surfaces the application of sodium silicate solution followed by a coat

of whitewash may be more efficient than either one used alone; but, as mentioned

before, no treatment of wood after erection can be expected to act as an efficient fire preventive, and the use of such materials should not be taken as an excuse for omitting

any precautions tending to prevent danger of fire starting or providing ample facilities for stopping any fire as soon as it starts. It is believed that wood construction, no matter how the wood is treated either before or after erection, will involve serious fire risk, and whenever practicable noncombustible material such as metal, cement, etc., should be used.

We, therefore, now recommend that claims as to fire-retarding

properties of paints be entirely disregarded, since practically all

paints have some slight value in this respect, and the difference

between the best and the poorest is practically negligible.

Paint Specifications

A very large amount of work was done in preparing specifications for paints for various purposes. For example, at the request

of Emergency Fleet Corporation, specifications were prepared for

white paint, outside slate-color paint, boot-topping paint, and

copper paint for use on wooden ships. These were sent with a

letter to the United States Shipping Board, August 3, 191 7. The Bureau cooperated with the Paint Manufacturers' Association in examining numerous specifications for paint for steel ships

recommended to the Shipping Board. Specifications for a paint

for steel helmets were prepared for the Chief of Ordnance of the

Army. After testing a number of samples of very rapid-drying

paints for use on projectiles, a specification was prepared and

sent with a letter to the Edgewood Arsenal at Baltimore. All

projectile paints of which the Bureau has any knowledge that

were used during the period of heavy production were of the type

covered by the above-mentioned specification, but the Bureau

has been unable to learn whether the proposed specification was

ever issued. The War Department has, however, specifications

for projectile paints of a different nature from the above, as they

are much slower drying and it has not been learned whether projectile paints according to the issued specifications have been used

or not.

Numerous paint specifications were prepared for the various

branches of the War Department, the War Industries Board, etc.

Paint Testing

A very large number of samples of paint have been tested for

the War and Navy Departments, and this work still continues.
220 WAR WORK OF THE BUREAU OF STANDARDS

The Railroad Administration specifications for all paint materials prescribe that methods of test approved by the Bureau shall

prevail in all cases of dispute, and considerable work has been

done in advising the railroad chemists regarding methods.

Since the signing of the armistice the Bureau has been called

upon by the Ordnance Department of the Army for advice relative to the painting of guns, shells, and other equipment for storage. Experiments were carried out to determine the thickness

of paint films on shells after brushing and spraying; it was found

that three coats of a suitable paint could be applied to shells

without increasing the diameter sufficiently to exceed the tolerance permitted, thereby obviating the necessity of cleaning the

shells should their use be required.

PUBLICATIONS AND INFORMATION

New Scientific Publications

The Bureau of Standards prepared and published during the

war many special reports, most of them confidential, on military

technologic subjects. For example, a series of confidential reports

on the strength and other properties of aluminum alloys; a series

of special aeronautic instruments circulars, describing a wide variety of aeronautic instruments, their design, construction, and

methods of test and calibration; and a series of power-plant re- ports, relating to the design and test of aeronautic engines and

auxiliaries, such as radiators, carburetors, etc., and the relative

merits of various types of airplane fuels. A series of confidential

news bulletins recounting recent developments in the Bureau's

military work, besides many thousands of scientific and technologic papers and circulars were distributed regularly to technical

officers and employees throughout the military services.

Metric Literature

General Order of the United States Army, dated January 2,

191 8, reported that the General Staff of the American Expeditionary Forces in France had adopted the metric system. The

order read in part:

The metric system has been adopted for use in France for all firing data for artil- lery and machine guns, in the preparation of operation orders, and in map construction. Artillery and machine-gun material intended for service abroad is being

graduated accordingly. Instruction in the metric system will be given to all concerned.

The urgent demands for metric pamphlets, charts, paper comparison scales, and tables of equivalents began at once and kept

up briskly throughout the war and, in fact, have not yet ceased.
PUBLICATIONS AND INFORMATION 221

The metric literature issued by the Bureau and thus distributed

by the thousands of copies among the technical services of both

the Army and Navy in France and America included

1 . A graphic wall chart of the international metric system (44K inches by 2 8^ inches)

giving tinted graphic and numerical comparisons of customary and metric measures, and metric tables.

2. A descriptive pamphlet of the international metric system showing the uses of the

various units, giving a brief summary, the important equivalents, and a statement of the legal status of the metric system.

3. A 30-cm (12-inch) comparison scale printed on paper, permitting direct visual

translation from centimeters or millimeters to inches or binary fractions of the inch.

4. A document entitled " Units of Weight and Measure—Definitions and Tables of Equivalents, ' ' a rather complete statement of tables of equivalents covering all the more commonly used units, together with official definitions and equivalents of basic

units of length, area, capacity, and mass.

5. The Metric manual for soldiers, which is described in the next section.

Soldiers' Manual of the Metric System

When the General Staff of the American Expeditionary Forces

adopted the metric system of weights and measures for use of our

forces during the war, the Bureau, as mentioned above, had many

demands for metric material for instruction work here and abroad.

To meet this demand in a manner especially adapted for the use

and information of the average soldier, the Bureau prepared a

metric manual of 16 pages (10 by 15 cm). This was known as Miscellaneous Publication No. 21 of the Bureau of Standards,

entitled "Metric Manual for Soldiers—The Soldier's Manual of

the System—An International Decimal System of Weights and

Measures, adopted as the legal standard by France and 33 other

nations and in world-wide use.

'

' The aim was to give the American

soldier a practical grasp of the system by graphic examples of the

units, citing dimensions of objects familiar to the average soldier.

The publication included a sketch of the origin of the metric system

with brief tables of equivalents and a glossary. About 100,000

of these manuals were distributed, and the plates were made

available to the bureaus of the Army or Navy desiring to use them

for printing special editions. The Superintendent of Documents

also placed the manual on sale. Abundant evidence has shown

the usefulness of this little manual in teaching the metric system of

weights and measures, which was used with such success by the

allied forces in the war.

Technical Information Activities

On account of rapidly changing conditions during the war with

its extensive use of all scientific and technologic resources, the

methods of combat and communication were being constantly

improved or replaced through the use of new inventions or as a
222 WAR WORK OF THE BUREAU OF STANDARDS

result of scientific discoveries. The rapid and continuous circulation of accurate technical information to the workers in scientific

and technologic fields having military application therefore became

of paramount importance.

Pertinent technical information was available from authorities

and experts in all branches of physics, chemistry, and engineering,

from the various offices of the War and Navy Departments and

from research agencies of civilian character engaged on military

problems here and abroad, such as the National Research Council,

National Advisory Committee for Aeronautics, etc.; as a means

for disseminating this material an "information section" was

inaugurated in the central office of the Bureau of Standards in

which confidential information of the type just described was re- ceived. All such information was carefully digested with reference

to the needs and activities of every section of the Bureau, and

notices of receipt and abstracts of such information were distributed

promptly to the experts concerned with the particular subject

of each document. In this way a means was provided by which

timely and effective contact could be accomplished among workers

in related subjects of military research, and results were obtained

in the way of speeding up exigent work which otherwise would

have been quite impossible.

The information work was further extended by the publication

at frequent intervals of a series of confidential bulletins giving

timely news items regarding military work carried on at the

Bureau of Standards. This series was made up of 26 numbers,

approximating 65 000 words. These were sent to a mailing

list comprising the principal technical officers and employees in

the Army and Navy organizations in this country and in France.

These bulletins give short abstracts of the method of solution and

often also a resume of the results obtained on new researches and

investigations, and so afforded a ready means of supplying technical experts throughout all services with up-to-date information

regarding recent advances at the Bureau in their respective

specialties, aiding also to set up contacts by which experts in any

field included might be enabled to obtain cooperation or assistance.

RADIO COMMUNICATION

Radio in Warfare

The use of electric waves for telegraphy without wires had

become recognized in 191 7 as indispensable to warfare. It made

possible communication with remote places and rapidly moving
RADIO COMMUNICATION 223

troops. The United States was far behind other countries in the

application of radio communication to the above purposes, but

its immediate importance was clear.

The absolute necessity of radio in modern warfare is apparent

when one considers the tremendous complexity of the fighting

methods. The firing of artillery no longer consists merely in the

pulling of a trigger by a man who looks at his target; the use of

heavy guns depends not only on the properties of explosives and

the application of ballistics, but also on aviation, radio, meteorology,

map making, and many other sciences and arts. The gunner

does not see the object at which he is shooting nor does he even

see the airplane which is watching the mark and telegraphing the

results of his shots to him. All methods of conveying signals are

used, from the most primitive to the most advanced, from a

human courier to electric waves. Radio has been used not only

to give orders, direct battle, and listen to the communications of

the enemy, but also for very different purposes, such as the issuing

of propaganda, the conduct of armistice negotiations, and the

saving of ships at sea. In the several allied countries large laboratories were established for the investigation of radio waves and

the development of apparatus which would utilize them in the

most efficient manner. Existing scientific laboratories were utilized for research on the more fundamental principles and instruments, and the military services established special laboratories

of their own to design the military equipment.

When this country entered the war, the Bureau of Stadnards was

ready with methods, apparatus, and trained personnel for the

solution of many of the fundamental problems which confronted

military men. Among the problems which had to be solved, and

solved quickly, were: (1) The establishment of high-power transoceanic radio systems for use in case all the cables should be cut;

(2) the development of low-power radio equipments which should

send out just enough but not too much power for communication in

the congested area of any given sector at the front; (3) a means for

the location of enemy radio stations and airplanes, submarines,

and ships; (4) apparatus for communication with and from submarines, particularly when totally submerged; (5) simple and

reliable apparatus for radio telephoning; (6) the production of

radio apparatus which could be easily carried and yet comprise

everything necessary to make the most effective use of radio

waves; (7) the training of great numbers of men in a complex and

rapidly changing subject.
224 WAR WORK OF THE BUREAU OF STANDARDS

Fortunately, certain radio devices existed which gave promise

of solving a number of the more important problems. Among

the most noteworthy of these devices are the electron tube and

the direction finder. Both were being developed at the Bureau

of Standards. The first of these, the electron tube, is a device

which makes possible radio telephony. The direction finder is a

simple apparatus, which not only receives the radio waves, but

which can also be turned in such a way as to determine the direction from which the waves come. At the beginning of the war,

although these devices were imperfect and their principles but

little understood, both scientists and military engineers saw in

them the promise of great utility and means for the solution of

problems which would give our Army great superiority over the

enemy. Much has been done in the application of the best

scientific knowledge to the development of these instruments.

Relation of Bureau of Standards Radio Laboratory to Military

Services

The Bureau of Standards has been a center for radio research

work. Besides its own radio laboratory, there were located at

the Bureau during the war the following Government establishments: Naval radio research laboratory; naval aircraft radio

experimental laboratory; research laboratory of Signal Corps;

intelligence division of Army, radio laboratory. The Bureau

furnished laboratory facilities for these independent organizations

and assisted by testing instruments, etc. Accommodations were provided for this work in the electrical

building of the Bureau and in another building which was erected

on the Bureau's grounds exclusively for radio work. Equipment

was provided and research undertaken for the many lines of

specialized measurements which were required.

The presence of the Signal Corps and naval laboratories assisted

the Bureau in planning its own radio work along lines which

would assist the military services. Besides contributing directly

to the military radio problems, much of the work on the Bureau's

radio research program was necessarily of a fundamental nature

on principles, measurements, and the efficiency of design of

apparatus. Without such work the Bureau would have been

unable to advise upon many of the problems submitted to it or to effectively carry out its other undertakings.

The Bureau was able to furnish information, advice, and

assistance upon radio matters to the National Research Council,
RADIO COMMUNICATION 225

as well as to the various branches of the Army and Navy Air

Services. The most direct relations were maintained with the

Signal Corps, a considerable part of the Bureau's work having

been done specifically for this organization. This work was

supported in part by funds transferred to the Bureau by that

Corps. During the war period the staff of the Bureau's radio

laboratory numbered about 40 men, and besides these, 5 men

were detailed from the Signal Corps to assist in special investigations. Six additional persons were detailed for short periods by

the Signal Corps and the Navy to receive instruction in laboratory

work.

That the Bureau's cooperation was appreciated by the military

services is indicated by the following statement contained in the

report for 191 9 of the Chief Signal Officer to the Secretary of

War:

The outcome of this research work has been of vital importance to the Signal

Corps, and it is felt that every additional facility should be afforded to the Bureau

of Standards so that it may continue to collaborate with the Signal Corps on these

special problems.

Cooperative Activities

A notable event following America's entry into the war was

the visit of the French Scientific Mission early in 191 7. The

Mission included Prof. Henri Abraham, of the University of

Paris, who has been a leader in applying electrical science to

radio apparatus for war purposes. The French mission brought

a large quantity of scientific military apparatus and deposited it

at the Bureau of Standards. This was demonstrated to Army

and Navy officers and scientific men employed upon military

problems.

In 191 8 an interdepartmental radio conference was organized

which held meetings every two weeks at the Bureau of Standards.

This conference was composed of the technical radio men of the

Navy, Signal Corps, and the Bureau of Standards, and at each

meeting one of the important problems of radio was discussed.

These meetings were very valuable, both for the interchange of

information and because through this means the radio men of

the Government were kept in touch with one another's work.

In a number of the problems upon which the several radio

organizations were working along related lines, cooperation was

furthered by informal conference. Many investigations were

carried on directly for the military services by the Bureau, as detailed later in this report. Besides those mentioned, many

26035°—21 15
226 WAR WORK OF THU BUREAU OF STANDARDS

special researches were undertaken at the request of the Army

and Navy.

Information and Reports to the Army and Navy

A considerable part of the time of the radio laboratory was

devoted to furnishing information by letter and informal consultation, and to aid in this work a systematic file of technical

data on radio subjects was established. The subjects covered in

this consultation work included principles of radio waves and

apparatus, scientific and commercial data, radio organizations,

instruction material, standard symbols and terminology, bibliographies, applications of radio to various purposes, and the whole

range of technical subjects covered in the laboratory work. On

a number of occasions demonstrations of radio apparatus and

instruction in radio methods and measurements were given to

Signal Corps officers.

General reports on the Bureau's radio work for the Signal

Corps were prepared and furnished to that organization under the

dates of July 31, 1918; October 11, 1918; December 17, 1918; and

July 30, 1919. A general report on the radio work for the Navy,

of December 20, 191 8, was supplied to the Navy Department.

Summaries of the radio work in progress, dated August 7 and

November 6, 1918, were sent to the Signal Corps, the Navy Department, Air Service, and to the other military organizations through

the National Research Council. Outlines of the radio work in

progress and planned were sent to the Signal Corps.

Numerous copies of about one hundred technical reports on

the various phases of the radio laboratory work were sent to the

military services. These reports varied from brief descriptions

of work done to extensive treatises on radio subjects.

Radio Instruction

Among the problems which the Signal Corps had to solve

immediately upon entering the war was the training of great

numbers of men for technical service in the field. This was a

task of peculiar difficulty so far as radio is concerned, since it is

a complex and rapidly changing subject. The available literature

was not up to date, either for students or instructors. Instead of

the few scores of trained radio operators and a handful of

experienced radio engineers that were available before the war,

there was need for thousands of men skilled in this subject.

Intensive training was carried on at the cantonments and in

colleges and schools designated by the War Department throughout
RADIO COMMUNICATION 227

the country. An acute need for suitable radio textbooks was felt

by the men secured to act as instructors in these schools. The

general plan of radio instruction was outlined by Signal Corps

officers at a conference of college and university representatives,

held at the Bureau of Standards on December 29, 191 7, and,

although the Signal Corps courses of radio instruction were decided

upon at that time, but little instruction material was available.

From the above date the Bureau of Standards' radio staff

assisted in the preparation of instruction material. This was

accomplished by consulting the data compiled by the Signal Corps

officers and by preparing original material. The principal

contribution of the Bureau was the preparation of a radio reference

book and a textbook for elementary training, both of which are described below.

A number of brief instruction pamphlets were prepared by the

Bureau of Standards and submitted for use in connection with

various parts of the Signal Corps course. In addition, pamphlets

compiled by the Signal Corps were submitted to the Bureau for

criticism and were revised to a greater or less extent by the

Bureau's radio staff.

"Radio Instruments and Measurements"

At the December 29, 19 17, conference, the Bureau of Standards

presented the nearly completed manuscript of a treatise on radio

principles, measurements, and theory. This was offered as a

reference book which would be useful to the instructors in giving

the radio courses and to students training for radio officers. The

Signal Corps approved this manuscript and requested its speedy

completion and publication. By concentrated effort the manuscript was completed and sent to the printing office in January.

It was finally issued on March 23, 19 18. The Signal Corps was

supplied with 2000 copies.

This book, "Radio Instruments and Measurements," Circular

No. 74 of the Bureau of Standards, covers the fundamental theory

of radio and the more important instruments, measurements, and

formulas actually used in this work, subjects not covered by any

other publication. Thus there were made available unpublished

results of radio work which had been carried out in the laboratories

of the Bureau. One of the chief characteristics of the book is its

treatment of the underlying principles of radio by the simplest

methods of ordinary alternating-current theory. Previous books

have presented radio as a complicated subject based upon abstruse
228 WAR WORK OF THE BUREAU OP STANDARDS

theories, thus making it mysterious and difficult to grasp. The

book, commonly referred to as "Circular 74," is a publication of

341 pages, with an index and 224 illustrations.

Thousands of copies of "Circular 74" were furnished to men in

the universities, the Navy, and the Army, besides those furnished

to and through the Signal Corps. It has been used in the training

of thousands of students. Many letters have been received by

the Bureau from various sources, military, commercial, and

academic, commending Circular 74, and stating that it has been

found very useful in many lines of work.

One criticism of Circular 74 was that it was issued in paper

covers, uniform with all other Bureau of Standards publications.

The demand for a cloth-bound edition was recognized by a commercial publishing company, the Wireless Press. This company

reprinted Circular 74 with a smaller page size and cloth covers and

has sold a great many copies.

"The Principles Underlying Radio Communication"

Circular 74 having been found satisfactory as a radio reference

book for the use of instructors and officers, the training section

of the Signal Corps requested the Bureau of Standards in April,

1 91 8, to prepare an elementary textbook for general use by enlisted men and others. It was desired that this book cover the

fundamental principles of electricity and dynamo-electric machinery, as well as radio circuits and apparatus. Such a book

was needed as the basis for various pamphlets to be issued on

Signal Corps radio apparatus. None of the previously available

books had been found satisfactory.

An understanding as to the outline of the book was reached with

the Signal Corps, and the active work of preparation was begun

in June, 1918. The book was required within three months. It

was prepared by a syndicate scheme of authorship which was

rather an innovation in the preparation of scientific textbooks.

The regular radio staff was temporarily augmented by six members

of college faculties who were well equipped for this task. Due

to the haste necessary in preparation and because of the collaboration of a number of writers, coordination of the material was particularly difficult.

The work was completed and turned over to the Signal Corps

in September. The Signal Corps was unable to proceed with

publication until December, and the book was finally issued in

March, 191 9. While the book was in preparation, a first edition
RADIO COMMUNICATION 229

of 50 000 was contemplated. After the signing of the armistice

this was reduced, and the first edition numbered 6000 copies.

The book is nonmathematical and profusely illustrated. It

contains 356 pages, 4^2 by 7^2 inches, in a flexible binding. It is

suitable for the instruction of men who have had the equivalent

of high-school education. It has been adopted as a radio textbook in the Army and the Navy, a number of colleges, Y. M. C. A.,

and other schools. The Bureau of Standards has received many

favorable comments on this book from schools, manufacturers,

inventors, amateurs, and students.

Radio Direction Finder

A few turns of wire wound around a wooden frame arranged

so that it can be rotated constitute an aerial which not only receives

radio waves but also determines the direction from which they

come. Detecting apparatus connected to this simple device

receives the wave in much the same way as the more familiar

antenna which is seen in connection with most radio stations.

The current circulates around the coil instead of oscillating up

and down as in an antenna. This direction finder is a much

smaller structure than an antenna, being, in fact, usually only

about 4 feet by 4 feet in size. It is not as powerful a receiver of

the radio waves, but its great advantage is that it determines the

direction. The wave produces electrical action in the coil only

when it is placed in the line of the advancing wave. If it is rotated

so that it lies across the line of the wave, no effect is produced.

As one turns the coil, the received signal changes from a certain

maximum loudness to a weaker and weaker and finally zero sound. From the position of the coil when the sound is thus

reduced to zero, the line of direction of the wave may easily be

determined. This simple apparatus was in constant use during the

war to locate the position of enemy radio outfits in the trenches, on

ships, in the air, and even under the ocean. Among the numerous problems presented for solution in connection with the direction finder was that of the accuracy of its

indications. Would the direction thus determined make it possible to aim a gun so as to destroy the transmitting station ? Was

it sufficient to permit replacing the magnetic compass on a ship

by a direction finder? (Incidentally, this use of the radio direction finder in navigation has led to the name generally adopted

among naval and flying men, the "radio compass.") Another

important practical problem was the determination of the abso-
230 WAR WORK OF THE BUREAU OF STANDARDS

lute direction of the transmitted wave. That is, could the direction finder determine not only the line of transmission of the wave

but also from which of the two possible directions along that line

the wave came? Other questions were: What was the best

detecting apparatus to use with the direction finder? How did

it compare with an antenna of a given size in the receiving of weak

signals ? Could this kind of aerial be used not only for receiving

but for transmitting radio waves ? From the work done at the Bureau of Standards upon these

and similar practical problems, it was found that direction could

be determined to about 1 °. This showed that the device could be

used to prevent the interference of radio waves. That is, it became possible to receive the particular wave desired and exclude

others. By turning the direction finder the waves from any

particular direction may be excluded, and a wave from any other

direction may be received without interference.

The indications of the direction finder are affected by its sur- roundings. A careful study of this subject was made, and it was

found that metallic objects, such as a tower, bridge, or trolley

wire cause very large errors of direction, since currents produced

in these structures by the waves affect the direction finder. (Fig.

23.) Nonmetallic objects, such as a tree or bank of earth, have

smaller effects. The effects of the surroundings can be corrected for

if the direction finder remains fixed relative to the surroundings.

It was found that when very long radio waves are used their

direction varies with time, especially at night. With the relatively short waves used on ships and in military operations, however, the variations are negligible.

One of the applications of the direction finder to navigation

developed by the Bureau is its use in fog signaling. (Fig. 24.)

The lighthouse lamp, made useless by a heavy fog, can be supplemented by a radio system, consisting of automatic apparatus for

transmitting radio waves as regular signals at definite intervals.

A ship equipped with a very simple radio direction finder can

easily steer toward the lighthouse or determine its location.

Coil Aerial as Transmitting and Receiving Device

The simple coil aerial used as a direction finder was carefully

investigated in comparison with the ordinary large antenna as a

radiator and receiver of radio waves. It is in general not as powerful as the large antenna, but when a sensitive amplifier is used

with the receiving apparatus the coil aerial is sufficiently powerful
RADIO COMMUNICATION 231

for many classes of radio communication. The coil is used in

series with a condenser, and to this simplest type of radio circuit

is connected the generating or detecting apparatus, no connection

to the ground being necessary. On account of the small size of

the coil aerial, the complete radio outfit may be contained and

used in an ordinary room. The coil aerial has advantages over

the ordinary form of antenna for certain applications, as in the

submarine work described in a subsequent paragraph.

A study of the principles of action of the coil aerial and the

ordinary antenna led to the development of transmission formulas

by which it is possible to calculate the current produced in the

receiving apparatus for any distance from the transmitting station.

The formulas have been verified by experiment. Laboratory

studies were made of the design and electrical properties of coil

aerials, thus leading to a knowledge of the best way to construct

such an aerial for any particular purpose.

In field tests with the coil aerial it was found to have directional

properties as a transmitting as well as a receiving device. That is,

it transmits more intense waves parallel to its plane than at 90

to it. This valuable characteristic, together with the facts that

more current can be gotten into it and that it can emit a narrower

band of wave lengths than the ordinary elevated antenna, makes

it valuable for certain applications, but its relative lack of power

precludes its general use as a transmitting aerial. When used as a receiving device, it will pick up waves coming from a source a

surprising distance away. By the use of exceedingly sensitive

amplifiers, with an aerial consisting merely of a few turns of wire

located inside an ordinary room, it is easy to receive in Washington signals transmitted from Germany or from the Pacific coast

of the United States.

Submarine Radio Signaling

It was generally believed that radio communication could not

be carried on below the surface of the ocean, since the water was

thought to be so good a conductor as to be impenetrable by the

radio waves. In the navies of this and other countries experiments had failed to develop a successful radio system for use

under water. Nevertheless, the Bureau investigated the coil

aerial as a possible solution of this problem.

In November, 191 7, the Bureau of Standards placed a direction

finder coil under water and received signals virtually as good as with the coil in the air. Additional experiments with the use of
232 WAR WORK OF THE BUREAU OF STANDARDS

the apparatus on a submerged submarine soon followed. Permission Avas secured from the Navy Department to make experiments

at the submarine base, and after experimental work on submarines had been conducted for several months very simple but

effective radio apparatus was developed.

The essential part of the apparatus is the antenna, of the coil or loop type, consisting of a single turn of wire, heavily insulated,

its circuit being completed by grounding to the metal hull of the

submarine. On June 20, 191 8, with every part of the submarine

and its equipment submerged, signals transmitted from Germany

were received in the submarine. Signals from Paris, Rome, and

California were received with equal ease. Furthermore, the apparatus was found to be a satisfactory direction finder just as when

used in air.

It was later found possible not only to receive but to transmit

radio messages when the submarine was totally submerged.

Transmission can not be carried on over very great distances, but

it is possible for a ship and a submerged submarine to exchange

recognition signals. This is the only thoroughly successful system

that has been developed for communicating with submerged

submarines, and the Navy has equipped a number of submarines

with it, as shown in Fig. 25.

Signaling System for Airplane Landing

The radio direction finder is very useful to the aviator. The

magnetic compass and other instruments to assist him in steering

his course are affected by the rapid changes of motion of the airplane and do not give him reliable information about his location

with respect to a known point on the ground. By using the radio

compass, he can steer toward his landing field, but a need was felt

for a device which would supplement the radio compass by telling

the pilot when he was exactly over the landing field even in fog

or darkness. The need for this had been felt particularly in the

Air Mail Service of the Post Office Department.

A localized signaling system which fulfills the above requirement

has been worked out as a result of the Bureau's experiments.

Either of two methods may be used. In one, a large coil of wire

consisting of one or a very few turns with a length of about 1000

feet on a side is laid on the landing field. This coil carries several

amperes of alternating current of about 500 cycles per second.

Magnetic induction from this coil extends over the space above the

landing field, and produces a signal in telephone receivers connected
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 25.

United States submarine equipped with coil antenna By this means the submarine can send and receive radio messages even when totally submerged.

The system of submarine radio transmission developed at the Bureau has been applied to

several vessels by the Navy Department
\

Miscellaneous Publications, Bureau of Standards, No. 46

IL m

Da Fo r I- st Ic'eccivi rte Tubes MM.

Qlo Tube 5 (GMAL CofiPJ Type, Nav» T>-pc. Receiving Tubs.

A

6.E. . V.E. . GE. ¥L

!?eceivirtG Tuoc. . Anpur-ymo Tuae. Til*, rtjitirrino Tuae. TaANsniTTiNG Tune.

Fig. 26.

Numerousforms of electron tubes

This little device has revolutionized radio communication, has made possible radio telephony, and

has aided in securing satisfactory multiplex wire telephony where as many as five connections

are possible over one pair of wires
RADIO COMMUNICATION 233

to a coil of wire on the airplane. The aviator hears the signal

only when he is over the landing field. In the second method the

result is produced by the use of specially constructed coils of much

smaller size on the landing field, employing radio-frequency

current.

Satisfactory signals are heard by the aviator at distances up to a

mile above the field. The advantage of this system is not alone

the actual utility to the aviator, but also the added sense of security

against his enemy, fog.

Electron Tubes

The use of electron tubes was practically unknown to the military forces of the United States prior to 191 7. All of the radioapparatus then used was of the damped-wave type. The development of military radio equipment employing electron tubes was

given the needed impetus by the visit of the French Scientific

Mission in the spring of 191 7, since they brought with them, and

exhibited at the Bureau of Standards, a great variety of equipments for radio communication which had been developed around

the electron tube as the essential element.

The three-electrode electron tube is a simple device, known by a

great many names, such as vacuum tube, audion, valve, lamp, thermionic bulb, triode, valve relay, etc. It looks much like an ordinary

incandescent lamp bulb (Fig. 26), but has in addition to the hot

filament two other metal structures, a simple wire grid and a metal

plate or cylinder. The operation of this device depends upon the

fact that every hot object is continuously giving off small particles

of electricity, called electrons. Some of the electrons emitted

from the hot filament go to the metal plate, and this flow of electrons constitutes an electric current. This electric current can

be influenced or controlled by the flow of electrons to the metal

grid. This control of one electric current by another very small

electric current makes it possible to use the tube as an electric

relay or amplifier and for many other purposes. A simple description of the fundamental theory of operation of the electron tube

is given in Circular No. 74 of the Bureau of Standards, " Radio

Instruments and Measurements," pages 200 to 215. This device

was invented less than 10 years ago, and most of its development

has been accomplished during the war. It is a remarkable instrument if only the variety of its uses is considered. Thus it serves

as the detector of radio waves, as a very powerful amplifier of

radio or any other electrical currents, as a generator or producer
234 WAR WORK OF THE BUREAU OF STANDARDS

of radio waves, and as the means for converting speech into a

modulated radio wave which can be again changed into speech by

a receiving radioapparatus. The reader will readily see that

these important applications justify the most extensive and profound research, development, and application. Thus the principal

work of the great New Jersey radio laboratories of the Signal

Corps was the development of apparatus using these electron tubes.

Certain research work and the standardizing of tubes and methods

of testing were carried on by the Bureau of Standards. The

principles of the operating and functioning of the tubes are, by

contrast with the structure of the tubes themselves, complicated

and difficult to determine. When one considers the extensive

applications of these devices which have already been made, it

seems strange that so little is known regarding the principles of

their operation.

The importance of electron tubes in military work is apparent

from the fact that for the American Armies alone 25 000 tubes

were made each week. These devices have revolutionized all

branches of radio and have produced many advantages for which

investigators have sought in vain for years. Electron tubes have

many applications outside of radio, as, for instance, their application to wire telephony, where they make possible five simultaneous

conversations over one pair of wires. On account of their great

sensitiveness as receiving devices, radio apparatus can be made

very compact. These devices must be credited with a considerable

share in the achievement mentioned above in describing direction

finders, namely, the receiving of messages from a distance of thousands of miles with a small apparatus contained in an ordinary

room. In fact, apparatus capable of concealment about a person's

clothing may now be constructed by which one can receive the

radio messages which are passing through space.

The electron tube has made communication between airplanes

successful. Obviously, airplane apparatus must be extremely

light in weight, and this is possible with the very sensitive electron

tubes. Airplane pilots can now talk to one another, using apparatus that adds only a few pounds to the weight of the machine.

Not only can the communication be carried on from one airplane

to another and from an airplane to a ground radio set, but the

apparatus can be connected to the ordinary telephone lines.

The radio telephone upon which the above apparatus is based

was brought by the French Scientific Mission to this country in
RADIO COMMUNICATION 235

191 7. Improvements in many points have been made since that

time and have rendered the apparatus more reliable and effective.

On account of the Bureau of Standards' work on the characteristics of tubes, amplifiers, and other electron-tube apparatus,

and on methods of measuring their constants and characteristics,

the Signal Corps requested the Bureau to take over the general

work of electron-tube standardization. The work included the

measurement of numerous characteristics of tubes in order to

check results obtained by field inspectors, a study of experimental

tubes under development by the various companies, and of the

methods of testing tubes in the field and in the laboratory, a

determination of the causes of behavior of power tubes in various

circuits, and a study of various amplifier circuits. The Signal

Corps was assisted in its inspection work by instructing a number

of electron-tube inspectors who were detailed to the Bureau of

Standards for that purpose and were given instructions for a

period of six weeks in the methods of testing tubes.

Special Military Researches on Electron Tubes

A number of rather extensive researches were carried on following a definite program laid out by the Bureau after receiving

a specific statement of the problem from the Signal Corps. One

of these was on the efficiency of electron-tube generators of highfrequency current as affected by the production of harmonics.

Investigation had shown that practically all the generating circuits used in Signal Corps apparatus were heavily loaded with

harmonics, so that the output hot-wire ammeter reading gave no

indication of the useful power output which is all contained in the

fundamental frequency. This was investigated both by measurements of current in tuned circuits and by direct observation of

the wave forms in the cathode-ray oscillograph. A complete

solution of the problem was obtained. The principles were

developed by which the amount and effects of the harmonics may

be determined, and by which apparatus can be so designed as to

reduce them.

A critical study was made of the Signal Corps testing sets for

receiving tubes. These sets had served well as factory testing

sets, but it was recommended that the Bureau make a critical

study of them, looking toward improvements in design, practice, or method, and having as particular objects increased uniformity

of the inspected product and decreased difficulty of manufacture.

It was found that a number of improvements could readily be
236 WAR WORK OF THE BUREAU OF STANDARDS

made in the amplification and in the detector test sets. It was

shown that the generator test set did not make a real test of the

generating properties of a tube, as it would be difficult to find a

tube which would not oscillate in this set. Furthermore, it was

easy for the operator to connect up the set so as to change its

indications radically. The following suggestions were made: (1)

A circuit which really tests the generating properties and which is

similar to actual receiving circuits should be used, and (2) a different method of indicating the presence of generated current

should be employed.

In using receiving tubes as high-frequency amplifiers the Signal

Corps had noticed that the input impedance of the tube, particularly that part contributed by the capacity of the grid to the other

electrodes, seemed to be a function of the electrical constants of

the plate circuit. A further knowledge of this was very desirable,

and the Signal Corps recommended that the Bureau make an

experimental study of the subject, using in particular the VT-i

tube. A complete solution of the problem was attained by a

theoretical investigation, checked experimentally. It was found

that the input impedance of a tube can be represented as a series

resistance and capacity, the values of which depend in a definite

and determinable manner upon the electrical characteristics of

the plate circuit and the capacities between the tube electrodes.

At the request of the Bureau of Steam Engineering, Navy

Department, a study was made of the use of high-power threeelectrode tubes for producing power at radio frequencies, particularly for radio telephony. For supplying the direct-current

power to the tubes without use of commercial high-voltage directcurrent generators, a rectification system was developed, using

three-electrode tubes in place of the two-electrode tubes usually

used as rectifiers. It was found that the third electrode, or grid,

could be used either for smoothing out the pulsation in the output

current or for increasing the efficiency of rectification, but not for

both at the same time. Accordingly, attention was directed

especially to the use of the grid control for increasing the efficiency,

while the desired smoothing out of pulsation was obtained by

other methods. For the latter purpose the output load was

shunted with a condenser and inductance in series, tuned to the

principal frequency to be eliminated. For converting the directcurrent power thus obtained into radio-frequency power, a study

was made of the use of large power tubes as radio-frequency amplifiers. In this system the tube or set of tubes operates into a
RADIO COMMUNICATION 237

high-power resonant circuit or antenna, while the grid alternating

voltage is supplied from an independent low-power resonant circuit which is excited by a low-power electron-tube radio telephone set. This radio-frequency power amplifier was found to

possess many advantages, especially in simplifying the design of

the high-power output circuit, and in placing most of the complicated apparatus in the auxiliary low-power radio telephone set.

Radio Measurements and Tests

An interesting portion of the work consisted in development

along the lines of technical measurement. The basic facts, the

knowledge of which has made possible the improvements above

described, could never have been discovered without careful

measurements of the phenomena which take place in connection

with the use of high-frequency radio currents. These measurements are far more complicated than most of the ones with which

we are familiar. In this matter of measurements the Bureau

naturally is the recognized leader in the country, and radio measurements in particular have been very highly developed by its

laboratories during the last few years.

The beginning of the work for the military forces was contemporaneous with improvements in radio measurements made possible

by the use of the electron tube. Tubes were put into service in

the laboratory as a source of current for measurement purposes,

particularly as generators of very steady high-frequency currents,

which have made possible measurements to an accuracy of 1 or 2

per cent, whereas 5 or 10 per cent has been the previous limit.

This greater accuracy of measurement made it possible to develop

more accurate radio instruments, and thus called for the development of special methods of measuring, special means for avoiding small errors in the measurements, and special measuring

instruments. Standards for the important measurements were

established. The theory of radio measurements was studied

extensively in the Bureau's laboratory, and the results of this

work were made available to the Army, Navy, and manufacturers

through special laboratory reports and printed publications.

A great deal of the measurement work was concerned with the

fundamental components of all radio circuits, capacity, inductance, and resistance. A typical instrument set-up for this work

is shown in Fig. 27. The elimination of errors in the laboratory

by carefully devised shields and other precautions was necessary.

Apparatus for the production and measurement of large current
238 WAR WORK OF THE BUREAU OF STANDARDS

and high voltage at radio frequencies was developed. (Fig. 28.)

For the measurement of small current, thermoelements were used,

while for the very smallcurrents, such as those in a receiving antenna,

electron tubes were employed. Special mention should be made

of the employment of these tubes in a special method of comparing

the received with a locally produced signal. Numerous types of

radio apparatus were designed, and this work made necessary an

extensive study of the inductance coil, one of the principal elements of every radio circuit. Electrically, a coil is a complicated

apparatus, and there has been no comprehensive information on

its behavior in a radio circuit.

A number of tests of radio operating apparatus, such as transmitting sets and antennas, were made. A particularly interesting

one consisted in a complete test of a Signal Corps airplane radiotransmitting set known as type SCR-73. It was modeled on a

French set, and comprised a self-excited, 900-cycle generator,

wind-driven by a small propeller, and a radio set of the spark type.

Provision was made for rapid change to any of 1 6 wave lengths or

to any of 6 signal pitches, for the purpose of reducing interference

with other transmitting sets. The tests included characteristic

curves and oscillograms of voltage and current from the generator

power output and tests of the self-excitation and other features

of the generator, study of capacity to produce best spark tone and

maximum quenching action, nature of wave radiated, and general

criticism of design.

Among other interesting tests was that of a novel type of

quenched-gap transmitting set. The operation of special features

of the set was clearly revealed by the use of the cathode-ray

oscillograph. The determination of the constants and behavior

of a submerged cable used as a receiving antenna formed another

investigation. Quite a number of tests were conducted and

studies made of the design of wave meters used as radio measuring

instruments. Detailed comparative studies were made of the

design of commercial, Signal Corps, and French wave meters, and

the Bureau's experience in measurements and design enabled it

to suggest improvements. One of the tests of wave meters intended for field or air use was a shaking test, in which was determined the effect on the instrument caused by placing it in apparatus which simulated the vibrations of an airplane.

The routine tests from May 1, 191 7, to June 30, 1919, included

467 electron tubes, 279 decrimeters, 78 wave meters, 40 condensers, 39 inductors, 13 ammeters.
Fig. 28.

Apparatusfor generating high voltages at radio frequencies tised in the study

of the radio properties of insulating materials for radio apparatus
Fig. 29.

Apparatus for testing self-luminous dials By means of this equipment it is possible to determine whether a sample possesses the requisite brightness
RADIO COMMUNICATION 239

Cathode-Ray Oscillograph

There is no mechanical instrument which can follow the exceedingly rapid alternations of the current used in radio circuits.

The only way this can be done is by the use of a stream of electrical

particles, as in the cathode-ray oscillograph. In this instrument

a beam of cathode rays is deflected by the currents, and the motion

of the beam is made visible on a fluorescent screen. Thus the

wave form of radio current can be seen, and the phase relations

of currents and voltages in radio circuits can be directly determined.

Two general types of cathode-ray tube have been used at the

Bureau of Standards, those using a high voltage to cause emission

of a stream of electrons from the plane cathode of metal and those

having a cathode consisting of a heated filament from which the

electron emission is spontaneous. Tubes of the former type are

suitable for the measurement of currents of the order of magnitude

of 1 ampere. The hot-cathode tube is suitable for measuring

the electron currents obtained in three-electrode electron tubes,

which are of the order of magnitude of 0.05 ampere.

Oscillograms were made with these tubes as a part of the tests

performed upon radio transmitters submitted to the Bureau of

Standards. The quenching action of different spark gaps is determined directly by passing the gap currents through suitable

deflecting coils placed around the tube. A time axis perpendicular to the current deflection thus produced is provided by connecting the electrostatic deflecting plates across the capacity in

the closed oscillatory circuit.

The cathode-ray oscillograph was also used in the investigation

of the harmonics produced in antenna circuits by electron-tube

generators. Dynamic characteristic curves are obtained for a

given generator by impressing the grid voltage upon the deflecting

plates and allowing the electron currents to flow through the deflecting coils. The wave forms of the antenna currents are determined by providing a sinusoidal time axis from a separate generator

tuned to a lower frequency, of which the frequency of the antenna

current is a suitable multiple.

The combination of an electron-tube generator, which is capable

of furnishing currents at any frequency up to that corresponding

to a wave length of a few centimeters, with a cathode-ray tube

having a slow-moving electron stream, whose deflections are

closely proportional to the instantaneous values of these currents,

offered an opportunity for much profitable research. By the

use of one of these tubes a study has been made of the characteristics of electron tubes under actual operating conditions.
240 WAR WORK OF THE BUREAU OF STANDARDS

Insulating Materials

The work which was in progress at the Bureau of Standards on

insulating materials during the war included the measurement of

all the properties which are of importance in determining the

value of the materials for radio apparatus. Both in regard to the

number of properties thus investigated and the numberof materials,

the investigation was a comprehensive one. The work was mainly

on the class of materials mostwidely used in radio equipment, known

as the phenol or bakelite type. Much of the work of measurement

was carried out by other sections of the Bureau, the only measurements made in the radio laboratory being those involving the

electrical properties at radio frequencies. While a wide variety

of electrical and mechanical properties of the materials were measured, the object principally in mind was the determination of the

suitability of the materials for radio uses. The work involved in this investigation can not be appreciated

without an understanding of the nature of the materials. They

all contain a phenol resin or varnish of the general type invented

by Dr. Bakeland and may be divided into two general classes, the

laminated and the moulded materials.

It was fortunately possible to make the measurements of electrical, mechanical, and thermal properties on the actual sheets of

material as regularly supplied for commercial use. Consequently,

the data obtained should be directly applicable, as it was not

necessary to manufacture samples especially for test purposes.

Thus, for instance, for the radio measurements condensers were

made up using an actual slab of material such as is employed in

the construction of apparatus; that is, regular stock as furnished

by the manufacturer. This is a far better way to conduct a test

than by making up a special condenser from specially prepared

thin sheets of the material.

Mechanical properties which were measured included tensile

strength, transverse strength, modulus of elasticity, permanent

warping, brittleness, hardness, density, and moisture absorption.

The thermal tests included thermal expansivity, a little work on

the effect of temperature on hardness, and some work on the effect

of temperature on the disintegration of the material by carbonization, etc. The electrical properties included volume resistivity,

surface resistivity, power factor, dielectric constant, and the effects

of high voltage at radio frequencies.

Investigations have been made of the effects of voltage at radio

frequencies upon insulating materials. This work has required the
RADIO COMMUNICATION 241

development of entirely new apparatus for the production of constant high-frequency voltages, for their application to insulating

specimens, and for their measurement. Essentially, the method

consists in placing a sample of material in a radio circuit with

electrodes upon its surface in parallel with a condenser and measuring the voltage required to produce certain effects, such as the

appearance of corona, flash over, and also puncture of the material.

The flash over and puncture voltages are of very different magnitude at high frequencies as compared with other values at low

frequency for the following reasons: Very much lower voltages

produce these effects at radio frequencies than at low frequencies,

because the dielectric carries a considerable dielectric current.

This current heats the specimen by virtue of the absorption phenomenon or dielectric loss in the material and soon raises the temperature to a point where breakdown occurs. The effect is then

not a puncture or rupture of the low-frequency type at all, so that

instead of hundreds of thousands of volts being required to break

down or flash over a specimen, 10 000 volts more commonly

suffices.

Measurements of the various properties which have been enumerated were made upon several hundred samples of material

representing various grades and thicknesses of the standard

products. These were mainly laminated materials, but some of

the work has been upon the molded phenolic materials. In

general, the more expensive grades are superior in their electrical

properties. The reverse is true in regard to mechanical strength.

For example, the cheaper materials have higher tensile strength

than the more expensive. The expense of the materials is usually

determined by the percentage of phenol varnish to paper, the

more expensive materials having a larger percentage of varnish.

The thermal properties do not in general furnish any means of

differentiating between the several materials. Above 50 C the

variation of dimensions with temperature is not reversible, and

many peculiar expansion and retraction effects have been noticed

upon raising and lowering the temperature. All the phenol

materials have smaller coefficients of expansion than hard rubber.

The insulating materials of the phenol type came into use largely

because a substitute for hard rubber was wanted, the value of the

latter material for electrical apparatus arising from the fact that

it is easily machined, has very small power loss or phase difference,

and very high puncture voltage at radio frequencies. It has,

however, certain other objectionable features; thus, it shrinks,

26035"—21 16
242 WAR WORK OF THE BUREAU OF STANDARDS

warps, is brittle, deteriorates in sunlight, and has high thermal

expansivity.

An interesting result which was observed in the power-factor

measurements was an apparent increase of power factor in a

particular sample of over 100 per cent after a lapse of time of six

months. Upon investigation this change was found to be an

actual change, and by a baking process the phase difference was

brought down again to approximately the value of six months

before. This and similar experiments on other materials suggested that the absorption of moisture from the atmosphere

changes the properties of these insulators.

Permanent Crystal Detectors

In March, 1918, the Signal Corps submitted a suggestion for a

crystal detector having a permanent contact and possessing high

sensitivity. The plan was to secure on the surface of the crystal,

by alternating-current electrolysis, needlelike deposits, perhaps

one-half mm high, and making a permanent soldered contact to

a number of these needles. It was thought that the additional

contacts would give increased sensitivity, besides possessing the

advantage of a permanent contact not disturbed by ordinary

mechanical jars. This was desirable for field work, as a crystal

detector was needed having a permanent contact which could be

used in the field Avithout the necessity of continually resetting the

contact wire on a sensitive spot of the crystal.

Experimental work was carried out along the suggested lines

by the Bureau. It was found that deposits could be secured by

electrolysis using a 60-cycle alternating current of the order of

50 milliamperes, and that in some cases deposits secured on car- borundum were sensitive. It was also found that no advantage

could be practically attained by using a number of contacts in

parallel, and that, in general, the signal obtained using two contacts in parallel was less than that obtained using alone the most

sensitive one of the two contacts. Difficulty was met in attempting to secure sensitive deposits on galena, because most electrolytes seriously affected the sensitiveness of the galena as a detector. Since galena is one of the most sensitive crystal detectors,

it was very desirable that a permanent-contact galena detector

should be obtained, if possible.

Later attempts were made to secure, electrolytically, deposits

on a number of different crystals, using a radio-frequency current

of 1 50 to 200 milliamperes. Some sensitive deposits were secured

in this way, but they were not satisfactory, as they were not
RADIO COMMUNICATION 243

adherent. In the work at radio frequency it was shown that the

sensitiveness of a deposit is dependent on the failure to obtain a

perfect contact with the crystal surface, and that really adherent

deposits are practically never sensitive. Work with direct-current

electrolysis also served to confirm the conclusion that sensitive- ness of a metallic deposit depends on failure to make perfect

contact with the crystal surface.

As a possible means of securing permanent contact, soldering

was attempted, but without success, except in the case of molybdenite. No flux was found which would cause the solder to

adhere either to galena or silicon. Both arc and spark welding

were tried. Wires as fine as No. 40 were welded to galena, silicon,

iron pyrites, and molybdenite by these methods, but in no instance

was the welded contact sensitive. Since in welding the surface

was melted and the surface immediately surrounding the weld,

which had been melted in the process, was found to be insensitive,

this method was not successful.

A fairly satisfactory detector was constructed by making a

contact between a slightly hollowed surface of Wood's metal and

the sharp point or edge of a galena crystal, the whole being

inclosed in paraffin or sealing wax. The chief difficulty encountered was due to alternation in the contact caused by expansion of

the wax with change of temperature. Some experimental

detectors so made remained fairly sensitive for several weeks, but

after a few months were usually found to be much less sensitive.

Two general conclusions were drawn as a result of these investigations: With the less sensitive crystals, such as carborundum

and molybdenite, plated-contact detectors of fair sensitiveness

can be made, but this is no practical gain, since these crystals

have previously been in use with fixed contacts. With the more

sensitive crystals, such as galena and silicon, the only method

which gives promise of success is that of a mechanically maintained

high-resistance contact.

Peace-Time Value of Work

The radio work carried out during the war presents a conspicuous example of scientific advancement of permanent value.

It has been estimated that in two years of war the progress in

radio was equal to that in 10 ordinary years. The work of the

Bureau contributed to the progress made upon the electron tube,

the direction finder, control of radio waves, radio measurements

and design, submarine signaling, airplane communication, and

radio instruction. Each of these, with the possible exception of
244 WAR WORK OF THE BUREAU OF STANDARDS

submarine signaling, has positive value in the normal pursuits

of peace.

As a result of the research work during the war, the electron

tube was developed from an unstable, experimental device, used

largely by amateur radio enthusiasts, to a dependable instrument

of standardized operating characteristics, produced on a commercial scale and used in large quantities. Besides increasing

greatly the effectiveness of radio-receiving apparatus, it is used

also as a generator of alternating current of any frequency from i to 100 ooo ooo. Reliable long-distance wire telephony has been

made possible by the electron tube; through its aid many telephone conversations are carried on over one pair of wires. It is

used in the construction of amplifiers which magnify very feeble

currents or signals hundreds of times. In consequence, radio

antennas can be reduced to very small dimensions and the range

of radio communication greatly extended. Music, as well as the

voice, is readily transmitted without wires, even across the ocean. A symphony concert can readily be given at one point and be

sent forth by radio so that it can be received anywhere in the

United States.

The direction finder has been developed into a very convenient

and portable apparatus. It replaces the antenna for receiving

radio waves and determines the direction of the transmitting station. It is useful in determining the location of radio stations, as

in the work of Government inspectors when violators of the radio

laws are sought. It is of the greatest value as a safety device on

either airplanes or ships in fog or other perilous circumstances.

Following the end of the war the Bureau of Lighthouses and the

Bureau of Standards took up actively the development of a fogsignaling system involving the use of the direction finder. Thus

aided, a ship can steer toward a lighthouse or determine its position during the heaviest fog.

The improvements in design of radio apparatus and the advance

in methods of radio measurement have increased the efficiency of

instruments and equipment. Progress in the understanding and

control of radio waves has increased the certainty with which the

range of communication of any radio set can be calculated. The

textbooks and other material prepared for the training of Signal

Corps men in radio have been found useful in universities and other

institutions.

One of the incontestable benefits which has been salvaged from

the war is the application of radio to airplane communication. In
RADIOMETRY 245

the future of aerial navigation, as in policing the air, radio will play

an important part. The electron tube has made possible conversation between airplanes and the ground, the direction finder is

the compass of the aviator, and radio methods supply the signals

by which a landing may be made in fog or darkness. The ordinary

wire telephone can now be connected to a radio system, so that

conversation between the ordinary city telephone and an airplane

is possible. Radio supplements the older systems of communication, and no spot on the earth or in the air is too remote for it to

RADIOMETRY

Researches

The following paragraphs summarize the most important investigations in Radiometry which had a direct military application:

Radiant Power Life Tests of Quartz-Mercury Vapor Lamps

This subject is treated under the heading "Aircraft Materials."

Optical Properties of Balloon Fabrics

This subject is treated under the heading "Aircraft Materials."

Photoelectric Sensitivity of Molybdenite and Various Other Substances

This subject is treated under the heading " Invisible Signaling."

Amplification of Bolometer Current for Signaling Purposes

This subject is treated under the heading " Invisible Signaling."

Infra-red Transmission Spectra of Various Substances

The spectral transmission of various substances, including special glasses, colored fluorite, salts in solution, etc., was determined.

The data were published in Scientific Paper No. 325.

Some of the substances examined (including material submitted

for official tests) were found useful in a device used for secret signaling by means of infra-red rays. As a result of this investigation, a prominent glass factory improved the infra-red transmission of a red glass by eliminating the iron impurities which cause

an absorption band at 1 /x.

Protection of Moving-Picture Film from Heat of Lamp

In certain military work it was desired to stop the movement

of the picture film in order to make an examination of the details

of a single picture projected upon a screen. As ordinarily used, the moving-picture film is protected from

injury by the intense infra-red rays from the lamp because it is
246 WAR WORK OR THE BUREAU OR STANDARDS

exposed to these rays for only a very short period of time. Applying the information obtained in the foregoing and in a previous

investigation, the intensity of the infra-red rays was greatly

reduced by using a dilute (1 to 2 per cent) solution of cupric chloride, which absorbs but little of the visible spectrum, while being

practically opaque to infra-red rays.

Glasses for Protecting the Eyes from Injurious Radiations

Information on the protective properties of glasses used in

oxyacetylene cutting and welding is very important. That this

Bureau's efforts in obtaining such data are appreciated by manufacturers is attested by the fact that the first issue of its technologic paper on this subject was exhausted within three months

after publication, one shipbuilding firm calling for almost a hundred

copies.

In addition to research work on this subject, quite a number of

official tests were made on the eye-protective properties of glasses

submitted by dealers and by the construction departments of the

navy yards at Washington and Philadelphia.

During the past year extensive new data were obtained on the

ultra-violet and infra-red radiations transmitted by various glasses

used for spectacles. The sources of radiation used were typical

of those to which one is exposed in occupational pursuits. For

example, the quartz-mercury vapor lamp and the iron (magnesite)

arc used in these tests were representative of the sources of ex- tremely intense ultra-violet radiation, while the gas-filled tungsten

lamp and the sun represented high intensities in the visible and

infra-red spectrum. These new data were published in a revised

and enlarged (the third) edition of Technologic Paper No. 93,

"Glasses for Protecting the Eyes from Injurious Radiations."

Reflecting Power of Stellite and Magnalium

Stellite is an alloy of chromium, cobalt, and molydbenum. It

takes a high polish and appears to be quite permanent in air. It

reflects from 60 to 65 per cent of the visible rays. (See Scientific

Paper No. 308.) From a military standpoint the use of stellite

was under consideration for reflecting mirrors in periscopes and

range finders.

In response to a request from the Chief Signal Officer, War

Department, for information on the reflecting power of magnalium

(aluminum-magnesium alloy) mirrors, data were obtained on

samples prepared by the division of metallurgy.
RADIOMETRY 247

It was found that the reflecting power of the best samples of

magnalium increases uniformly from about 85 per cent in the blue

to 90 per cent in the red. The average sample would probably

reflect 85 per cent depending upon the polish.

Instruments and Methods of Radiometry

While the investigations of thermopiles, photoelectric cells,

etc., were not undertaken with a view to direct military application, it is known that the method of construction and general

technique developed in this Bureau were useful to others who had

military problems under investigation. For exemple, on the

basis of Scientific Papers Nos. 188, 229, 282, and 319, the thermopiles were constructed for the purpose of detecting the presence

of airplanes, etc., at night by the heat emitted by the engines.

Apparatus was sent to France for testing out this device.

Thermopiles made by the Bureau were lent for measuring the

intensity of searchlights. One thermopile was lent to the United

States Naval Experimental Station to determine its usefulness in

detecting ships at night by the heat emitted from the smokestacks.

Reports of the official tests on this device made by the National

Research Council were very favorable, and it was suggested that

further work be done.

Lacquers for Protecting Tarnishable Metallic Surfaces

Owing to the scarcity of optical glass it was desirable to find

suitable metal mirrors as a substitute for lenses used in range

finders, periscopes, airplane cameras, searchlights, etc. Silveron-glass mirrors are easily prepared, but a lacquer covering is

required to prevent the silver from tarnishing.

From the experience gained in this laboratory, it appears that

unlacquered mirrors which are inclosed to the extent afforded in

a camera will not tarnish appreciably in one to two years. This

tarnish is quite soluble and easily removed by dipping the mirror

in water or by polishing it with soft chamois skin and opticians'

rouge.

Tests were made of water-white silver lacquers, such as "Albaline," "Zapon," etc. They were diluted, filtered, and poured

upon the freshly polished silver. The excess material was allowed

to drain off and then the mirror placed in a level position to dry.

Theoretically, a lacquered-silver surface should reflect almost

as much light as does an unlacquered surface. In practice,

however, the reflecting power was found to vary greatly with the

condition of the lacquered surface. A newly lacquered silver
248 WAR WORK OE THE BUREAU OF STANDARDS

mirror reflects from 70 to 75 per cent of the incident yellow light,

while in the red it reflects from 80 to 85 per cent, depending upon

the homogeneity of the lacquer. Uncoated or bare silver reflects

from 90 to 95 per cent of these rays.

In the near infra-red, where nitrocellulose is free from absorption bands, the reflecting power increased gradually to about 95

per cent.

For reflecting heat rays of long wave lengths, which are absorbed

by the lacquer, mirrors of nickel or gold (which reflect 95 per

cent) should be used.

At the request of the General Engineer Depot of the War

Department for information on lacquers suitable for protecting

metal searchlight mirrors an examination was made of the effect

of ultra-violet light upon the various lacquers commercially

available.

It was found that the photochemical action of ultra-violet

light such as obtains in a searchlight liberates sulphides and

nitrous oxides which may be present as impurities or which are constituents of the lacquer and which then attack the silver. As

a result the silver under the lacquer, following exposure to a

carbon arc or a quartz-mercury vapor lamp, is quickly turned

brown in color. For example, after 6 hours' exposure at a distance of 0.5 from a small (15-ampere) carbon arc a lacquered

silver-on-glass mirror had changed to a brownish color, which

strongly absorbed the yellow, green, and violet lights. As a

result the reflecting power of the lacquered mirror for wavelength X = o.55/x (greenish yellow) was decreased from 74 per

cent to 68 per cent. Similarly, at X = o.65/j (orange-red color)

the reflecting power was decreased from 82 to 79 per cent, and

at wave length X =0.7/* (red light) the reflectivity was decreased

from 85 per cent to 83 per cent. In a powerful searchlight such

a lacquered silver mirror would be injured in a few hours. A

bare nickel-plated glass mirror would be just as efficient. A

gold mirror would be more satisfactory.

Specifications and Methods of Test

In connection with the preparation of standards for head-andeye protection which is being carried out by the Bureau in conjunction with the safety engineers of Federal industrial establishments considerable experimental work was done on the protective properties of glasses already in use in the navy yards.

This was done for the purpose of obtaining a glass of suitable
RADIOMETRY 249

transparency for oxyacetylene cutting and welding, and at the

same time of providing ample protection against injurious radiations. Specifications were then drawn defining the maximum

transmission of injurious radiations permissible, especially for

infra-red rays. Sources of radiation which are readily obtained

by manufacturers were also investigated. A gas-filled tungsten

lamp was found suitable for testing the protective properties of

glasses for infra-red or so-called heat rays.

For the General Engineer Depot tests were made and specifications written for glasses for soldiers and engineers to provide

protection against glare from snow, etc.

Conferences, Consultations, Etc.

Under this caption there are enumerated some of the military

problems presented by Government bureaus and manufacturers.

The subject most frequently presented related to thermal-radiodynamic devices for secret signaling, and for detecting submarines

or battleships in a fog by the heat radiated from the smokestacks,

etc. Many of the inquirers did not seem to realize that for radiations of wave lengths such as would be emitted by a smokestack

water vapor is the most opaque substance known, and that, consequently, during a fog, when this sort of signaling device would

be most needed, the radiations to be detected would be completely

absorbed within a very short distance from the source. Many of

the questions submitted were so impractical that it was easier to

advise what not to do than to suggest improvements.

The selenium cell had its share of suggested applications, nearly

all of which, as it turned out, seemed impractical. For example,

in reply to inquiries from the Naval Proving Ground, Indian Head,

Md., on the applicability of photoelectric devices (selenium cell)

for registering the speed of projectiles, some laboratory tests were

made which indicated that such devices are not sufficiently positive

in action to use in such tests.

Another inquirer desired to obtain a series of photographic ex- posures at frequent intervals throughout the day, and wished to use the selenium cell (in some manner that he had not yet worked

out) to regulate the diaphragm opening of a camera. The inapplicability of the selenium cell was indicated to him, and a series of

tests was made which demonstrated the adaptability of the Callendar sunshine receiver and the sliding mechanism of the recorder

to the actuation of the diaphragm opening of a camera. By connecting the diaphragm with the sliding arm of the recording mecha-
250 WAR WORK OF THE BUREAU OF STANDARDS

nism, the to-and-fro motion of the latter regulates the diaphragm

opening of the camera, and hence the amount of light reaching the

photographic plate.

Members of the National Research Council conferred on the

applicability of the selenium cell as a means of communication for

airplanes, etc. The potassium photoelectric cell device described

elsewhere in this report was suggested as best adapted for such

signaling.

In reply to inquiries from the General Engineer Corps on the

feasibility of using thermal radiations for destructive purposes, as, for example, igniting a captive balloon, it was shown that terrestrial sources of radiation were not powerful enough. Another

inquirer thought sunlight could be used; but among other things,

the method had not been thought out of producing the concave

mirror 20 to 40 feet in diameter which would be required in order

to obtain sufficient intensity to ignite an object at a distance of 3

to 5 miles.

To a manufacturer of quartz mercury vapor lamps, and to a

paper manufacturer using such lamps in fading tests, information

and specific directions were given on making radiant power life tests

of mercury vapor lamps, and their applicability in fading tests of

this kind.

The feasibility of testing toxic gases by radiometric instruments

was discussed with military officials from the Bureau of Mines,

and selenium cells made at the Bureau were provided for experimental work in the development of tests for the presence of

these gases.

In response to a request from the National Research Council,

a representative of the Bureau attended a conference at Columbia

University, New York (August, 1918) , at which were presented the

results of experiments on the detection of various objects such as

airplanes, human beings, etc., which give off a certain amount of

heat, by means of a thermopile (after this Bureau's construction)

placed at the focus of a 2 -foot concave mirror.

By invitation from the special board, a representative of the

radiometry section demonstrated the Bureau's thermal radiodynamic secret-signaling apparatus in September, 191 8, at the

naval experimental station, New London, Conn. In addition to

the specific cases just cited, information was given on various

radiometric matters such as the reflective properties of metals

useful in searchlights, etc.; the thermal radiodynamic signaling devices; photo-electric substances; eye-protective glasses; the
RADIUM 251

constancy and methods of standardization of sources of ultraviolet radiations of high intensity ; emissivity of paints to be used

for preventing the heating of certain kinds of electrical machinery

construction of ironclad Thomson galvanometers ; standard blackening of radiometer receivers; and various other radiometric

questions having a military application.

Publications

The following recent publications in radiometry contain data

which have a military application, though, of course, some of the

earlier investigations were not undertaken with that specific end

in view

Technologic Paper No. 93 (3 ed., rev. and enlarged). Glasses for protecting the

eyes from injurious radiations.

Scientific Paper No. 229. Various modifications of bismuth-silver thermopiles

having a continuous absorbing surface.

Scientific Paper No. 282. Sensitivity and magnetic shielding tests of a Thomson

galvanometer for use in radiometry.

Scientific Paper No. 300. Emissivity of straight and helical filaments for tungsten.

Scientific Paper No. 308. Reflecting power of tungsten and stellite. Scientific Paper No. 319. Instruments and methods used in radiometry, III—the

photo-electric cell and other selective radiometers.

Scientific Paper No. 322. Photo-electric sensitivity of bismuthinite and various

other substances.

Scientific Paper No. 325. Spectroradiometric investigation of the transmission of various substances.

Scientific Paper No. 330. The decrease in ultra-violet and total radiation with usage

of quartz-mercury vapor lamps.

Scientific Paper No. 338. Some optical and photo-electrical properties of molybdenite.

Scientific Paper No. 344. The spectral photo-electric sensitivity of silver sulphide

and several other substances.

Thermal-Radiophonic Devices for Secret Signaling

This subject is treated under the heading " Invisible Signaling."

RADIUM

During the war self-luminous materials were very extensively

used for the illumination of aircraft instruments of all kinds, of

gunsights, of targets for indirect fire, of marching compasses, of

watches, of navigation instruments; in short, they were used

wherever an entirely self-contained light of low brightness was

desired.

In determining the suitability of these materials for given purposes and in drawing specifications for their use numerous questions arose. Many of these questions related to points concerning

which much misinformation existed, others to details that were

easily and commonly overlooked, and others to features that
252 WAR WORK OF THU BUREAU OF STANDARDS

were but little understood. The answers to some were to be

found scattered through the literature of physiological optics, of

radioactivity, and of phosphorescence. The answers to others

required a knowledge of the properties of commercial self-luminous

materials. Up to June, 191 7, no article treating of the properties

of such materials had been published, and but two bearing directly

upon (noncommercial) self-luminous materials were available.

Nowhere was to be found in collected form information covering

the many important practical points involved in the efficient use

of these materials.

Early in 191 6 the Bureau of Standards began an investigation

of these materials to collect information concerning them and

to study the problem of the precise measurement of their brightness. Suitable apparatus was constructed (Fig. 29) and a long

series of measurements of many specimens obtained from different sources was begun in October, 191 6; some of these materials

are still under study. In the spring of 191 7 a study of the various

problems connected with their practical use was begun.

Consequently, when in the summer of 191 7 these materials

acquired a military importance, the Bureau was in a position to

answer many of the questions that arose and to undertake the

investigation of various problems that presented themselves

from time to time. It soon became the recognized source of information on the subject.

The Bureau's war activities in this field embraced four distinct

lines:

1. The furnishing of information and recommendations.

2. The investigation of specific problems.

3. The preparation and standardization of equipment for the

factory testing of dials.

4. The routine precise measurement of the brightness of the

markings on articles submitted for test.

Information and Recommendations

Information and recommendations were disseminated by means

of six typed circulars, many letter reports, and numerous confer- ences with representatives of those branches of the Army and the

Navy who were especially interested in the subject and with representatives of the companies manufacturing and applying these

materials. Special reference should be made to the large number

of conferences in the last half of 191 7 between representatives

of the Bureau and representatives of the National Research
RADIUM 253

Council and of the science and research division, Signal Corps,

U. S. A.

A few of the questions that had to be answered and of the

errors that had to be corrected will illustrate the nature of the

information that was required.

1. Shall the dial plate be silvered? Dial plates illuminated

before the summer of 191 7 were frequently silvered. These

dials present a very pleasing appearance by day and in total

darkness, but under certain moonlight conditions the contrast

between the dial plate and the markings is so slight that the

markings can not be seen. The dial plate should be black.

2. It was commonly believed that the effective life of radium

luminous materials is comparable to that of radium (radium is

half disintegrated in 1760 years). Actually the effective life of

these materials is relatively short.

3. It was urged that the material should be specified by its

radium content. Actually a specification of the radium content

is not sufficient to determine the brightness or life of the material.

4. It was suggested by some that a high brightness should

be specified in order to insure a long life. While increasing the

initial brightness does increase the effective life, the increase in

cost is out of all proportion to the increase in life.

5. What is the effect of replacing the radium by other radioactive material ?

6. Shall dry material or that mixed with varnish be vised?

How does the brightness differ in the two cases?

7. How soon after the material is made shall the illuminated

article be inspected for acceptance ?

8. Should the dial contain many marks or few?

9. What brightness is required? How does the brightness

required vary with the size and style of the luminous markings?

10. Shall the luminous lines for rear sights be made very

narrow ? It was found that under working conditions the apparent

width of luminous lines for rear sights is practically the same

whether the line be 0.5 or 1.7 mm in width. Throughout this

range the apparent width is about 5 or 6 mm. Hence very narrow

lines, requiring brighter material, are desirable.

It was to answer and to furnish the information needed to

enable one to discuss intelligently such questions as these that

the six typed circulars were issued. They were rather hurriedly

prepared to meet immediate needs, in some measure overlapped,
254 WAR WORK OF THE BUREAU OF STANDARDS

and were in no sense intended to be regarded as finished products.

They were issued in small editions and supplied to those most

interested. They do not lend themselves to abstracting, but an

idea of the ground covered may be indicated by the following

table of contents:

REC-i. Self-luminous materials containing radioactive excitants; a report from

National Bureau of Standards, March 10, 1917; revised November 16, 1917. pp.17.

General description of these materials; Properties of the phosphorescent base;

Properties of the radioactive excitants—Radium, Mesothorium, Radiothorium , Polonium; Growth and decay of brightness; Manufacturers, materials, prices; Applied

material ; Legibility ; Specifications and testing.

RLC-2. Supplement to the preceding report, April 10, 1017. pp. 5. This treats mainly of the life of dry material contained in tubes. RLG-3. Specifications for self-luminous dials, pointers, scales, etc. Proposed to science and research division, Signal Corps, U. S. A., September 24, 1017. pp. 3. (Superseded by RJX-6.)

RIX-4. Notes and suggestions concerning luminous instruments, November 16,

1917. pp. 6. Size of characters, Spacing, Number of marks, Positional reading, Symbols, Brightness, Application, Pointers.

RLC-5. Self-luminous materials: Brief notes covering a few points of practical

importance. January 8, 1918. pp. 14. Unapplied material—General remarks, Growth in brightness for 3 weeks, Decrease

in brightness after 3 weeks, Effect of light, Brightness, Fineness of grain; Applied

material—Brightness reduced on application, Initial growth after application, Ulti- mate decrease in brightness; Manufacturers and prices; Relative values of different products.

REC-6. Notes and recommendations regarding specifications for the illuminating

of articles by means of self-luminous materials containing radioactive excitants.

August io, 1 918. pp. 24. Basis of specifications, Self-luminous materials, Unit of brightness, Total light,

Brightness of markings, Summary, A form of specifications, Appendix.

An illustrated report (9 pp., 4 illus.), describing in detail the equipment used by

the Bureau of Aircraft Production for the factory inspection of dials, was prepared

February, 1919, for and at the request of the New York Navy Yard.

Investigation of Specific Problems

Some of the problems that have been investigated especially

for the purpose of obtaining information of military value are the

following

Variation of brightness with the thickness of the material.

Variation of brightness with the width of line.

Effect of immersion in kerosene.

Methods for applying the luminous material.

Brightness required for specific dials, gun sights, targets, indicators, compasses, etc.

In dealing with the last-named problems the Bureau cooperated

closely with the parties interested. Usually the Bureau prepared

apparatus by means of which an article of the desired type could
RUBBER 255

be seen with markings of variable or various brightnesses. Then

the parties interested examined the article at night and in conference with representatives of the Bureau. In this way the

brightness that seemed most desirable was determined.

Certain stencils were designed to use as the rear lights for

trucks. This work was undertaken by request for the purpose

of determining what form will give the driver of the following

truck the most information regarding his distance from the preceding one. The parties requesting the work lost interest in it

after the armistice was signed, and the work was not completed.

Equipment for Factory Inspection of Dials

Apparatus was prepared and standardized for the use of the

Bureau of Aircraft Production in the factory inspection of luminous dials. A carefully cut stencil of the luminous dial under

test is backed by a sheet of milk glass and illuminated from the

rear. The lamp illuminating the stencil is moved until the openings in the stencil appear to be of the same brightness as the cor- responding markings on the dial. If such a match can be obtained

only by moving the lamp farther from the stencil than a predetermined distance, the dial is too faint and is rejected.

Five of these outfits were adjusted and calibrated, and the nec- essary lamp renewals were provided.

Routine Precison Measurements

Routine precision measurements of the brightness of selected

articles were made for several purposes: (1) to enable a prospective bidder to ascertain if a proposed material will meet the

requirements; (2) to serve as a basis for the award of contract;

(3) to serve as a check on the factory inspection; (4) to furnish

information regarding the uniformity of the work; and (5) to

determine the permanence of the brightness.

The study of these materials and problems is being continued^

and it is expected that in the course of the year a circular treating these materials will be issued by the Bureau.

ROPE, MANILA

This subject will be found under the title "Manila Rope."

RUBBER

Solid Tires

Early in 191 7 the attention of the Bureau was called by the

Quartermaster Corps of the War Department to the unsatisfactory

quality of solid motor truck tires which the Government was
256 WAR WORK OF THE BUREAU OF STANDARDS

obtaining in the open market. Although these tires were bought

from various manufacturers, they all appeared to be about the

same grade, which was no better than that of the relatively poor

solid tires with which American motor trucks had been equipped

during their service on the Mexican border.

At the suggestion of the Bureau samples of all these tires were

secured for tests and analyses, and the results of the investigation were correlated with the service rendered by the tires. The

results of this combination of laboratory and field work were

used as a basis for a series of conferences between tire manufacturers, officials of the Quartermaster Corps, and the Bureau of

Standards. After a number of such conferences a set of specifications was drawn up jointly for solid-rubber tires for motor

trucks and artillery wheels, and were first adopted in November,

191 7, followed by revised editions on December 5 of that year.

These specifications were adopted subsequently by the Motor

Transport Corps and finally as standard specifications by the

purchase, storage, and traffic division of the War Department.

The specifications call for physical tests of the rubber compounds and fabric, chemical analyses of the rubber compound,

and physical and chemical tests of the steel base bands. The

Bureau of Standards' methods are specified for making these

tests and analyses. During the period of the war following the

adoption of these specifications, inspectors were stationed at the

various plants. These inspectors took 1 tire from every 500 and

cut out appropriate samples for test. The physical tests of the

rubber compound were made at the plant, while the samples for

analyses of the rubber and tests of the base bands were forwarded

to the Bureau. Difficulties were encountered in the anylysis of

the rubber stock in the tires, because two relatively new compounding ingredients, glue and gasblack, were being used. Methods, therefore, had to be devised for the quantitative determination of these two ingredients. It was found that by making a

modified Kjeldahl determination to arrive at the quantity of

nitrogen present, the percentage of glue in the stock could be

estimated quite closely. The determination of gasblack was much

more difficult, but a procedure was soon arrived at for this determination, which with slight modifications and improvements was

used during all of the tests. The research work on this determination forms the subject of technologic papers No. 136.

Although much of the routine physical testing at the various
RUBBER 257

plants was done by local inspectors, samples were sent regularly to the Bureau as a means of checking their results.

During the year beginning with March, 191 8, over 500 complete

rubber analyses were made, representing the purchases of 250 000

solid tires having a value of about $20 000 000. It will thus be

seen that the War Department through the Bureau's aid was

enabled to buy this material on rigid specifications and to have

all purchases tested for compliance with these specifications. The

tires had to pass tests made at the Bureau before they were

finally accepted by the War Department. The result of this cooperative work was a vast improvement in the quality of solid tires

furnished the War Department. Through the specifications the

department was able to buy goods of standard quality on the

basis of competitive bids.

Pneumatic Tires and Tubes

Experience in connection with the development of specifications

for and the testing of solid tires as described above led to a similar

procedure for pneumatic tires. The results of the solid-tire testing had been so satisfactory that it was deemed advisable to buy

pneumatic tires on the same basis. This, however, was a much

more complicated and difficult matter, since pneumatic tires are made of so many different types and qualities of materials. Specifications would be required for each particular type, and a decision as to what constituted a good tire was a very difficult one to

reach. Manufacturers differ greatly as to the grade of materials

they use and as to the methods of manufacture. A great many

conferences were held concerning these specifications, and although

the work was started in November, 191 7, its tremendous quantity and the great differences of opinion involved halted the work

temporarily until the outcome of that on solid-tire specifications

should be known. The work on pneumatic tires was again taken

up during the summer of 1918, and in the following October specifications were issued as a result of the cooperative efforts of the

Motor Transport Corps, the War Industries Board, the Rubber

Association of America, and the Bureau of Standards.

The details of these tests are in accordance with the Bureau's

methods, and references are made in the specifications to the effect

that tests and analyses shall be in accordance with the methods in

current use at the Bureau of Standards. The tests to be performed on a pneumatic tire are numerous and of a very diverse

26035°—21 17
258 WAR WORK OF THE BUREAU OF STANDARDS

nature. The dimensions of the tire must fall within definite limits,

the fiber must be of a certain quality, and the different rubber

stocks must be subjected to physical tests and chemical analyses.

Determination of the adhesion or "friction" between the different

layers of rubber and fabric must also be made. As it was neces- sary to reduce this testing as far as possible, while still retaining a

good check on the quality of tires delivered, it was agreed that one

tire in every thousand or less should be tested. As soon as the

specifications were issued manufacturers commenced to make

tires in conformity with them. Before placing a manufacturer on

the list for competitive bidding, his tire had to be tested and approved by the Bureau, and, as a result of this requirement, practically all of the larger manufacturers sent two or more tires to the

Bureau of Standards for test. The increase in work thus brought

about required the use of much more extensive quarters for the

rubber and chemical laboratories. Because a large majority of

these tires were produced in the district near Akron, Ohio, and

since there was no further room for expansion at the Bureau, it

seemed desirable to locate a branch laboratory at Akron. As the

result of an agreement between the University of Akron and the

Bureau, suitable rooms for this work were fitted up in their chemical laboratory. The funds for the equipment were made availble by the Motor Transport Corps, and the resulting laboratory was

well equipped to handle the routine analytical work necessary.

This work was so largely curtailed by the singing of the armistice

that the laboratory was never used to its full capacity. It was

expectedjthat should the war continue, the Government would buy

about $5 000 000 worth of pneumatic tires a month, necessitating a laboratory force of 1 5 chemists to do the analytical work

called for by the specifications. As in the case of solid tires it was

the intention to station inspectors at the factories to secure samples and do the physical testing, their results to be regularly

checked by figures obtained on duplicate samples sent to the

Bureau.

Supplementing the specifications for pneumatic tires were specifications for inner tubes. The tests of tubes were handled in all

respects in the same way as pneumatic tires, in nearly all cases manufacturers making both tubes and tires.

Since the specification plan for pneumatic tires was put into

effect at about the time of the signing of the armistice, the full re- sults expected were not attained. There is every indication that
RUBBER 259

had hostilities continued, the results from this work would have

been as satisfactory as those obtained in connection with solid

tires.

Gasoline Hose

The preparation of specifications for a large number of parts

used in the construction of airplanes formed some of the earliest

work of the standards committee of the Society of Automotive

Engineers in cooperation with the Aircraft Production Board.

Among other things were included specifications for rubber tubing

to conduct gasoline from the tank to the engine of an aircraft.

Before specifications could be written for such a tube, considerable

experimental work had to be done to determine whether rubber

was suitable for this purpose, and if so, what kind of rubber compound and what type of tube construction would be most satisfactory. The Bureau cooperated with both the Aircraft Production

Board and the Society of Automotive Engineers in carrying out

this work. The Bureau's part consisted in the laboratory testing

of various types of tubes as they were submitted by manufacturers.

The type developed as a result of this work was made up of a combination of rubber and fabric containing a metal spiral reinforcement in the center of the tube, which prevented the tube from

closing because of the distortion of the inner rubber by absorption of gasoline. Specifications drawn up for this type of rubber

gasoline hose were used as a standard by the Aircraft Production

Board.

Oil-Proof Packing

The Ordnance Department needed a special oil-proof rubber

packing for the recoil mechanism of a particular type of gun.

The French had been using a rubber packing called " Dermatine"

in a similar gun, and this proved to be fairly satisfactory. As

the Ordnance Department was not satisfied with the packings

originally submitted by manufacturers samples of Dermatine

packing were obtained from France and were tested at the Bureau.

Samples of Dermatine obtained through the Ordnance Department, together with the Bureau's analysis of the material, were

furnished to various manufacturers, who then carried out research

work of their own and submitted samples for test. These were

tested in a practical way by the Ordnance Department, while a

check chemical analysis was made in each case by the Bureau. As

a result of these tests a certain product was picked out as the most

satisfactory, and this was then supplied to the department, the
260 WAR WORK OF THE BUREAU OF STANDARDS

individual deliveries of packing being checked by chemical analyses

made at the Bureau of Standards.

Insulated Wire

Throughout the period of the war the Bureau made physical

tests and chemical analyses for controlling the quality of insulated

wire and cable, particularly submarine cable which was being

purchased under specifications issued by the Panama Canal and

the torpedo depots of the Coast Artillery Corps of the Army.

A joint committee on the analysis of rubber insulation, comprising

members of the American Institute of Electrical Engineers, the

American Society for Testing Materials, and the Bureau of Standards, was requested by the Navy Department to furnish a set

of specifications with details of test methods for a 40 per cent

rubber compound for insulated wire. The specifications recommended by this committee were adopted by the Navy Department

and later by the Signal Corps.

Mechanical Rubber Goods

Rubber hose of different kinds, including that used for steam,

water, air, etc. , together with miscellaneous rubber goods, such as

belting, valves, and packings, commonly classed as "mechanical

rubber goods," were investigated by the Bureau at the request of

the War Department, with the object of developing standard

specifications for materials of this sort to be used as a basis of

award in the purchase of supplies for military purposes. The

methods followed in investigating and correlating the physical

and chemical properties of the various kinds of rubber goods had

for the most part previously been developed at the Bureau in

connection with similar work for other Government departments.

In addition to chemical analyses to determine the percentage of

rubber present and its quality, physical tests were made to determine the quality and strength of fabric and the strength, stretch,

and elasticity of the rubber as an indication of the correctness of

vulcanization. A comparative study was made of various

samples in each of the numerous classes as a means of judging the

excellence of the fabrication and when practicable the materials

were subjected to conditions approximating those of service, and

in some cases accelerated aging tests were carried out to estimate

the relative life of the rubber compounds used. As a result of

these laboratory investigations and of numerous conferences with

manufacturers and representatives of the War Department,

standard specifications have been adopted for practically all
SAFETY STANDARDS FOR INDUSTRIAL ESTABLISHMENTS 26

miscellaneous rubber goods used for military purposes, and these

specifications have been issued by the purchase, storage, and traffic

division of the War Department as one of their catalogues. In

all of the above-mentioned work the complete laboratory equipment at the Bureau, such as the small rubber mill (Fig. 30), was

of great assistance in the prompt handling of the investigations.

Rubber Jar Rings for Canning

It is perhaps not generally known that a very important item

in connection with the matter of food conservation is the subject

of rubber jar rings. At the request of the States Relations

Service of the Department of Agriculture the Bureau cooperated

in the production of standard specifications for jar rings in order

to establish a standard of quality for use by the public and to

eliminate the many inferior brands of rings which have been the

cause of extravagant waste as a result of food imperfectly preserved. The method adopted by the Bureau was to investigate

the physical and chemical properties of the various grades of jar

rings on the market and to compare the results obtained with

the known behavior of rings in service. It was found that of the

many different grades of commercial rings obtainable, those

having certain physical properties that are easily measurable may

be depended upon to give satisfactory results. Specifications

including a series of simple tests and measurements were written

by the Bureau and are now published by the Department of

Agriculture and recommended for use by the public.

Druggists' Supplies

At the request of the General Purchasing Office of the Field

Medical Supply Depot of the Army, an investigation was con- ducted on a number of rubber articles classed as druggists' supplies, such as rubber hospital sheeting, hot-water bottles, rubber

tubing, etc. Physical and chemical tests were made in accordance with the Bureau's standard procedure for such materials,

and the award of contracts for hospital supplies was made on the

basis of results obtained.

SAFETY STANDARDS FOR MILITARY INDUSTRIAL

ESTABLISHMENTS

In 191 7 a field inspection of the military and naval industrial

establishments was made through the initiative of the United

States Employees' Compensation Commission. This field inspection resulted in the submission of a number of recommendations
262 WAR WORK OF THE BUREAU OF STANDARDS

for increasing the safety in the arsenals and navy yards. Among

these was a recommendation that a safety engineer be appointed

for each industrial establishment in the Army and Navy. As a

result safety engineers were appointed by the War and Navy

Departments and stationed at various arsenals and navy yards

for the purpose of assisting in accident prevention.

At the time of appointment of the safety engineers an organized

effort was made in the Federal industrial establishments to reduce

accidents, but no standards for the methods of guarding and for

material specifications for such guards were available in either the

War or Navy Departments. It was accordingly necessary to

effect an organization by which this work of drawing up safety

rules could be accomplished.

The safety engineers held conferences at Washington on

November 14 and 15, 191 7; at Brooklyn on January 15, 191 8;

and at Norfolk on March 14 and 15, 191 8, and invited representatives of the Bureau of Standards to be present. Committees were

appointed to draw up safety rules and the Bureau was asked to

cooperate with these committees in perfecting and codifying the

rules. For this purpose, representatives of the Watertown

Arsenal and the Boston Navy Yard were detailed to the Bureau of

Standards for several weeks in the spring of 191 8. Preliminary

drafts of these safety standards were distributed for criticism and

suggestions and after final correction were adopted by vote of

the safety engineers. Illustrations were prepared and the whole

submitted to the officials of the War and Navy Departments for

formal approval and promulgation. These standards have not

been published by the Bureau of Standards.

The safety rules cover the following subjects: Building construction, crane construction, elevators, fire appliances and equipment,

toilets, wash rooms and locker rooms, power plants and prime

movers, power-transmission apparatus, machine guarding, remotecontrol apparatus, head-and-eye protection.

Each of the codes represents the collection in codified form of the

best existing methods and practices then in vogue arranged in a form to afford easy reference. Nothing original is claimed for

them, although considerable new material has been added.

Arrangements were made whereby the safety engineers were to

prepare and submit to the Bureau suitable illustrations for each

of the codes. At the time the armistice was signed, illustrations

for five of the codes had been received.
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 30.Small experimental rubber mill

This mill permits the Bureau to study the processes employed in rubber making. During the war

rubber was employed on a vast scale for tires, hospital supplies, etc.

wring the time at which the sound wave caused by the gun's discharge reaches successive points
Miscellaneous Publications, Bureau of Standards, No. 45

Fig. 32.

Exterior and interior views of plant for the recovery of toluol from the manufacture of illuminating gas

Large quantities of toluol were needed in the manufacture of explosives, and the Bureau investi- gated the problem of recovering toluol without impairing the gas furnished
SEARCHLIGHTS 263

The preparation of these safety rules involved in some cases

tests and investigations of the devices on the market and of the

properties of the material employed for protection. This was

notably the case in connection with protection of eyes of workmen

from flying particles and from injurious radiation, where it was

necessary to investigate the transmission of the different kinds of

glass, especially for ultra-violet radiation, and to test glass of

various kinds with respect to its ability to resist blows.

A widespread demand that these Federal standards be made

available for general use has resulted in the Bureau undertaking

to elaborate them and more fully perfect them from the standpoint of general application and mandatory enforcement by State

and municipal officials. It is expected that this work will result

in the development of a series of national industrial safety codes.

SEARCHLIGHTS

The high-power search lamps have acquired tremendous importance in the last few years. Few data, however, are on record

regarding some of the fundamental characteristics of these search

lamps or bearing upon some of the more important problems of

searchlight illumination. An investigation in cooperation with the

Engineer Corps of the Army was carried out, using the combined

facilities of the colorimetry section of the optics division and the

photometry section of the electrical division of the Bureau. This

work is briefly described below.

From data collected by the Bureau, two distinct types of distribution appear: That in the medium-intensity arcs resembles a

"rose" distribution; that in the high-intensity a "cardioid" distribution.

The development of high-intensity arcs by the use of specially

prepared carbons has resulted in the production of a light which

is very blue relative to artificial incandescent sources. In a

general investigation of searchlights, including the effectiveness

and suitability of their illumination for various purposes, it

appeared desirable to have at least approximate quantitative data

on the color of this light.

An investigation was made by spectrophotometric and special

colorimetric methods, and a report was issued to the Engineer

Corps and others, January 23, 191 9. Another report was made to

the American Physical Society, April 25, 191 9, and wns published in

the Physical Preview.
264 WAR WORK OF THE BUREAU OE STANDARDS

The result of these investigations may be roughly summarized

by saying that the color of the light from these arcs is approximately equivalent to the light of the noon sun in Washington,

although relatively more intense in the blue-violet.

The diffusion or scattering of light along the path of a searchlight

beam is very important from several standpoints. The diffusion

of the light out of the beam decreases the intensity of light falling

upon the target. This diffused light limits the visibility of the

target for an observer near the search lamp who must look through

and along the beam. On the other hand, this diffusion of the light

along the beam makes possible the use of the searchlights as landmarks for military and other purposes, and also facilitates the training of the beam in a given direction, particularly when combined

action of two or more search lamps is desired.

Measurements from various directions have been made of the

brightness of the path of the beam due to the diffusion of the light

by the atmosphere. The percentage of polarized light in the diffused light has also been determined.

In order to make any conclusions as to the size and distance

of a given target that may be seen in a searchlight beam, there is

demanded some knowledge as to what is the minimum difference of

brightness that the eye can detect. Laboratory experiments were

made to collect data upon the contrast sensibility of the eye under

conditions closely simulating those under actual searchlight illumination. Very definite results have been obtained.

In connection with the testing and use of search lamps, the question of how much light is lost as the beam penetrates the atmosphere must be considered. It is important to know what the

transmission of the atmosphere is when tests are made at great

distance from the search lamp.

Very meager definite data exist upon the transmission of the

atmosphere under all weather conditions—clear, hazy, foggy, rainy,

etc.

It is important also to have a knowledge of the relative transmission for different-colored lights.

A method has been devised to procure relative data on the transmission of the atmosphere throughout the spectrum, and some

observations have been made for a clear atmosphere, for one of

rather high humidity, and for rains.

These data are not only valuable for the searchlight engineer,

but are important also in aerial and in other photography and to

the illuminating engineer interested in automobile head lamps, etc.
SOUND-RANGING APPARATUS 265

A chart has been made showing where all losses of light in the

search lamp take place, and their magnitude from the moment the

current flows through the arc to the time that the beam impinges

upon the target.

A physical photometer was constructed for use in connection

with the photometry of search-lamp arcs. On account of the high

intensity of the light from arcs, they are admirably adapted to

the application of such an instrument.

SOUND-RANGING APPARATUS

Introduction

The process of locating a distant or concealed piece of artillery

by means of the sound waves produced when the gun is fired is

a new and very important development of the present war. Let

us assume that a gun is fired at a position which we may call i . This gives rise to a sound wave that passes out in all directions.

If now, we have an instrument similar to a telephone transmitter

located at each of three different stations 2,3, and 4, which may

be selected more or less at random, but whose positions are known( it will be evident that the sound wave will, in general, arrive at

these stations and affect telephone transmitters at different times.

If wires are brought from the telephone transmitters to the central station located at any convenient point and connected to a

telephone receiver, the sound of the gun would be heard successively as the wave front arrived at each station and the intervals of time between sounds would be a measure of the differ- ences in distance from the gun of the various stations. It has

been found possible to provide apparatus which will record the

instant of arrival of the wave at each station and so afford a measure of the time intervals between the arrival of the sound at the

several stations. The principle is, therefore, very similar to that

of a telephone system except that a recording apparatus is used

instead of the usual telephone receiver. The time intervals having

been measured and the locations of the stations 2,3, and 4 being

definitely known, it is possible that any one of a variety of methods will locate definitely the position of the gun. This is the

fundamental principle of sound ranging which has been worked

out in several practical embodiments used by the French and

British services.

The principle of sound ranging can be easily understood if we

consider that a sound wave passing from a gun has a wave front

which is circular in form. In due time this will reach the first
266 WAR WORK OF THE BUREAU OF STANDARDS

listening station, which we have called 2. A short time later the

sound wave will reach station 3, and still later station 4. If now,

we draw a circle about point 3, tangent to the circle of the wave

front through station 2, the radius of this circle dx will be the

distance traveled by sound in the time interval between the ar- rival of the sound wave at stations 2 and 3. Similarly, the radius

d2 represents the distance traveled by sound in the interval between the arrival of the sound at 2 and 4. Since the velocity of

sound in air under given conditions is definitely known, if we have

determined the relative time of arrival of the sound wave at the

three stations, the distance d1 and d2 can be directly calculated.

As an illustration of the method of determining the gun position,

let us consider that the distances dt and d2 have been determined

as above stated. Then let us draw a circle about the point 3

with radius dx and another about the point 4 with the radius d2

. It is evident that the problem is now the familiar geometrical one

of finding the center of a circle which passes through the given

point 2 and is tangent to two given circles drawn about the points

3 and 4, and having the given radii dx and d2 , respectively. The

solution of this problem has been worked out in a variety of ways

both graphically and analytically.

In actual practice the determination of the position of the gun

is by no means as simple as outlined above. The velocity of

sound varies with the temperature and humidity of the air, and

the position of the wave front at any time is affected by the direction and velocity of the wind. All these variable factors have to

be observed at frequent intervals and corrections applied. Further, even if only one gun is fired, three distinct sounds are produced as a rule; one due to the firing of the gun, another due to

the passage of the projectile through the air which is very pronounced when the velocity of the projectile is much greater than

that of sound, and the third which may be produced by the explosion of the shells. These sounds, in general, do not reach the

recorder in the order mentioned above. It is necessary to distinguish between these if a correct solution of the problem is to

be had. Further, it will often happen that a number of guns are

fired so nearly at the same time that the number of sounds produced by all of them will be recorded on the same portion of the

chart, and it often becomes necessary for one to distinguish between the record produced by firing the gun and those produced

by the shell, but it is also necessary to determine which portions
SOUND-RANGING APPARATUS 267

of the record received from the different stations belong to any

particular gun. It will thus appear that in actual practice sound

ranging involves a rather complex practice. However, the apparatus and methods of use have now been developed to such a

high degree that it is possible under average practical conditions

to determine all the information referred to above and make the

necessary corrections for the variable factors involved, and determine quite closely the position of the gun within one to two minutes after the gun is fired.

Upon the entrance of the United States into the war, the matter

of sound ranging was brought to the attention of this Government by the French Scientific Commission. This commission

strongly urged that an investigation of the matter be taken up at

once for the purpose of determining upon a system to be used by

the American Army, either by selecting from the systems already

in use the one best adapted to the purpose of sound ranging, or developing a new and improved system. The portion of this

investigational work which has been done at the Bureau of Standards forms the subject of the present report.

The work of the Bureau of Standards on sound ranging was

taken up following a conference held in the office of the Council of

National Defense. This conference was attended by the officer

who had been placed in charge of the sound-ranging work, a member of the National Research Council, two officers representing the French Scientific Commission, two members of the staff

of the Bureau of Standards, and others. At this conference the

sound-ranging problem was discussed in its general aspects and

an agreement was reached whereby the War Department's staff,

then located at Princeton, would take up an investigation of the

Dufour and Bull systems, and the Bureau of Standards would

make a study of the Cotton-Weiss system and the so-called T-M

system.

The work of the Bureau in this connection was preceded by a

careful study of various descriptions of sound-ranging apparatus

and of reports bearing on its operation which had been placed at

the Bureau's disposal by the French Scientific Commission. Two

sets of apparatus were designed and constructed, one embodying

the Cotton-Weiss system and the other the T-M system, and

after a little preliminary work in the laboratories of the Bureau of

Standards these two sets of apparatus were taken to the Sandy

Hook Proving Ground for field tests.
268 WAR WORK OF THE BUREAU OF STANDARDS

Preliminary Work

The first of the two types of apparatus investigated by the

Bureau, the so-called Cotton-Weiss system, is a nonrecording

system which was used to a considerable extent on the French

front quite early in the war, but, according to the Bureau's information, was after a short time used only in a few special cases. In this system two sets of apparatus are used at a distance of a

kilometer or more apart, each set having two receiving stations

located perhaps 100 m distant from each other. An indicating

device on each set shows the difference in time of arrival of sound

at the two listening stations. These differences in time determined at the two separate locations afford sufficient data for

calculating the approximate position of the gun.

In the second type of apparatus, the so-called T-M system,

three or more receiving stations are used, each of which is con- nected by a pair of wires to a central recording station. At the

recording station there is an oscillograph or galvanometer actuated

by changes in current on the lines to the receiving stations, and

the pointers of the oscillograph trace a line on a smoked paper

tape run at uniform speed. The difference in time of arrival of

the sound from the gun at the various receiving stations is determined by measurements of distance on the smoked paper, and

these differences in time determined for three or more stations

provide data for calculating the position of the gun.

Complete sets of both Cotton-Weiss and T-M types of apparatus

were constructed and taken to Sandy Hook, where several days

were spent in making tests. During the same period the War

Department's staff at Princeton made similar tests on both the

Dufour and Bull types of apparatus. As a result of these early

tests it was decided at a conference between representatives of

Princeton and the Bureau to abandon for the present further

development work on the Cotton-Weiss system, chiefly because

it appeared that the recording types of apparatus presented marked

advantages over the nonrecording Cotton-Weiss system.

The first series of tests with the T-M apparatus did not yield

satisfactory results, due partly to troubles with the microphones

and partly to a lack of sufficient sensitivity in the oscillographs.

A sufficient number of tests were made to bring out fully the

weaknesses in the preliminary design, after which the apparatus

was brought back to the Bureau of Standards and remodeled.

Improved microphones were constructed, and a new type of oscil-
SOUND-RANGING APPARATUS 269

lograph which will be described in detail later was developed, and

the apparatus was again taken to Sandy Hook for test. During

this series of tests the entire apparatus worked in a very satisfactory manner and three receiving stations were laid out roughly on

rather short base lines, and some actual ranging tests were made.

These ranging tests, although only partially satisfactory, were very

instructive and served to bring out certain minor defects in the apparatus which required elimination. This second series of tests

revealed the desirability of conducting rather extensive studies of

several phases of the sound-ranging problem, and a series of such

investigations was planned and carried out by the Bureau prior to

designing and building the improved sets, which were finally developed. A brief account of these experiments is given below; detailed descriptions of the apparatus and methods developed and

used by the Bureau will be given later.

Brief Review of Investigations of Various Phases of the SoundRanging Problem

The preliminary work showed that the original form of T-M

microphone was not sensitive enough for effective practical use. Furthermore, the resistance of the microphone buttons is so low

that a relatively low-line resistance is necessary in order that the

latter will not be too large in comparison with the frame. In general, it is not practicable to secure this low-line resistance by using

heavy wire because of the bulk and weight of line equipment as

well as the cost of the wire. The Bureau set to work on the problem of developing a more sensitive microphone and one which

could be used with a relatively high-resistance line wire. These

objects were finally accomplished by using a four-diaphragm microphone, each diaphragm having a separate microphone button

attached to it. These four microphone buttons were connected

electrically in series, thus giving a total line resistance of four times

that of a single button. This arrangement was found to work very

satisfactorily, and it was found possible to give all the sensitivity

that was desired and still use a line resistance of the order of 1000

ohms.

Another phase of the microphone problem that was given special

attention was that of making the microphones selective to the

muzzle wave. It was found desirable to secure records that are

free from the effects of the bow wave, or so-called crack, due to the

velocity of the projectile moving through the air. A record with

these effects eliminated is greatly simplified and rendered much
270 WAR WORK OF THE BUREAU OF STANDARDS

easier of accurate analysis. The Bureau finally developed a microphone which contained extremely high sensitivity to the muzzle

wave, but which would not give any appreciable response to the

crack even though the shell was so near the microphone that the

crack of the bow wave was many times greater than that of the

muzzle wave. The microphones can be very readily rendered

sensitive to the crack for special work, as occasion requires, without any change whatever in construction of the microphone; that

is, a given microphone can be changed in the field to one very sensitive to a crack or to one which is unresponsive thereto, as may

be required.

A microphone was finally developed which was found to be very

much less sensitive to wind pressure than the original T-M microphone.

The original T-M oscillograph was of the moving-iron type, and

the Bureau's preliminary work indicated that it was not one

adapted to this work. Accordingly, a moving-coil oscillograph

was developed, using a very short pointer and an electromagnet

which gave a surplus of sensitivity for all practical purposes.

This oscillograph has proved very rugged and reliable under service

conditions, and it is believed to fully meet the requirements of

the sound-ranging service.

In the original apparatus used by the French Army the smoked

chart was fixed after the record had been removed from the re- corder by laying an additional strip of paper over it and passing

it through a number of rolls. This was found to give rather

unsatisfactory results, such records being poorly fixed and rather

easily smudged. Another method used for some time consists of

dipping the smoked record in a thin solution of shellac and then

permitting it to dry. The objections to both these methods were

chiefly the danger of losing the record in handling, due to accidental smudging, and also the time elapsing before the record was

available for study. This was important, particularly in the case

of the shellac fixing. After considerable experiment the Bureau

developed a method of fixing by causing the tape to pass over a

drum which applied melted paraffin to the inside of the tape, which

promptly soaked through and fixed the record on the other side.

This was made a process continuous with the making of the

record itself, so that the record came out of the recorder all fixed

and ready for use. The danger of losing the records due to

smudging and handling was thus entirely eliminated and the
SOUNDS TRANSMITTED THROUGH THE EARTH 271

record was immediately available for analysis upon coming out

of the recorder. This method of fixing has proved eminently

satisfactory in practice.

In addition to the above a large amount o* experimental work

was done in connection with the design of a suitable type of transformer for the recorder, the development of timing devices for

accurate recording of time on the record, and, particularly, much

attention was given to methods of procedure in sound ranging.

A number of methods of analyzing the charts, working up the

data, and calculating the position of the gun, including the making

of various corrections for wind, temperature, and humidity, were

developed in connection with this work.

The final form of this apparatus (Fig. 31) was completed and went

to France in the autumn of 191 8, arriving there only the day before

the armistice was signed, so that opportunity was not afforded

for trying it out under actual war conditions. The apparatus has

been very thoroughly tested, however, at the Naval Proving

Ground at Indianhead, Md., and its success was fully demonstrated.

SOUNDS TRANSMITTED THROUGH THE EARTH

When the French Scientific Commission visited this country in

the spring of 191 7, they brought with them various devices for

the detection of sounds which were transmitted through the earth.

These were particularly valuable in listenting for mining operations. In October, 191 7, the Engineer Corps and the Bureau

undertook to develop these types of apparatus for the use of our

troops abroad.

Two types of apparatus for detecting earth vibrations of high

frequency (sound waves through the earth) have been studied.

The first type of apparatus is entirely mechancial and is called thi

geophone (Fig. 33) ; the second type is electrical, and is called a seismomicrophone.

Geophone

The geophone consists of a heavy mass suspended by two

diaphragms inside of the case with thin air spaces above the

upper diaphragm and below the lower diaphragm. One of these

air spaces is connected by rubber tubing to one of the ears of an

observer. If the geophone is placed firmly in contact with the

earth, an earth vibration causes the case to move with the earth,

but the steady mass due to its inertia and its suspension tends to
272 WAR WORK OF THE BUREAU OF STANDARDS

remain at rest, so there is a relative displacement between the case and the steady mass. This displacement sets up in the air space

alternate condensation and rarefaction, which are transmitted

through the rubber tubes to the ear, thus producing the sensation

of sound.

Two geophones are usually used, one being connected to each

ear of the observer. Then, if the two geophones and the connecting tubes are identical, they become listening devices by which

the ear can detect the direction of the sound through the earth,

in the same way that the direction of sound coming through the

air can be detected.

The geophones which were brought by the French Commission

were very sensitive, but it seemed worth while to see if a still more

sensitive instrument could not be produced, especially one which

would more faithfully reproduce the character of the sound

which was received. Accordingly, a considerable number of

instruments were constructed, using different sizes of instrument,

methods of suspension, kinds of case, sizes of tube running to the

ear, and practically every other factor which could be readily varied.

The resultant instruments were tested in dugouts, which were constructed to simulate as far as possible actual field conditions. A

standard source of sound was used and the results carefully

collected. The tests of the apparatus constructed as a result of

these investigations showed that it was appreciably better than the

French instrument on which it was based and was also more con- venient to use. Seismomicrophone

The seismomicrophone or telegeophone consists of a microphone

which is attached to a geophone. However, a number of modifications can readily be introduced, so that the finished instrument

does not resemble the geophone.

As the microphone is a very sensitive instrument, it is not

necessary to use as large a mass as in the case of the geophone.

In fact, an ordinary microphone to which is attached a small

weight gives quite satisfactory results.

The seismomicrophone can not readily be used for determining

the direction of sound, as the binaural effect is not satisfactorily

transmitted through a microphone. However, it is a very useful

instrument in mining operations. The complete outfit which was

developed for the U. S. Army was lighter and more compact than

that used by the French.
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 34.Print of radiograph of a repaired shoe

One of a series taken for the purpose of studying the clinching of nails by different types of soling machines
Miscellaneous Publications, Bureau of Standards, No. 46

Fig. 35.Steel artillery wheel tested to destruction in the large Emery precision

testing machine

This illustrates only one of the thousands of physical tests of materials which the Bureau carried out for the Army and Navy. The design of the wheel used on the Army's "Class B" motor

truck was based upon a complete wheel investigation conducted at the Bureau
SUBMARINE DETECTION 273

It was reported from the front that the development of listening

apparatus on both sides reached such a high standard that mining

operations could be carried out only with the greatest danger to

those concerned. Sounds of digging, picking, and the like,

could be detected at such a distance as to give ample time for the

development of counter measures. Hence, mining operations

very largely ceased along most parts of the front before trench

warfare was abandoned. In some places, however, it was still found possible to carry on mining operations where soil conditions

were such as to prevent effective counter measures.

The instruments described in this report were used very little

on the front, though the fact that they were available had important bearing on the conduct of mining operations.

SUBMARINE DETECTION

Means for Visual Detection

Immediately after the United States entered the war, the

detection of the submarine was perhaps the most pressing of all

problems. In the course of time various means of detection were

developed, some of them of a highly technical and complicated

nature. At the outset it appeared that the simplest means of

detection—viz, sighting the submarine or its periscope—should

not be neglected but developed to its highest possible efficiency.

The National Research Council appointed a committee, on which

the Bureau of Standards was represented, to consider and make

recommendations on this subject, in particular in regard to aids to

vision, methods of observation, and development of the lookout

service.

The report of this committee was prepared at the Bureau and

transmitted to the National Research Council on July 23, 191 7. A supplemental report was issued on October 6 of the same year.

Among the recommendations contained in these reports the following aids to vision were called to the particular attention of

the council as being of undoubted value and capable of practical

application: (1) Goggles to protect the eyes from top, bottom, and

side lights; (2) orange glasses, such as that known as "Corning

G~36;" (3) binoculars of low power, large field, and (for twilight

and night) highest possible brightness. Recommendations were

likewise made as to the organization of the lookout service, with a

view to aiding in the prompt detection of the submarine or its

periscope.

26035°—21 18
274 WAR WORK OF THE BUREAU OF STANDARDS

TELEPHONE PROBLEMS

Study of the Telephone Situation in the District of Columbia

The extraordinary situation which confronted the telephone

company in Washington as a direct and indirect result of the war

was called to the official attention of the Public Utilities Commission

of the District of Columbia through the company's formal petition

for relief, filed November 30, 191 7. The size and activities of the

Government departments grew by leaps and bounds; many new

bureaus were created; tens of thousands of war workers were

required; and several military camps were established in and

around the District. All this resulted in an enormous and rapid

increase in the demand for telephone service and facilities, both

local and long distance. In addition, the demand for war workers

seriously handicapped the telephone company in maintaining its

operating staff. The telephone company petitioned the commission for both traffic and financial relief. The Federal Government

was, of course, vitally interested in prompt, accurate, and adequate

telephone service.

Under date of December 15, 191 7, the Public Utilities Commission formally requested that this Bureau be represented at

the hearings. These were held during December, 191 7, January,

February, and July, 191 8. The efforts of the Bureau's telephone

engineers were primarily directed to determining the facts in the

case and to devising measures for temporary as well as permanent

relief.

On March 15 the Postmaster General, through the Secretary of

Commerce, requested the Bureau of Standards to prepare a report

on the local telephone situation, to include

:

1 . A digest and analysis of the telephone situation in Washington

as brought out in the hearings held up to that time.

2. The relative advantages and limitations of the manual, the

semiautomatic, and full automatic systems of telephone.

3. The relative adaptability of manual, semiautomatic, and

automatic central-office installations to prompt and economic

enlargement.

4. The practicability of "physical connection" and manual

systems, especially with reference to long-distance working.

5. An analysis of the methods proposed for immediate and for

permanent relief of the local telephone situation, including comparative investment data, maintenance, and operating expenses.
TELEPHONE PROBLEMS 275

The Bureau's report, subsequently published as Part II of H. R.

Report 379, accompanying H. R. 10337, entitled "Extension of

the Telephone System in the District of Columbia," was submitted to the Postmaster General in April, 191 8. More than half of the report was taken up by a rather detailed

analysis of the lo_al telephone situation as developed in the

hearings. The materials of this section, Part I, which included a

number of tables, was grouped under the following headings:

Line and station data, Service, Traffic, Adequacy of equipment,

Availability of automatic appliances, Revenues, expenses, and

return on fixed capital, and Distribution of charges between the

Government and public.

In Part II was discussed (1) the relative ability of the manual,

semiautomatic, and full automatic systems to handle traffic;

(2) the quality of telephone service that might be expected of

each system from the standpoint of reliability, accuracy, speed,

supervision, continuity, and secrecy; and (3) the relative number

of employees required for operation and maintenance for the

three systems.

No detailed discussion of the relative adaptability of manual,

semiautomatic, and automatic central-office installations to

prompt and economical enlargement was possible in this report

because of the lack of reliable data and the brief time available

for the preparation of the report. Part III was therefore necessarily very brief. Part IV was also brief, the practicability of

physical connection between the several systems having been

already fully established. In Part V was discussed the telephone

company's proposed method for immediate and permanent relief as outlined in the hearings, and there was also set forth in this

section a method of relief proposed by the engineers of the Bureau.

The company's plan was in brief the development of its plant

through additional equipment of the same type already in use and the corresponding enlargement of its operating force. The

method proposed by the Bureau for meeting the immediate needs

of the Government contemplated the installation of automatic

equipment in the Government departments and independent

establishments, beginning with the War Department, where the

telephonic demands were greatest, by providing for the handling

of interdepartmental business through an automatic switchboard

to be located in the main central office, and the enlargement of
276 WAR WORK OF THE BUREAU OF STANDARDS

the latter so as to permit connecting selected local subscribers

responsible for the bulk of the incoming and outgoing Government

traffic. By this means the Government's requirements would

have been adequately and promptly met through what might

be described as a telephone system within the local system.

It was further proposed to undertake a piecemeal conversion

of the company's central offices from manual to automatic operation, beginning with those having the largest number of subscribers

and the largest volume of traffic.

At the July hearings the experts of the Bureau were on the

stand for direct and cross examination relative to the data set

forth in the above report and in other exhibits submitted at the

request of the commission.

The hearings were adjourned on July 31 without any decision

by the commission, whose jurisdiction in the case was terminated,

for the time being at least, when the Federal Government took

over the telephone systems of the country.

In the meantime the company had acquired control over the

situation, and the unexpectedly early termination of hostilities

in the following November entirely changed the aspect of the

problem.

TESTING MACHINES, CALIBRATION OF

This subject is treated under the title "Calibration of Testing

Machines."

TEXTILES

Cotton Fabrics

The assistance of the Bureau of Standards was requested by

various purchasing branches of the war organization in the summer

of 191 7 in the development of methods of dyeing and of testing the

various olive-drab cotton fabrics needed. The American textile

industry was at that time just recovering from the shortage of

colors which had followed the cessation of foreign importations.

Supplies of dyestuffs were limited. Many of the fast colors which

now again are obtainable were not to be had. Those on the

market were not standard either in strength or in quality. The

situation favored the use of inferior colors and unsuitable methods

of dyeing. The work undertaken by this Bureau at the instance

of the War Department is described below under the following

heads: (1) Development of test methods; (2) study of dyestuffs

by tests of laboratory dyeings; (3) study of mechanical processes

by frequent tests of samples from representative dyehouses.
TEXTILES 277

In 191 7 the War Department was using test methods which

had been adopted when foreign colors were available. These tests

were exceedingly severe. The chemicals used included many

which are never encountered in either the wearing or the laundering of textile materials. In one test, for example, a sample of

the fabric was soaked for several minutes in concentrated hydrochloric acid, in another a sample was given alternate treatment

with potassium permanganate and sodium bisulphite, and finally

a sample was steeped in bleaching-powder solution. These tests,

operated to enforce the use of a fast hydrosulphite vat color

formerly sold in this country by a German dyestuff factory, and

only recently offered by American manufacturers.

This Bureau believed that tests which do not reproduce the

conditions of wear tend to limit the dyer in his choice of colors without advantage to the purchaser, and that moreover they restrict

development on the part of the color makers. Accordingly, it

was recommended that simpler tests be adopted which should

reproduce service conditions and that the tests adopted be rigidly

applied. The recommendations of the Bureau were largely

accepted.

Prior to the recommending of these tests it was necessary to

assemble data as to laundering methods and the expected life of

garments and equipment in service. At one stage of the investigation a number of representative fabrics were sent to a Washington laundry to be put through the regular washing process

several times. The results were compared with those obtained

under the application of the laboratory test methods.

The sulphur colors, which ultimately were universally used in

this work, differ more in their properties than is generally recognized. Particularly noticeable is their variation in fastness to

light. Certain sulphur colors are so extremely fugitive that dyeings from them fade seriously upon a few hours' exposure to

bright sunlight. The good sulphur blacks, on the other hand, are very fast to light. The fastness of the browns and olives varies

considerably. The variety of sulphur colors which appeared on

the market made it desirable to include a light fastness test in the

specifications. Exposure to sunlight is the natural method of

testing. Unfortunately such exposure takes several weeks and

can not be carried out in a manner which is both fair and reproducible.
278 WAR WORK OF THE BUREAU OF STANDARDS

Data on the performance of various lights sold for the testing

of dyestuffs were obtained from the radiometric section, whose

investigations of the nature of the light produced are described

in Bureau of Standards Scientific Paper No. 330, and obtained also

by comparing the action of the lights with that of sunlight on

representative fabrics. The incorporation of a light test in the

specifications was followed by a noticeable decrease in the number of samples on which it was necessary to make an unfavorable

report because of deficiency in this respect.

The wood colors, such as cutch, can be used to obtain the desired

shade for Army fabrics. The shades so produced are quite fast

to washing and to light. Unfortunately they are changed by

perspiration. Accordingly, it was necessary to incorporate in the

specifications tests with organic acids to duplicate the effect of

perspiration and to prevent the use of wood colors. Acetic acid

was recommended on account of its general availability.

At the request of the office of the Quartermaster General and

the War Industries Board, a collection of all the available colors

for dyeing the olive-drab shade on cotton was made. From

these, small strips of cloth were dyed by following closely on a

laboratory scale the directions of the manufacturers. These

dyeings were tested carefully, and the test samples were then

mounted on cards for easier comparison. The samples were

tested for the effect of sunlight and of the dye-fading artificial

lights, of washing and rubbing, and of acid, both before and after

treatment with the various metallic salts used to increase the

fastness of sulphur colors. The cards, containing about 4000

samples, were much used in conferences with representatives of

the War Department. They were of special value in that they

afforded a ready means of demonstrating the defects of particular

dyestuffs. They also showed the necessity of adopting proper

methods of after treatment, and were of considerable value in

interpreting the results of tests of commercial dyeings made at

the Bureau. At the time of the signing of the armistice they

were being used to determine whether or not further limitation of

the supply of toluene allotted to color makers could be made by

the substitution of certain dyestuffs not containing toluene or

its derivatives without leading to the production of unsuitable

colors.

Cotton military fabrics are commonly dyed in the piece in the

continuous machine. This may be operated so as to produce
TEXTILES 279

excellent dyeings with the sulphur colors, or to produce dyeings

in which the color is only superficially fixed. Other mechanical

dyeing processes can also be operated so as to reflect the skill and

care of the dyer. To determine the effect of variations in the

speed of operation of dyeing machinery, in the placing and position of squeeze rollers, in the temperature and composition of the

dye bath, and in methods of after treatment and finishing, samples

from representative mills were frequently tested in cooperation

with the inspection division of the cotton-goods branch of the

Quartermaster General's Office. Tests of these samples led to

the recommendation of certain processes and the criticism of

contractors who were producing faulty material. In general,

the fabrics which were shown by tests in 1918 to be deficient in

fastness failed because of defects in the mechanical process of

dyeing rather than because of the use of inferior colors.

While engaged in this work the Bureau was called upon for

information as to a large number of related topics, such as methods

of redyeing garments and the stripping of tailor's clippings for

paper making.

Woolen and Mixed Fabrics and Felts

The expansion of the Army following the entrance of the

United States into the war was followed by a great increase in

the amount and variety of woolen materials purchased. This

led to a large increase in the testing work requested of the Bureau.

The work included the following: (1) Testing fastness of color;

(2) studies of methods of dyeing; (3) determining fiber composition of mixed materials.

Colors for the production of fast olive-drab shades on wool are easy to make in comparison with the colors used on cotton and

were available at the time the demand arose. The properties of

the colors were also well known to dyers, as the dyestuffs were

identical in composition with those which had formerly been

imported. The test methods in use in 191 7 had been employed

by the War Department for several years. They consisted of

boiling in dilute-soap solution, boiling in dilute sodium-carbonate

solution, and exposure to light. In the summer and early fall of

19 1 8, as part of the general movement toward the standardization

of tests and their better correlation with service conditions, the

Bureau recommended that the use of the boiling solutions be

discontinued, on the ground that they are not generally used in

washing woolen material. It was suggested that the use of luke-
280 WAR WORK OF THE BUREAU OF STANDARDS

warm solutions be substituted, and that in the washing tests

emphasis should be placed on the rubbing. Boiling solutions

were, however, generally used throughout the war. Their use

affords a quick method of demonstrating the presence of inferior

dyes.

The light tests were made in a similar manner to those used for

cotton fabrics. It was customary to make tests of the fastness to

laundering on rather larger pieces than were used for the cottonfabric tests and to determine simultaneously the amount of

shrinkage.

A collection of the dyes used in producing the military shade

on woolen fabrics was made and used for the preparation of dyed

fabrics. The latter were tested and mounted in the same way

as the dyed cotton fabrics and were applied to the same uses. The bichromate used for mordanting or fixating the wool colors

becoming scarce toward the end of the war, a number of experiments were undertaken to determine the feasibility of substituting

other mordants. These experiments were not completed, but in

general it was found that the bichromate is so superior to other

readily available mordants that it would be more wise to attempt

to increase the supply of chrome ores than to attempt to substitute another material.

Wool being considerably higher in cost than cotton, it is advisable in the manufacture of certain types of woolen fabrics and

felts to mix with it such an amount of cotton as can be used without resulting in diminished usefulness of the finished article. For

example, saddle blankets were made for military uses with a cotton warp and a woolen filling. In this way the strength of the

cotton yarn was obtained without sacrificing the desirable characteristics of wool for this particular use. Similarly, in the manufacture of felt considerable saving in cost may be made without

loss of utility.

Quite a variety of such mixed materials were purchased by the

military branches, and a large number of samples were submitted

to this Bureau for determination of the fiber composition. After

some experimentation a convenient method of manipulation of the

customary process of making such analyses, which consists, essentially, in dissolving the wool in boiling sodium-hydroxide solution,

was agreed upon and recommended to the War Department for

the guidance of inspectors.
TEXTILES

Waterproofed Canvas

Waterproofed canvas was purchased in large quantities by various branches of the War Department. The conditions of use were

so severe that it was necessary to make a very careful inspection

of material for purchase. Practically every manufacturer had a

different formula or mechanical process. Waterproofed canvas for

military uses must not only be thoroughly waterproof, but must

also be resistant to mildew, free from objectionable odor or poisonous material, permanently pliable in cold weather and after prolonged exposure to sunlight, and reasonably cheap. The War

Department requested in the fall of 191 7 that the Bureau cooperate

with the purchasing agents in establishing methods of testing and

in selecting the material for purchase.

Most of the methods of testing suggested in the literature on the

subject were found to be too lenient. Others did not reproduce

service conditions. Two methods of testing for waterproof properties were eventually agreed upon. The first was designed to

reproduce the penetrating effect of beating rain. In this test a

sample of the fabric was stretched over a wide-mouthed bottle,

fastened in place, and subjected to a continued spray at considerable pressure for several hours. As tarpaulins are at times spread

upon the ground to protect materials placed upon them from

water, another test was used to duplicate this condition. A generous sample of the fabric was formed into a bag, filled with heavy

articles, and placed in a pail of water for several days. These

tests were found to be quite severe. To determine the resistance to mildew, strips of the various

fabrics were prepared for the tensile-strength machine and then

suspended for several weeks in loosely covered jars in which there

was a growth of mildew. The jars were kept in a warm, dark, and

damp place. After the exposure the strips were cleaned and, ex- cept in the cases where the fabric had completely disintegrated,

were tested for tensile strength. It was found that the mildew

growths could spread over the surface of some fabrics without

injuring the fabric itself.

The effect of the probable extremes of temperature was determined by careful inspection of the material after heating for several hours at 45 C, and again while immersed in a freezing

mixture.
282 WAR WORK OF THE BUREAU OF STANDARDS

A number of representative fabrics were exposed to sunlight on

the roof for several weeks. It was found that in some cases the

waterproofing material was decomposed by the action of light.

It was realized that the construction of the canvas used had an

important bearing on the wearing qualities of the finished fabric

and a number of samples were subjected to the regular analysis

of cotton fabrics carried out by the textile section.

An analysis of the coating material was made on about 150

samples. The materials found included asphaltum, wood tar, drying oils, paraffin, resin, glue, petrolatum, starch, inorganic and

organic antiseptics, and various inorganic weighting materials and

pigments.

Several ready-mixed waterproofing preparations were offered by

manufacturers for use in recoating fabrics. Many of these were

analyzed and tested by applying the usual tests to fabrics coated

in the laboratory.

An interesting feature of the study of waterproofed canvas was

the examination of a number of French, English, and German

fabrics obtained through the War Department. Few of these

were as good as the average American canvas.

Airplane Fabrics

The Bureau conducted a series of experiments which led to the

choice of mercerized cotton fabric of a certain construction as a

substitute for the linen fabric employed as a covering for airplane

wings used before the war and later unobtainable. In the routine

examination of samples submitted for criticism by manufacturers,

the Bureau cooperated by making the tests for amount of sizing

and freedom from acidity or alkalinity, which were incorporated

in the specifications.

It was found in the course of tensile strength determinations

and other physical tests that the mercerized yarns produced by

various mills differed more than was to be expected from variations in their construction. It was believed that these differences

were due to the various mercerizing processes employed. A study

was undertaken of the effect of certain changes in the customary

process of mercerizing on the physical properties of mercerized

yarns. The results of this study will be published.

Cordage

Manila fiber is the best material of its class for the manufacture

of ropes. Other fibers which are considerably cheaper do not

resist rotting as well as manila and are not as strong. Conse-
TEXTILES 283

quently, the mixture of these fibers with manila in the manufacture of rope is not only fraudulent adulteration, but may lead to

serious accidents or the premature lessening of the utility of

articles or appliances in which the rope is used. Because of its

longer life, manila rope is economical in spite of its higher cost.

Prior to 191 7 the use of the inferior fibers was rather common.

In that year a test was devised elsewhere for distinguishing between manila and the other fibers. The accuracy of this test was

determined by making many analyses, under different conditions,

of known mixtures of manila and nonmanila fibers. It was

eventually incorporated in the standard specifications for manila

rope issued by this Bureau for the guidance of manufacturers

working on Government cordage contracts. Reports of the

Bureau of Standards certifying to the presence of inferior fibers

in rope sold as manila have been successfully upheld in the courts.

A number of rope samples were examined chemically for military

organizations. (See article on "Miscellaneous Physical Tests.")

Military Textile Equipment, Uniforms, Blankets, etc. When this country entered the war the facilities of the military

departments for the inspection and testing of military textile

equipment were rather limited. The facilities of the Bureau were,

therefore, made available to the Quartermaster Corps and the

Ordnance Department. All of the materials purchased by the

last-named department were tested in the Bureau's laboratories,

and this work constitutes a very large part of that carried out on

military textiles.

The old Army fabrics and specifications covering them were

entirely satisfactory, but the shortage of raw materials and

manufacturing equipment made the use of substitutes necessary.

It was definitely known that the substitution of structure alone

would not necessarily duplicate an article, and the Bureau was

called upon to devise test methods which could be used to predict

the performance of proposed fabrics. The general procedure

adopted was to study the old satisfactory fabrics to determine

their performance and to compare the submitted fabrics with the

results. The tests included the heat-retaining properties, resistance to abrasion, and resistance to repeated stress. As was the

case in the design of airplane fabrics, the textile manufacturers in

this country and abroad had never constructed clothing materials

to have definite properties, and the Bureau experienced considerable difficulty in determining the characteristics of raw stock and
284 WAR WORK OF THE BUREAU OE STANDARDS

of manufacturing which governed the exact properties previously

mentioned. The opposition to the manufacturing of fabrics to

meet definite requirements was so great that the Bureau installed

a small experimental woolen manufacturing plant to demonstrate

the value of such work.

A great deal of valuable information was obtained in determining the heat-retaining properties of materials, and it was conclusively demonstrated that the old theory that cotton is not so warm as wool was entirely wrong and that the heat-retaining

properties of any textile material depend entirely upon the manner in which the fibers are arranged. Many lines of possible

research were thus thrown open to determine the best combinations

of fibers and structures to make Army clothing lighter and more

satisfactory than that commonly used.

The study of the wearing properties of Army clothing was centered about an investigation of the resistance of certain textiles

to abrasion and to repeated stresses. In one or two cases laboratory methods were checked up by actual performance tests, and

here again much valuable information was obtained for use in

constructing more satisfactory Army clothing materials.

The information obtained through these military tests may be

applied equally well to civilian clothing, and it seems reasonably

certain that methods are available which will enable the manufacturer as well as the Government to study more intelligently

the characteristics of this class of goods.

The abrasion test is an attempt to reproduce by mechanical

means the wear on fabrics received in everyday use. In this test

the machine appears to gradually cut, break, and eliminate the

fibers from the surface of the fabric until the loss greatly lessens

the strength of the material. One of the chief difficulties presented in this test is the lack of an abrader which will offer an even

and homogeneous abrading surface at all times, so that each

sample will receive the same treatment. The abrasion is measured

indirectly by the resulting change in some other property, such

as lowering of the tensile strength, or tear resistance, deterioration in appearance, etc.

All of the investigations for the standardization committee of

the Director of Purchase and Storage, Quartermaster Department, including chemical and physical testing, were carried out

in the textile laboratories of the Bureau of Standards, and the

results have been incorporated in the standard specifications.
TEXTILES 285

The section was in direct touch with the manufacturers of

American dyes and had available at all times information as to

the best way to dye materials to obtain the best results. Records

were kept at all times which showed the exact performance of any

American dyestuff. Information of this character was frequently

supplied the military purchasing departments, and it is believed

that the service rendered was of considerable value.

Dyestuff Chemistry

In addition to the work in dyestuffs already described, war

work in dyestuff chemistry of quite a different character was

undertaken under the direction of the colorimetry section. This

is also described in the report on "Chromatic Camouflage."

It is well known that solutions of individual dyestuffs differ

widely in light-absorption properties. The spectroscopic examination of light which has passed through such solutions affords a method for the identification of colors. During the war period considerable progress was made in the projected development of a comprehensive method for the identification and analysis of dyes by

spectroscopic measurements. To aid in this work the chemistry

laboratory contributed about 30 carefully purified dyes, made

from purified intermediates by selected processes. The lightabsorptive properties of dye solutions are found also in dyed fabrics, films, colored glasses, paint pigments, leaves, flowers, and

other colored objects. In the case of dyed fabrics the effect of

viewing materials under different lights is so great that the dyer in

matching shades must consider carefully the nature of the light

under which a fabric will be used.

By extending and applying the principles involved it was found

to be feasible to apply the light-absorptive properties of colored

bodies to military uses. An example is a method by which signals

may be conveyed to aviators by the use of fabrics dyed the color

of grass. These, if carefully made, can not be distinguished from

grass by the unaided eye at relatively short distances. When

viewed through an appropriate color screen, however, the fabric

will appear to be of quite a different color from the grass and thus

will be distinguished at considerable distances.

To try combinations which were suggested by the measurements of the colorimetry laboratory, it was necessary to dye a number of fabrics and films. For this purpose use was made of the

collection of dyes maintained by the chemistry laboratory and,

where necessary, dyestuffs were synthesized from the intermediate
286 WAR WORK OF THE BUREAU OF STANDARDS

compounds. Several well-matched fabrics and films were obtained

which when viewed through the proper color screen were easily

discriminated. The results of these experiments were reported in

detail to the military organizations interested.

TIMEPIECES

Information and Specifications

From the beginning of the war the Bureau of Standards in its

work on timepieces performed a valuable service which it was perhaps better qualified to undertake than any other existing agency.

For a number of years the Bureau had carried on the investigation and testing of high-grade pocket watches, and the experience

thus secured formed an admirable preparation for the drawing up

of specifications involved in the purchase of all classes of timepieces.

So far as is known, the Bureau was consulted at least as to cer- tain details of the specifications for practically all of the timepieces which were purchased by the Government during the war. For one year after the United States declared war on Germany,

one member of the Bureau's staff served in an advisory capacity

to the National Research Council on questions relating to procuring an adequate supply of serviceable navigating instruments for

the new Government-owned merchant marine and later gave up

his position at the Bureau to join the Emergency Fleet Corporation, so that he might be able to devote his entire time to this one

problem.

Chronometers

A particularly important phase of this problem consisted in the

securing of marine chronometers or, what was the final outcome

of the problem, the obtaining of an adequate supply of acceptable

substitutes. At the beginning of the war there were no chronometer factories in America, and the only available domestic

source of supply was the local jewelers scattered throughout the

country, from whom an exceedingly small number of chronometers

were obtainable. Some could likewise be obtained from the

British Admiralty. The production of new chronometers is not

the work of only a few months, but involves years. The total

supply accumulated from all sources satisfied only about one-third

of the demand, and the remainder was met by using high-grade

American-made watches called "ship watches." These were all

tested, and each watch accepted for this service had to pass the

rigid performance test adopted by the Bureau.
TIMEPIECES 287

The Beginning of a New Industry

As has been the case in many other lines, the necessity for the

use of watches as substitutes for chronometers has called the

attention of the American people to this need, with the result that

one of the leading watch manufacturers in this country has commenced the making of marine chronometers. In all probability

these will not be placed upon the market for some time, but it is

to be hoped that eventually this will become another industry in

which the United States will not be dependent upon a sister nation

in time of public emergency.

Testing of Timepieces

The amount of routine testing performed by the Bureau has

been exceedingly large, since all of the timepieces purchased by

the Emergency Fleet Corporation were given their acceptance

test here. The timepieces tested for this organization include

not only ship watches but also comparing watches and desk

clocks. Since many of these instruments were to be used for a

purpose requiring special accuracy and because large numbers

had to be rejected, this routine work was considered well worth

while, even though each test covered about a month and the

number of timepieces tested amounted to approximately 15 000.

Stop Watches

The most important work of this section of the Bureau for the

War Department was the aid furnished to the Ordnance Department in obtaining a supply of satisfactory stop watches. As stop

watches are not made in America, the only ones available had

to be imported, and the errors of these instruments in practical use either influenced the accuracy of scientific data or jeopardized

the safety of troops. The inspection or acceptance testing of

these watches was conducted at the Bureau. The value and

necessity of this work will be appreciated when one considers that

even with specifications having only moderately close tolerances,

the number of rejections for the best types of watches was as large as 7 per cent, while for the poorest type it ran as high as 67 per cent.

Airplane Clocks

When the construction of airplanes on a large scale was first

undertaken, practically the only available kinds of timepieces

at all suitable for mounting on the instrument boards of airplanes

were large, heavy automobile clocks which were not sufficiently

accurate to meet the requirements of this class of service. The

Bureau, with the active cooperation of one of the leading watch
288 WAR WORK OE THE BUREAU OE STANDARDS

manufacturers, developed a suitable type of instrument having

all the accuracy that was required even under the most adverse

circumstances and for which the weight was only a small fraction

of that of all known previously existing types. This new design

was adopted by the Signal Corps, and, so far as is known by this

Bureau, was used to the end of the war without a change in any

detail. A peculiar feature of this problem which was admirably

taken care of by the manufacturer was that of the proper lubrication of the movement so that the clocks would not stop when

exposed to the extremely low temperature met with at high

altitudes.

TOLUOL RECOVERY

Preliminary Work, Conferences, etc. On April 1 1 , 191 7, there was presented before the Pennsylvania

Gas Association an article urging the attention of the gas industry

to the matter of the recovery of toluol from city gas supplies, in

order that there might be available for the Federal Government

the necessary quantities of tuluol for the production of T.N.T.,

which is the preferred high explosive for military uses. Discussions on this subject between members of the Bureau's staff and a

member of the Gas Institute likewise took place, and the subject

appeared to be of such importance that during the remainder of

April, 191 7, one of the Bureau's engineers made a careful study of

British gas journals to obtain information of interest to the American industry. When this work was completed, it was found that

the information obtainable, while valuable, was not particularly

applicable to similar problems which confronted American gas

companies. On May 2,3, and 4, representatives of the Bureau also

took up with the engineering, physical, and chemical divisions of

the National Research Council the question of securing by cooperative effort the maximum amount of information on this subject.

As a result of a conference between the chairman of the American

Gas Institute's committee on "The Relation of the Gas Industry to

the Military Needs of theNation," andrepresentatives of the Bureau,

it was suggested that a committee be organized including representatives of the gas industry, of the Federal Government, and of State

and city authorities , to undertake a comprehensiveinvestigation that

would make available to the Government the following facts : ( 1 ) To

what extent toluol could be secured from the American gas works ; (2)

what procedure would benecessaryin ordertomakethistoluol available; (3) what changes in standards would be required in order that
TOUJOIy RECOVERY 289

the tuluol be removed from the gas without violation of local re- quirements; (4) what financial arrangements could be considered

acceptable and proper to compensate the gas companies for the

service rendered; and (5) what companies would be most available

to undertake this work at an early date.

As a result of this decision, the Bureau conferred with a number

of agencies and endeavored in every way to render assistance looking toward the necessary readjustments of standards of gas service,

elimination of high-candlepower standards, and substitution of

heating values in general well below 600 Btu per cubic foot.

Beginning in the latter part of May the Bureau received from

several State commissions, city authorities, and gas company

officials numerous inquiries on questions relating to toluol recovery

and to the adjustment of standards under the existing abnormal

conditions of supply of labor and materials.

After consultation with representatives of all the parties interested it was decided to hold a conference on the subject of toluol

recovery on July 31 and August 1 and 2 at the Bureau. The three

questions for discussion at the conference, as stated in advance of

the meeting, were as follows

1. The recovery of toluol from gas, including the methods and

equipment required for such recovery, and various questions of

operation, including standards, costs, yields, and other interesting

and pertinent information.

2. The extent to which the present costs of material and labor

are affecting the gas-company operation, this to demonstrate to

what extent the present situation is making necessary changes in

existing standards or existing rates for gas apart from the question

of toluol recovery.

3. The relative advantage of changing standards instead of

changing rates for gas.

During the meeting a general presentation of the need for some

relief to gas companies was offered, and some suggestions were

made upon the relative desirability of changing the standards for

service instead of changing the price of gas to the customers. However, no definite conclusions were reached at this session.

A great deal of time was devoted to the discussion of the need

for toluol and suggestions as to the best means for accomplishing

its recovery.

On the last day of the conference the State and city representatives, meeting by themselves, voted unanimously to adopt reso- 26035°—21 19
290 WAR WORK OF THE BUREAU OF STANDARDS

lutions appointing a joint committee to further investigate the

subject, the chairman of the committee being a member of the

Bureau's staff.

The Bureau of Standards then undertook to inform itself more

fully as to the current practices in the production of toluol from

city gas supplies. For this purpose representatives of the Bureau

visited a considerable number of plants where this work was being

done and secured the maximum amount of information possible

in the limited time available. Information was also sought by

correspondence with others familiar with toluol practice who

could not be met in conference. The information secured served

as the basis for the report on "Recovery of Light Oils and the

Refining of Toluol."

The preliminary draft of this report was submitted to the members of the special gas committee on September 19, and the first

meeting to discuss this matter was held September 24. With the

assistance of the committee's suggestions the Bureau revised this

report and issued it in mimeographed form on October 15.

Report on Toluol Recovery

This report covered the subject of toluol recovery in a general

way and was divided into three parts : Part 1 , The technical relation of the gas industry to the military needs of the nation; part

2, Principles underlying benzol and toluol recovery; part 3, Construction and operation of light-oil recovery plants. Part 1 gave

a general discussion of the problem and described briefly the various methods used in manufacturing gas; part 2 described briefly

the methods used in the recovery of toluol, while part 3 presented

in detail the apparatus and equipment of one type of toluolrecovery plant installation. The adaptability of light-oil recovery

by small gas plants was also discussed, and the cost of installation

and operation of light-oil recovery plants was touched upon.

This paper was published in the Gas Age, of November 15, 191 7,

the Gas Record, of November 14, 191 7, and the Journal of Industrial and Engineering Chemistry, of January, 191 8. Through

these publications the paper reached a large number of persons

interested in the work, and in addition the Bureau distributed

many reprints to gas companies, State commissions, and individuals. A great many were asked for by the Ordnance Department

of the Army and used in connection with its work.

Additional Committee Work

Following the publication of this paper a second meeting of the

above-mentioned committee was held on October 22, at which
TOLUOL RECOVERY 291

time it was expected to discuss at considerable length plans for

further work and particularly questions relating to the technical

features of the proposed toluol contracts between the Government and gas companies. Preceding this committee meeting the

Bureau had held a number of conferences with members of the

Ordnance Department of the Army, suggesting certain principles

bearing upon the question of toluol contracts, and the Bureau had

forwarded to the department as a confirmation of these confer- ences a memorandum outlining certain principles which it suggested as worthy of consideration by the Ordnance Department

in planning these contracts.

On the same day (Oct. 20) a member of the Ordnance Department handed to a representative of the Bureau a copy of the

outline of the plans of the former organization relating to the contracts for toluol and expressed his willingness that these matters

be discussed by the committee two days later. These suggestions

emananting from the Ordnance Department were therefore laid

before the joint committee at its meeting on October 22.

In connection with the toluol-contract work done by the Ordnance Department the Bureau of Standards was able to be of

great assistance. Several members of the gas-engineering staff

spent periods varying from a few days to six months acting as

technical advisers of the Ordnance Department.

Publications on Toluol Recovery and Gas Standards

During the early part of January, 1918, the need of a publication giving in some detail the effect upon standards of gas quality

of the removal of light oil became apparent. Accordingly, a

brief resume was prepared of the standards of gas service then in

force in those cities which would probably be considered for the

erection of toluol recovery plants. The method of estimating

influence of toluol recovery upon gas quality was described, and

the following conclusions set forth. These conclusions represented substantially the attitude of the Bureau on toluol recovery.

As a summary of these points, the following suggestions are

offered

1 . Eliminate all candlepower requirements now in force, except

for the cities where 18 candles or higher has been supplied, in

which localities reach an understanding that at least 1 2 candles

will be maintained for a period, say a year, during which time readjustments of appliances and substitution of mantle lamps would

be accomplished to such an extent as to justify complete elimination of candlepower regulations.
292 WAR WORK OF THE BUREAU OF STANDARDS

2. For plants making coal gas (or practically only coal gas)

let the heating-value standard be from 550 to 570 British thermal

units.

3. For plants making water gas, either alone or as a major

constituent, let the heating-value standard be 570 to 600 British

thermal units monthly average total heating value, the adjustment being made between these limits according to the economic

conditions of operation.

In order to make the conclusions clear and as far as possible,

specifically applicable to all the cases in question, there was given

in the paper a list of the localities where such changes of standards

as are suggested would probably be necessary.

This publication also had a wide circulation and was reprinted

in the Gas Age, of January 15, 1918, the Gas Record, of January 9,

1 91 8, and the Journal of Industrial and Engineering Chemistry

of February, 19 18. In addition to reaching about 20 000 persons, a number of reprints were distributed.

Previous Publications Combined in Technologic Paper

The supply of both of these publications was exhausted early

in 1 91 8, so they were combined and published as Technologic

Paper No. 117 of the Bureau of Standards, entitled "Toluol

Recovery." Much additional matter was gathered, and changes

which had been suggested were incorporated.

This paper is in four parts. Part 1 is the introduction which

deals with the need for toluol and the scope of the paper; part

2 is practically the original paper on

J 'The Recovery of Light

Oil and Refining of Toluol," previously described, but, in addition,

contains a number of tables and other data assembled from various sources and presented through the courtesy of the authors;

part 3 is a discussion of the relation of toluol recovery to standards

for gas service, and is the paper previously referred to as a separate

publication; part 4 gives a typical form of contract which the

Ordnance Department made with various companies for the

operation of toluol-recovery plants in connection with city gas

works. %

Increased Production of Toluol in the United States

Notwithstanding the great importance of high explosives in

the war the necessity for recovery from city-gas supplies of toluol,

the base of trinitrotoluol (T. N. T.) was not appreicated in the

United States until this country entered the conflict in 191 7. Previous to 1 914 the production of toluol in the United States prob-
WHEELS, INVESTIGATION OF ARTILLERY, TRUCK, AND AIRPLANE 293

ably did not exceed 500 000 to 750 000 gallons per year. Most of

this toluol came from coal-tar distillation, but smaller amounts

were prepared by refining the light oils which were removed from

coke-oven gas in a few plants. After beginning hostilities the

demand for toluol greatly increased, and it was evident that the

common sources of this material would not meet the new commercial demands. As a consequence a large increase in the recovery

of toluol from coke-oven gas immediately followed, and later

the recovery of this constituent from city-gas processes was undertaken as mentioned in the preceding paragraphs.

To give an approximate idea of the magnitude of the industry

thus developed, one need only compare the small output of pure

toluol in 191 2 and 191 3 of approximately 500000 gallons with

the probable output for the year 191 8. If the war had continued

for the entire year, it was expected that the output would have

exceeded 20 000 000 gallons, and by the end of the year 191 9 it was

hoped that the rate of production would reach 30 000 000 gallons.

At the time of the signing of the armistice there were 2 1 Government-owned toluol plants in operation in city gas works, a typical

plant being illustrated in Fig. 32, and a number of other plants

were nearing completion or were actually ready to begin operation.

Practically all of the increase was made possible because of the

recovery of toluol from coke ovens and city-gas supplies.

WHEELS, INVESTIGATION OF ARTILLERY, TRUCK, AND

AIRPLANE

The Bureau's superior testing facilities resulted in its being

called on repeatedly in connection with development and standardization work of various kinds. Among the investigations

carried out were three series of tests on wheels, namely, (1) artillery or gun-carriage wheels in cooperation with the Ordnance

Department, (2) truck wheels in conjunction with the Motor

Transport Corps, and (3) airplane wheels with the Bureau of

Aircraft Production. In all cases the wheel manufacturers

worked hand in hand with this Bureau in the development work,

and it may not be out of place to remark that this cooperation of

private interests with the Government was typical of that experienced by the Bureau during the war.

Wheel-Strength Requirements

On all types of wheels the basic requirements are essentially

the same. Such vital requirements are (1) resiliency or elasticity,
294 WAR WORK OF THE BUREAU OF STANDARDS

(2) strength, (3) durability and economy, and (4) lightness. In

the war emergency the military authorities found themselves

without any reliable comparative data and there was no time for

service tests. The Bureau of Standards was therefore called upon

to make laboratory tests.

Types of Laboratory Tests

Each type of wheel, for whatever purpose it was designed, was

subjected to two tests. The first of these is the radial compression test in which the wheel is supported on a block and

stressed radially by applying load through an axle passing through

the hub. The second one is the side- thrust test in which the wheel

is supported on an axle which is held rigidly with its axis parallel to

the line of application of the applied load. The load is applied to

the side of the rim of the wheel through a suitable bearing block.

The parallelism of these two tests to the stresses encountered by the

wheel in service is easily seen. The radial-compression test subjects the wheel to the same form of loading it receives in service

when supporting the loaded truck at rest. The side-thrust test

parallels the stresses introduced by the skidding or turning of the

truck.

Value of Tests

The value of the radial-compression and side-thrust test in determining the efficiency of the wheel in question, on the basis of the

requirements outlined in paragraph 2 of this section, is readily

apparent. The resiliency or elasticity is determined by plotting

the deformations or deflections against corresponding loads and

determining the area under the resultant curve. The elastic

resiliency of the wheel reported in inch-pounds is taken as the area under the part of the curve cut off by a vertical line through the

proportional limit. The strength of the wheel is determined by

carrying the tests outlined above to a point where fracture occurs,

or, in some cases, only to a load which represents an adequate factor

of safety when there is no sign of failure up to that point. Durability and economy can not, of course, be determined in a laboratory

test, except in so far as the minimum required weight represents

the minimum cost for metal. Lightness, with strength, constitutes

the final basis for comparison of various wheels. Elastic resiliencies and u1 timate strengths are all reduced for comparative purpose to a unit-weight basis.
WHEELS, INVESTIGATION OF ARTILLERY, TRUCK, AND AIRPLANE 295

Artillery Wheels

The Bureau subjected about six artillery or gun-carriage wheels

to a radial-compression and side-thrust test (Fig. 35). These tests

were conducted on the Bureau's 2 300 000 pound Emery hydraulic

testing machine, as were the tests of the motor-truck wheels

described below. L,oad was applied to a section of the rim midway between two spokes. These wheels were of cast steel, and most

of them were about 155 mm tread by 1350 mm diameter, or 6 by

53 inches in size. The Bureau's tests on these wheels were not so

definitely a part of a development program as were the motortruck-wheel test series. However, certain elements of weakness,

including defective welded joints, were discovered and comparisons

between various manufacturers' products were furnished the

Ordnance Department.

Truck Wheels

In designing the class B military truck, the Army found it

desirable to develop a metal wheel having the good qualities of

all the motor-truck wheels on the market. The laboratory tests

of these wheels were conducted at the Bureau.

The wheels tested were made of cast steel, pressed steel, wrought

iron, and wood, and by various manufacturers. The metal wheels

included both solid and built-up designs. The series included

examples of U spokes, tubular spokes, solid spokes, and disk

wheels. The wood wheel included in the series had seen some

service, but most of the metal wheels came directly to the Bureau

from the factory or foundry.

Radial-compression and side-thrust tests were made on each

type of wheel, and the elastic resiliency, strength, and deformations were determined. Using the information obtained from

these tests, a hollow spoke and rim cast-steel wheel was designed

for the Quartermaster's Department (motor transport section),

which was called the "composite wheel." This type of wheel

demonstrated the value of the laboratory tests by giving satisfactory results in service.

Technologic Paper on Wheels

The results of the motor-truck wheel test series have been published as Technologic Paper No. 150. The results of tests on 21

wheels are given. The deformations of the wheels in the radialcompression tests were recorded for four points on the rim spaced

90 apart. Load-deformation graphs plotted from these data
296 WAR WORK OF THIJ BUREAU OF STANDARDS

are given, from which the proportional limit and elastic resiliencies

of the wheel are computed. The proportional limits are then

divided by the weight of the wheel to furnish unit-weight figures

for comparison. The same program was followed in the sidethrust tests.

The Bureau publication gives a photograph of each wheel and

a chemical analysis of the material for each metal wheel. Valuable

suggestions for use in the design of truck wheels to afford maximum

strength and resilience for minimum weight are included.

Unique Stress Analysis of Wheel

In addition to the data determined for each type of wheel, as outlined above, a complete strain-gage analysis was made of one

cast-steel wheel with hollow spokes and rim in a radial-compression test. A 2-inch Berry strain gage was used. Deformations were

measured in gage lines established on the rim, on the spokes, and

on the hub. After the radial-compression test had been finished,

specimens were cut from the wheel and tested in tension. The

average modulus of elasticity as determined from these tests

(28 500 000 pounds per square inch) was used to reduce the

strain-gage data to corresponding stresses. From these data

graphs (or stress contours) were plotted showing the stresses

in the wheel at 48 gage lengths for loads on the wheel up to 60 000

pounds. Due to the short gage length (2 inches), results of great

precision were not to be expected, but in this case the results were

very satisfactory.

Analysis Aids Efficient Design

Compressive stresses were found in all parts of the rim except

the section between the spokes adjacent to the loading block.

That section was subjected to tensile stresses by the behavior of

the spokes. The only excessive stress in the hub was at the

junction of the two spokes adjacent to the loading block, where

the tensile stress reached the proportional limit of the material for

an applied load of 50 000 pounds. The stresses in the spokes

were all less than the proportional limit of the material, except

for two gage lines on one spoke adjacent to the hub. There is

a possibility that these two gage lines were located at a thin section

of the casting.

To the best of the Bureau's knowledge, this stress analysis by

use of the strain gage is the first of its kind ever attempted in

connection with wheel design. It is believed to afford a profitable

line of study in connection with further wheel design. Only
WHEELS, INVESTIGATION OE ARTILLERY, TRUCK, AND AIRPLANE 297

by such a stress analysis can the most satisfactory distribution of

the material in the wheel be obtained. Such data allow the modification of a wheel so as to avoid excessive stresses which cause

failure in service tests.

Airplane Wheels

One or more each of eight types of shock-absorbing wheels for

airplane landing gears were subjected to radial-compression and

side-thrust tests in the manner heretofore described. As these

wheels are, of course, designed for smaller loads than are the artillery and truck wheels, the tests were conducted on the 230 000-

pound emery hydraulic testing machine.

Palmer Wire-Spoke Wheel

Most of the wheels tested were of the wire-spoke type. There

were also included samples of disk-type wheels with spring unit

rods and wheels with S -spring steel spokes. Partly on the basis

of these tests the Bureau of Aircraft Production adopted the Palmer swedge-spoke type of wheel as the standard construction.

These wheels, size about 750 mm diameter by 125 mm tread,

weight 8.7 to 9.2 pounds, averaged about 3000 pounds ultimate

strength in side thrust and 7000 pounds in radial compression.

These figures are based on tests conducted at the Bureau on about

a dozen Palmer type wheels from four manufacturers.

The average results of the above tests enable the designer to

establish a fair criterion for judging the performance of any other

wheel under similar test conditions.

The ultimate strength in side thrust for unit weight averaged

355 for five Palmer type wheels tested, and the corresponding ratio

of strength to weight in radial compression was 810. These two

values can be taken as fair entertons for judging the value of other

types of wheels for this service.

Comparison with Early American Wheel

By way of comparison it may be noted that the strength-weight

ratio for S-spring spoke wheels was found to be 160 in side thrust

and 380 in radial compression; for the spring unit rod spokes with

sheet-steel casing, 40 in side thrust and 430 in radial compression

average of two early American type wire-spoke wheels, 255 in side

thrust and 820 in radial compression. The Palmer type wheel

has a hub which is not placed symmetrically in the plane of the

rim, but which gives added strength to resist the side thrust

encountered by the wheels and chassis when the plane lands.

Elastic-resilience comparisons also showed the relative superiority
298 WAR WORK OP THE BUREAU OF STANDARDS

of the Palmer type wheel. This wheel was extensively used for

equipping airplanes manufactured in England before these tests

demonstrated its superiority over other designs and resulted in its

general adoption for the use of American-made aircraft.

X-RAYS

Owing to the fact that the X-ray work of the Bureau was not

initiated until the summer of 191 7, the Bureau was not in a position

to be of as much assistance to the military authorities in this field as it would have been had the work been started at an earlier date.

The work done falls under two heads: (1) The study and testing

of protective materials; (2) the radiography of various objects.

The work included under the second head was strictly of a cooperative nature, the radiographs being taken for the purpose of

furnishing to the respective branches of the War Department

information regarding the internal structure of specific articles

and the applicability of radiography to the examination or inspection of supplies.

Protective Materials

Lead-impregnated materials (glass, rubber, etc.) are widely

used for protecting the roentgenologist and the patient from

harmful exposure to X-rays. The protection of the roentgenologist, who under war conditions had to work many hours a day

in close proximity to the X-ray tube, was especially important.

A study of these commercial materials demonstrated not only

that they differed widely in the protection afforded, but that some

of them, even the most expensive, were practically worthless, and

that all might be improved in quality. Radiographs were taken

of various pieces of lead glass. In one case it was found that of

two pieces tested, the one casting the denser shadow, while but

3 mm thick and weighing only 2 pounds per square foot, was of a

good quality of lead glass, the other glass, 25.4 mm thick and weighing 12^ pounds per square foot, was practically worthless for

X-ray protection. This piece was, however, representative of

some of the most expensive glass that was bought by the Bureau

in the open market in 191 7. It was also representative of some

of the glass that was offered to the Surgeon General's Office.

The Bureau advised the Surgeon General's Office and the larger

dealers in X-ray supplies of the presence of this fraudulent material,

and urged manufacturers to produce material of a better quality

than any that was on the market in the spring of 191 7. The
X-RAYS 2 99

response of the manufacturers was most gratifying, and materials

of superior quality are now available.

In connection with this work protective materials were tested

for the Surgeon General's Office, inspectors of that office were

furnished with data by means of which approximate information

concerning the quality of these materials could be determined

expeditiously by the simple process of measuring and weighing

the specimens, and improved supplies were brought to the attention of military authorities

Radiography

At the request of the reclamation division of the Quartermaster

Corps of the Army repaired shoes (Fig. 34) were radiographed for

the purpose of obtaining information regarding the driving and

clinching of nails by different types of soling machines.

Aluminum propellers for airplane apparatus were examined for

the presence of internal flaws.

Thin specimens of steel were similarly examined for the Ordnance Department of the Army.

At the request of the Bureau of Aircraft Production the practicability of applying radiography to the inspection of wood was

investigated in some detail. Although under suitable conditions

radiographs can give much information regarding internal structure, it appears that in the case of unfabricated wood it can

reveal but little of importance that can not be detected by a

trained inspector. In the case of finished articles, however, it

can in many cases yield valuable information regarding the

fabrication, information that can be obtained in no other way.

For example, in one piece of wooden construction examined it

was evident that certain wooden pins had not been driven home.

The radiography of a number of articles of an unpromising

nature, such as censored manuscripts, charcoal, etc., was attempted

at the request of the military authorities interested. Although

the possibility of successfully radiographing these articles appeared

slight, the Bureau studied each case thoroughly, using various

techniques before giving up the problem as hopeless.

Somewhat similar to the preceding was the attempted radiography of thick specimens of steel. No satisfactory result was

obtained either by the use of X-rays or of radium.

J*