nnual Report 1950

National Bureau

of Standards

Miscellaneous Publication 200

UNITED STATES DEPARTMENT OF COMMERCE

Charles Sawyer, Secretary

NATIONAL BUREAU OF STANDARDS

E. U. Condon, Director

Annual Report 1950

National Bureau

of

Standards

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 50 cents

CONTENTS

1. General Review

Page

1

2. Electricity and Optics 17

Precise electrical measurements 18, Static electricity hazards 18, Application of high-speed computers to lens design 18, Planeness of optical surfaces

19, New type of interferometer 19, Permanent gloss standards 19, Revision of the Union colorimeter scale 21, Photometry of mercury vapor lamps

21, Lighting at the Shrine in the Library of Congress 22, Lighting of the Senate and House chambers 22, Refractometry 22.

3. Metrology 22

Standard weights for microbalances 23, New system for weight calibration

23, Rate drift of timepieces 23, Dental materials 24.

4. Heat and Power 25

Temperature measurements 27, Rheological physics 28, Automotive research

29, Aircraft accessories 31, Gas turbines and jet engines 31, Low-temperature

physics 32.

5. Atomic and Radiation Physics 34

Omegatron 34, Electric and magnetic field mapping 35, Electron optics

36, Semiconductors 36, Negative ions 37, Radioactivity 38, Protection

against radiation 38, Field X-ray equipment 41, Analysis of solids by mass

spectrometry 41, Standard wavelengths for spectrometer calibration 42, Ulti- mate standard of length 43, Spectra of artificial elements 43, Absorption spec- trum of water vapor 43, Atomic energy levels 44, Tables of nuclear data 44.

6. Chemistry 45

Spectrochemistry 45, Color phase-contrast microscopy 46, Standardization

of pH 46, Combustible gas indicator 47, Standard methods of gas analysis

47, Hydrocarbons 48, Thermochemical measurements 48, Electrodeposition

49, Research in analytical chemistry 49, Commercial solid adsorbents 49,

Punch-card catalog of infrared absorption spectra 50, Carbohydrate chemistry 51.

7. Mechanics 51 NBS stick force indicator 52, Photo-grid technique 53, Aircraft structures 53,

Ship structures 54, Water levels in shallow lakes 54, Flow of stratified liquids

55, Drainage systems in buildings 55, Humidity apparatus 56, Dispersion of

sound in gases 56, Standards for calibration of microphones 57, Sound

absorption 57.

8. Organic and Fibrous Materials 57

Synthetic rubber 57, Low-temperature potentialities of the silicone rubbers 58, Resin bonding of offset papers 58, Abrasion studies 59, Properties of laminated plastics 59, Surface of cotton fibers 59, Volume changes at high pres- sures 60, Water-vapor relations of leather 61, Deterioration of furskins 61.

Ill

" 1
9. Metallurgy

Corrosion 62, Properties of metals at high and low temperatures 62, Fatigue

of metals 63.

Page

26

10. Mineral Products 64

Ceramic coatings for metals and alloys 64, Ceramic dielectrics 65, Properties

of graphites 66, Phase-equilibrium relationships 66, Crystal synthesis and

growth 66, Heat of hydration of portland cement 67, Permeability of

refractories 68.

1 1 . Building Technology

Structural properties of reinforced concrete 69, Fire protection 70, Greasefilter test methods 70, Equipment for accelerated tests 70.

68

12. Applied Mathematics

Numerical analysis 71, Computation 71, Statistical engineering 72.

71

13. Electronics 73

NBS Electronic Currency Counter 73, Ceramic thickness gage 74, Characteristics of electrocardiographs 74, Electronic miniaturization and printed

circuits 75, Electron tubes 75, Curve generator for electron tubes 76, Highspeed reversal of electric motors 78, Rapid selector for microfilm copying 78,

Shaft seal for the NBS Magnetic Fluid Clutch 78, Loud-speaker clutch 79,

Wire-transporting device 79, Rapid-action punch 79.

14. Automatic Computing Machines 80

15. Radio Propagation 82

Reflection of low-frequency radio waves by the ionosphere 83, Effect of the moon on the ionosphere 84, Ionospheric winds 84, Radio astronomy 84,

Radar observations of meteors 85, Propagation research 86, Attenuation of

microwaves by rainfall 86, Atmospheric radio noise 87, Field-intensity recording equipment 87, High-frequency standards 88, Microwave power standards 89, Dielectric measurements 89, Microwave spectroscopy 90, Further

development of atomic clocks 90, Ultra-high-frequency instrumentation 91,

Electroforming of microwave components 92.

16. Testing, Calibration, and Standard Samples 92

Electricity and optics 93, Metrology 94, Heat and power 94, Atomic and

radiation physics 94, Chemistry 95, Mechanics 95, Organic and fibrous materials 96, Metallurgy 96, Mineral products 97, Building technology 97,

Electronics 98, Radio propagation 98.

17. Technical Services and Cooperation 99

Advisory services 99, Federal specifications 100, Radio propagation 101,

Building technology 101, X-ray problems 102, Failure of airplane propellers

102, Portable electric hot-water heaters 102, Rubber technology 102, Automotive tire tests 103, Codes and specifications 103, Weights and measures

103, Research associate program 104, Scientific and technical groups 105,

Office of international relations 106.

Scientific and Technical Divisions and Sections 107

IV
1. General Review

The National Bureau of Standards is the principal agency of the Federal

Government for basic and applied research in physics, mathematics, chemistry, and engineering. In addition to its general responsibility for basic

research, the Bureau undertakes specific research and development programs, develops improved methods for testing materials and equipment,

determines physical constants and properties of materials, tests and calibrates standard measuring apparatus and reference standards, develops

specifications for Federal purchasing, and serves the Government and the

scientific institutions of the Nation in an advisory capacity on matters re- lating to the physical sciences. The Bureau also has custody of the national

standards of physical measurement, in terms of which all working standards in research laboratories and industry are calibrated, and carries on

necessary research leading to improvement in such standards and measure- ment methods.

Most of the Bureau's work was conducted at its laboratories in Washington. Four materials testing stations, chiefly concerned with cement analysis, were maintained in Allentown, Pa. ; Seattle, Wash. ; Denver, Colo. ; and

San Francisco, Calif. Two proving grounds were in use during the year

(one in Maryland, the other in New Jersey). A railway-scale test-car station was maintained in Clearing, 111., and a lamp-inspecting station in

Brookline, Mass. Research in certain fields of applied mathematics was

conducted at the Bureau's Institute for Numerical Analysis, Los Angeles,

California. Radio propagation activities involved the maintenance of field stations at Sterling and Fort Belvoir, Va.; Puunene, Territory of Hawaii;

Puerto Rico; Greenland; Guam; Trinidad, British West Indies; White

Sands Proving Ground, Las Cruces, N. Mex.; Cheyenne Mountain, Colo.;

and Anchorage and Point Barrow, Alaska. Eleven other radio propagation field stations were under contract to the Bureau. In addition, two

transmitting stations were operated: WWV at Beltsville, Md., and WWVH

in Hawaii.

Research and Development

A significant accomplishment of the year was the completion and successful operation of SEAC—the National Bureau of Standards Eastern Automatic Computer. SEAC is the fastest general-purpose, automatically se- quenced electronic computer now in operation. It was developed and

constructed, in a period of 20 months, by the staff of the National Bureau

1
of Standards under the sponsorship of the Department of the Air Force to provide a high-speed computing service for Air Force Project SCOOP

(Scientific Computation of Optimum Programs) , a pioneering effort in the

application of scientific principles to the large-scale problems of military

management and administration. SEAC will also be available for solving

other important problems in such fields as atomic physics, ballistics, and

aerodynamics. In addition, SEAC is expected to aid in further development of computing machines at the Bureau and to provide important training and operational experience for personnel of those Federal agencies that

plan to operate other electronic computers as soon as they are completed.

SEAC automatically performs all of the logical and arithmetical operations required to solve a particular problem once it is supplied with coded

instructions and numerical data. Its high speed permits the use of many

simple steps that can be combined into a complex and powerful sequence

for the solution of difficult problems. This makes it possible to solve important mathematical, computational, and statistical problems which would

otherwise be impossible of solution in any reasonable period of time, or which would be prohibitive in cost if attempted by conventional methods.

The design and construction of SEAC was part of an extensive program

on electronic computers undertaken by the National Bureau of Standards

in cooperation with the Office of Naval Research, the Bureau of the

Census, the Department of the Army, and the Department of the Air

Force. This program involves the research, design, and development work

necessary to produce faster, simpler, and more versatile electronic computers and to make more effective use of the machines already in existence.

In addition to constructing machines for its own use, the Bureau is acting

as the technical coordinating ageny for the construction by industry of

five large-scale computers for other Government agencies.

At the close of the fiscal year, a second high-speed, general-purpose

electronic computer was nearing completion at the Bureau's Institute for

Numerical Analysis in Los Angeles. This machine will be known as SWAC—the National Bureau of Standards Western Automatic Computer.

Sponsored by the Office of Air Research of the Air Force, it will be operated

by the National Bureau of Standards to provide a fast and powerful

computational tool for three large types of problems : ( 1 ) problems of the

Office of Air Research of the Air Force and aircraft problems originating

with contractors of the Air Force (in particular, the aircraft industry of

the West Coast) ; (2) problems in engineering, physics, and mathematics

originating in the laboratories of the Bureau and other Government agencies; and (3) problems in research in numerical analysis and those arising

in connection with the development of the art of machine computation.

Another electronic development, the NBS Electronic Currency Counter,

is expected to save the Government about a quarter of a million dollars

annually. This device, designed and constructed under the sponsorship of

the Treasury Department, automatically counts old paper bills at the rate

2
An extremely sensitive method was developed for testing the planeness of optical

surfaces (p. 19). Additional fringes are interpolated between the half-wavelength fringes of the usual interferometer pattern. Above: interference pattern

of an optical flat; contour interval, one-half wavelength, or 0.00001 inch. Below:

portion of same surface greatly magnified; contour interval one-thirtieth wavelength, or 0.0000006 inch. (Photographs awarded second prize in the Fourth

Annual Photography-in-Science Salon of the American Association for the Advancement of Science.)

3

?
of 30,000 per hour. Although new paper money has been machinecounted for many years, the mechanical handling of worn-out notes has

until now been a difficult problem. Old money is limp, wrinkled, and

difficult to work with. Single, torn notes are occasionally taped together.

These and similar problems have meant that the condition of returned

notes is variable, and tedious counting by hand has been necessary.

Money returned to the Treasury is in the form of stacks of 100 notes,

cut in half lengthwise. The NBS Electronic Currency Counter counts

the half-notes in these packets and automatically rejects those with more

or less than 100. Counting is achieved by means of an electronic sensing

device consisting of a beam of light and a photoelectric system. As the

notes are unfurled, interrupting the beam of light, the photoelectric tube

counts them by sensing the interruptions of the beam. Impulses from the

electric eye go into an electronic arithmetic unit, which tallies the individual impulses. In this way, rapid counting combined with accuracy, the

principal objective of the development program, has been achieved.

Research and study in atomic physics at the Bureau extends back to 1913,

when a radium laboratory was established. At that time the primary standard of radium, prepared by Madame Curie, entered the custody of the

Bureau, and commercial preparations of radium were measured in terms of

this standard. As a result of recent scientific advances, atomic and radiation

physics is now clearly recognized as a large and increasingly important

branch of physics, and an expanded interest on the part of the Federal

Government in this field is now required to establish standards of measure- ment for new industries in such fields as radioactivity and high-voltage

X-rays, to provide for the proper protection of workers and consumers,

and to protect its own investments as a consumer of new products. In

addition to fundamental research, studies necessary for the extension of

measurement and standardization are conducted.

During the past year, the program for the calibration of standard

samples of artificially produced radioactive isotopes continued to grow as the demand for such standards increased in medicine, science, and industry. Efforts were directed toward more precise calibration and toward

the development of uniform standards for isotope measurement. Thus, a new system of calibration was developed for laboratories using radioactive

phosphorus and iodine which materially increased the consistency of their

results. Similar work is under way on other radioactive isotopes.

The increased availability of large quantities of radioactive materials and

the greater diversity of machines for generating radiation have caused

problems of radiation measurement and protection to grow steadily more

complex. Investigation of two general problems of instrumentation in this

field was initiated during the year : ( 1) the development of instruments

for measuring the properties of beta-rays, and (2) the development of instruments for measuring dosages of high-intensity, low-voltage X-rays.

These investigations will be of particular value in new methods of therapy

4
NBS laboratory in which ammeters, voltmeters, and other electrical indicating in- struments are calibrated in terms of the national standards of resistance and voltage.

now being utilized by the medical profession, for various kinds of research

being performed by the Atomic Energy Commission, and to answer the

demands of research laboratories and industry, where use of such radiations

is increasing.

With the installation of a new 50-million volt betatron, work in radiation physics was also extended into the region of extremely high energies.

This new program in high-energy radiation has four main aspects: the investigation of shielding and protection against high-energy X-rays, the

medical applications of these radiations, their industrial applications, and

their basic physical properties.

X-rays with energies between 10 and 70 million volts are now widely

used in the medical treatment of deep-seated tumors. These high-energy

radiations can be directed to burn out a pinpoint of afflicted tissue deep

within the human body without damaging the surrounding area, but proper

protective precautions are of the greatest importance—both to the patient

and to the radiologist administering the treatment. The Bureau has al- ready established standards for protection against low-energy X-rays, and

the new betatron research program will fill the need for standards of protection in the higher regions now available to medicine. The much deeper

penetration of high-energy X-rays requires entirely new scientific standards for full exploitation of these sources of radiation while maintaining

adequate protection.

Standards for protection against radiation have not only a safety aspect

but an economic one. Today, the exact wall thicknesses and best struc5
tural materials are not known for high-energy X-rays. In order to be on

the safe side, high-energy installations are over-protected, with excessively

thick walls and barriers which add greatly to the cost. In many installations the cost of protective walls and barriers exceeds that of the X-ray or betatron equipment itself. Accurate recommendations for barrier thicknesses in the high-energy field, similar to those previously developed by the

Bureau for lower energies, will result in large savings.

In connection with the work in atomic physics, a new instrument, the

omegatron, was developed to discriminate between atomic particles of different masses. The omegatron is basically a miniature cyclotron, operating on the same fundamental principle as a large cyclotron, but the heart

of the instrument is little larger than a package of cigarettes. Its successful development makes possible the determination of the values of several

important atomic constants with exceedingly high precision. For example,

the faraday—a constant of basic interest to both physicists and chemists

is now being evaluated for the first time directly by physical methods; all previous measurements of the faraday have been electrochemical. Since

the faraday was defined as a unit of quantity of electricity, many attempts

have been made, over a period of 100 years, to determine its precise value.

The present discrepancy between the two best determinations thus far

with the iodine voltameter and with the silver voltameter—has been distressing to scientists engaged in revising the tables of atomic constants since

the faraday is a key component of these tables. The work now under way

at the Bureau provides an independent check on the electrochemical method,

and preliminary results indicate that use of the omegatron will give increased

accuracy. Development of the omegatron has also made possible the very

precise determination of the magnetic moment of the hydrogen nucleus,

or proton, so that the ratio of the mass of the proton to the mass of the electron can now be known with greater precision than ever before.

In addition to absolute measurements of mass, the omegatron has many

other possible uses. For example, its high resolution and extreme sensitivity make it ideal for analysis of gases and vapors and for the measure- ment of nuclear packing fractions (the excess of actual mass value over mass number for any isotope) , which are very important in atomic physics.

In another project, the electron-optical shadow method, recently developed at the Bureau for photographing and studying minute electric and

magnetic fields, was further extended. Modification of the method resulted

in an accurate, sensitive technique for experimentally determining the

electric-field distribution and space-charge density within a magnetron,

a vacuum tube widely used for generating power at microwave frequencies.

The high space-charge density within a magnetron is known to have

an important bearing on performance, but very little is actually known

concerning the electric-field distribution and space-charge configuration

within the tube. Although the problem has been investigated theoretically

by many workers, the formidable mathematics involved have not permitted

6
Calibration of a Mueller bridge in the Bureau's resistance measurements laboratory.

If the instrument is frequently calibrated, it can measure resistance with an accuracy

of a few parts in a million.

an exact solution, and the various simplifications of the theory that have

been suggested have led to widely divergent results. Attempts at direct

measurement have also proved unsuccessful because the very critical symmetry of the field under study was disturbed. A promising approach to the problem has now been provided by the method developed at the Bureau.

Further application of the method should lead to a much better understanding of magnetron operation and should yield information of considerable value to the engineer who is interested in designing improved types

of magnetrons or in predicting the performance of existing types.

In a continuing program of research on the properties of matter at extremely low temperatures, significant discoveries were made concerning

superconductivity and the properties of liquid helium n. At the temperature of liquid helium, metals such as lead and tin, ordinarily poor conductors of electricity, become superconductors with a complete loss of electrical resistance. The Bureau is now making studies seeking a more complete explanation of this and other low-temperature phenomena. Included

in the program is an investigation of the extraordinary properties of liquid

helium near absolute zero, which seem to constitute a fourth state of matter.

In liquid helium n, a form of helium exising at very low temperatures,

heat is transmitted as a kind of wave motion analogous to sound and known

as "second sound." During the year, the Bureau succeeded in measuring

for the first time the velocity of second sound at temperatures well within one Centigrade degree of absolute zero. The results obtained, in addi7
tion to settling a point of long-standing disgareement among low-temperature physicists, provide a useful orientation for mapping future research

efforts in this field and should eventually lead to a better understanding

of the nature of matter.

The two-fluid theory of liquid helium u states that, in the presence of a heat current, two kinds of atoms which make up helium n flow in opposite directions to produce second sound. A striking demonstration of the

validity of this theory was provided by the development of a very simple

yet highly accurate mechanical technique, known as the Thermal Rayleigh

Disk Method, for investigating second sound. The method constitutes the

first mechanical means for detection of this phenomenon. By its use, it has been possible to study the relative amounts and properties of the two

fluid components, and the results fully confirm theoretical expectations.

In superconductivity, a new and wholly unexpected relationship was

discovered between loss of electrical resistance at very low temperatures

and the constitution of the atomic nucleus. Until now it has been generally

supposed that superconductivity is concerned exclusively with the properties of the atomic configuration outside the nucleus. However, the results

obtained at the Bureau, in combination with an independent and almost

simultaneous discovery of the same phenomenon at Rutgers University,

establish the validity of the nuclear effect beyond question.

As in previous years, much work was done in the general field of aeronautics. For example, methods were devised for determining the stiffness

of typical aircraft wing structures with discontinuities such as bulkheads

and cut-outs and with varying amounts of sweepback. To aid the Department of the Navy in the flight-testing of aircraft, an instrument was designed and constructed which automatically indicates the force applied by

the pilot to the control stick of an airplane. Another instrument was developed for detecting gasoline vapors or other combustible gases in airplane

cabins or cargo holds. The development of improved equipment and

methods for testing aircraft accessories was continued, with particular

emphasis on the components of the fuel and electrical systems. As part of a comprehensive program on the properties of laminated plastics for

aircraft use, projects were completed dealing with the effect of simulated

service conditions, fuel immersion, and extreme temperatures on these

materials. An improved photogrid technique for determining elongation

of aircraft sheet metal was developed. The effect of chromium plating on

the fatigue characteristics of steels used in aircraft was investigated, and

study of the corrosion of aluminum, magnesium, and stainless steel sheet

metal for aircraft was continued.

The field of jet engines and fuels received justified emphasis during the

year. Although jet engines are being increasingly utilized for high-speed

flight, much research and development remains to be done in order to

attain the desired reliability, economy, performance, and safety. Through

continuing projects, sponsored by the military services, the Bureau is aiding

8
Calibrated chromatic reflectance standards (foreground), covering 10 important

commercial colors, are now available from the Bureau for use with photoelectric

reflectometers.

in the solution of these problems. Thus, operation of the combustion

chamber at high altitudes has been the subject of much investigation. In

the field of basic combustion studies, an extensive program was undertaken

which seeks to measure true burning velocities and flame temperatures by

a spectral line-reversal method. Further development of temperaturesensing devices for indicating performance and controlling operation is also urgently needed. Work in this field included the development and

evaluation of reliable pneumatic temperature-sensing devices and the development of a new type of thermocouple capable of withstanding the

mechanical stress to which thermocouples installed in turbo-jet engines are

subjected. Another area in whch important technical improvements were made was the development of high-temperature coatings to protect metals

and alloys used in jet engines against rapid deterioration from the effects

of hot gases. In automotive research, studies were directed toward the improvement

of engines, fuels, tires, and accessories and the development of better

methods for their evaluation. The Bureau has been active in this field

since World War I, when a need for research on automotive problems first

arose, and has contributed materially to the design and development of

the test engines, equipment, and instrumentation now used to rate motor,

aviation, and Diesel fuels. Since the development of standardized engine

tests in 1932, the Bureau has served as the agency for the calibration of

9
reference fuels, such as normal heptane and isooctane, used throughout

the country for the knock rating of gasolines. These reference fuels are now

available at a purity of 99.99 percent as a result of improvements in the

Bureau's purification process.

To learn more about the knocking characteristics of the individual hydrocarbons found in gasoline, an apparatus for investigating the burning

mechanism of fuels was constructed. As this equipment can give more

detailed information concerning the entire combustion process, it is expected

to lead to a better understanding of engine knock and to point the way to improvement of engines and fuels. Other important studies completed

or in progress included the effect of gasoline additives on valve deposits, the

effect of oil additives on piston and piston-ring deposits, and a rather broad

investigation of the behavior of tires under a variety of conditions which

is expected to provide a means for predicting the expected normal service

life of a tire. A large part of the Bureau's research and development work is performed

for other agencies of the Government, in particular the National Military

Establishment, the Atomic Energy Commission, and the National Advisory

Committee for Aeronautics. Typical projects are concerned with ordnance

electronics, guided missiles, and atomic energy. Significant broad values

are obtained for the Nation as a whole through the general research and

development programs in these areas. The projects discussed briefly above are indicative of the over-all achievements during the year. More detailed information on typical projects will

be found in the sections of this report which treat separately the work of

the scientific and technical divisions.

Testing, Calibration, and Standard Samples

The Bureau's testing and calibration activities stem from its custody of

the Nation's basic physical standards. In many cases, master standards

used in industry must be checked periodically against these national standards. The Bureau is also responsible for testing many of the materials

purchased by the Bureau of Federal Supply, the Treasury, and other Federal

agencies. In the course of this test, calibration, and standard samples work,

new methods of measurement and new instruments are devised, and new

technical data on the properties of materials are obtained.

Over 250,000 tests and calibrations were performed for other Government agencies and the public. This work provides the basis for accurate

measurement in industry, laboratories, and institutions throughout the Nation. In addition, about 19,000 standard samples were prepared and distributed by the Bureau. Typical services of this kind included the sampletesting of about 9,000,000 barrels of cement, the testing and certification

of over 2,000 radium preparations sold in this country, distribution of about

1,100 standards of radioactive materials, about 900 measurements of radon

in breath samples from radium dial painters or in the workroom air, the

10
life-testing of more than 5,000 light bulbs (a sampling of over 4,000,000

purchased by the Government this year) , the testing of 2,500 samples of

microfilm for hypo content, and the sample-testing of about 74,000 clinical

thermometers.

Codes and Specifications

The results of a large part of the research and testing have a direct bearing on the development of technical requirements designed to assure safe

working and living conditions. The Bureau thus provides a central source

of information to which Federal, State, and municipal authorities, as well

as industrial and trade associations, can turn when dealing with problems

of safety or with building and plumbing codes. During the year, representatives of the Bureau took an active part in work on revision of the National Electrical Code, the National Electrical Safety Code, the Code for

Protection Against Lightning, the American Standard Elevator Safety Code,

and other codes in the safety field. Other work in process was concerned

with codes for mechanical refrigeration, electrical equipment in coal mines,

electrical raceways, wood poles and crossarms, and plumbing systems.

Assistance was rendered to industry in the development of voluntary programs for the elimination of waste, and the Bureau also cooperated with

organizations of manufacturers, distributors, and consumers in the development of qualitative and quantitative voluntary standards.

Cooperative and Consulting Services

One of the important factors in the successful prosecution of the diversified programs at the National Bureau of Standards is the availability of

experts in nearly every special field of physics, applied mathematics, chemistry, and engineering. This combination of experts means that almost

any problem in the physical sciences can be undertaken within the Bureau.

At the same time, the results of investigation and the knowledge of its experts are available for additional uses. Thus, the Bureau serves every

agency of the Federal Government and many State and municipal governments by rendering advisory and technical services. An important role of

this type is played in the development and establishment of Federal specifications, which are necessary for economy in Federal purchasing. The

Bureau also cooperates extensively with scientific and technical associations

both in this country and abroad, on problems of concern to the Government

and the Nation.

During the year, services of an advisory or consulting nature were ren- dered to almost every agency of the Federal Government. Typical services

included consultative assistance to the Veterans' Administration in the

preparation of specifications for medical X-ray equipment; aid to the State

Department in the design of language record reproducing systems ; determination of the causes of aircraft failures for the Civil Aeronautics Board;

assistance to the Los Alamos Scientific Laboratory in planning improve11
ment of its timing equipment; development of methods for the modification of diathermy equipment for the Office of the Surgeon General, U. S. Army; technical advice and testing in connection with the relighting of

the Senate and House Chambers; work on the preservation of the Constitution and the Declaration of Independence for the Library of Congress;

and study of static electricity hazards in Government hospitals.

The Bureau also participated in the work of hundreds of technical committees, societies, associations, and commissions organized to bring new

advances of science into the technology of industry, to standardize materials and products for greater economy and improved quality, and to establish uniform scientific standards throughout the world. Bureau staff members now hold approximately 1,600 positions on such national and

international groups. An example is the Bureau's participation in the

American Society for Testing Materials, in which the Bureau is represented

by 434 committee memberships. The Bureau also holds about 250 memberships on committees of the American Standards Association and is the

managing agency for several ASA projects.

Work in Progress

Several major programs, each encompassing a large number of specific

projects, were in progress during the year. The continuing programs in

electronic computers, atomic and radiation physics, low-temperature physics, aeronautics, jet engines and fuels, and automotive research have already

been discussed. Other current programs important to science, industry,

and the Nation deal with high polymers, building technology, radio propagation, electronics, applied mathematics, metallurgy, corrosion, optical

instruments and optical glass, and dental materials.

Many new mathematical methods and experimental techniques are being employed at the Bureau in an integrated approach to the study of high

polymers. Recent developments in this branch of chemistry have created

synthetic plastics, rubbers, and textiles. The Bureau's program seeks not

only to improve present knowledge of high polymers but to develop new

materials of this type and to provide for their practical application. During

the year, for example, fundamental research on the water-vapor relations

of leather and collagen was extended to a practical study of the permeability of leather to water vapor, an important factor in determining the comfort of shoes. An important phase of the rubber program is the work on the

standardization of Government synthetic rubbers, which involves the- development of methods both for chemical analysis and physical testing.

Another major continuing program at the Bureau involves a unified

approach to the problems of the construction industry. The work is so organized that groups are simultaneously engaged in investigations of properties of materials ; structural strength ; fire resistance ; acoustics and sound

insulation: heating, ventilating, and air conditioning; durability; exclusion

of moisture; building and electrical equipment; and other related projects.

Attention is focused on methods of saving materials, on the use of less ex12
The luminous intensity of a mercury-vapor lamp (extreme right) is measured.

During the year new luminous flux values were derived for mercury vapor

lamps (p. 21).

pensive and more readily available materials wherever feasible, and on the

development of more economical designs based on information concerning

the properties of materials which was not known a decade ago. Engineering principles are being applied to the design of houses, providing a complete and logical method for determining allowable loads for walls, floors,

and roofs. This, in turn, makes it practicable to develop structural designs

and to make use of nonconventional building materials that provide suffi- cient strength but require a minimum amount of material and labor.

An intensive program is under way in radio propagation. All uses of

radio, particularly over long distances, require a radio prediction service

analogous to the weather service. This service is provided by the Bureau

on the basis of its own ionospheric observations and research. To further

the work in radio propagation, comprehensive programs are being carried on in radio physics and related geophysical phenomena of the upper atmosphere and troposphere. In addition, primary standards and measurement

methods are under development for electrical quantities at all radio fre- quencies. Important problems in this field still remain unsolved ; and, as a

result of the tremendous postwar extension of the available frequency range,

new problems are constantly arising in measurement, instrumentation,

standards, and calibration services. Microwave standards of frequency,

power, attenuation, dielectric, and other electric quantities for frequencies

up to 100,000 cycles or more have been intensely developed since the war. In connection with this work, an atomic clock, invariant with age and independent of astronomical observations, has recently been developed which

promises to provide an atomic standard of frequency and time. During

the past year, work was in progress on a new type of clock or frequency

standard utilizing atomic-beam techniques; it is expected that this clock

932986—51 2 13
will have unprecedented accuracy, with a variation of not more than one

second in 300 years. Studies are also under way on microwave propagation, and measurements of cosmic and solar radio noise at very high fre- quencies are being carried forward.

Also important both to the Nation's peacetime economy and to the

armed forces is the Bureau's program in electronics. The NBS Electronic

Currency Counter has already been mentioned. Other new and highly

specialized types of electronic circuits and devices are being developed to meet the particular requirements of industry and national defense. Much

of the work is classified and involves the development of new ordnance

devices for the National Military Establishment; a large part of the re- mainder consists of projects in basic and applied electronics conducted

primarily for other Government agencies. One of the projects in this

field is concerned with printed electronic circuits, in which printed wiring,

resistors, and coils replace the conventional wires and independent elements

common in electronic equipment. Work on the development and application of printed circuit techniques is continuing as part of a general program

of electronic miniaturization. Other important phases of the electronics

program include the development of rugged electron tubes for civilian

and military use under conditions of vibration, shock, or acceleration; investigations of the fundamental behavior of cathodes and gases in electron

tubes; development of electron tubes for special purposes; design and development of components for electronic digital computing machines; and

design and development of electronic instrumentation for remote indication

of steam turbine clearances and temperatures and for measurement of air

temperature in wind tunnels.

The basic function of applied mathematics is to provide more economical

and efficient methods for conducting scientific research and development.

The Bureau's mathematics division engages in basic mathematical research

and in addition acts as a service organization, particularly in the fields of

engineering statistics and quality control, for the Bureau, the armed services,

other governmental agencies, and industry. Assistance is given to other

agencies in planning experiments in engineering and physics, and commercial sampling plans- are prepared for inclusion in Federal specifications and

commodity standards. The computation laboratory solves a variety of

mathematical problems which arise in the work of other agencies and

computes mathematical tables needed in many scientific and technical

fields by the Navy, the Army, and other Federal agencies.

For many years the Bureau has carried on an extensive program of service

work on metallurgy. This has included studies of failures of airplanes,

automotive parts, and welded ships. An extended investigation of the

flow, fracture, and ductility of metals and alloys is now in progress, involving measurements at high, low, and room temperatures. Attempts

are also being made to determine why metals fail in fatigue and how

incipient damage can be detected and corrected. A new instrument for

14
the measurement of X-ray diffraction patterns has been developed to aid

in this work.

The work on corrosion of aluminum alloys in marine atmosphere, sponsored by the Navy Bureau of Aeronautics, the Air Force, and the National

Advisory Committee for Aeronautics, has been instrumental in the development of modern high-strength, corrosion-resistant, lightweight alloys for

aircraft use. The knowledge thus gained of corrosion problems of light

metals has recently been found of value in housing applications. In this

connection, the Bureau was able to establish the suitability of certain alloys

for housing and to determine the precautions to be observed in installation.

The problem of national research in optical instruments and optical

glass is an important one. The peacetime requirements for precision optical

instruments are almost negligible in comparison with the need for military

optical instruments in wartime. Moreover, the demands made on industry

for the production of nonmilitary optical instruments are relatively stable,

for the required characteristics of the various instruments do not change

greatly within short periods of time. In military optical work the reverse

is true, and the necessity for specialized laboratory research is correspondingly increased.

In view of this need for a continuing, integrated program of research and

development in optical science, the Bureau, with the cooperation of the

Army and Navy, has conducted for many years a coordinated series of

projects basic to the production of all types of optical instruments, with

special emphasis on military fire-control devices. The Bureau is the only

scientific institution in the world which has complete facilities for making

an optical instrument beginning with the raw materials and producing, in

turn, the glass, the optical design, lenses and prisms, mechanical parts, and

finally the finished instrument.

Of the $864,000,000 spent for dentistry by this country in 1948, over $100,000,000 was for dental materials. Yet for many years the only information available to the practicing dentist on the properties of these products

came from the limited amount of research, mostly clinical, that was done

in a few dental schools and from the research that could be financed by

manufacturers of dental products. This information was very often incomplete, conflicting, and in many instances completely erroneous. To meet the needs of the dental profession, the Bureau therefore established a broad program of research on dental materials, which over the

past 30 years has aided in the solution of many of the problems encountered

in dentistry. This program—sponsored by the American Dental Association, the Veterans' Administration, and the dental services of the Army,

Navy, and Air Force—includes investigations of the fundamental physical,

chemical, and engineering properties of dental products, the development

of special equipment and methods for evaluating these properties, and the

clinical application of the findings. In addition, specifications for dental

materials are developed, and dental materials are tested and certified for

15

I
High-precision methods were developed for calibrating small weights as standards

for modern microbalances (p. 23). Above: standard weights for microbalances

are compared with the standards of mass (below) which the Bureau maintains for calibration of these weights. Values of the NBS standards range from 1 gram

down to 0.05 milligram.

16
conformance to specifications. During the past year, for example, an investigation of the causes of the cracking of artificial dentures was extended

;

progress was made toward a better understanding of the curing mechanism

in denture resins; the effect of the use of mechanical condensers on the

properties of dental amalgam was investigated ; and data were obtained on

the instability of dental impression materials, providing an explanation for

the difficulty encountered by the armed services in the use of these materials

in tropical areas. In order to develop satisfactory methods for preventing tooth decay, there

must be some adequate explanation of the processes which occur in the

decalcification of teeth. Great differences exist in the resistance of different teeth to decalcification, and these differences are thought to be associated in some way with the manner in which the hard, calcified tooth structures are deposited. To learn more about the problem, the Bureau, in

cooperation with the American Dental Association, has begun an investigation of the structure of teeth. This program has included work on determination of the hardness of enamel and dentin and studies of the abrasion

and decalcification of tooth structures due to the chemical and mechanical

action of certain toothpaste ingredients. In the course of an investigation

of the possibility of remineralization of teeth through the use of fluorides

and calcium salts, some of the first electron-microscope studies of the struc- ture of enamel were made. The present program includes an investigation of the chemistry of the basic calcium phosphates, the major inorganic

constituents of teeth.

The remainder of this report attempts to suggest the nature and scope

of the Bureau's work through examples of typical projects.

2. Electricity and Optics

The work in electricity and optics is for the most part closely connected

with problems of measurement in these fields and relates to the establishment of units of measurement, the development of improved or new methods of measurement, the design of improved or new standard apparatus,

the development of standards for issuance, and studies of the properties of

materials.

The electrical work includes the establishment and maintenance of the

units of resistance and voltage; their application in the development of

standard apparatus for measuring inductance, capacitance, electric current,

power, energy, magnetizing force, and magnetic induction; and the dissemination throughout the Nation of standard values of these quantities.

The work in optical standards and measurements includes problems of

luminous intensity and flux; spectrophotometry, color, transmittance, reflectance, opacity and gloss; refractive index, focal length and resolution

of lenses, cameras, and other optical systems; and sensitivity and contrast

of photographic emulsions.

17
Precise Electrical Measurements

The Bureau's development of standard equipment for testing a-c ammeters and voltmeters at frequencies ranging up to 20,000 cycles per second

has been extended to cover currents up to 50 amperes and voltages to 400

volts with an accuracy approaching 0.01 percent. The use of large electrical powers at these frequencies is rapidly increasing in the fields of aeronautics, metallurgy, and woodworking machinery.

Static Electricity Hazards

Static charges are built up in a great variety of industrial operations and

often cause sparks which create serious fire or explosion hazards. This

is especially true in the operating rooms of hospitals, where explosive mixtures of anesthetic gases and air may be ignited by the static charges that

are built up by the movement of personnel or equipment over the floor. An interdepartmental committee, initiated by the Public Buildings Administration, requested the Bureau's assistance in formulating specifications

for a flooring construction which would provide sufficient electrical conduction between persons and objects resting on it to assure the harmless dissi- pation of electric charges as fast as they tend to develop. It was found

that a terrazzo floor with a cement matrix containing a small percentage

of acetylene carbon black is satisfactory over a wide range of atmospheric

humidities. Such flooring will be specified in the future for Government

hospital construction.

Application of High-Speed Computers to Lens Design

Modern photography, microscopy, and astronomy are demanding optical

instruments of greater precision than ever before. Progress in optical

theory has kept pace with the demand, but the mathematical computations

are, in many cases, so involved that ordinary methods employing desk

calculators become too lengthy and expensive.

To remove this restriction, a new system of equations for tracing skew

rays through an optical system was developed, making possible the application of SEAC (National Bureau of Standards Eastern Automatic Computer) to the problem. An advantage of the new system of equations is that the same formulas can be applied for the different combinations of

spherical and plane surfaces; this greatly facilitates the programming of

these equations for automatically sequenced electronic computers.

SEAC, in solving a skew-ray problem, traced a total of 32 light rays

through 11 optical surfaces. About 10 seconds were required for each

ray. In a similar manner, the machine can compute an unlimited number

of light-ray paths through as many as 100 or more lens surfaces. This

means that for the more complicated systems SEAC can solve as many

problems in one hour as an experienced operator can solve in 15 weeks

using the best desk calculator, or in about six years without mechanical

aids.

18
Planeness of Optical Surfaces

An extremely sensitive method was developed for testing interferometrically the planeness of optical surfaces up to 10 or 12 inches in diameter.

By means of a new photographic technique, a complete contour map of the

optical surface is produced having contour intervals from % to Vso of a wavelength of light, rather than one-half of a wavelength as in conventional test methods. Because of the close spacing of the contours, local

variations in the surface that would escape detection by the usual methods

are made clearly visible. New Type of Interferometer

Preliminary tests of a new type of interferometer recently designed at the Bureau indicate the possibility of making interferometers with apertures as large as those of the largest astronomical telescope. The new instrument also promises to lessen the cost of large interferometer installations

by reducing the number of transmitting elements required. The only trans- mitting component is the beam splitter, which need not exceed 2 inches

in diameter and 0.25 inch in thickness. Thus the maximum aperture is determined not by the aperture of a transmitting element, as in the usual

interferometer, but by the maximum realizable apertures of reflecting

elements.

Permanent Gloss Standards

Measurement of gloss is becoming increasingly important in many industries. For example, high-gloss paper is required for good reproduction of

half-tone prints, and low-gloss paper for easy reading of materials in type.

Outdoor finishes, such as automotive enamels, have high gloss for permanence while matte finishes are given most war goods for low visibility.

Gloss measurements are also important in defining the wear resistance of

plastics and ceramics.

Measurement of gloss is essentially very simple. When a specimen is illuminated at some angle from the perpendicular, the proportion of the

light reflected at angles near that of mirror reflection is defined as gloss.

A critical part of the definition of gloss, however, is the amount by which

the reflected beam may depart from the strict direction of mirror reflection

and still be counted as contributing to gloss. With glossmeters commercially available at the present time, replacement of the lamp, for example,

may introduce instrumental error unless readjustment is made. The

Bureau has therefore prepared and made available new permanent gloss

standards which permit a rapid check of instrument calibration at any

time and give a basis for readjustment of the instrument if required. These

standards, which may be used to calibrate any 60-degree specular glossmeter in the range from matte to high gloss, are made of ceramic materials

for permanence, and the surfaces have been specially chosen for similarity

to commercial materials whose gloss is important.

19
Investigations of the physical, chemical, and clinical properties of dental materials

are conducted at the Bureau (p. 24). Above: experimental dentures are processed

under controlled conditions to obtain clinical data on materials and techniques.

Below: casting of a dental gold alloy at the Bureau for experimental study.

20
Revision of the Union Colorimeter Scale

A number of complicated processes are employed in the refining of

petroleum to produce gasoline, kerosine, and lubricating oils and greases. Measurements of the color of the product are used to follow the progress

of these processes and also as a basis for the purchase and sale of petroleum

products in various stages of refinement. For the past 20 years, such measurements have been made by visually comparing the color of the oil with a

series of glass color standards making up the scale of the Union colorimeter.

At the request of the American Society for Testing Materials, a suggested

revision of the Union colorimeter scale has now been developed. This

revised scale duplicates the colors of petroleum products more closely than

the original scale and has much more uniform color intervals. Glass color

standards prepared in accordance with the revised scale are expected to permit more accurate color measurements to be made of petroleum products and thus to facilitate their purchase and sale.

Photometry of Mercury Vapor Lamps

Since 1936 the determination of the light output of mercury-vapor lamps

in this country has been based on the values of luminous flux assigned to two groups of mercury-vapor lamp standards: a group of 250-watt lamps

and a group of 400-watt lamps. These two sets of standards were originally

calibrated at the Bureau by visual comparison with incandescent lamp

standards viewed through color-matching filters. In spite of the resulting

approximate color match, major differences in spectral energy distribution

persisted. Because of these differences, the visual measurements were made

only with great difficulty and resulted in considerable doubt as to the

reliability of the values thus assigned to the mercury-vapor standards.

Within the past year, the light output of the two groups of mercury-vapor

lamp standards has been redetermined by the use of a physical photometer

which embodies a thermopile and an accurate luminosity filter. This

recalibration was in terms of the new photometric units which became

effective on January 1, 1948.

The new values assigned to the 250-watt mercury-vapor lamps are 4.5

percent lower than those originally assigned visually while the new values

assigned to the 400-watt mercury-vapor lamps are 9 percent lower than

the visually assigned values. Intercomparison of the two groups of standards in a photoelectrically equipped integrating photometer indicates that

the uncertainty in the new values assigned to the mercury-vapor lamp

standards does not exceed 2 percent. By mutual agreement, effective

August 1, 1950, all calibrations of mercury-vapor lamps are to be on the

new basis.

21

I
Lighting at the Shrine in the Library of Congress

In connection with the Bureau's development of a method for the preservation of the Constitution and the Declaration of Independence, a detailed

study of the lighting and viewing conditions at the Shrine in the Library

of Congress was made. The new lighting units that were suggested have

now been received, and a method of support has been chosen that will add

no load to the arched ceiling. Suggestions for redecoration to conceal the

ceiling ports have also been worked out.

Lighting of the Senate and House Chambers

During the year the relighting of the Senate and House Chambers was

completed. The Bureau cooperated both in a consulting capacity and by

making tests of samples of materials intended for use in refinishing the

chambers. Measurements of the illumination on the desks and of the

luminance of the ceilings and walls were carried out at various stages of the

work.

Refractometry

Equipment was developed for extending precise measurements of the

index of refraction of glasses and other optical materials into the infrared.

Three different types of detectors and two types of sources were studied.

With this and other equipment, extensive measurements of index of re- fraction were made on selected glasses over the entire spectral range trans- mitted. Refractive-index measurements were also made on silver chloride

crystals for wavelengths ranging from 0.578 to 20.6 microns. From the

data, constants were evaluated for dispersion formulas from which the indices may be computed for any wavelengths in this range with an accuracy

of approximately ±0.0001.

3. Metrology

Measurement, instrumentation, and standardization problems, involving

the basic concepts of length, mass, time, capacity, and density, constituted

the greater part of the work in metrology. In addition, a broad program

of research on the physical and chemical properties of dental materials was

continued. The Bureau extended its mass standardization service to include weights for microbalances, which are becoming increasingly important

for research in atomic energy, vitamin therapy, and microchcmical techniques. An instrument was developed which provides a convenient graphic

record of the drift in rate of a timepiece over an interval of several days.

In connection with the work on dental materials, a method was developed

for mounting metallurgical samples in acrylic resin for polishing and examination, without the application of heat. A study of the instability of al- ginate materials for dental impressions under tropical conditions was also

completed, and the precautions necessary to prevent deterioration were

determined.

22
Standard Weights for Microbalances

To provide standards for modern microbalances, the Bureau has recently

developed methods for calibrating small standard weights below 100 mg

with a precision of one or two ten-millionths of a gram. This precision

perhaps the highest ever obtained with the knife-edge type of balance—will

permit the weighing of samples about one-tenth as large as formerly. The

resultant increase in the field of usefulness of microbalances should mean

great savings to workers in such fields as atomic energy, vitamin therapy,

and microchemical techniques, where minute samples must be weighed

with high accuracy.

Development of methods for calibration of extremely small weights has

greatly simplified the problem of calibrating quartz microbalances directly

in terms of known standard weights. This, in turn, makes possible the sav- ing of much time, equipment, and labor formerly spent in indirect methods

of calibration. The quartz microbalance itself is now being intensively

studied as part of a broad program which the Bureau is undertaking for

the improvement of precision balances. Efforts are being made to improve

the uniformity of its fabrication and to increase its capacity. The construction of the equal-arm knife-edge type of balance is also under study,

with the object of attaining greater accuracy through improved design, use of new materials, and avoidance of troublesome temperature effects. New System for Weight Calibration

In recent years, the increasing interest in scientific research in this country

has brought about a corresponding increase in the number of standard

weights submitted to the Bureau for calibration. The largest part of this

vvork involves sets of weights in the following combinations of units:

5, 3, 2, 1, 1; 5, 2, 2, 1, 1; and 5, 2,—lj 1, 1. At present all computations

involved in the separate calibration schemes used for each of these combinations are performed with a slide rule or a desk calculator and are then

checked in detail and reviewed. Plans are under way to do a large part

of this work by means of a computing machine designed to give a simultaneous solution for the values of the weights from a series of equilibrium

points as observed on a balance. For this purpose, a single series of observations has been devised by means of which weights in all three of the

above combinations may be calibrated. Such a scheme makes possible

the construction of a machine designed for the simultaneous solution of

the one series of observations and its use to compute values for sets of

weights in all three combinations of units. This should largely eliminate

errors of computation and result in great savings of time and effort in the

Bureau's weight calibration program.

Rate Drift of Timepieces

An instrument was developed which provides a convenient graphic rec- ord of the drift in rate of a timepiece over an interval of several days.

23
In this device a simple relay-type servo system keeps the phase of a crystalcontrolled standard frequency in step with the frequency of the timepiece,

j The amount by which the phase of the standard frequency must be shifted

to match the unknown, varying frequency is then automatically plotted | against time, providing a curve from which both the instantaneous and

integrated frequency error are obtained. Although specifically designed

to measure the rate drift in watches, clocks, and marine chronometers, the

device can be modified to record the frequency drift in oscillators having

frequencies of 10 cycles per second or less. Frequencies as low as one

cycle in thirty seconds have been monitored using this device.

Dental Materials

The work on crazing of denture resins has been extended to all types

of acrylic resin teeth now on the market. This investigation has demonstrated conclusively that water absorbed during the curing cycle is the

factor primarily responsible for the introduction and subsequent release of

strains in the surface of those artificial teeth that are subject to crazing.

In order to understand why certain teeth craze more readily or bond to the

denture base more satisfactorily than others, and to explain the mechanism by which crazing is produced in certain teeth, an investigation is being conducted on the fundamental physical properties of plastic teeth,

denture base resins, and self-curing resins. Preliminary measurements of

flow, stress-strain, relationships in compression, and the bonding of teeth

have been made.

In studies of resins which cure at high temperatures, progress was made

toward a better understanding* of the mechanism of polymerization and

the factors which affect the rate and completeness of cure of acrylic resins.

Experimental work on samples of monomer containing varying amounts of

catalyst, inhibitor, and water definitely established that water is an important

factor in the polymerization process, probably associated with the rate of

production of peroxides in the monomer. Methods were developed for

detecting the presence of and removing impurities from the monomer.

Quantitative data obtained on samples of highly purified monomer containing varying amounts of catalyst and water confirm previous qualitative

measurements of the accelerating effect of water on the induction period

of benzoyl peroxide-catalyzed methyl methacrylate. Further experiments

will be made to determine the effect of water in the presence of hydroqui- none inhibitor. It is believed that the data obtained from these sfudies will

be of value in explaining some of the difficulties of processing acrylic resin

for dental use and in solving some of the problems encountered in the stor- age of these resins.

The development and widespread use of mechanical condensers for packing amalgam have led to an investigation of the effect of mechanical condensation on the properties of amalgam. Data obtained from comparative tests on hand- and mechanically-condensed amalgam indicate that the

24
! mechanically condensed amalgam has less expansion, less flow, and a higher

l early crushing strength. Additional experiments using amalgam with a

I high mercury-to-alloy ratio (20:5 instead of the usual 8:5) have produced

' an amalgam with an average crushing strength and a microstructure similar

to that of amalgam having an 8 : 5 ratio. The dimensional change ( + 3

microns) is reported to be approximately that specified as a lower limit by

American Dental Association specifications. Further studies concerning

the effect of annealing the alloy on the resultant physical properties of

amalgam are being conducted.

In the course of this investigation a simple, inexpensive method was

developed for mounting metallurgical specimens, such as dental amalgams,

at temperatures only slightly above room temperature and without the external application of heat. The technique employs a denture material of

modified acrylic resin as the mounting. This material consists of a polymer

and monomer which, when mixed in the proper proportions, will polymerize or set under pressure at room temperature. As the amount of heat

generated by the polymerization reaction can be controlled by varying the

amount of resin present, the new procedure makes it possible to mount a wide variety of specimens for polishing and microscopic study without disturbing the crystal structure. Data were obtained on the instability of the alginates used in the preparation of many impression materials. This information offers an explanation

for the difficulty encountered by the Armed Services in the use of these

materials in tropical areas. A report summarizing these data and the

precautions necessary to prevent deterioration of alginate impression materials under tropical conditions is being prepared.

A project for the study of the structure of tooth enamel and dentin was initiated during the year. Sections of teeth were photographed at high magnification by means of the fluorescence excited by ultraviolet light,

and the spectra of the fluorescence were studied. New methods and equipment are now under investigation to overcome difficulties due to the low

intensity of the fluorescence.

4. Heat and Power

To provide a fundamental basis for precise measurements of heat and

power, the Bureau has established and maintains a scale of temperature

from the lowest obtainable to the highest temperatures of incandescent

bodies and flames. Instruments are certified for the measurement of temperatures in this range on the International and Kelvin scales. From the

measurement of temperature alone, the work broadens to include the

determination of quantities of heat by calorimetry in temperature regions ex- tending over a large part of the scale. Coordinate with the calorimetry is a

study of the thermodynamic properties of solids, liquids, and gases. From

these basic fields of research, the work branches into engineering applications

25
Above: superconductivity (p. 33) is dramatically demonstrated by the floating

magnet experiment. Immersed in liquid helium II, the magnet remains suspended

above a superconducting tin plate. The superconducting current induced in the

plate by the magnet sets up a magnetic field which repels the magnet. Below:

study of the velocity of second sound near absolute zero (p. 33) settled a point

of long-standing disagreement regarding the nature of liquid helium II.

26
to automotive and aircraft engines. One branch extends into the fundamentals of combustion, with applications to gas turbines, jet engines, and jet

propulsion. Another branch covers lubrication problems that arise not only

in automotive engines but in all mechanical devices.

The Bureau is also responsible for determining and maintaining standards of viscosity and for certifying the viscosities of fluids used for calibrating viscometers. It maintains standards for the metering and carburetion

of liquid fuels in internal combustion engines, and for the determination of

the octane and cetane numbers of automotive, aviation, and Diesel engine

fuels. Research is conducted to increase the accuracy of these standards

and to develop improved measuring instruments and apparatus. Thermal

properties of pure substances and commercial materials are determined,

upon requests from other Government agencies, either by direct experiment or by calculation from the fundamental atomic and molecular properties of the substances; and published data on thermal properties are

critically reviewed and compiled.

Temperature Measurements

As a result of the increasing need for reliable temperature measurements

at both very high and very low temperatures, research to develop suitable

instruments and methods of calibration has been in progress during the

past year. Two sensing elements, an iridium—iridium-rhodium thermocouple probe for use at extremely high temperatures and a germanium resistance thermometer for use near absolute zero, were developed. Both of

these instruments represent marked advances in the measurement of ex- treme temperatures.

Because of the high temperatures (up to about 3,800° F) prevailing in

the primary burning zone of turbojet and ramjet combustion chambers,

conventional immersion-type temperature-sensing instruments are unsuitable for use in these applications. A water-cooled thermocouple probe was

therefore developed which is capable of withstanding the thermal and mechanical stresses present in combustion chamber operation. One element

of this thermocouple is iridium, which has a melting point of about

4,400° F, and the other is an alloy of iridium and rhodium, which melts in

the neighborhood of 3,800° F. The thermocouple is supported directly in

the combustion zone by means of a water-cooled mounting. Satisfactory results have been obtained in service tests in the ram-jet installation at the

Bureau and also at a number of other laboratories. In one installation the

instrument was used for a total of about 15 hours at temperatures ranging

from 3,000° to 3,750° F. In another, the unit was successfully subjected

to a gas stream at 3,200° F flowing at sonic velocity. The instrument is

relatively simple in design and is readily adaptable to both laboratory and

test-stand installations. The emf-temperature calibration of the iridium—

iridium-rhodium thermocouple has been carried out to a temperature; of

27
Left: an optical pyrometer is used in the calibration of a high-temperature

thermocouple. Right: a single-cylinder supercharged test engine at the Bureau

determines the preignition rating of aircraft and automotive sparkplugs.

2,800° F. Work is at present under way to extend the calibration up to the temperature limit of the thermoelements.

At very low temperatures (below 50° K) the research on thermometry

has two major objectives: First, the absolute determination of temperatures

by means of a gas thermometer and second, the development of convenient,

sensitive, and reproducible secondary thermometers which can be calibrated by means of the gas thermometer. Since the development of a

highly accurate gas thermometer for this purpose requires painstaking and

time-consuming precision, the work on the secondary thermometer is being

pursued concurrently. Resistance thermometers have been constructed

of the semiconducting elements, silicon and germanium, and have proved

to be extremely sensitive; in some cases the resistance changes more than

50 percent per degree. While satisfactory reproducibility still remains a problem, some of the thermometers already tested are quite acceptable in

this respect, being reproducible within the present precision of calibration.

Rheological Physics

Two important investigations were completed in the field of rheological

physics, which deals with the flow and deformation of matter. These were

(1) an accurate determination of the absolute viscosity of water and (2)

measurement of the absolute viscosity of bulk rubber (synthetic and natural) and of high-concentration synthetic rubber solutions.

Measurement of the absolute viscosity of liquids—of fundamental importance in many scientific fields—is almost universally based upon the

absolute viscosity of water at 20° C as a primary reference standard. In

view of the increasing need for a more accurate determination of this

standard, the Bureau undertook to redetermine its value with the cooperation of the Society of Rheology and the Chemical Foundation. The

28
viscosity of water was found to be 0.010019 poise, as compared with the

value of 0.01005 poise in use at the present time. The accuracy of the new

determination is 0.000003 poise, which far exceeds that of any previous

measurement of this constant. Adoption of the new value as an international standard is anticipated. Its use at the National Bureau of Standards

for the calibration of viscometers and standard sample oils will make

possible the evaluation of the viscosities of other liquids with an accuracy

of 0. 1 percent or better.

The development and extensive commercial use of the various types

of synthetic rubber have made it necessary to learn more about their flow

properties both from the standpoint of industrial processing of the raw

rubber and of over-all quality in the finished products. In the past, chiefly

because of the lack of suitable instruments, it has been possible to measure

the flow properties of bulk rubber only to a very limited extent. Higher

rates of flow could only be measured on relatively dilute solutions; otherwise the material had to be subjected to low stress. Through the use of

the McKee Worker-Consistometer, recently developed at the Bureau,

measurements have now been made for the first time of the viscosities of

solutions containing 5 to 100 percent of rubber at widely different rates of flow. The data on lOO^percent rubber serve as the first absolute calibration of the industrial laboratory instrument (Mooney Viscometer) which

tests synthetic rubber for processing into manufactured articles. Data have

been obtained showing the effects on viscosity of such variables as temperature, rate of flow, kind of rubber, sample preparation, aging, and concentration and nature of solvent. Further work is in progress, primarily on bulk

rubbers and high-concentration solutions.

Automotive Research

Automotive research at the Bureau embraces fundamental studies directed toward the improvement of engines, fuels, tires, and accessories and

the development of better methods for their evaluation. In addition, the

Bureau maintains the national standard for knock-testing of gasolines.

To learn more about the knocking characteristics of the individual

hydrocarbons of gasoline, an apparatus for investigating the burning mechanism of fuels was constructed in which measurements of pressure and

volume are automatically made as a function of time. This equipment

is capable of giving more detailed information concerning the entire combustion process, including the pre-flame reaction of the gaseous mixture,

which is, in some manner, associated with knocking combustion. Future

results from this study should lead to a better understanding of engine

knock and point the way to engine or fuel improvement.

It is extremely important to the oil industry that errors made in measuring octane number of gasolines be kept at a minimum. The Bureau maintains national standard reference fuels, on which all octane number measurements throughout the country are based. These reference fuels,

932986—51 3 29
"isooctane" and n-heptane, are now available at a purity of 99.99 percent as a result of improvements in the Bureau's purification process. A

new technique for evaluating commercial reference fuels involving a precise measurement of the difference between the refractive indices of the

national standard and commercial reference fuels, is now being used. This

procedure is carried out in a Rayleigh interferometer in which the precision

is about 0.000003 unit of refractive index.

Another way in which the Bureau aids in maintaining uniform gasoline

quality is through its analysis of knock rating data obtained by several

laboratories on exchange fuels. These exchange fuels are circulated each

month by a member of the group and include motor, aviation, and Diesel

fuels. In this way each laboratory is provided with a monthly check on

the precision of its measurement. This program is a joint endeavor between the Federal Government, petroleum refiners, and the American

Society for Testing Materials.

The use of resistances in series with automotive spark plugs considerably

reduces interference to radio reception. The Ordnance Department of

the U. S. Army requested the Bureau to determine whether resistor spark

plugs would operate effectively in military vehicles at low temperature.

A series of tests at temperatures down to —40° F disclosed that there was

no essential difference between resistor plugs and conventional types in

their ability to start the engine.

The Bureau cooperates with the Federal Trade Commission and the

Post Office Department by providing technical information and data on

fraudulently advertised materials, including gasoline "dopes", oil additives, and antifreezes. Because of the numerous engine and operating

variables, it is difficult to evaluate the effect of gasoline or oil additives on

engine deposits. However, in investigating the effect of gasoline additives on valve deposits, it was found possible to eliminate these variables by comparing the average deposit per valve for a group of 20 single-cylinder

engines run on a gasoline of high gum content with that for a similar

group of engines run on the same fuel plus the additive. Work is in progress to develop a similar procedure for evaluating the effect of oil additives on piston and piston ring deposits. None of the gasoline dopes aided in

removal of engine deposits.

The Federal Government spends about $12,500,000 each year for automobile tires. Since the service life of tires of the same make may range

from 5,000 to 55,000 miles, the Bureau has undertaken an extensive program to study the behavior of tires under many different conditions. A

machine of unique design has been built which will give the amount of

power lost in a tire under variations of load, tire pressure, speed, tractive

effort, and cornering. Most of the power loss is manifested as heat generated in the tire and contributes to tire breakdown by subjecting the rubber and fabric to excessive temperatures. Thus a measure of the power

loss should provide a basis for predicting the expected normal life of a tire.

30
Aircraft Accessories

During the past year, the National Bureau of Standards, under the

sponsorship of the Bureau of Aeronautics, Department of the Navy, continued to work toward the development of improved equipment and

methods for testing aircraft accessories, particularly those which are components of the fuel and electrical systems.

The performance of carburetors, fuel nozzles, and the float-type flowmeters used for carburetor testing has been found to depend upon the

density and viscosity of the test fluid. Since liquids of widely differing

properties are currently used for this purpose in various laboratories, an

effort is being made to promote agreement on a single pure, or nearly

pure, hydrocarbon compound which will be generally acceptable as a universal calibrating fluid for all fuel accessories. The problem has become

more urgent and more complex with the advent of jet engines, which must

operate on fuels varying from light gasoline to heavy kerosine. Meanwhile, a calibration procedure has been developed for the flowmeters which

makes possible accurate corrections for the density and viscosity of the fluid,

and modifications to the floats have been made which reduce the sensitivity of existing flowmeters to viscosity. A prototype instrument, designed

for continuous indication of viscosity, shows considerable promise. Other

work in this field included studies of the effects of carburetor-jet configuration upon metering characteristics, of test methods applicable to regulators for the injection of water, and of methods for reconditioning

fixed spray nozzles.

Work on aircraft electrical network equipment consisted mainly of evaluations of various experimental devices produced under development contracts. These included such 400-cycle a-c devices as trip-free circuit breakers and frequency relays, and such d-c equipment as magnetic-type circuit

breakers, a latching relay, special-purpose switches, and hermetically sealed

toggle switches. Studies were made to determine the cause of failure in

service. Qualification tests were also conducted on circuit breakers and

electrical connectors for rockets in accordance with military specifications.

Gas Turbines and Jet Engines

Although gas turbines and jet engines are becoming increasingly important, particularly to the military services, much research and development remains to be done on components in order to attain the desired

reliability, economy, performance, and safety. Thus, operation of the combustion chamber at high altitudes has been the subject of much investigation. Further development of temperature-sensitive devices for indicating

performance and controlling operation is also needed urgently. Through

continuing projects sponsored by the military services, the Bureau is contributing to the solution of these problems.

To permit studies of combustion in streams of moving air at pressures

below one atmosphere, large vacuum pumps have been procured, and addi31
Reference fuels for the knock rating of gasolines are calibrated by the Bureau

(p. 29).

tional facilities are being designed in which burners for ramjet and turbojet engines can be operated at the pressures prevailing at high altitudes.

In the field of basic combustion studies, an extensive program has been

undertaken which seeks to measure true burning velocities and flame temperatures by the spectral line-reversal method.

In the field of gas-temperature measurement, shielded tragets for optical

and radiation pyrometers were investigated and found to have small promise

for such an application. On the other hand, reliable pneumatic temperature-sensing devices were developed and evaluated. These employ two

small orifices or nozzles in series, and permit calculation of gas temperature

from an observed drop in pressure across the hot orifice. It has been

demonstrated that the hot orifice may be cooled, to a limited degree, without decreasing the accuracy of the caluculated temperature. Thus instruments of this type may be used in gases which are above the melting point

of the orifice. The mechanical stresses to which thermocouples installed in turbo-jet

engines are subjected have proved to be unexpectedly high, so that conventional units have very short service lives. Metallurgical studies of

units that have failed in service show that alumel thermoelements are subject to changes in crystal structure which greatly reduce their ability to withstand vibrations induced by the gas streams. To overcome this difficulty, a promising prototype instrument has been developed with complete

and effective support of the thermocouple wires from the measuring junction to the terminal head.

Low-Temperature Physics

Significant discoveries were made in those areas of low-temperature

physics which deal with superconductivity—the loss of electrical resistance

32
at very low temperatures—and the properties of liquid helium n, a form

of helium existing at temperatures near absolute zero. Both these subjects

are now of active interest in low-temperature laboratories because of the

unusual effects involved and the lack of completely satisfactory fundamental theories for their explanation.

A new and wholly unexpected relationship was discovered between superconductivity and the constitution of the atomic nucleus. It was found

that the pure mercury isotope of atomic weight 198 becomes superconducting at a temperature about 0.02 Kelvin degree higher than does natural

mercury, a mixture of five different isotopes having an average atomic

weight of 200.6. As the difference between the isotopes depends entirely on their nuclear masses, this shift, which is proportionately quite large for a temperature so near absolute zero, indicates that the nucleus must exert an important effect on the superconducting properties of the metal.

Until now it has been generally supposed that superconductivity is con- cerned exclusively with the properties of the electronic configuration outside

the nucleus. However, the results obtained at the Bureau, in combination

with an independent and almost simultaneous discovery of the same phenomenon in other mercury isotopes at Rutgers University, establish the

validity of the nuclear effect beyond question. The two researches are complementary and when taken together provide a conclusive demonstration of the effect. Since the initial discovery of the isotope effect in the superconductivity

of mercury, a sample of tin consisting mainly of Sn124 has been investigated

at the Bureau and found to exhibit a similar shift in transition temperature.

In both cases the effect is very small, 0.007° K per mass unit for mercury

and 0.012° K per mass unit for tin. However, it has been observed that

these shifts are such that the thermal energy of the lattice is the same for

each isotope at the transition temperature. The work is being carried

forward, and other isotopically enriched elements are under investigation.

The theoretical understanding of liquid helium ir, often referred to as the fourth state of matter because of its unique properties, is sufficiently

well advanced that crucial experiments may be performed for testing

specific postulates. During the last year the Bureau discovered that there

is a considerable increase in the velocity of second sound, a unique wavelike

process of heat transfer occurring only in helium ii, as temperature is lowered

below 1° K. This result, which had been sought by a number of lowtemperature laboratories in several countries, enabled a definite decision

to be made between two fundamentally different postulates that had been

advanced concerning the nature of liquid helium ir. Certain consequences

of the apparently correct postulate are very interesting: for example, it appears that one component of liquid helium u, the so-called superfluid,

may be completely lacking in thermal energy. If so, there is a possibility

that extremely low temperatures may be reached by forcing liquid helium h

33
through narrow orifices. This possibility is now under investigation in

several other laboratories.

A striking demonstration of the validity of the two-fluid theory of liquid

helium n was provided by the development of a very simple yet highly

accurate mechanical technique for investigating second sound. The twofluid theory states that in the presence of a heat current two kinds of atoms

which make up helium n flow in opposite directions to produce second

sound. The new technique, known as the Thermal Rayleigh Disk Method,

makes use of the torque exerted on a light disk suspended in the path of

standing waves of second sound. It thus constitutes the first mechanical

means for detection of this phenomenon. By quantitative evaluation of

the torque on the disk at various temperatures, the relative amounts and

properties of the two fluid components have been studied, and the results

fully confirm theoretical expectations. An associated effect that has also

been predicted and observed is a hydrostatic pressure difference between

regions of different heat-flow density, which is the thermal analogue of the

Pitot tube. It has been found possible to include both effects as conse- quences of a generalized theory of the hydrodynamics of liquid helium ir, similar to the Bernoulli expression of ordinary hydrodynamics but with an

additional term relating heat current and hydrostatic pressure. These

studies are also being actively pursued and extended.

5. Atomic and Radiation Physics

The results of basic research in atomic and nuclear physics are now

being applied to an increasing extent in medicine, industry, and national

defense. This has made necessary new techniques, instruments, standards

of measurement, safety provisions for workers and consumers, standard

samples for calibration purposes, and methods of testing and evaluation in

this rapidly expanding field. The Bureau is now engaged in a broad

program of fundamental research and standardization dealing with atomic

and molecular spectra, radiometry, physical electronics, electron optics, mass spectrometry, X-rays, radioactivity, and atomic and nuclear constants. A portion of the work specifically directed toward the atomic energy program is supported by the Atomic Energy Commission. Much of the

remainder is in closely related lines of research and is carefully coordinated

to avoid duplication of effort.

Omegatron

A new instrument was developed which makes use of the cyclotron reso- nance frequency of ions to discriminate between particles of different masses. This device, known as the omegatron, is basically a miniature cyclotron.

Its successful development for the first time permits the use of the simple

cyclotron resonance condition for the determination of the values of several

important atomic constants. For example, the faraday—a constant of

basic interest to both physicists and chemists—can now be evaluated directly

by physical methods in addition to the usual electrochemical procedure.

34
This work provides an independent check on the electrochemical method,

and preliminary results indicate that use of the omegatron will provide

increased accuracy. In addition, development of the omegatron has made

possible the very precise determination of the magnetic moment of the

proton in nuclear magnetons, so that the ratio of the mass of the proton

to that of the electron can now be known with greater precision than ever

before.

The resolution attained with the omegatron for light masses is already

comparable with the best that has ever been reached with precision mass

spectrographs that have been built in the past. This makes it ideal for

analysis of gases and vapors and immediately suggests its use in measuring

atomic masses, which are so closely related to atomic energy. In the past

year the instrument was used to measure the mass difference between the

hydrogen molecule and an atom of heavy hydrogen.

Electric and Magnetic Field Mapping

An accurate, sensitive technique was developed for experimentally determining the electric-field distribution and space-charge density within a magnetron. The new method, which is also well suited to investigations

of electron-optical lenses, gas discharge, and other space-charge problems,

is a modification of the electron optical shadow technique developed last year at the Bureau for the quantitative study of minute electric and magnetic fields. A magnetic lens is used to produce shadow images of two

fine wire screens placed at either end of the magnetron in the path of an

electron beam. Then, from the distortion in the shadow network caused

by deflection of the electron rays as they pass through the magnetron field,

the radial electric field is computed. These results are used to obtain the

space-charge distribution.

The magnetron is a vacuum tube widely used for generating power at microwave frequencies. The high space-charge density within the tube

is known to have an important bearing on performance. However, very

little is actually known concerning the electric-field distribution and spacecharge configuration within the tube. Although the problem has been in- vestigated theoretically by many workers, the formidable mathematics in- volved have not permitted an exact solution, and the various simplifications of the theory that have been suggested have led to widely divergent

results. Attempts at direct measurement have also proved unsuccessful

because the very critical symmetry of the field under study was disturbed.

A promising approach to the problem has now been provided by the method

developed at the Bureau. This technique has been used to map the charge

distribution within a cut-off or steady-state magnetron. Further application to oscillating magnetrons should lead to a much better understanding

of their operation and should yield information of considerable value to the engineer who is interested in designing improved types of magnetrons

or in predicting the performance of existing types.

35

1
To protect the health of persons engaged in the handling and processing of radium,

the Bureau maintains careful check over the quantity of radium ingested by these

workers (p. 93). Left: a sample of a worker's breath, obtained by inflation of a balloon (right), is drawn from a sampling flask submitted by a manufacturer of

radium-painted dials.

Another problem still under investigation is the application of the electron-optical shadow method to the measurement of the domain structure

of ferroelectric and ferromagnetic materials. This subject has assumed

considerable technical importance in recent years because of its bearing on the usefulness of commercial magnetic materials. Until the shadow

method was introduced, only indirect or qualitative methods existed for

the study of domain structure.

Electron Optics

Many of the devices that make use of the focusing and dispersive properties of magnetic fields must undergo considerable improvement before

they can be considered ideal. Examples are the beta-ray spectograph,

which is used to identify radio isotopes, and the mass spectograph, which

has become the chief analytical instrument of the petroleum industry.

Until now much of the design of these instruments has been on a trial-and- error basis since the theory of the magnetic fields used is incomplete and

the mathematics are formidable. During the past year these difficulties

have been attacked, and progress has been made in developing better design methods. A start has also been made on a systematic study of electron lenses, which it is hoped will fill important gaps in present knowledge

and allow improvement of the performance of the electron microscope and

other instruments.

Semiconductors

At present, one of the most active fields of physics is the study of the

semiconductors. The Bureau is conducting a program of research in this

36
field to investigate promising semiconductor materials and to evaluate their

utility as rectifiers, transistors, and eventually as photocells.

The first material to be studied was titanium dioxide in the form of rutile.

This material, while normally an excellent insulator becomes a semiconductor with controllable properties when it has been treated to cause a

loss of oxygen. A study was made of the Hall effect and conductivity in

both single crystals of titanium dioxide and ceramic rutile for various conditions of preparation, and a reasonably clear picture of their properties was obtained. A parallel development was carried out on rectifiers using

titanium dioxide, and a very promising technique, which uses a film of

oxide produced directly on titanium metal, was evolved.

As the exploratory work on rutile is nearing completion, another material, "grey" tin, has been chosen for a similar study. This interesting

substance, which is a low-temperature form of ordinary "white" or metallic tin, has the same crystal structure as silicon or germanium, the elements

that are used in most of the present-day high-frequency rectifiers and

transistors. Grey tin has recently been shown to be a semiconductor but

has not yet been obtained in a useful crystal form, only powder samples

being available. Some evidence has been obtained for a successful electrolytic codeposition of grey tin with germanium. Since this material

should have very desirable electrical properties, it is planned to carry the

work forward on a larger scale. At present, a complete understanding of

conduction in semiconductors is prevented by the absence of information

about the number of lattice defects in the crystals. New apparatus for

studying these defects has now been developed and applied to alkali halide

crystals, where the data can be compared with those obtained with other

techniques. A considerably revised and improved version of the apparatus

has recently been placed in operation; and when further precise information has been obtained on insulating crystals, the instrument will be

applied to available semiconductors.

Negative Ions

Studies have been initiated to determine the processes by which negative

ions are formed at the surface of oxide-coated cathodes. Results to date

show that some kinds of ions are formed which have not been previously

accounted for, but their identities have not yet been established. Since

these ions occur at comparatively high yields and may be presumed to occur in any vacuum tube in which an oxide-coated cathode is used, the

successful completion of this phase of the study will be of considerable importance to the electron tube industry in addition to solving a long-standing

problem in basic physical phenomena.

In connection with this work, a nonmagnetic radio-frequency mass

spectrometer was developed in which a radio-frequency field replaces the

usual magnetic field. The new mass spectrometer has been found ideally

suited for use in rockets to determine the composition of the upper atmosphere. It also appears that a modification of the device should be well

37

I
suited for the direct observation and identification of ions in the upper

atmosphere; development projects for this application have been undertaken jointly by the Bureau and other Government-supported laboratories.

The uniquely high sensitivity of the spectrometer makes possible its use

for the rapid scanning of an entire mass spectrum and the presentation of

the spectrum on an oscilloscope screen. The instrument provides a new

experimental method of value in a wide variety of investigations—for ex- ample, biological studies employing stable isotopes and the control of industrial processes such as helium mining and oil refining.

Radioactivity

The Bureau's program for the calibration and distribution of standard

samples of artificially produced isotopes has continued to grow with the

increase in the demand for such standards in medicine, science, and in- dustry. Effort has been continuously directed toward more precise cali- bration and toward the development of uniform standards for measure- ment of radioactive isotopes. For example, a system of calibration was

devised for users of radioactive phosphorus and radioactive iodine receiving

these substances from Oak Ridge, in order to reconcile a divergence in

calibrations amounting in some cases to as much as 200 percent. As a

result, participating laboratories are now consistent to ± 10 percent. In

addition to their value to hospitals and laboratories, these measurements

will also help to establish the true value of the absolute millicurie of radioactive iodine and radioactive phosphorus. Work is being done to establish

similar standards for other radioactive isotopes. Thus a 4tt absolute beta

counting chamber is now being prepared to further refine the calibrations

of iodine 131 and phosphorus 32, and a new statistical procedure has been

devised for the calibration of radium D + E standards.

A table of Fermi functions was completed and is now being printed.

The Fermi function is widely used in determining the maximum energy

of a beta spectrum and in comparing such a spectrum with that predicted

by the Fermi theory of beta emission. However, the accurate computation

of this function is so difficult and tedious that it has been necessary to make

use of various rather inadequate approximations. The table will provide

a convenient and accurate tabulation of the Fermi function applicable

throughout the useful range of atomic number and energy ; it should prove

extremely useful to all workers in the field of beta-ray spectroscopy.

Protection Against Radiation

The recent availability of large amounts of radioactive materials and the

diversity of machines for generating radiation have caused problems of

radiation measurement and protection to grow steadily more complex. Investigation of two general problems in this field was initiated during the

year: ( 1) the development of instruments for measuring electrons and (2)

the development of instruments for measuring high-intensity X-ray dosages.

These investigations will be of particular value in new methods of therapy

38
now being utilized by the medical profession, for various kinds of research

being performed by the Atomic Energy Commission, and to answer the

demands of Government agencies, research workers, and industry, where

use of such radiations is increasing.

With the large-quantity availability of radioactive materials emitting

beta-rays (streams of electrons) and their use for experimental animal

therapy, a serious protection problem has arisen. However, ionization

chambers now used for measurement of X-rays and gamma radiation are not readily adaptable for electron measurement. Photographic film is therefore being calibrated for this use in terms of the equivalent dose for

gamma rays. Low-voltage, high-intensity X-ray units are now available commercially.

Here again, radiation-measuring instruments made for use with ordinary

X-rays do not give the proper reading, largely because of absorption of the

radiation and loss of ionization due to recombination. The Bureau has

therefore undertaken the development of an instrument without these

disadvantages.

At the request of several military agencies, the sensitivities of various

photographic emulsions are being investigated for a wide range of energies

of penetrating radiations. The ultimate goal of the work is the design and

construction of film badges for monitoring exposure of personnel to various

quantities and qualities of radiation. The emulsions studied cover, within

their useful density ranges, exposures from about 0.1 to 105 roentgens. The

effect of secondary electrons from objects in the path of the primary radiations and the influence of spectral distribution on emulsion response at various exciting potentials have been studied. The results of these studies

have led to the employment of sheets of bakelite in the film badge in front

and back of the film packet to effect electronic equilibrium and have suggested the use of a metal filter over the packet to compensate partially for

the increased sensitivity of the emulsion for radiations excited at potentials

between 30 and 100 kv.

A study of the quality dependence of survey-type Geiger counters and

ionization chambers, as well as pocket chambers and dosimeters of the

health physics type, was carried out in connection with a project supported

by the Atomic Energy Commission for the X-ray calibration of these instruments. The results of this study have permitted the manufacturers to ef- fect improvements in their instruments.

With the support of the Office of Naval Research and the Atomic Energy

Commission, the problem of protection against radiation has also been at- tacked theoretically. The study has involved a theoretical approach to the penetration and diffusion of X-rays through thick barriers—a complex

problem which has never yet been satisfactorily solved. At the close of the

year the principal elements of the problem appeared to be well under control. Attractive possibilities have opened up for applying the same methods and techniques to a study of the penetration and diffusion of electrons

39
The NBS 50-million-volt betatron with its associated control cubicle for research

in high-energy X-rays.

and to the major problem of the development of electromagnetic cascade

showers.

With the installation of a new 50-million volt betatron, NBS research in

radiation physics has now been extended into the realm of extremely high

energies. The Bureau's program in this field involves the investigation of

means for measuring high-energy radiations, the setting up of standards

for the calibration of medical instruments and other radiation-measuring

devices, and the determination of dosage and shielding requirements. This

program is basic to the continued use of high-energy accelerators by industry, Government, and the medical profession. The essential measuring

equipment for this work has now been installed ; it is so designed that it can

be remotely controlled and moved in three directions in the path of the

X-ray beam. By interposing shielding materials, such as lead, concrete, or

steel, the attenuation of X-rays of different energies can be determined and

suitable shielding requirements established.

Considerable progress has been made toward removing the electron beam

from the betatron. The "peeler" or removal unit has now been constructed

and tested. In this way, radiation can be delivered at controlled depths

for the treatment of deep cancer. However, before hospitals can use the

treatment, adequate instructions for measurement of the radiation and for

the protection of personnel must be provided by the Bureau. Progress has

also been made in the measurement of betatron radiations by means of

nuclear emulsions. This information is important to medicine in determining the distribution of energy within the X-ray beam for medical and

industrial purposes.

40
Field X-ray Equipment

Ordinary civilian hospital X-ray apparatus is not suitable for field

service in wartime: it is too heavy and bulky; at the same time it is not

rugged enough to withstand the rough handling of military use. Field

equipment should combine ruggedness with light weight, using standardized components and as few separate parts as possible. These features

must be embodied in apparatus which is easily assembled, simple to operate,

and flexible enough to be used for diagnostic work under a wide variety

of conditions.

Experience in World War II revealed the need for good field X-ray

equipment and led to a program at the National Bureau of Standards to coordinate the development of field X-ray components for the Research

and Development Branch of the Surgeon General's Office. At the request

of the Army, the Bureau began work on the initial phases of the program,

in which research consultants, X-ray manufactures, and Army roentgenologists, as well as the Bureau, combined their efforts. The intial phase

of the development work has been completed with the production of prototype models for laboratory studies and field tests. These studies and tests are now under way, and it appears probable that a large part of the equipment will soon be ready for standardization as items of supply for the Armed

Forces. The advances in design resulting from this program promise also

to be significance in the improvement of civilian X-ray apparatus. For

example, a civilian version of the military tilting X-ray table designed for

field use has already appeared on the market in a form that results in significant saving in weight and cost.

Analysis of Solids by Mass Spectrometry

A method for analysis of solids by mass spectrometry was developed and

applied to samples of stainless steel. The simplicity of interpretation of the

new method and the linearity of the reponse as a function of concentration

make it apparent that this technique will be a powerful addition to present

analytical methods.

Although mass spectroscopy has been applied with outstanding success

to the analysis of gas mixtures during the past 10 years, until now none of

these techniques has been found applicable to solids. Ordinarily the

vacuum spark is the best source of ions, but it is too erratic for use with

conventional instruments except with photographic detection, which has a number of limitations. In addition, the absence of the rich spectrum of

lines which are available in optical spectroscopy presents further difficulties

in mass analysis.

The method developed at the Bureau combines electrical recording

with the use of the spark source. To demonstrate its effectiveness, the

percentage of nickel and chromium in six standard samples of stainless

steel was determined. In the least accurate case the maximum range for

41
A new electron-optical technique was developed (p. 35) for experimentally mapping

the electric-field distribution within a magnetron. Electron rays are deflected as they pass through the magnetron's field, causing distortion of the shadow network

on the fluorescent screen. From this distortion, the electric field distribution is obtained. Below: specially designed cathode-ray tube developed at the Bureau for

application of the method.

five different measurements was 5.3 percent of the mean value, and in

most cases the maximum range of values was 3 percent or less. This is considerably better than had been anticipated, and it seems likely that these

early results may be improved.

Standard Wavelengths for Spectrometer Calibration

Use of photoconducting detectors has made available high-resolution

techniques for the one-to-three-micron region of the infrared spectrum,

42
sometimes called the combination-band and overtone region. For correct

and adequate interpretation of the new data, better wavelength determinations are necessary. This is also true in the region beyond 3 microns,

where other types of sensitive detectors may be employed. To meet the

needs in the short-wave region, 19 lines in the emission spectrum of mercury

between 1.0 and 2.3 microns were selected as secondary standards. Wavelengths of those lines which occur beyond the photographic limit were

determined by grating measurements. In addition to determinations of

27 wavelengths from the emission spectrum of mercury 198, wavelengths

of lines in the emission spectra of neon, argon, and krypton were precisely

obtained.

To provide adequate standards for the calibration of prism spectrometers

in the region from 3 to 25 microns, wavelengths of many absorption bands

of several materials were accurately determined with grating spectrometers.

The bands were selected from the absorption spectra of polystyrene, 1,2,4-

trichlorobenzene, methylcyclohexane, and toluene.

Ultimate Standard of Length

Continued investigations of the artificially produced mercury isotope of mass number 198 have determined the relative wavelengths of 27 characteristic radiations with higher precision than ever yet attained. These

measurements demonstrate (1) that the green wavelength of mercury 198

provides a practically perfect primary standard of length and ( 2

) that the

spectrum of artificial mercury provides superior spectroscopic standards

for critical tests of the constancy of differences among vacuum wave numbers and for tests of the validity of various formulas relating the refractivity

of standard air to wavelength.

Spectra of Artificial Elements

Several milligrams of technetium and promethium, new chemical ele- ments produced by uranium fission, were loaned the Bureau by the Atomic

Energy Commission for spectroscopic study. Preliminary description of

the emission spectra of these artificial elements is almost complete, providing reliable wavelengths and intensity data for about 5,000 new spectral

lines. Regularities were discovered in the first two spectra of technetium.

The absorption spectrum of promethium was also observed.

Absorption Spectrum of Water Vapor

Since the beginning of infrared spectroscopy, the existence of a region

of strong atmospheric absorption near 2.7 microns has been recognized.

With each advance in experimental techniques permitting higher resolution, more and more fine structure has been observed in this absorption

band. During the year, still greater resolving power was realized by the

development of a new high-resolution grating spectrometer utilizing a 15,000-line-per-inch grating and a lead sulfide photoconducting cell as the

43
detector. With this instrument, the band structure between 2.43 and 2.87

microns was resolved into over 450 lines. These lines have been identified

as components of two fundamental vibrational-rotational bands of the

water vapor molecule and two combination bands of the carbon dioxide

molecule. Of the three fundamental vibrations of water vapor, two fall

within this region, and in this work their respective components have been

distinguished for the first time. The new instrument clearly resolves lines

0.30 cm"1 apart and frequently makes it possible to distinguish the pres- ence of two components in lines separated by 0.15 cm"1

. This high resolution was indispensable in the theoretical analysis.

Atomic Energy Levels

The first volume of Atomic Energy Levels was completed by the Bureau

and is now available from the U. S. Government Printing Office as NBS

Circular 467. Designed to meet the needs of workers in nuclear and atomic

physics, astrophysics, chemistry, and industry, this volume is an up-to-date

compendium of all energy levels for the first 23 elements exclusive of those

due to the hyperfine structure ascribed to atomic nuclei. Similar data on

the next 19 elements, chromium through niobium, has been compiled and

sent to press; this information will constitute a large part of volume II of

Atomic Energy Levels.

Volumes I and II of Atomic Energy Levels are the first of a series being

prepared at the Bureau as part of a general program on atomic energy levels

derived from observations of the optical spectra of atoms and ions. The

new series represents the cooperative effort of scientists throughout the

world and will constitute the first compilation of atomic energy levels in

the last 18 years, during which time the number of known energy levels has

increased by a factor of 4 or 5. New descriptions and essentially complete

interpretations of Cr r, Cr il, Mn r, and As i spectra will be included as NBS contributions to volume II, and considerable progress has been made

on Mo \, Mo rr, Ta i, Ta ir^ Re i, Re n spectra as contributions to volume III.

Tables of Nuclear Data

The first edition of the tables of Nuclear Data, containing information

available up to January 1, 1950, was completed. These tables present a comprehensive collection of experimental values of important physical

constants, such as half-lives of radioactive materials, radiation energies,

relative isotopic abundances, nuclear moments, cross-sections, and nuclear decay schemes.

At present over a thousand new measurements of different nuclear

properties are being reported each year in some 30 different journals and

in the technical reports of dozens of laboratories. The first table, and

the supplements to follow, are therefore designed for easy assimilation of

new material in loose-leaf form. The reactor engineer and the industrial or medical user of radioactive tracer materials, as well as the nuclear

44
Left: techniques employed in the construction of the new three-stage nonmagnetic

mass spectrometer (p. 37) resemble those used in the manufacture of radio tubes. Right: the omegatron, a new instrument developed by the Bureau for absolute

measurements of mass (p. 34), is basically a miniature cyclotron.

physicist, have long been in need of such a compilation of available data

which can be kept up to date automatically.

All the more recent values of a given nuclear property are listed in the

tables. Thus, from the degree of uniformity of the results, the reader can

tell at a glance which nuclear constants are now fairly certain and which

are doubtful. Work is now in progress on the first supplement, which is

to contain new information obtained between January 1 and July 1, 1950.

6. Chemistry

A wide range of fundamental and applied research is carried on in physical, analytical, organic, and inorganic chemistry. Special laboratories

are devoted to organic protective coatings, detergents and adsorbents, car- bohydrates, metals and alloys, pure substances, electrodeposited coatings,

gases, acid-base indicators and pH standards, and hydrocarbons. Highly

varied techniques are used in the analytical work of the several groups;

many types of physico-chemicahmeasurements are made: an entire section,

by way of illustration, is occupied with emission spectroscopy as an analytical tool. Most of the Bureau's Standard Samples, critical in industrial

quality control and in research throughout the Nation, originate in this

division.

Spectrochemistry

Spectrochemical analysis offers advantages of speed, high accuracy for

minor and trace constituents, and small sample consumption. Methods

utilizing these advantages were developed and applied to the analysis of

various materials. The flame photometer was adapted to the determination of calcium in sugar solutions, spectrographs procedures for the analy932986—51 4 45
sis of tin metal and bronze alloys were improved with a gain in speed of

testing, and methods were developed for the determination of magnesium

in cast iron and for the identification of extremely small samples weighing

as little as one microgram. The latter method was applied to studies of

deposits in special electronic tubes for radio research.

The application of a direct-reading spectrometer to the electronic recording of line intensities promises marked improvement in the speed with

which spectral analysis of materials can be made. During the year the

direct-reading equipment was modified, making the procedure more precise than the older photographic method. The instrument is now being

used for the rapid testing of standard samples of steel for homogeneity.

Work continued on the preparation and testing of steel standards, including stainless steel and alloy tool steels. A high-manganese steel standard was issued at the end of the year; it is planned to issue several of the

high-alloy steels during the coming year.

Color Phase-Contrast Microscopy

During the war, a German optical firm developed the phase-contrast

microscope, in which hitherto indistinguishable details of microscopic objects are made readily visible. In 1948, Professor F. Zernike, who discovered phase-contrast microscopy, suggested a modification of the phasecontrast method by means of which details of structure might be shown as differences in color. His attempts at realization, however, were unsuccessful.

The Bureau has now developed new color phase-contrast equipment with

which ordinarily invisible differences in texture are revealed as bright differences in color. The color at any place is an indication of optical density

and hence gives an intimation of chemical constitution. These color effects are superimposed upon differences in darkness which may also be exhibited

by the sample. The results are very striking, but the importance of the

method will only be known after biologists, pathologists, bacteriologists, and

other users of the optical microscope have had an opportunity to put it into actual service.

Standardization of pH

Measurements of the degree of acidity and alkalinity play an important

part in the research laboratory and in the regulation of such modern industrial processes as food preparation, sugar refining, and the manufacture of

paper, textiles, and dyes. These measurements are expressed in terms of

hydrogen ion concentration, or pH, on a scale ranging from a pH of almost

zero (very high acidity) to a value near 14 (very high alkalinity) . Three

NBS standard samples are used widely here and abroad to provide fixed

points for the practical scale of pH at pH 4, 7, and 9. Unfortunately, this

scale is not uniform at its ends, and additional standards are needed to re- duce the error of measurement at low and high pH. During the past year,

46
I 20 possible pH standards were studied in detail. This work has recently

culminated in the selection of four of these, at pH 2, 3.5, 10, and 11.7,

1 which are expected to improve the accuracy of measurements below pH 4

and above pH 9. The four new standards are, respectively, potassium

I tetroxalate, potassium hydrogen tartrate, a mixture of sodium carbonate and

bicarbonate, and trisodium phosphate.

Combustible Gas Indicator

At the request of the Bureau of Aeronautics, Department of the Navy,

a new type of instrument was developed for detecting gasoline vapors or

other combustible gases in such spaces as airplane cabins or cargo holds.

In the past, the more common devices for this purpose have made use of

the heating effect of combustion at the surface of a wire. However, the

wires are subject to change at the high temperature necessary for combustion, and the older instrument is also greatly affected by changes in pressure.

The instrument developed at the Bureau, which is based on thermal conductivity, is independent of altitude and rate of air flow, moderately independent of applied voltage, and is direct-reading. It has a full-scale range

of 20 percent of the lower explosive limit but can also be made to read to the explosive limit by throwing a switch. The instrument will also indi- cate the presence of carbon dioxide.

Standard Methods of Gas Analysis

Gas analyses are performed on samples that are only momentarily available, and their interpretation, which is often of great importance, must

be made immediately. As a result, gas analysts have tended to become isolated workers with varied individual techniques which they have had little opportunity to compare with the methods used by other analysts. In an

effort to standardize gas analysis methods, the Bureau conducted an extensive investigation in which identical samples of gas were supplied to a large

number of cooperating laboratories. The laboratories made detailed re- ports to the Bureau on the results of analyses and the methods employed in

obtaining them. From a study of all the data, the better procedures were

chosen, and "standard" methods were recommended. Two of these standard methods (ASTM Tentative Method for Analysis of Natural Gas by

Volumetric-Chemical Methods, and ASTM Tentative Method for Analysis

of Natural Gas by Mass Spectrometer) were prepared in detail and have

been adopted as tentative standards of the American Society for Testing

Materials.

One great difficulty in gas analysis has been the fact that the most used

and generally the best of the reagents employed for determining oxygen

produce small but sometimes significant volumes of carbon monoxide, which

cause erroneous results. Employing for the first time a sensitive reagent

for carbon monoxide recently developed at the Bureau, a thorough study

47
was made of the conditions under which the unwanted gas develops. This

study has resulted in the preparation of a reagent for determining oxygen

which produces a minimum of carbon monoxide and thus gives reliable

results.

Hydrocarbons

Several paraffin hydrocarbons were isolated from petroleum, and samples

of recycle styrene were analyzed for C4 hydrocarbon and styrene contents. Some mixtures of olefins produced by codimerization of the butenes were

also analyzed. A large number of hydrocarbons obtained from other laboratories were purified and added to the list of standard samples of hydrocarbons which are made available to various laboratories, mainly for

spectrometer calibration. In connection with this program, the purities

of three sulfur compounds which were synthesized and purified by the

Bureau of Mines were determined by measurement of freezing points, and

the three sulfur compounds were issued as standard samples. Measurements were made of the boiling points at 20 pressures, densities at three

temperatures, and refractive indices at three temperatures and seven wavelengths of seven monoolefin and six diolefin hydrocarbons. Approximately

30 loose-leaf sheets were issued listing such properties of hydrocarbons as

viscosity, density, vapor pressure, boiling points, and refractive index. Numerous tables of infrared, ultraviolet, Raman, and mass spectral data were

also collected from various experimental laboratories and issued in loose-leaf

form.

Thermochemical Measurements

Heats of combustion in oxygen in a flame at constant pressure were determined for the four butenes (1-butene, m-2-butene, iran^-2-butene, and

2-methylpropene) . A report was prepared on the heats of formation, combustion, isomerization, and hydrogenation of the four butenes, the two

butanes (n-butane and 2-methylpropane) , the two butadienes (1,2-butadiene and 1,3-butadiene) , and the two butynes (1-butyne and 2-butyne).

This report clears up a former discrepancy between calorimetric data and

equilibrium data on the heat of isomerization of n-butane to 2-methylpropane. It confirms direct data on heat of hydrogenation, except in the

case of trans-2-butene, and yields thermochemical data on some compounds

for which data were not previously available. Most of the experimental

work has also been completed on the determination of the heats of combustion in a bomb at constant volume of liquid rz-decylbenzene, n-hexadecene, ?z-hexadecane, n-decylcyclopentane, and ?i-decylcyclohexane. These

data will yield heats of vaporization of these compounds since values have

been previously published on their heats of combustion in the gaseous

state. Heats of formation, combustion, and vaporization of homologous

series of these compounds will also be obtained from these data.

48
The heat of formation of boron trichloride and the heat of reaction of

i diborane with water were determined. These heats of reaction confirm

I the data obtained earlier by the Bureau for the heat of formation of boric

oxide, which differed greatly from previously published data. An investigation now under way on the heat of formation of decaborane will provide

additional data on the peculiar molecular structure of the boron hydrides.

Electrodeposition

The work on electrodeposition was principally concerned with the application of electroplating to weapons and other military devices, but some

time was also devoted to projects of interest to industry and the general

public. For example, a novel method was developed for measuring the

adhesion of electroplated coatings. In this method, a nodule of some

metal such as cobalt, for which the conditions of very adherent deposition

are known, is deposited on a small defined area of the plated surface that

is to be tested. The force required to remove the nodule is then measured

with a spring balance. From the measured force and the observed area of

detached plating, the adhesive force per unit area is computed.

Efforts to deposit such metals as molybdenum and tungsten from

aqueous solutions at temperatures up to 300 °C proved unsuccessful. Studies were therefore begun on the possibility of plating these metals, and others

such as titanium and zirconium, from nonaqueous media, either fused

salt electrolytes or organic solvents. In the course of this investigation

many new types of compounds and solutions are being investigated.

Research in Analytical Chemistry

Three new methods of analysis were developed. One of these, a rapid

semimicro method for determining nitrogen in steel, was related to an investigation of the hardenability of boron-treated steel. Another, a method

of determining small amounts of magnesium in cast iron, was required in

connection with the production of the new "modular" or "ductile" iron.

The third was for the analysis of thallium bromide-iodide crystals, which

are used in optical parts for transmission of radiation in the far infrared

region.

The ratio of carbon to hydrogen in synthetic rubbers was determined to the highest precision yet reported. This analysis is the basis for a physical

method of controlling the composition of the rubber during its manufacture. As small differences in the ratio are important, the highest precision

is desired.

Commercial Solid Adsorbents

Bone char is used in enormous quantities in the refining of sugar. In- creased understanding of the properties of this material, as well as those

of other solid adsorbents, has resulted from a long-range cooperative program of research initiated at the Bureau in 1939 for a fundamental study

49
of sugar-refining problems. The work is so planned as to yield information

not only of direct interest to the sugar-refining industry but also of basic

scientific value. During the year substantial progress was made in several

phases of this program.

Many properties of solid adsorbents depend appreciably on particle size,

which is determined by sieve analyses. A detailed investigation just completed shows that the testing sieves constitute the largest source of error in

these determinations. However, corrections can be made if the actual

sizes of the openings of the sieves are determined independently. Promising results were obtained using glass spheres of known size distribution to determine the effective openings of the sieves. Samples of the glass spheres

have been prepared and are now being tested in service by the laboratories

of the sponsors of the program.

The industrial regeneration of carbon adsorbents, such as bone char,

is accomplished by thermal treatment. This operation may consist of a

destructive distillation (absence of oxygen), a controlled oxidation (air

roasting), or some combination of these two treatments. An analysis of

the several methods of thermal treatment was made, providing much useful information on the kilning operations employed in the revivification of

bone char.

The presence of combined oxygen within or on the surface of carbonaceous

materials has long been known to have significant influence on their sur- face properties. In an investigation now in progress, an experimental procedure has been developed by which oxygen balances can be obtained.

The new technique separates the process of burning from that of chemisorption. This method shows that repeated adsorption of oxygen and

desorption of oxygen products has a gradual aging effect which influences

the properties of the adsorbent. Apparently, a prior treatment with

hydrogen has an important effect on the subsequent adsorption of oxygen.

Although enormous quantities of water are employed to wash bone char

in each cycle of operation, considerable ash is retained by the char, and this

is detrimental to efficient operation. It was discovered that the accumulation of adsorbed ash can be prevented and much water can be saved by the

inclusion of simple ammonium salts in the wash water. The recommended

process has now advanced from the laboratory to pilot-plant stage.

Punch-Card Catalog of Infrared Absorption Spectra

Probably no branch of chemistry is developing more rapidly than the

study of the infrared absorption spectra of chemical compounds. Not only

are these spectra useful analytical tools, but they also provide important

information on the intermolecular forces which determine chemical properties. As the available literature on the subject is already large and

rapidly expanding, there has been a need for some means by which workers

in the field could quickly find what has already been done. To meet this

need, work has begun on the preparation of a comprehensive card catalog.

50
By use of these cards, the reported spectra of any compound can be quickly

found, the more important chemical linkages associated with a given spectral line can be determined, the work of any given author can be quickly

assembled, and the properties of a compound which will aid in its identification can be found without loss of time. Many industrial laboratories

will supply data they have collected and will subscribe to the punch-card

"library."

Carbohydrate Chemistry

In the continuing program on the fundamental chemistry of sugars, further progress was made toward an understanding of their structure and

the mechanisms of the reactions by which they are formed and through

which they take part in life processes.

From studies of the hydrolysis and mutarotation reactions of the glycosylamines, an electronic interpretation was developed to account for the effect

of acid and base catalysts in addition reactions. The glycosylamines were

found to have alpha and beta modifications like the sugars. They were

acetylated, and proof was established that acetyl derivatives of glucosyl-,

mannosyl-, and galactosyl-amines all contain the pyranose ring. Optical

rotation was found to provide a means for the classification of pyranosyl

amines.

A project for the study of the infrared spectra of sugars was initiated

July 1, 1949, with the partial support of the Office of Naval Research. To

date, about 100 compounds have been purified and more than 60 have been

examined. Ultimately this work will throw light on those details of the

structure of sugar molecules that have escaped other methods of study.

Pure samples of difructose anhydrides I, II, and III, products of re- peated crystallization, were prepared for X-ray studies. Observations of

the refractive indices of maltose in concentrations from 1 to 65 percent were completed, and a method for the separation of dextrose, maltose, and

dextrins was developed for the analysis of syrups and molasses.

7. Mechanics

The mechanics of solids, liquids, and gases are the broad topics of re- search in this field. In scope the work varies from long-range investigations of basic mechanical phenomena to short-range studies of the mechanical action of practical apparatus.

Research and development now under way in mechanics include studies

of "talking book" systems for the blind, improvements in techniques for

measurement of sound pressure, development of methods of measuring

hearing loss in the deaf, development of techniques for the calibration of

pressure gages for extremely high pressures and of altimeters for extreme

altitudes, extension into the supersonic range of the hot-wire technique

for measuring air turbulence, development of calibration methods for

hygrometers, determinations of stress distribution and strength of large

51
The first step in the preparation of an NBS standard sample of steel (center) is a

lathe operation (upper left), in which chips of a special form are cut from a bar. The cuttings are next broken up into finer size (upper right), sifted, thoroughly

mixed, and then analyzed (lower left). When the composition of the metal has

been established, it is packed (lower right) in bottles for distribution.

structures such as bridge columns and bulkhead intersections of ships, stress

analysis of structural elements of aircraft with sweptback wings and with

large cutouts, development of techniques for determining the effect of high

temperature on the strength of aircraft structures, analysis of the vibration

in aircraft caused by the landing impact, development of a precise method

of measuring forces up to 3,000,000 pounds for the calibration of the

largest testing machines, and the development of a theory for the capacity

of plumbing systems based on hydraulic principles and on statistical

methods.

NBS Stick-Force Indicator

An important consideration in flight-testing new types of aircraft is the

relation between the force applied to the controls by the pilot and the

actual deflection of the controls in various maneuvers and at different air

speeds. To aid the Department of the Navy in this work, an instrument

52
was developed which automatically indicates the force applied to the control stick of an airplane. The new instrument, which makes use of the

flexure in a cantilever spring incorporated in the stick handle, is compact,

easily attached to the aircraft, and requires little attention from the pilot.

As it is unaffected by the ordinary fluctuations of aircraft battery voltages,

is of adequate sensitivity, and permits the taking of a photographic record

of stick-force indications, it is expected to aid materially in aircraft test

ork.

Until the NBS Stick-Force Indicator was developed, the two components

f the force exerted on the stick were generally measured in one of two

ays : either by pressing a single-component grip-type spring scale succesively in the two required directions or by attaching strain gages to some

art of the system used to transmit the control force. Both of these methods had their disadvantages. The first was inconvenient and distracting

to the pilot, did not give simultaneous measurements of the two force components, and did not permit a permanent record to be made. Strain gages

are still used and useful, but their readings are sensitive to voltage variations, and an amplifier is required if more than one indicator is used.

The instrument developed by the Bureau, on the other hand, operates

satisfactorily on varying aircraft voltages and makes possible a complete

photographic record of the forces in the two required directions without

disturbing the pilot in the normal operation of the controls.

Photo-Grid Technique

With the use of higher-strength sheet metal in the aircraft industry, interest in the formability of sheet has increased markedly since processes

which improve strength frequently reduce ductility. The requirement on

elongation in a 2-inch length usually found in sheet-metal specifications

is not a reliable guide for predicting formability because the elongation

may not be uniformly distributed and may often be confined to an ex- tremely small area. In a recent investigation at the Bureau, an improved

photogrid technique for determining elongation of sheet metal was developed, overcoming difficulties involved in other methods as well as providing a more reliable procedure for establishing the behavior of sheet

metal during forming. The new technique is now proving useful in the

investigation of plastic deformation in the vicinity of holes and in studies

of other structural discontinuities which result in excessive stresses.

Aircraft Structures

With the increase in size and speed of modern aircraft, it has become

increasingly important that aircraft structures have adequate stiffness as well as sufficient strength. High stiffness raises the flutter speed, prevents

wing divergence and aileron reversal, and decreases the dynamic response

of the airplane to landing impact, gust loads, and maneuvering loads. It

S3
is thus desirable that the aircraft designer be able to compute the stiffness

of a proposed design in order to determine whether the completed airplane

will give adequate performance. To an increasing extent, influence coefficients are being used as a measure of stiffness. During the year methods of computing influence coefficients of typical

aircraft wing structures with discontinuities such as bulkheads and cutouts,

and with varying amounts of sweepback, were developed for a wide range

of loading conditions. The methods make use of stress analysis of the structure based primarily on equilibrium considerations. Where equilibrium

conditions are not sufficient in themselves to specify the stress distribution, use is made of the fact that the actual distribution corresponds to a minimum

of the strain energy.

An experimental check of these methods was undertaken in cooperation

with the Massachusetts Institute of Technology. Tests were conducted

at the Bureau on wing specimens with cutouts and with both single- and

multiple-cell construction. Those at MIT were made on wing specimens with sweepback and with taper. The experimental results indicate

that the techniques developed for computing influence coefficients are

satisfactory.

Ship Structures

7'he failure of several welded steel ships during the early part of World

War II indicated that many problems relating to welded ship structures remain to be solved. Design details at structural discontinuities in welded

tankers are of special interest since failures have been known to originate at hatch corners, bulkhead intersections, and in interrupted longitudinal

members.

The Ship Structure Committee, through the Department of the Navy,

is now sponsoring at the Bureau a program of research on the stress distribution in bulkhead intersections and interrupted longitudinals as part

of a general study of design details in welded ships. Four full-size bulkhead-intersection tensile specimens and four interrupted longitudinal specimens, each differing in design detail, have been tested in the Bureau's

1,150,000-pound tension testing machine. Elastic stress distribution at room temperature, strain distribution to failure at 0° F, and energy to fracture at 0° F were determined. The results indicate considerable difference

in the load carrying capacity of the different designs for the bulkhead intersections and suggest desirable changes in design details.

Water Levels in Shallow Lakes

The emphasis in the investigation of water waves was shifted this year

to studies of the changes in water levels of shallow lakes and reservoirs

caused by wind. The Corps of Engineers of the Department of the Army

became interested in these studies early in the year because the results can be

applied directly to the "setup" produced by tropical hurricanes in Lake

54
Okeechobee and in large artificial reservoirs under construction or planned

in Florida. Further theoretical work was done on this problem, and

numerous tests were conducted under various conditions in the 70-foot flume

built for such studies the previous year. This flume has a closed cross section and has blowers mounted at both ends to create an artificial wind over

the water. The experimental work is now complete and will soon be

published.

Flow of Stratified Liquids

A comprehensive theoretical and experimental investigation of the flow

of stratified liquids, known as density currents, was continued with the

financial assistance of the Office of the Chief of Engineers, Department of

the Army. An important objective of this work is to develop model laws

pertaining to models of rivers, harbors, and canals, where density currents

are involved. The problem is of considerable economic importance, since

it involves contamination of public water supplies, as in New Orleans, and

of farm lands by intrusion of salt water from estuaries in the Sacramento

River and possibly from navigation canals. The experimental work was

completed on the movement of a wedge of salt water issuing from a lock

and progressing through a canal, and the problem is now being analyzed

theoretically. The final tests were made in a new glass-walled flume 9

inches wide and 200 feet long. Tests have begun on the next phase of

the investigation, an experimental study of conditions that exist when a

stream of fresh water flows over a layer of salt water at the mouth of a

river.

Drainage Systems in Buildings

The question of how heavily a vertical soil stack of a given diameter can

be loaded with drainage from plumbing fixtures in a building is a very

controversial one on which little experimental data have been available.

Plumbing codes differ widely in the number of fixtures that they permit

to be discharged into a stack of given diameter and in the way in which

these fixtures may be distributed between different floors. A fundamental

investigation of this problem, sponsored by the Housing and Home Finance

Agency, was continued. The experimental work was completed with tests on an actual 3-inch stack. Pressure conditions at the horizontal branch

connections and the distribution of air and water over the cross section

of the stack were studied. Another investigation, also sponsored by the

Housing and Home Finance Agency, was begun to study the minimum safe

sizes of pipes for use in the sanitary drainage system of a small dwelling.

Various arrangements of connecting fixture drains to 2- and 3-inch stacks are being investigated, and pressure conditions in the stacks and drains

are being measured. The effect of adding food waste disposal units to the drainage system is also under study.

55
Left: square panels of the type used as a stressed covering for airplanes are subjected to compressive loads in a horizontal testing machine. Right: the NBS

Stick-Force Indicator (p. 52), developed by the Bureau for the Department of

the Navy, shows the force applied to the control stick of an airplane at any instant.

Humidity Apparatus

The problem of production and measurement of relative humidity was

successfully solved by the development of a recirculator type of apparatus

which produces a known relative humidity from about +40° C to about — 40° C. The apparatus was developed principally for the test of radiosonde and other small hygrometer elements. In this device, air is first saturated at a measured, controlled temperature and then warmed to a second measured controlled temperature; from these data relative humidity of the warmed air is computed. The tester has four humidifiers and

four test chambers so arranged that a hygrometer element can be conveniently subjected to four relative humidities at the same temperature or

the same relative humidity at four temperatures, or combinations of these,

at controlled ventilating speeds up to 1,500 feet per minute.

Dispersion of Sound in Gases

Dispersion in the velocity and attenuation of sound at high frequencies

and low pressures was observed for the first time in monatomic gases. Ultrasonic measurements gave results in good agreement with both classical

and modern theory insofar as the two are consistent.

The kinetic theory of nonuniform gases is of importance in the study of

explosion-wave phenomena and upper-atmosphere research. Until these

dispersion studies, however, no experiment capable of assessing the value

of this theory had been designed except for simple cases. Indications are

that more refined experiment will make it possible to distinguish between

the classical and modern theories of nonuniform gases and perhaps furnish a basis for their modification.

56
Standards for Calibration of Microphones

For many years the Bureau has maintained standards for the absolute

[ calibration of microphones over the frequency range from 50 to 10,000

[ cycles. Recently, increased interest has been shown in the supra-audible

i range of frequencies by medical and military groups. Work was therefore

begun on the design and construction of equipment for extending the basic

j reciprocity technique for absolute measurement of sound pressure to frej quencies of the order of 100 kilocycles.

Sound Absorption

Determination of the absorption coefficients of acoustic materials after

they are installed has long been a problem of considerable economic importance. A long tube for making such measurements has now been developed and has been successfully applied in determining the effect of

different methods of painting on preservation of the sound-absorbing

power of the acoustic treatment in the Pentagon Building.

8. Organic and Fibrous Materials

Rubber, plastics, textiles, leathers, and papers—the organic and fibrous

materials investigated by the Bureau—have important characteristics in

common. All are high polymers of very complex chemical structure, and

their long, chainlike molecules have intricate physical arrangements. Consequently, the relatively simple chemical and physical techniques of a few

years ago are inadequate for obtaining more than the most elementary data

about these materials and their behavior. In recent years, however, rapid

progress has been made in the theoretical science of high polymers, and

new techniques have been developed for measuring their properties and

studying their reactions. Many of the new mathematical methods and

experimental techniques are being used by the Bureau in an integrated

approach to the study of high polymers. This program seeks to improve

present knowledge of high polymers, to develop new materials of this type,

and to provide for their practical utilization. Emphasis is placed on

methods that are applicable to several high-polymeric substances, so as

to get the greatest possible yield of results in proportion to the resources expended.

Synthetic Rubber

A program for the standardization of Government synthetic rubbers,

involving the development of methods for chemical analysis and physical

testing, is being carried on at the request of the Office of Rubber Reserve.

During the year, comprehensive chemical and physical measurements were made on the reference lots of GR-S and GR-I rubbers that were used to standardize testing and thus to insure uniformity of production in different

plants making synthetic rubber. New test recipes were developed for

57
GR-I and for GR-S rubbers made with the incorporation of carbon black.

A number of improvements were made in the strain tester previously

developed for the accurate measurement of the modulus of elasticity of

rubber samples. A complete-solution method was developed for the analysis

of GR-S rubber, and significant improvements were made in various other

physical and chemical tests.

Low-Temperature Potentialities of the Silicone Rubbers

In an investigation sponsored jointly by the Office of Naval Research and

the Quartermaster Corps, it was shown that the silicone rubbers, developed

especially for high-temperature applications, have better potentialities for use at extremely low temperatures than any synthetic or natural rubber

studied thus far. The silicones are synthetic rubbers in which some of the

carbon atoms normally present are replaced by silicon and oxygen. Since

these materials are highly resistant to heat, retaining their elasticity and

electrical resistance at temperatures as high as 200° C, they have been found

especially well suited for hose and gaskets in airplane engines and for

insulated cables. In recent years a need has also arisen for a type of rubber

capable of withstanding low temperatures without loss of its characteristic

rubberlike properties. Tires, belting, or other articles of ordinary rubber

lose their elasticity around —50° C, presenting many difficulties in connection with the operation of motor vehicles and machinery in the arctic

or of airplanes at great height. To learn more about the possibilities of

using the silicones for such low-temperature applications, the Bureau undertook an investigation to determine the lower limit of the temperature range

in which they retain their characteristic elasticity.

This lower limit was determined by locating the second-order transition

temperature, a temperature at which a marked change in the slope of the

length-temperature curve occurs. Such a change is observed in all rubbers

and plastics and can be recognized as a discontinuity in the derivatives of

volume, heat content, index of refraction, compressibility, dielectric constant, and other quantities with respect to temperature. A second-order

transition differs from the ordinary first-order transition, or change of phase,

in that no volume change or latent heat is involved. However, below the

second-order transition temperature the type of molecular motion responsible for the useful properties of a rubber ceases, and the material behaves

essentially as an ordinary solid.

Resin Bonding of Offset Papers

Further advances in making resin-bonded papers indicate that vast

quantities of hardwoods may be effectively utilized in the manufacture of

offset papers. The synthetic resin, which imparts the desirable printing

properties to these papers, acts as a substitute for the natural fiber-bonding

gel usually developed through the use of large amounts of softwood pulps.

58
Current investigations in the Bureau's experimental paper mill show that

resin-bonded papers containing 75 percent of hardwood pulps compare

favorably with papers made in the conventional way with the customary

combination of equal parts of hardwood and softwood fibers. An increase

in the proportion of hardwood fibers in printing papers would greatly ex- tend critical pulpwood resources not only in this country but also in Europe,

where the stands of hardwood suitable for paper-making are much more

extensive than those of softwood.

Abrasion Studies

The Schiefer Abrasion Machine, developed by the Bureau two years ago

for studying the abrasion resistance of textiles, is now being applied in other

related fields. For example, it is being used to produce uniform soil in a

fabric sample in connection with the evaluation of different detergents and

washing procedures, to grind plastic disks accurately for precise measure- ments of dielectric properties, to measure the effects of chemical modifications of cellulose and wool on abrasion resistance, and to test the pile of

carpets.

Another important application is the determination of the abrasion resistance of yarns without the expense of weaving or knitting them into

fabrics and without the introduction of effects due to complex geometrical

form factors of weaving and knitting. Thus, the tests can be made on

small lots of yarn in the laboratory under widely varying but carefully controlled conditions. The effects of finishing materials, chemical modifications of fiber, kind of fiber, fiber blends, amount of twist, and number of

plies on the abrasion resistance of the yarns are being determined.

Properties of Laminated Plastics

Use of laminated plastics in aircraft has increased during the past few

years, especially in accessories and semistructural parts, such as bulkheads,

partitions, linings, propellers, wing flaps, and ducts. A need has thus

developed for more comprehensive information on the properties of these

materials in order to evaluate them for aircraft application and to prepare

suitable specifications. To provide the necessary data, the Bureau has con- ducted a continuing program, sponsored by the National Advisory Committee for Aeronautics, on the properties of plastic laminates. During the

year, projects were completed on the effect of simulated service conditions,

fuel immersion, and extreme temperatures on laminated plastics.

Surface of Cotton Fibers

At present very little is known concerning the external and internal surfaces of cotton fibers. Inasmuch as these surfaces may have an important

bearing on the performance of the fibers in processing and use, further

information about them should be of considerable practical importance.

59
A welded ship girder is studied under tension in the Bureau's large horizontal testing

machine. Strategically placed strain gages indicate deformations to the seated I observers. This girder failed at a load of 843,000 pounds.

The external and internal surfaces of a series of cottons differing in variety

and in previous chemical and mechanical treatments are now being measured at the Bureau. The external surface is calculated from the quantity

of nitrogen adsorbed at — 196° C by the original fiber. The internal surface is obtained by subtracting the external surface from the total surface,

which is calculated from the nitrogen adsorbed at — 196° C after the fiber

has been swollen in water and dehydrated with absolute methanol and

benzene. In all cases the internal surface is large in comparison with the

external surface; in some instances the internal surface is as much as eighty

times the external surface.

Volume Changes at High Pressures

Many important properties of matter are affected by the independent

variables temperature and pressure. While the effect of temperature has

been the subject of intensive studies for many years, the effect of pressure

has received scant attention, primarily because of the difficulties involved

in experimentation at high pressures. To obtain information on the behavior of natural and synthetic high polymers under pressure, an apparatus was constructed to evaluate the volume change of solids and liquids at pressures between 1,000 atmospheres (15,000 lb/in. 2

) and 12,000 atmospheres (180,000 lb/in.2 ). In collaboration with the Geophysical Laboratory of the Carnegie Institution of Washington, data in this pressure range

have been obtained on the natural organic polymers, leather and cellulose; on synthetic polymers such as fluorocarbons and synthetic rubbers, and

60
on feldspathic and pyroxenic minerals such as jadeite and oligoclase, which

are inorganic polymers.

Compressibilities of the minerals were approximately the same as that

of steel, while those of the organic polymers were 20 to 50 times as large.

The results appear to classify organic polymers in a category lying between

true solids of low compressibility and true liquids, which have high compressibilities. All materials appeared stable under pressure, and no secondorder transitions were observed. Polytetrafluorethylene (Teflon) exhibited a polymorphic transition in a small pressure interval centered at 5,500

atmospheres.

Water-Vapor Relations of Leather

An example of fundamental research which rapidly developed into a

practical application was the work on the water-vapor relations of leather.

The adsorption of water vapor by collagen and by leathers was determined

at relative humidities from near to 96 percent at 28°, 50°, and 70° C.

From the results, the heats of adsorption, free energy, and entropy values were calculated for the adsorption. Methods were also derived for esti- mating moisture contents under conditions not studied experimentally.

The change of water adsorption with temperature was expressed by a relation involving the logarithm of the percentage of water adsorbed and the

inverse of the absolute temperature.

The investigation was then extended to a practical study of the permeability of leather to water vapor, an important factor in determining

the comfort of shoes. The permeability of shoe leather to perspiration in

the form of water vapor is inherently high, but the use of fats and greases

to improve the resistance of shoes to liquid water may lower their permeability so as to make them uncomfortable. Studies on leathers impregnated with different materials showed that water-vapor permeability

decreases in the following order: Sulfonated oils, acrylate resins, rubber,

and stuffing greases. A new method was developed that permits the meas- urement of the water-vapor permeability within 1 day, instead of the 4

or 5 days required by the older method. This new method is being incorporated into Federal Specifications for leather and leather products.

Deterioration of Furskins

The occasional rapid deterioration of fur coats, evidenced by brittleness

of the skin and loss of resistance to tearing, is a cause of concern to consumers, retailers, and manufacturers alike. Chemical and physical analyses

of aged pelts of Karakul lambskins, furnished by the Department of Agriculture, and Alaska sealskins, made available by the Department of the

Interior, showed the presence of small quantities of copper salts in weakened

pelts. It thus appears that the presence of copper, sometimes used as a mordant in dyeing the pelt, may be a cause of deterioration. The extent of

932986—51 61
deterioration was conveniently measured by determining either bursting

strength, breaking strength, or furrier-sewn stitch-tear values. These losses

in strength were accompanied by lowered grease content, increased watersoluble content, and increased soluble nitrogen.

9. Metallurgy

The work in physical metallurgy is concerned with the melting, working,

and heat treatment of metals and alloys; determinations of their structure

and properties; and studies of the effect of various factors on structure and

behavior under normal and abnormal conditions of service. In general,

this program is directed toward a better understanding of the properties

and behavior of metals in order that improved or new metals and alloys

may be developed for better performance in established uses and to meet

the requirements of new applications. Projects now under way are con- cerned with iron, steel, copper, aluminum, magnesium, zinc, tin, lead, and

alloys of two or more of these metals.

Corrosion

The investigation of the corrosion of aluminum, magnesium, and stainless steel sheet metal for aircraft use was continued with exposures in a marine environment at Hampton Roads, Va., and in an inland atmosphere

at Washington, D. C. Specimens of titanium and its alloys are being

included in the test program as rapidly as the material can be obtained.

This program is sponsored by the National Advisory Committee for Aeronautics; the Bureau of Aeronautics, Department of the Navy; and the

Air Force.

A study of the susceptibility of some wrought magnesium-base alloys to

stress-corrosion was completed. Results showed that the susceptibilities to atmospheric corrosion of all the alloys tested increased when the specimens were exposed under stress, but the various alloys differed in the minimum

stress required to produce an appreciable effect. Experimental work on the corrosion of aluminum alloys for use on

building exteriors was completed. The results show the importance of

proper installation in preventing early failures of aluminum roofing or

siding.

Properties of Metals at High and Low Temperatures

Precise measurements of the creep of metals, i. e., their gradual extension

under load at elevated temperatures, showed that the extension is nonuniform or cyclic rather than continuous. The nonuniformity is ascribed to periodic "relaxation", or internal readjustments to correct strains developed

in the specimen during the test. These internal readjustments frequently

result in small but actual decreases in length. The phenomenon was

62
demonstrated for ingot iron and has been confirmed for copper. Additional

studies of the deformation and failure of metals at elevated temperature are

in progress.

In a study of the formation and propagation of cracks in ship plate at temperatures slightly below room temperature, an apparent relationship was developed between the carbon and silicon contents of the steel (within

specification limits) and the tendency to crack. Certain phases of this

work are sponsored by the Ship Structures Committee, representing the

Army, Navy, Coast Guard, Maritime Commission, and American Bureau

of Shipping.

Determinations of curves of true stress versus true strain for ingot iron

from room temperature to —196° C showed that the tensile properties in

general increase with decreasing temperature within this range, but that

ductility decreases irregularly with decreasing temperature. Irregularities

in the ductility of this metal are ascribed to precipitation, either by cold

working or by strain aging, of carbon previously in solution in the iron

because of prior heat treatment. This investigation was made possible by

the development of a reduction-in-area gage for use at low temperatures.

Work is now in progress on the effect of nitrogen and aluminum on the

impact properties of carbon steels at low temperatures.

Fatigue of Metals

The service life of many metals in numerous applications is limited by

the susceptibility of the metals to fatigue, i. e., to failure under repeated

loading at stresses below the ultimate tensile strength. In attempts to determine why metals fail in fatigue, and how incipient damage can be

detected and corrected, it was found that progressive changes in the strained

lattice structure, as revealed by X-ray diffraction, reflect hardening by cold

working and do not relate to fatigue damage as had been proposed by

Slocker in Germany. A new instrument for the measurement of diffraction

patterns was developed to expedite this work. In another phase of the

investigation, it was shown that prestressing by static or dynamic procedures

may improve materially the fatigue characteristics of aluminum alloys.

The fatigue characteristics of steels used in aircraft were found to be

appreciably affected when the steels are plated with chromium. Extent

of the damage varies with the thickness of the chromium plating and with

conditions of deposition; the damage may be partially avoided by baking

the specimen at the proper temperatures.

In an investigation of printing plates used by the Bureau of Engraving

and Printing, it was found that the fatigue failures originated in the spot

welds and metallic solder used to bond the electroformed printing sheet to the supporting metal plate. It was shown, experimentally and in service

tests, that bonding the plates with a plastic adhesive, instead of spot welds

and solder, materially reduced the fatigue failures of the printing plates.

63
Left: special apparatus used at the Bureau to measure the flexural strength of

laminated plastics for aircraft use (p. 59). Right: plastic specimens are subjected

to a 240-hour accelerated weathering test approximately equal to 1 year of outdoor

exposure.

10. Mineral Products

Research in the general field of nonmetallic mineral products was con- cerned with pottery and porcelain, the high-temperature oxides, glass,

refractories, enameled metals, building stone, concreting materials, lime,

and gypsum. The efficient application of these products in commerce,

industry, and national defense requires an understanding of their chemical

and physical properties. During the year, the Bureau investigated the

chemical constitution and phase-equilibrium relationships of the refractory

oxides and the viscosity, density, and other physical properties of the molten

optical glasses. Study of the corrosion and the weathering of glass and

of building stone was continued. The properties of graphite at elevated

temperatures were studied as background information for the proper

utilization of materials in atomic energy installations. Work on the growing

of thallium bromide-iodide crystals for transmission of infrared light was

practically completed. A better understanding was obtained of the chemical

reactions that take place in the manufacture, setting, and hardening of

portland cement. Important technical improvements were made in ceramic

dielectrics for capacitors, high-temperature ceramics for jet and rocket

propulsion, large glass elements of high optical quality for special lenses,

and protective ceramic coatings for metals and alloys used at high

temperatures.

Ceramic Coatings for Metals and Alloys

A project is under way, sponsored by the National Advisory Committee

for Aeronautics, for the development of high-temperature coatings to protect

metals and alloys used in jet engines against rapid deterioration from the

effects of hot gases. ^During the past year one of the coatings developed

64
by the Bureau was adopted as an item of regular current production for

coating heat exchangers used in large aircraft. This protective coating,

coupled with certain design changes, has resulted in a multifold increase

in service life of the heat exchangers.

Laboratory experiments showed two sources of deterioration of heatresisting alloys which can be minimized by ceramic coatings. One such

source is attack by the lead bromide fumes present in the exhaust gases

from combustion of leaded fuels. Another source of deterioration is carbon

penetration, which occurs at high temperatures when the exhaust atmosphere contains carbon monoxide or hydrocarbons. The effect of these

several vapors was found to vary among the different high-temperature

alloys, but the deterioration was greatly reduced by the presence of the

ceramic coatings.

A new type of coating that shows considerable promise has been developed

for the high-temperature protection of molybdenum, a metal which has a

higher melting point than any other of equal availability but which burns

rapidly in air at elevated temperatures when not protected. The new coatings, unlike conventional ceramic coatings, consist of powdered chromium

suspended in varying amounts of a vitreous, alkali-free ceramic medium,

fired in a hydrogen atmosphere in the temperature range from 2400° to 2700° F. The particles of chromium under these conditions are bonded to each other and to the molybdenum base by diffusion welding, forming a

glass-metal network that is firmly anchored to the molybdenum. The

imperviousness imparted to the coating by the glassy phase contributes

largely to durability. Loaded specimens heated in air at 1,800° F lasted

as long as 3,275 hours before failure, under a load that produced 1.2 percent

elongation.

Ceramic Dielectrics

The constantly increasing requirements for ceramic dielectrics of high

capacitance for use in miniature electronic devices for the Armed Forces

has resulted in two types of studies: one concerning materials of low

temperature coefficient and high dielectric constant, the other involving

special development of dielectric components. As a part of the first study, an investigation of the properties of dielectrics in the system calcium oxidebarium oxide-titanium dioxide was completed. Many of these dielectrics

have properties fitting them for use in the field of special electronic instrumentation. A study of the possibility of mixing two ceramic dielectric

compounds, one with a negative temperature coefficient and the other with

a positive coefficient, has shown that it is possible in this way to obtain a

useful dielectric material having a temperature coefficient of practically

zero over a fairly wide range.

A technique was developed for the laboratory fabrication of ceramic

dielectric wafers, 3 to 6 mils thick and possessing a high degree of flatness. These dielectric shapes are well adapted to the fabrication of miniature

65
multiple-plate capacitors. Such capacitors are potentially of unusually

high capacitance and favorable temperature compensation. Moreover,

when silver-coated, they can be die-stamped into capacitor components of

exact dimensions and intricate shapes.

Properties of Graphites

As background information for the the proper utilization of materials in

atomic energy installations, the properties of graphite at elevated temperatures are under study. For observations of elongation and ultimate strength, a furnace was developed in which the uncoated graphite is exposed under

tension at temperatures ranging from 1,800° to 2,400° F for many hundreds

of hours. The extremely low resistance of graphite to oxidation at these

temperatures made it necessary to pass a controlled stream of very pure

helium through the furnace chamber. With this apparatus, it is believed

that length changes as great as 230 microns can be determined with a precision of ±6 microns. Elongation data and strength values were collected

for three grades of graphite in several orientations with respect to the

direction of extrusion or the direction of pressure when molded.

Phase-Equilibrium Relationships

The determination of phase-equilibrium relationships over a wide range

of temperatures provides important background information for the development and use of a variety of nonmetallic mineral products such as hightemperature oxides for jet and rocket motors, optical glass, steel-making

refractories, and portland cement. Studies of this kind during the year were concerned with the systems BaO-Al2 3 -Ti02 , MgO-BeO-Zr02 , MgO-BeO-ThOo, BeO-Al2 3 -Zr02 , BaO-B2 3 -Si02 , Mn3 4-Fe3 4 , BaOA12 3 -H2 0, and systems of portland cement constituents. In connection

with this work, much progress was made in developing instruments and

apparatus for attaining high temperature under controlled conditions and

for measuring temperatures of phase changes. The thoria-resistor furnace

used for very high-temperature work was modified and improved so that

useful phase-equilibrium experiments can be carried out at 2,000° C. A

centrifuge was developed which permits separation of crystals from liquids

at temperatures in the neighborhood of 1,100° C. Improvements in apparatus for differential thermal analysis were introduced, including an arrangement by which the material can be pressed as a pellet on the differential thermocouple junctions.

Crystal Synthesis and Growth

Studies of crystal synthesis and growth continued with emphasis on

infrared transmitting crystals, fluorine-substituted artificial minerals, and

crystals for X-ray analysis. Work on thallium bromide-iodide crystals for

transmission of infrared light was practically completed during the year.

Extreme care in purification of the raw materials and use of a principle of

66
Left: apparatus developed at the Bureau for studies of the water-vapor permeability

of leather (p. 61). The ultimate aim of this work is to discover a material for shoes that will be highly permeable to perspiration but not to liquid water. Right:

measurement of the thermal expansion of a rubber sample.

crystallization from the top down enabled crystals to be grown which, for

clarity and transmissivity in the far infrared, are far superior to specimens

hitherto available. Control of the direction of growth of crystals of

fluorine-containing mica was achieved by subjecting the growing crystal to

vertical as well as lateral temperature gradients. Minute crystals of a

fluorine-substituted amphibole asbestos were grown, and experiments are

in progress on the crystallization of a fluotourmaline for piezoelectric uses. An ingenious method was devised for growing crystals of pure cement

compounds suitable for X-ray structure analysis. Raw materials from

which the desired crystal can be formed are fused into a globule at the junction of a thermocouple by the passage of a high-frequency current through

the thermocouple wires. Crystallization is induced by reducing the temperature at the junction. The growing crystal is observed through a microscope, and adjustments can be made in the composition of the liquid by

adding the proper raw materials. By the use of filters, the d-c potential

produced by the electromotive force at the junction can be separated from

the a-c voltage and the temperature thus determined. Well crystallized

homogeneous tricalcium aluminate was grown in this way.

Heat of Hydration of Portland Cement

During reactions between cement compounds and water a considerable

amount of heat is liberated. In massive concrete structures, such as dams,

the low thermal conductivity of the concrete prevents rapid radiation of

the heat of hydration, and the mass of concrete may thus attain high

temperatures. These temperature rises cause expansion while the concrete

is hardening and may result in contractions and cracking when the struc- ture eventually cools.

Determination of hydration heats of the cement used in the construction

of the Hoover Dam required the work of two shifts a day, consisting of four

67
and five men per shift, for a period of several years. Since then a simpler

calorimeter has been devised, but the method and the calculations involved

are still rather time-consuming.

Recently the Bureau made a statistical study of the reproducibility and 1

bias of repeated heat-of-hydration measurements made by three relatively j inexperienced operators on a single sample of portland cement in accord- ! ance with the Federal Specification Method. Similar studies were made 1

of the results obtained by the same observers using two simplified methods

of calculation. These simplified methods require only three observations

of the calorimeter temperature at 20- or 25-minute intervals and reduce

to a minimum the attention necessary by the operator during the test, thus

making possible the simultaneous operation of two or more calorimeters

by a single worker. No significant bias or differences in reproducibility were found among either the three operators or the three methods of

calculation.

Permeability of Refractories

An investigation of the air permeability at room temperature of fireclay

and other types of refactory bricks in the flatwise, endwise, and edgewise

directions is under way. Permeability, although a difficult property to measure, is useful in indicating uniformity of structure, resistance to slag

penetration, and heat losses through furnace walls. It was found that,

within the range of pressures used to measure the permeability, the volume

of air passing through a specimen was directly proportional to the pressure

differential across the specimen. Porosity, dynamic modulus of elasticity,

and bulk density of the specimens, although correlating well in some cases with permeability, apparently cannot be considered reliable indicators of

this property. In general, within the broad range of temperatures used,

the permeability increased directly with the heat treatment the refractory

received. Bricks formed by the dry-pressed process were found to be least

permeable in the flatwise direction, which is the direction of application of

pressure during manufacture.

11. Building Technology

The Bureau continued to conduct laboratory research on technical problems relating to building construction and maintenance, and to assist Government and industry in applying scientific principles and information to building design and standardization. Projects were active in structural

engineering, fire protection, heating and air conditioning, and the chemical

and physical properties of bituminous materials.

Study of the factors affecting the strength of reinforced concrete beams

was continued, with special emphasis on resistance to diagonal tensile and

bond stresses. A concrete was developed which is believed to be superior

in durability, moisture resistance, and heat insulation value. Fire resist68
Left: special apparatus assembled at the Bureau for the X-ray measurement of strain

in metals (p. 63). Right: the Bureau's new ceramic thickness gage measures directly

v the thickness of nonconducting coatings on nonmagnetic metals without destruction

if of the coatings.

ance classifications were determined for 12 floor, wall, and column constructions; and 136 panels were tested to evaluate the fire hazard

properties of such finishing materials as acoustical tile and paints. Other

activities in the field of fire protection included research and development on improved methods for determining self-heating, flash, and ignition temperatures; studies of the spontaneous heating of liquids, films, and plastics;

and determination of the fire hazards of such emergency equipment as

signal flares and smoke bombs.

In the field of heating and air conditioning, numerous measurements

were made of the thermal conductance of materials and of heat transfer

through wall, roof, and floor constructions. Heat exchangers for aircraft

and base-board heating elements for buildings were investigated. Improved apparatus was developed for measuring the water-vapor permeability of coatings for buildings, and studies were made of the durability of

such materials. Further progress was made toward the formulation of a code for safe walkway surfaces.

Structural Properties of Reinforced Concrete

Under the sponsorship of the American Iron and Steel Institute, the

Bureau is conducting a long-range program on reinforced concrete. The

object of this program is to develop technical information as a basis for

specifications for reinforcing bars and to obtain engineering design data for

the preparation of codes and specifications for reinforced concrete structures. The initial phase of the investigation was the study of bond strength. As

a result of the findings, the first standard for deformations on reinforcing

bars was adopted, and major changes in allowable bond stresses were

proposed by the Committee on Bond Stress of the American Concrete

i Institute.

The current phase of the study deals with the resistance of reinforced

concrete to diagonal tension. It has long been recognized that this property

69
is determined not only by the quality of the concrete and the amount of

web reinforcement but by the amount of longitudinal reinforcement as

well. Research by the Bureau had also indicated the importance of certain

geometrical properties of the beam and the support and load systems. The

current program is designed to furnish data on the effect of these variable

factors in order to determine the shearing resistance of beams reinforced

with the improved deformed bars.

Fire Protection

The Bureau conducted research on the fire resistance of building materials

and constructions and on the severity of fires in ship staterooms. Constructions subjected to fire tests included eight floor constructions, two walls,

two fireproofed steel columns, and one type of corrugated steel sheet with

asphalt coatings. One hundred thirty-six horizontal panel tests were made;

these included tests to classify three types of acoustical tiles, two types of

structural fiber insulation boards with factory-applied fire-retardant

finishes, and 12 types of fire-retardant paints.

Grease-Filter Test Methods

A new approach was made to the problem of measuring the efficiency of a filter for removing grease from an air stream. The new method made

use of sampling tubes upstream and downstream from the test filter. One

of the downstream tubes was maintained at the temperature of the greaseladen air while the other was cooled with ice water. It was found that

the removal of grease was partly a filtering process and partly a condensation process since the cold sampling tube caught considerable grease that

passed through the warm sampling tube.

Equipment for Accelerated Tests

Materials intended for outdoor use are frequently subjected to regular

cycles of exposure to light, heat, and water to accelerate deterioration.

While such exposure is generally accepted as a means for determining the

relative resistance to weathering of similar materials in a short time, results

from different laboratories, or from the same laboratory at different times,

do not always show good agreement. The principal causes of this lack of

correlation are uncontrolled variables such as temperature, solids content

of the water supply, and irregular operation of the system.

During the year, the Bureau put into service a conditioned room for

accelerated testing which eliminates most of these variables. Automatic

control of all functions assures uniform operation at all times. Air and

water temperatures and water purity are kept within narrow limits. While

the equipment was designed primarily for testing asphalts and other organic

coating materials, it is sufficiently flexible to meet the requirements of

most materials subjected to weathering.

70
12. Applied Mathematics

The mathematics laboratories of the Bureau were established in recognition of the need for a centralized national computational facility equipped

with high-speed automatic machinery, capable of providing a computing

service for other Government agencies and staffed to undertake further

development of electronic computing machinery. In this area the Bureau

engages in basic mathematical research and in addition acts as a service

organization, particularly in the fields of engineering statistics and quality

control, for the Armed Forces, other governmental agencies, and industry.

Numerical Analysis

Many important problems in physics, engineering, astronomy, and other

sciences involve directly or indirectly the solution of large systems of

simultaneous linear algebraic equations. Examples are found in such

fields as stress analysis, least squares, reduction of data, and heat transfer.

A concerted attack was made this year on the solution of simultaneous

equations and related problems in matrix theory, with a view to selecting

optimum methods for various types of computing machinery. Several

definitely new procedures were developed. One of these, an iterative

method, has proved valuable for use with punched-card machinery in

solving certain types of systems of equations.

Progress was made on the general problem of finding the eigenvalues, or characteristic values, of matrices and systems of differential equations.

Considerable effort was also expended in seeking methods of solution for

the differential equations of physics, which describe the phenomena of

motion and change in the physical world. Emphasis was placed on solution by the Monte Carlo method, in which a physical or mathematical

system is represented by a statistical sampling operation set up in such a way as to satisfy the same probability laws as the system itself.

Computation

In addition to performing computations requested by Federal agencies,

universities, and private industries, the Bureau works continuously to create a stockpile of mathematical tables which can be used to facilitate

such computations. At the same time, an effort is made to develop new

or improved techniques for numerical computation, particularly those

adaptable to automatic computing machines, and to train mathematicians

in the application of numerical methods. In this way, the use of mathematical techniques for the solution of technical problems is promoted and

extended, bringing increased effectiveness to the national research program.

With the completion of SEAC (the National Bureau of Standards East- ern Automatic Computer, page 80) and the acquisition of several new types

of punched-card computers, the Bureau is now provided with the most

up-to-date equipment available for carrying out its function as a central71
ized national computational facility. As a result, solutions are rapidly being obtained for problems in science, engineering, and administration

which would have required a prohibitive amount of time by desk machine

methods.

Twenty mathematical tables were completed or in progress during the

year. In general, the tables prepared by the Bureau are of a type essential

in the solution of problems in such fields as atomic energy, aerodynamics,

radio and radar navigation, and military ordnance. To date, considerable

work has been done on the tabulation of the Jacobi elliptic functions,

Gamma functions for complex arguments, and spheroidal wave functions.

Of considerable importance to workers in nuclear physics are the tables

of Coulomb wave functions which were recently completed. These tables, soon to be published, will tabulate the solutions of an important differential

equation which arises in the quantum mechanical treatment of two particles moving in a Coulomb field of force, particularly in problems of

proton-proton and proton-neutron interaction.

Statistical Engineering

The program in statistical engineering is concerned with the application

of modern statistical inference to complex engineering experiments and

sampling problems and with the analysis of data arising in physical experiments. Work in this field at the Bureau has shown that statistical principles and techniques are even more useful in physical-science and engineering measurement than they are in agricultural and industrial work, where

many of them were first developed. Thus special statistical designs, such

as cross-overs, Latin squares, and Youden squares, have been adapted in

the road testing of truck tires, in precise determinations of radioactivity, in

rating the adherence of enamel, and in measuring the temperature of

chemical cells. A large part of the statistical engineering program takes the form of

cooperation with other laboratories on the statistical phases of scientific

experimentation and engineering tests. In addition to these consulting

services, several other activities are carried on which contribute to the

further development of statistical theory and statistical methodology. Manuals on selected phases of statistical methods, glossaries of statistical en- gineering terms, and guides to statistical literature are prepared; special

tables of statistical functions, as well as other aids to the application of modern statistical methods, are compiled and published as the need arises; and

basic research is conducted on appropriate topics in the mathematical

theory of probability and mathematical statistics.

13- Electronics

In electronics the Bureau carries on research relating to electronic materials and methods as well as pioneering development work on the frontiers

72
Left: the thermal conductivity of cement is measured in a Bureau laboratory. Right:

baseboard heating elements for buildings were studied (p. 69) in the Bureau's test bungalow. Note the thermocouples suspended from the ceiling for measurement

of temperatures at various heights.

of applied electronics. New and highly specialized types of electronic circuits and components are developed to meet the particular requirements

of industry and national defense. Much of the work is classified and involves the development of new ordnance devices for the National Military

Establishment; a large part of the remainder consists of projects in basic

and applied electronics conducted primarily for other Government agencies.

During the past year, the work in electronics included investigations of

the fundamental behavior of cathodes and gases in electron tubes; development of testing and evaluation procedures for electron tubes ; development

of special-purpose electron tubes; investigations in circuit miniaturization,

embracing printed circuitry as well as the use of subminiature components ; design and development of components for electronic digital computing

machines; and design and development of electronic instrumentation for

remote indication of steam turbine clearances and temperatures, the tele- metering of information on the stresses encountered in parachutes, and the

measurement of air turbulence in wind tunnels. In addition, several specialized electromechanical devices were under development for other

Government agencies.

NBS Electronic Currency Counter

At the request of the Treasury Department, an automatic electronic

machine was developed for counting old paper money. This machine,

known as the NBS Electronic Currency Counter, counts 30,000 bills an hour.

Rapid counting, combined with accuracy, was the principal objective of

the program. The removal of worn bank notes from circulation before

new ones are substituted involves the redemption of some 8 tons of currency

every day. The bulk of this—about 5 million dollars' worth—consists of

73
$1 bills. Although new paper money has been machine-counted for many

years, the mechanical handling of worn-out notes has until now been a

difficult problem. Old money is limp, wrinkled, and difficult to handle.

Single, torn notes are occasionally taped together. These and similar

problems have meant that the condition of returned notes is variable, and

tedious counting by hand has been necessary.

Money returned to the Treasury is in the form of stacks of 100 notes, cut

in half lengthwise. The NBS Electronic Currency Counter counts the halfnotes in these packets and automatically rejects those with more or less than 100. Packets of stapled half-notes are automatically fed into the

machine and clamped to a revolving spindle. The ends of the currency

are released as they come around in turn and are swung outward individually

by a jet of air, which breaks a light beam actuating a phototube. The

resulting current changes in the phototube circuit are formed into suitably

shaped pulses and applied to an electronic counting mechanism.

Ceramic Thickness Gage

An electronic thickness gage for measuring the thickness of nonconducting

coatings on nonmagnetic metals was developed under the sponsorship of

the National Advisory Committee for Aeronautics. The new instrument

provides a simple, direct, nondestructive measurement. Such measure- ments have become important with the increasing use of ceramic materials

as protective coatings for metals and alloys in high-temperature service.

The new electronic gage can be used with nonmagnetic high-temperature

alloys on which magnetic thickness gages cannot be used. The instrument

consists essentially of a small probe coil, an inductance-indicating system,

and a device for positioning the coil and measuring its distance from the

test surface. The measurement is based upon the change in inductance

of the probe coil due to the proximity of the coated metal surface.

Characteristics of Electrocardiographs

A study of the characteristics of electrocardiographs, undertaken at the

suggestion of the Veterans' Administration, was essentially brought to completion. The object of this project has been to determine the adequacy

of commercially available electrocardiographs for recording the electrical

signals derived from the beating of the heart. The investigation has been

directed primarily at the band-width and response requirements of such

instruments and has involved a series of laboratory tests supplemented by

the clinical evaluation of wide-band electrocardiograms by cardiologists.

This work is of direct importance in providing a quantitative basis for

specifications to be used in the Government's procurement of electrocardiographic equipment. It will also aid scientific research in cardiography by

providing an initial step toward the standardization of electrical characteristics of cardiography recorders and the recordings which they provide.

74
Electronic Miniaturization and Printed Circuits

In a program of electronic miniaturization, sponsored by the Bureau of

Aeronautics, Department of the Navy, progress was made on several different projects. The project for the development of a subminiature highgain wide-band intermediate-frequency amplifier of radar type is now concentrated on a single and final model. Construction of the prototype of

this model is about two-thirds complete. The outstanding feature of the

new design is its simplified construction. Practically all electrical connections are available as test points and for servicing without any disassembly of the unit. Newly developed circuit elements incorporated into

the design are much smaller than any equivalent components previously

used.

Design and development work is very nearly complete on a miniature

self-contained battery-powered radio transceiver for use by the Navy in

rescues at sea. At the close of the fiscal year, two models of the transceiver were in process of fabrication.

Progress was also made on a subminiature radio-range receiver for the

Bureau of Aeronautics, Department of the Navy. During the year the

first model of this device was constructed.

Development of improved techniques for printing electronic circuits continued under Navy sponsorship. Properties of capacitor dielectrics were

studied to determine those materials and construction processes capable of

high-quality performance and to determine their adaptability to mechanized

production. Carbon-composition resistor formulations were studied to improve electrical characteristics under high-temperature conditions.

Properties of miscellaneous printed-circuit assemblies involving combinations of ceramics such as steatite and zirconite porcelains with vitreous

enamel coatings were investigated. In connection with this program,

efforts are being made to utilize printed circuits in the development of a high-temperature mutual-inductance probe for instrumentation in steam

turbines.

Electron Tubes

Studies of the effects of impurities in cathode base metals were continued, with special attention to magnesium. This impurity was studied

in gross by carefully eliminating all contaminants from the magnesium

insofar as possible. The next step was the addition of controlled amounts

of magnesium to the cathode base metal. Significant results were obtained

regarding the effect of magnesium as an impurity on the activation of

cathodes and on the total emission and life of cathodes.

A new technique that proved useful in this work was the application of

pulsed voltages to the tubes under study. An investigation was made of the

effects of pulse loading on diodes when the number of complicating factors is carefully controlled. In this way, information of significant value to industry for the improvement of vaccum tubes was obtained.

75
An important new concept was developed regarding the prevailing

mechanism responsible for the disappearance of filler gases in electron tubes

filled with noble gases such as argon, neon, or helium. This phenomenon

known as "gas clean-up"—at present limits the performance of such tubes.

Rugged electron tubes are indispensable wherever electronic equipment

is used under severe conditions of vibration, shock, or acceleration. In

view of the importance of tubes of this type in civilian as well as military

use, considerable emphasis was placed on the program of tube ruggedization

initiated the previous year. Efforts were continued to improve and calibrate

high-impact shock-testing and vibration equipment for use in studying

the mechanical conditions to which tubes may be exposed. In connection

with this work, an accelerometer for use at vibration frequencies higher

than those obtainable through the use of other instruments was brought

to a promising stage of development.

A project for the investigation of noise in microwave tubes has emerged

from the preliminary stages of noise-source study and instrumentation,

yielding a method which promises to be very valuable in the study of noise

output from microwave tubes under conditions of mechanical vibration.

Further development of the new method, which clearly indicates the

mechanical resonances of internal tube parts, should eventually provide a means for obtaining quantitative information on frequency and amplitude

modulation resulting from mechanical shaking. It is expected that standards for permissible internal tube noise will be established during the coming year.

Curve Generator for Electron Tubes

A curve generator was developed which gives an instantaneous visual

display of electron tube characteristics. The new instrument plots directly on the screen of a cathode-ray oscilloscope the family of plate-current-versusplate-voltage curves for any receiving tube. A standard rectangle is dis^

played along with the characteristic curves to provide a direct scale for

voltage and current readings. In cases where the tube characteristics are not known or where an unusual combination of supply voltages is to be

used, the curve generator can provide the necessary tube data at a great

saving in time and labor.

In addition to producing plate-characteristic curves, the curve generator can provide a visual representation of plate current versus grid voltage.

In this case the oscilloscope display is particularly convenient since grid

voltage increments are directly defined by calibrated vertical bars appearing on the oscilloscope screen; a standard current reference is given by a

horizontal bar. All of the possible displays are produced by the curve generator without overloading the tube under test. Over-all accuracy of

voltage and current readings from the oscilloscope screen is within ±5

percent.

76
View of SEAC (National Bureau of Standards Eastern Automatic Computer) with

operator's control table in the foreground. The teletype is used to transmit numbers

and instructions to the machine.

A complete family of curves is retraced 60 times a second; the resulting

image is stationary and free from flicker. Characteristic curves may be

quickly obtained in permanent form by photographing the screen image

with a regular oscillograph camera. This procedure should prove ex- tremely valuable to electronic research and development organizations.

High-Speed Reversal of Electric Motors

A method was developed for reversing a small electric motor in three to four milliseconds. Designed specifically to meet the need for high-speed

932986—51 6 77
reversal of magnetic tapes in the memories of electronic digital computing

machines, the technique may prove useful in many other applications.

While it is relatively easy to stop a motor quickly by the use of brakes,

rapid starts in either the same or the reverse direction are limited by the

low torques which can be obtained by electromagnetic means alone. In the

Bureau's rapid-reversal motor, the kinetic energy of the rotor, instead of

being dissipated as heat in a brake during deceleration, is converted into

potential energy in a spring, which is then used to accelerate the rotor

rapidly in the opposite direction.

Rapid Selector for Microfilm Copying

An unexposed-film transport that will keep pace with a high-speed microfilm transport in a transcriber was developed to operate in conjunction with

a rapid selector designed for the Office of Technical Services, Department

of Commerce. The rapid selector consists essentially of a machine for

scanning a master microfilm recording which contains many thousands of

entries, each accompanied by a black-and-white dot code. This film is run without interruption at 300 frames per second past the reading head

and through a copying camera. Whenever the dot pattern of the code

matches the holes of a pre-punched card, a copy of the data frame is made

on a piece of unexposed film by a flash gun at an exposure of 2 microseconds. The unexposed film is immediately advanced to a new position to be ready for the next flash. The difficulty with the machine has been that

the fresh film could not be advanced fast enough to keep pace with the

master film.

In a new copy camera now under construction, the fresh film can be

advanced or stopped in approximately a millisecond. This is accomplished

by means of clutches and brakes operated by mechanisms similar to those

used in dynamic loud speakers. Designs for a completely new machine

are also being prepared with a view to considerable simplification of the

entire device. Machines of this kind will find wide application in both

Government and industry wherever large quantities of data must be

searched and copied.

Shaft Seal for the NBS Magnetic Fluid Clutch

In certain applications of the NBS Magnetic Fluid Clutch, the Bureau

of Ships, Department of the Navy, experienced an undesirable amount of wear in the clutch shaft. It was found that this wear was due to the heat

developed during slippage, which caused evaporation of the lubricant in

the magnetic fluid, resulting in oxidation and other chemical changes in

the internal parts of the clutch. To prevent oxidation due to "breathing,"

in which oxygen is alternately drawn into the clutch and given out by the

expansion and contraction of the gases within, a hermetic seal seemed

indicated. However, the presence of abrasive iron particles in the magnetic

78
fluid soon destroys ordinary shaft seals. A new type of hermetic seal was

therefore developed by the Bureau under sponsorship of the Bureau of

Ships. This seal consists of a reservoir of clear oil, mounted adjacent to the clutch proper, so designed that the clear oil is continuously pumped

along the shaft into the interior of the clutch. The clear oil is then returned

to the reservoir through a magnetic separator which prevents iron particles

from flowing with the oil. Clutches sealed in this way have operated at speeds from 120 to 1,440 rpm, and at slips varying from zero to 200 percent, for 30 days with no visible evidence of iron particle leakage.

Loud-Speaker Clutch

To provide a means for rapid starting and stopping of rotary motion, a

novel type of clutch was developed which utilizes the principles of the

dynamic loud-speaker. The new device is a friction clutch in which the

actuator is a coil moving in a permanently energized magnetic field. The

coil form is the input member of the clutch; the output member is a

metal disk connected to the output shaft. Because no large magnetic field

must be built up or destroyed in operating the clutch, the action can be

made very rapid. In the latest model of this device, response times of

one-half millisecond have been obtained. This length of time includes

both the electrical and mechanical delays.

Wire-Transporting Device

Wire-recording equipment that can be started or stopped very rapidly

has been required in connection with the further development of SEAC

(the National Bureau of Standards Eastern Automatic Computer) . However, one of the problems in designing such equipment has been the inertia

in large reels of wire. Recently the Bureau solved this problem by constructing a wire-transport device in which the wire is put off and onto

the reel by mechanisms similar to those used in the textile industry. Thus,

the reels of wire do not turn, but two rigid arms spin about the reels,

guiding the wire on and off. In the first model of this device, the wire

moves at 10 feet per second and starts and stops in approximately 15

milliseconds. In a second model, now being designed, the speed of the

wire will be increased to 50 feet per second, with a further decrease in

starting and stopping time.

Rapid-Action Punch

A high-speed device which punches holes in any combination of 60 spaces on a standard IBM card at the rate of 600 cards per minute was developed

for the Bureau of the Census. Such a punch was needed since the punches

that have been used operate at speeds far lower than that at which the

cards are read on sorting equipment. The new punch is electrically set and mechanically operated; that is, a mechanically oscillated plate moves

79
Small electric motor, modified by a new method developed at the Bureau which

permits quick reversals in three- to four-thousandths of a second (p. 78). During

deceleration the kinetic energy of the rotor is converted into potential energy in a

torsion bar (left), which is then used to accelerate the rotor rapidly in the opposite

direction.

at 600 strokes per minute without actuating the individual punches until

electrically-operated interposers set each punch into operation.

14. Automatic Computing Machines

The completion and successful operation of SEAC—the National Bureau

of Standards Eastern Automatic Computer—was achieved by scientists of

the Bureau's Applied Mathematics Laboratories and its Electronics Division.

SEAC is the fastest general-purpose, automatically sequenced electronic

computer now in operation. It was developed and constructed, in a period

of 20 months, by the staff of the National Bureau of Standards under the

sponsorship of the Department of the Air Force to provide a high-speed

computing service for Air Force Project SCOOP (Scientific Computation

of Optimum Programs), a pioneering effort in the application of scientific

principles to the large-scale problems of military management and administration. SEAC will also be available for solving other important problems of general scientific and engineering interest.

SEAC automatically performs all of the logical and arithmetical operations required to solve a particular problem when it is supplied with coded

instructions and numerical data. Its high speed permits the use of many

simple steps that can be combined into a complex and powerful sequence

for the solution of difficult problems. This makes it possible to solve important mathematical, computational, and statistical problems which would

otherwise be impossible of solution in any reasonable period of time, or which would be prohibitive in cost if attempted by conventional methods.

SEAC's high computing speed is largely the result of two design features:

its rapid pulse rate (1 megacycle per second) and its large memory (512

words) capacity. They make it possible for SEAC to add or subtract pairs

of 11 -digit numbers 1,100 times a second and multiply or divide them 330

80
times a second. These rates include the time it takes for the machine to search its memory for the numbers, operate upon them, and return the

result to the memory. An arithmetical operation of addition or subtraction alone is completed in 50 microseconds; multiplication or division is completed in 2,500 microseconds.

SEAC has already solved an important problem in optics in the design

of lenses and one in thermodynamics; and several mathematical problems

of general interest to pure mathematicians were solved earlier for the purpose of testing the machine. In one of these the machine was directed to compute the factors of any given number up to 100 billion. It rapidly

determined, for example, that the number 99,999,999,977 has no factors

and is therefore a prime number. In order to do this, the machine divided

99,999,999,977 by 80,000 different trial divisors. SEAC generated each of

these trial divisors, automatically establishing that each was a prime number. This problem, which would be two months' work for a man operating a desk calculator 8 hours a day, required 30 minutes for its solution.

In the development of SEAC, emphasis was placed on designing circuits

especially for computer use rather than adopting the standard procedures

of television and radar circuitry. All computing and switching in SEAC is performed by germanium crystal diodes rather than by electron tubes; tubes

are used only for power amplification. Standardized tube-and-transformer

combinations are used throughout the machine to simplify maintenance.

The transformer method provides high-frequency coupling with a minimum

of cross-talk between circuits. These advances in circuit design as well as

several unique construction features make it easy to add units to the machine, and the present version of SEAC could serve as the nucleus of a much larger computer.

At the close of the fiscal year, a second high-speed, general-purpose

electronic computer, sponsored by the Office of Air Research of the Air

Force, was nearing completion at the Bureau's Institute for Numerical

Analysis in Los Angeles. This machine will be known as SWAC—the

National Bureau of Standards Western Automatic Computer.

The NBS computer program includes the research, design, and development work necessary to produce faster, simpler, and more versatile computers and to make more effective use of the machines already in existence.

In addition to the construction of machines for its own use, the Bureau is acting as the technical coordinating agency for contracts placed with industry by other Government agencies for five other large-scale computers

:

One for the Bureau of the Census to tabulate and compute statistical information, one for the Air Force Comptroller for further work on program

planning problems, one for the Army Map Service for calculations arising

in map adjustment, one for the Office of Air Research to handle engineering

computations, and one to be operated by the NBS Computation Laboratory

for the Office of Naval Research.

81
Left: work on printed electronic circuits (p. 75) emphasized the development of

improved techniques. The press shown was recently designed for automatic

printing on cylinders. Right: the NBS Electronic Currency Counter (p. 73) auto- matically counts 30,000 notes per hour.

15. Radio Propagation

The radio propagation laboratory of the Bureau is the primary agency

of the United States Government for research in radio wave propagation

and for the coordination and centralization of information in this field. The laboratory is also assigned responsibility for development and mainte- nance of the national primary standards for electric quantities at frequencies

above 10 kilocycles per second.

Comprehensive programs of basic and applied research are undertaken in

radio physics and associated geophysical phenomena of the upper atmosphere and the troposphere. Extensive laboratory studies are also under

way dealing with properties of matter at radio and microwave frequencies

and the development of techniques for precise measurement of electric

quantities in this region. In addition to such research activities, the Bureau does a large amount of advisory and consulting work on radio for

other agencies of the Government such as the National Military Establishment, the State Department, and the Federal Communications Commission,

and participates in an advisory capacity in international radio conferences.

The work in radio propagation is divided into three branches : The Ionospheric Research Laboratory, the Systems Research Laboratory, and the

Measurement Standards Laboratory. The Ionospheric Research Laboratory conducts basic research on the nature of the upper atmosphere and

its ability to reflect radio waves. The Bureau maintains a widely separated

network of 14 ionospheric sounding stations extending over the American

continents and the Pacific area, the largest network operated by any one

government. Seven of these stations are controlled directly; the other seven are operated in close cooperation with other agencies. Data supplied

by these observatories provide basic material for scientific research and for

82
determining frequencies to be used in long-distance radio communication.

In addition, a radio propagation field station is operated at Sterling, Va.,

for performance of special experiments. Because of the important influence of extraterrestrial effects on ionosopheric phenomena, solar and cos- mic phenomena are studied. These include radio waves emitted by the sun and other celestial bodies, which also afford a new means for exploration of

the universe.

The Systems Research Laboratory applies radio propagation information

to the practical problems involved in such uses of radio as communication,

navigation, and traffic control, with particular consideration to the advantages and limitations of the types of radio systems concerned. It prepares

and publishes a monthly series of charts predicting, three months in advance, the best frequencies for long-distance communication throughout the

world. These charts are based on data collected by the network of field

stations and by agencies of other national governments. It also conducts

research in propagation at frequencies in the VHF and UHF bands which

are not reflected by the ionosphere. During the year this laboratory began an extensive program of research on the propagation factors affecting the

use of radio for aircraft navigational and traffic control, and an experimental

field station for making these studies -was set up at Cheyenne Mountain,

Colo.

The Measurement Standards Laboratory conducts research in methods

for measuring electric quantities at radio and microwave frequencies. Advances of the last few years have carried this work to higher and higher

frequencies, across the border where classical electromagnetic theory and

quantum theory overlap, and have opened up a new field of basic research

in physical science. An important function of this laboratory is the maintenance of standards of electric quantities at all radio frequencies, including

time and frequency standards which are broadcast continuously from the

Bureau's radio station, WWV, at Beltsville, Md., and from an experimental

station, WWVH, at Maui, T. H.

Reflection of Low-Frequency Radio Waves by the Ionosphere

Advances were made in the theoretical study of the reflection of radio waves at very low frequencies by the ionosphere. The ray-type treatment,

which has been used in previous investigations almost exclusively, was re- placed by wave theory. The results thus obtained account for many of

the effects observed experimentally. It was shown theoretically that, be- cause of the high collision frequency in the lower part of the ionosphere,

vastly different wavelengths are reflected from almost identical heights.

It was also shown that when a radio wave of a given frequency progresses

into the ionized region, reflections should be obtained at twice the frequency

of the wave, or if radio waves of two different frequencies traverse the same region under certain conditions, radio reflections should be observed

at frequencies equal to the sum and the difference of the frequencies of the

83
two primary waves. It is planned to extend this theoretical investigation

to include low-frequency radio waves propagated at oblique incidence on

the ionosphere, a matter of great concern for radio communication, particularly in Arctic regions, during times of radio disturbance, when communication of higher frequencies is ordinarily blacked out.

Effect of the Moon on the Ionosphere

Continued study of the effect of the moon on the F2 layer, or outermost

region, of the ionosphere has revealed that at certain phases of the moon

and at certain hours of the day this layer divides into two, the upper part of

the layer rising to heights several hundred kilometers above normal. At

opposite phases of the moon, the reverse action takes place, the upper part

of the layer being pushed down to much lower heights. These results,

which were obtained by direct study of photographic recordings made at Huancayo, Peru, explain the mechanism whereby lunar effects on the

ionosphere are produced. They point to the existence of strong tidal actions

in the ionosphere far greater than had previously been anticipated. The

effects of this lunar variation on radio propagation are pronounced. At

certain times of the day, the frequency which the ionosphere over Huancayo

is capable of propagating over a distance of 4,000 kilometers changes from

37 to 25 megacycles, entirely as a result of the lunar action.

Ionospheric Winds

By observing the simultaneous fading of radio waves on several receivers

connected to antennas spaced about 200 meters apart, winds were found to

exist in the outer part of the atmosphere, where radio waves are reflected.

These winds have velocities of the order of 100 to 200 kilometers per hour.

During the day their directions over Washington, D. C, appear to shift so

as to flow always toward the point on the earth at which the sun's rays

fall most vertically. The interpretation of the results not only sheds considerable light on phenomena of the upper atmosphere but also indicates

how radio receiver fading may be reduced by changing antennas.

Radio Astronomy

Cosmic and solar radio waves reaching the earth from outer space are manifested audibly as frying and hissing noises in a receiver at the higher

frequencies. These forms of radio noise limit the range and minimum

useable signal levels for frequency-modulation broadcasting, television, and

communication and radio navigation services in the very-high-frequency

range.

During the year regular recordings of steady background and sudden

outbursts of radio noise from the sun were continued, and special detailed

studies were made of small bursts of solar noise. The analysis of these

observations yields information as to the breadth of the spectrum of the

84
Special wide-band electrocardiographic recorder used by the Bureau in a study of

commercial electrocardiographs for diagnosis of heart disease (p. 74).

outburst of solar energy and the basic nature of the processes taking place

in the sun.

Radar Observations of Meteors

Use of radar techniques to receive the reflections from the ionized trails

left by meteors in the earth's upper atmosphere makes it possible to observe

meteors during daylight hours as well as at night. These observations,

pioneered by the Bureau as early as 1940, have yielded considerable data on diurnal and seasonal variations in the rate of arrival of meteors at the

earth. The diurnal rate has been found to reach a maximum near sunrise

and a minimum near sunset. The rate at midnight is generally about the same as at noon. Seasonal minimums occur at the vernal and autumnal

equinoxes.

The observations show that the intensity of the radio reflections from a meteor trail pulsates rapidly. Such an effect would result if the ions produced in the meteor trail spread over an extended volume at a rate five to ten times faster than the normal diffusion speed. This rapid expansion

could be caused by a shock wave traveling outward from the core of the

trail as a result of volatilization of the meteor from impact with the

molecules of the atmosphere. Thus, from this meteor research considerable

information may be deduced regarding processes of recombination and

diffusion of ions in the atmosphere. The work affords a basis for studying

the behavior of hypersonic particles passing through an atmosphere, a

field of research where experiment has lagged because of the difficulty of

producing particles with velocities comparable to those of the meteors.

85
Propagation Research

The proper allocation of radio-frequency channels to very-high-frequency

communication and broadcasting services requires a knowledge of the

nature of radio wave propagation in the bands allocated to such services.

During the past year, extensive research was done on this problem. Studies

of the effects on propagation of irregularities in the terrain and of variations

in the lower atmosphere were made. These effects were translated into

the service areas to be expected for radio and television stations allocated

in various ways. During the course of the investigation, a better understanding of the effects of irregularities in terrain on wave propagation was

achieved; an understanding of the effects of correlation of the statistical

variations of several television signals received at the same location was

obtained; and a sample study of the effects of irregular distributions of

population on efficient methods of television station allocations was made.

The experimental study of radio propagation at low frequencies was

continued using pulse techniques. A pulse transmitter capable of developing peak-pulse output power in excess of 1 million watts was completed

and put into experimental operation together with associated antennas

and receiving equipment. In this way pulse observations of the ionosphere were extended down to 37 kilocycles. From the data obtained thus far,

there is strong evidence that radio transmission at low frequencies is not

insensitive to ionospheric disturbances, as had been believed. The effects

of these disturbances on low-frequency transmission are being investigated

' further.

A broad program of propagation research in the frequency range from

1,000 to 1,600 megacycles was undertaken for the Air Navigation Development Board. Initial experimental efforts will be devoted to field-intensity

measurements for simulated air-to-ground paths, with emphasis on the

region near and below the horizon, where interference effects become

important. The transmitting site chosen for this experiment is Cheyenne

Mountain, Colorado, at an elevation of 9,000 feet above sea level, over- looking a plain at 5,000 feet which gradually slopes to 4,000 feet. A wide

variety of terrain conditions is available for different radial directions from

the mountain transmitter site.

Attenuation of Microwaves by Rainfall

Microwave radio signals decrease in intensity as they travel through the

earth's atmosphere because absorption and scattering by oxygen, water

vapor, or precipitation. The attenuation increases sharply for microwave

frequencies above 10,000 megacycles, and quantitative information on this

effect is important in the selection and allocation of microwave radio

frequencies. While the severest attenuation is caused by rainfall, such

attenuation cannot be immediately calculated from rainfall rates at a single

point because rainfall intensities are not usually uniform in the horizontal

86
plane. Previously there has been no definite basis for using point rainfall

data to calculate attenuation for extended lengths of path. Recently the

Bureau developed an approximate relation of point data to instantaneous

long-path data, and annual probability curves for the expected duration

and magnetitude of atmospheric attenuation at microwave frequencies for

both one-kilometer and 50-kilometer path lengths have now been prepared.

These attenuation statistics were derived from meteorological records, using

accepted theoretical and experimental coefficients for converting rainfall

values into radio attenuation values.

Atmospheric Radio Noise

In the absence of interference from other stations, the minimum field

strength useful for radio reception at frequencies below 30 megacycles is determined principally by atmospheric radio noise, which originates in

lightning discharges. Thus, to evaluate properly the field strength re- quired for a given radio service, an accurate knowledge of existing atmospheric noise levels is desirable. The Bureau therefore -initiated a program

to develop suitable atmospheric noise recorders, and two experimental re- corders were developed and installed at the Sterling Field Station, Va.

Continuous recordings are now being made of the "average atmospheric

noise" field intensity in a 1-kilocycle band-width centered on 539 and

2,180 kilocycles. Concurrently with the development of suitable atmospheric radio noise recorders, an analysis of noise data obtained by other

agencies operating recorders distributed throughout the world was in

progress.

Field-Intensity Recording Equipment

Instruments available for continuous measurement of radio field intensity

have proved inadequate in several respects, particularly in regard to stability to gain with aging of tubes and changes in temperature, humidity,

and supply voltage. The Bureau has therefore conducted a program for

the development of field-intensity recording equipment that would be as

free of these shortcomings as possible. The ultimate goal has been the

development of a field-intensity measuring instrument that is fundamentally

a stable, logarithmic, radio-frequency voltmeter or wattmeter, sufficiently

rugged for use either in the laboratory or in the field. In connection with this program, a totalizing voltage recorder was developed for use in analyzing radio field-intensity measurements. At present

the most common field-intensity record consists of a plot of signal strength

versus time. Much tedious work is required to obtain the necessary statistical information from such a record. The totalizing recorder, on the

other hand, gives this information directly, without intermediate recording.

The device consists of 10 channels, which are actuated by the direct-current

output of the receiver. Each channel can be preset to record the time in

87
Apparatus with movable receiving antenna (left center and insert) used in the Bureau's program for the standardization of radio field-intensity measurements.

minutes that the signal strength has exceeded a different desired level. The

resulting statistical distribution is recorded by photographing the counter

associated with each channel.

High-Frequency Standards

A thermoelectric radio-frequency microvolt standardizing device, known

as a micropotentiometer, was developed to provide simple, accurate voltage

standards requiring no frequency correction at frequencies up to 300 megacycles and higher. It is expected that this development, which consists

essentially of a thermoelement and thin metal disk, both well shielded,

88
will in part meet the great need for practical voltage standards in the r-f microvolt range.

A vertical one-meter air-dielectric impedance-measuring line of high precision was obtained. Methods of improving standard piston-attenuators were verified theoretically and experimentally. Construction of two improved attenuation standards was initiated. Intensive study and experimental work was under way to provide highly stable wide-range voltageamplitude indicating devices for use in maintaining and improving standards of power, voltage, impedance, and attenuation.

The guarded-electrode method for determining dielectric constants was

extended to 1 megacycle. The precision of dielectric-constant measure- ments was increased to 0.02 percent for frequencies up to several megacycles; accuracy was 0.1 percent. At frequencies above 100 megacycles a

precision of about 0.1 percent was obtained. Two new r-f bridges were put

in use, extending considerably the frequency range for dielectric measurements.

The noise properties of two-terminal and four-terminal networks were

investigated experimentally and theoretically. A precise noise-figure measuring service was made available for frequencies up to 40 megacycles, and

a method of determining impedance using a noise generator and noisefigure technique was formulated.

Microwave Power Standards

The problem of developing suitable microwave power standards is a

difficult one, but it is fundamental to the entire microwave field. The

effective range of search radar, blind-landing systems, and microwave relay

systems is dependent upon their output power and detection sensitivity.

Power measuring equipment is necessary to determine this range. As no

really good power standards have been available, there has been a lack of

agreement among different groups making power measurements in the

microwave region.

During the year a microwave calorimeter was developed as an independent method for the accurate determination of power in the 1 -milliwatt

range. In this device radio-frequency energy is absorbed in two reflectionless loads of polyiron that are identical in every respect but are thermally

isolated. Results obtained with the calorimeter were in agreement with

power measurements by a bolometer method within a few tenths of one

percent.

Dielectric Measurements

Since water vapor is a primary constituent of the atmosphere, knowledge

of its dielectric properties is useful in the study of radio propagation. The

dielectric constant of water vapor was measured at a wavelength of 3.2

centimeters over the temperature range 28° to 102° C. As was expected on theoretical grounds, no measurable dispersion (change in dielectric con89
stant) was found in the region of 9,000 megacycles, although an earlier

investigation in England had shown a difference at this frequency from the

low-frequency value. A dielectrometer was obtained for the accurate

measurement of the dielectric properties of solids, and a method was developed for measuring the dielectric properties of very small samples of

liquids and solids. By these techniques, the dielectric properties of a number of substances, including different types of plastics, wood, many

kinds of liquids, and special insulating materials, were measured in the

microwave region, some for the first time.

Microwave Spectroscopy

An improved precision-type of Stark-modulation spectrograph incorporating new features is being built. It will be used for the precise meas- urement of microwave spectrum lines as secondary standards in connection

with a program for the compilation and publication of all known lines by

the Bureau in cooperation with Columbia University. In addition, further refinement of the spectrograph is being attempted in order to provide

a method for measuring the rotation of the earth against a spectrum line. Such a measurement will provide a new tool for geophysicists.

Further Development of Atomic Clocks

Since the first atomic clock, based on the constant natural frequency

associated with the vibration of atoms in the ammonia molecule, was an- nounced by the Bureau, improvements have been made in circuit designs

and in the ammonia absorption cell. It is expected that accuracy of control will be improved from about 1 part in 10 million to 1 part in 100 million. This will provide a considerably more constant method for measuring time than astronomical methods which use the rotation of the earth.

Since the "Q", or line sharpness, of oxygen at 60,000 megacycles is very

much greater than that of ammonia at 24,000 megacycles, its use in the

absorption cell of an atomic clock shows much promise for obtaining greater

accuracy.

The Bureau now has three new types of atomic clocks, or frequency standards, under development, and a fourth type is being planned. One of the

new clocks will make use of atomic oscillators, by means of which the fre- quency of a transmitter, laboratory oscillator, signal generator, or frequency

divider can be controlled with microwave spectrum lines to high precision.

Another clock under development is similar to the first atomic clock but

uses a beam of cesium atoms instead of ammonia gas. Much of the equipment for the development of this clock was designed and constructed during

the year. With atomic-beam techniques, very much sharper spectrum lines are obtained since the broadening of the line due to collisions and the

Doppler effect is eliminated. This method is expected to provide an ac- curacy of 1 second in 300 years—about 300 times that obtained with the

ammonia absorption cell.

90
Noise-figure calibration of a radio receiver (p. 89). The noise figure, a fundamental measure of the quality of linear electrical networks, is of basic importance

in communication and radar.

The aim of the Bureau's program in this field is a new atomic standard

of time and frequency to replace the mean solar day. Such a standard

may make it possible to change all of the present arbitrary units for physical

quantities to atomic units. In fact, it should be possible to base both

length and time standards on one spectrum line by multiplying the fre- quency of an atomic clock up into the millimeter bands and making use of an "atomic ruler," that is, an interferometer driven by the multiplied fre- quency from the clock. This would automatically give a new precise value

for the velocity of light. More precise measurement of the mean sidereal

year also seems to offer a means of comparing Newtonian and atomic time

to an accuracy of at least one part in a billion. This would yield important

results for relativity theory and cosmology.

Ultra-High-Frequency Instrumentation

Several precision instruments were designed for making accurate

standing-wave ratio and impedance measurements in the UHF range of

300 to 3,000 megacycles. These devices are necessary for impedance determinations involved in developing and measuring the performance of

antennas for television, guided missiles, and radar. The new instruments were made with the highest mechanical precision, and several unique

91
machining methods were developed for their fabrication to assure uniformity in coaxial cross sections. Theoretical and experimental analyses were made to determine the expected accuracy of such equipment.

Electroforming of Microwave Components

An electroforming technique was developed which assures consistently

good results in the fabrication of microwave components. This process,

in which a thick layer of pure metal is electrodeposited over a precisionbuilt mandrel, takes on increased importance in the upper microwave

region, where physical dimensions decrease and the need for mechanical

accuracy increases in inverse ratio. In many cases where intricate geometrical shapes are involved, electroforming is the only possible method of

fabrication. Mandrels for the electroforming process are machined to the

highest accuracies and, if necessary, are ground and lapped to optical

tolerances. Both expendable and permanent types are used. The ex- pendable mandrels, made of duralumin, are dissolved away by a solution

such as caustic soda while the permanent mandrels, made of invar steel, are removed by heating.

16. Testing, Calibration, and Standard Samples

The Bureau's testing and calibration activities are an outgrowth of its custody of the Nation's basic physical standards. In many cases master

standards used in industry or by other laboratories must be checked

periodically against these national standards. The Bureau is also re- sponsible for testing many of the materials purchased by the Government

to assure conformance with specifications. In the course of this work,

many new instruments, new methods of measurement, and much technical

data on the properties of materials are developed.

During the year, over 250,000 tests and calibrations were performed for

other Government agencies and the public. In addition, about 19,000

standard samples were prepared and distributed. Services of this kind

included the sample-testing of about 9,000,000 barrels of cement, the assay- ing of about 2,300 raw sugar samples to aid the Customs Service in determining import duties, the testing of nearly 500 samples of soaps and

detergents for other Government agencies, the life-testing of more than

5,000 light bulbs (a sampling of over 4,000,000 purchased by the Government this year) , the testing of 2,500 samples of microfilm for hypo content,

and the sample-testing of about 74,000 clinical thermometers.

For many years, all radium preparations sold in the United States have

been tested and certified by the Bureau as no commercial laboratory is equipped to do this work. During the year over 2,000 tests of such materials—principally medical preparations for hospitals and clinics—were made

for the Government and private concerns. Nearly 1,100 radioactive standards were distributed, reflecting the constantly increasing demand throughout the country for this service by the Bureau. These included radium

92
gamma-ray standards, radium D + E standards, radioactive iodine, radioactive phosphorus, radioactive carbon, radioactive cobalt, radon standards,

and rock samples.

To protect the health and safety of workers in occupations involving the

handling or processing of radium, the Bureau maintains careful check,

throughout the United States, over the quantity of radium ingested by such

workers and over the quantity of radon present in their working areas. The

breath of these workers or the air in the work room is sampled periodically

and is measured for its content of radon, the gas produced by radioactive

disintegration of radium. This analysis reveals the amount of radioactivity

present and provides the basis for the establishment and maintenance of

proper safety measures. During the year 898 radon determinations were made for Government agencies and commercial firms.

The radon testing program was inaugurated in 1941, when the Surgeon

General's Office, Department of the Army, requested the Bureau to establish a program designed to prevent injury or death to personnel working

with radium. Using highly specialized electronic equipment and ionization

chambers that are continuously monitored by the national standards of

radioactivity, the Bureau has developed a method for measuring radon of

very low concentration to a high degree of precision. As a result of the

cooperative efforts of the Bureau and the officials hygienists responsible

for the protection of workers fron unrealed radium, deaths and injury from

radium poisoning, such as occurreJ In the years following the first World

War, are now being prevented.

Standard Samples are materials that are certified for chemical composition or for some physical or chemical property, such as heat of combustion,

melting point, or index of refraction. Standard samples of steels control

the quality of the steel industry's output. Primary chemical standards and

metals with certified melting points make possible uniform measurements

of heat and temperature in the same way that standard weights provide

uniformity of measure in buying and selling. Standard pigments define

the colors of paints, and a large variety of hydrocarbons, supplied as single

substances of high purity, calibrate the instruments that control the composition of motor gasolines, aviation fuels, and synthetic rubber. The list of standard samples issued by the Bureau now includes about 500 materials.

Electricity and Optics

Standard apparatus was tested for manufacturers, electric power companies, State public utility commissions, university laboratories, and private

testing laboratories, as well as for many agencies of the Federal Government.

In the electrical field this work involved over 14,000 separate exact determinations, and in the optical field nearly 20,000. In addition, more than

5,000 light bulbs (a sampling of over 4,000,000 purchased by the Government this year) were life-tested. Another service was the testing of over

G329S6—51 93
2,500 samples of microfilm for hypo content to make sure that the records

would be permanent when stored in the archives.

Metrology

A major responsibility of the Bureau is the maintenance of the Nation's

basic standards of physical measurement. This involves the testing and

calibration of standard measuring apparatus and reference standards for

precise measurement of length, area, angle, mass, volume, density, and

similar quantities throughout the United States. During the year, 63,366

measurement standards were calibrated, certified, and sent out for service

in laboratories, manufacturing plants, and commercial establishments.

Heat and Power

During the fiscal year, 214,521 separate determinations were made. A

total of 3,078 liquid-in-glass laboratory thermometers, 132 resistance thermometers, and 289 thermocouples were calibrated; 11,819 clinical thermometers were tested for the Veterans' Administration, the U. S. Public

Health Service, and the U. S. Department of Agriculture. Tests and

calibrations were made of special types of thermometers and thermometric

devices. The investigation for the Air Materiel Command of experimental

thermometers and temperature control equipment for use in jet engines was continued and expanded.

Twenty-seven viscometers were calibrated, and 560 standard samples of

oils were supplied to other laboratories for use in the calibration of viscometers. Seventy-three fuels and lubricants, 100 miscellaneous materials,

and 53 oil filters were tested for compliance with Federal specifications.

Automobile gasoline economizers, fuel additives, antileak preparations, and

other automotive devices and materials were tested for the Federal Trade

Commission and the Post Office Department for detection of dishonest and

fraudulent advertising. Simulated service tests of various automotive antifreezes were made for the Federal Supply Service and for the Federal Trade

Commission. Other automotive products tested for Government agencies

included 5 pursuit cars, 18 motor truck speed governors, and 615 automotive

spark plugs. A device for timing the speed of racing cars was tested for

the American Automobile Association. Twenty-five nonroutine tests on

aircraft electrical network equipment and tests and calibrations of flowmeters, spray nozzles, and aircraft carburetors were conducted for the

Bureau of Aeronautics, Department of the Navy.

Atomic and Radiation Physics

Three hundred sixty-nine chemical and isotope analyses were carried out. A total of 2,140 tests on radium and radium compounds and 898 measure- ments of radon in the breath of workers or in the workroom air were made.

In addition, 1,076 radioactive standards were distributed. Several neutron

sources were calibrated for other laboratories in terms of the Bureau's pri94
II

mary neutron standard; requests for this service are steadily increasing in

number.

All types of X-ray equipment and accessories used in general hospitals are now being studied in detail for various government agencies, especially the

Veterans' Administration, to determine their suitability for use in the

agencies' facilities. These studies include the electrical characteristics of

transformers, control units, generating equipment and tubes, as well as

their cooling and radiation output, the functioning of mechanical parts,

and compliance with purchase specifications. Much of the testing program

is devoted to the development of special tests and equipment for a better

evaluation of the X-ray equipment submitted.

Chemistry

A total of 3,776 samples were received for spectrographic analysis; this was more than double the number received the previous year. Reports were made to other Government agencies on 843 samples of paint and

related materials, nearly 500 samples of soaps and detergents, nearly 800

samples of metals and alloys, and about 500 samples of carbon paper, inks,

and related materials. To aid the Customs Service in determining import

duties, 2,275 raw sugar samples were assayed. Umpire analytical work on

classified materials for the Atomic Energy Commission was continued. In

addition to the testing of commodities there was, as usual, a considerable

volume of investigative testing such as becomes necessary in connection with

research projects. Devices submitted for calibration included 213 Magnegages, 13 saccharimeters, and 83 standard quartz plates for saccharimeters.

Approximately 19,000 standard samples, having a total fee value of about

$100,000, were issued during the year. Six new standards for spectrographic analysis were issued. In the group of standards certified for conventional analytical procedures, six renewals were prepared for materials

that had been exhausted, and three new samples were added to the list. Among the hydrocarbons there were 18 renewals and 22 additions to the

list. Five more sulfur derivatives of hydrocarbons, prepared by the U. S. Bureau of Mines, were certified and made available by the National Bureau

of Standards. Eleven benzoic acid thermometric standards were issued.

Developmental work on diphenyloxide as a thermometric standard near

25° C has been completed, but samples have not yet been prepared for

public issue.

Mechanics

There was again a pronounced increase over the previous year in tests made for other Government agencies. The number of water-current meters

tested increased from 920 during 1949 to 1,239 during 1950. The number

of master beer meters tested increased from 245 to 266; accurate calibration

of these meters is essential for the correct computation of the Federal tax on beer, amounting to about $800,000,000 per year. Two hundred fifty932986—51 8 95
eight elastic calibrating devices were tested in 1950, as compared with 221

such devices in 1949. These devices are relied upon for the calibration of

testing machines as well as for the weighing of aircraft before takeoff.

Thirteen talking book reproducers were tested as part of an investigation

of talking book systems for the blind which is being conducted for the

Library of Congress. The test results were used as a basis for the purchase

of 10,000 reproducers costing approximately $300,000. About 150 mechanical appliances, such as floor polishers, vacuum cleaners, and padlocks were

tested for compliance with Federal specifications. Parking meters and

postage meters were tested in connection with the development of standards

of security; adding machines were tested for the Census Bureau; 40 oxygen

regulators and associated apparatus were given evaluation tests for the

Bureau of Aeronautics, Department of the Navy; about 100 pressure gages

and barometers were tested for both public and Government agencies. A

number of radiosondes and other humidity measuring instruments were

tested for the Navy and the Weather Bureau. Several Pirani, thermocouple, thermopile, and cold-cathode ionization gages were tested against

the new NBS low vacuum standard. Cup and propeller-type anemometers

used in meteorological work and pitot tubes and vane- and thermal-type

anemometers for measurements of air flow in heating and ventilating

systems were tested for performance and accuracy in the Bureau's wind

tunnels at speeds up to 180 miles per hour. Tension, compression, bending,

torsion, and hardness tests were made' on 1,267 specimens submitted by

other Government departments, State institutions, and private organizations

to determine mechanical performance and compliance with specifications.

Organic and Fibrous Materials

During the fiscal year, 48,983 separate determinations were made on

11,940 samples of products containing organic and fibrous materials. The

major portion of the items tested were from individual Government purchases. Road tests of tires, carried out in collaboration with the Post Office

Department and the National Capital Parks Police, showed a variation of

almost 2 to 1 in the tread life of tires made by different manufacturers.

Approximately 3,400 standard samples of ingredients for use in rubber

compounding were issued to the rubber industry for specification testing

of production. The paper being developed for the calibration of lamps

employed in testing colorfastness of fabrics is now being used in 600 laboratories in the United States and foreign countries.

Metallurgy

A total of 311 items were tested for quality of material and compliance

with specifications. One large item was 58 fusible plugs for marine boilers,

examined for the U. S. Coast Guard. Material submitted for determination

of causes of failure during transportation included 11 items from the Civil

Aeronautics Administration, 32 items from the Civil Aeronautics Board,

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and 13 items from the Interstate Commerce Commission. Five hundred

forty-six salt-spray tests were made, and 322 items were heat-treated for

various Government agencies. The experimental foundry prepared 1,033

castings of aluminum alloys, copper alloys, cast iron, lead, tin, and special

compositions for Government agencies. Miscellaneous services included

rolling, forging, swaging, and wire-drawing of metals and metallographic

and X-ray diffraction examinations.

Mineral Products

As in previous years, the largest testing program engaged in by the

Bureau was that on portland cement and related concreting materials for

use in Federal construction projects. To insure compliance with Federal

specifications, about 9,000,000 barrels of cement were tested during the

year at the central laboratory in Washington and at four field stations.

Shipments of approximately 7,500,000 barrels of portland cement, 15,000

tons of fly ash, and 4,000 tons of silicious materials were sampled and inspected by Bureau inspectors at cement mills. Testing and inspection increased 27 percent over that of the previous year. Tests for other agencies were also made on 4,800 samples of concrete, 300 samples of aggregates,

250 samples of soil, and 200 samples of fly ash.

Closely related to this work is the program of the Cement Reference

Laboratory, which inspects the apparatus and test methods of cement-testing

laboratories. This laboratory is located at the Bureau and is jointly supported by the Government and the American Society for Testing Materials.

Field work in the laboratory includes demonstrations and inspections of

test methods and cement-testing apparatus. During the year, 65 cement

laboratories were inspected throughout the country. The Public Roads Administration contributes to the financial support of the project and requires

that laboratories testing cement for Federal-aid projects must be inspected

regularly by the Reference Laboratory.

In addition to the cement-testing program, refractories used for boiler

settings, incinerators, and power plants in Federal installations were tested.

Tests were also made on lime and gypsum for structural purposes and

building stone for monumental purposes.

Building Technology

Many varieties of building materials, constructions, and equipment were

tested for other Government agencies during the year. These included masonry units; pipe; various roofing materials; 2,100 samples of bituminous

materials; prefabricated wall, floor, and roof panels; flashing materials;

specimens of prefabricated steel bents for portable buildings; bonding

compounds for concrete ; and electric drinking-water coolers.

Many items such as signal flares, smoke bombs, and distress signals were

tested for the U. S. Coast Guard for certification as lifeboat emergency

equipment. Other items submitted by the Coast Guard included various

97
ship's stores which were tested for safety in stowage and use. Matches were

tested for the Post Office Department, Veterans' Administration, and the

Quartermaster Corps. Flammabilities of 22 lots of fabrics were determined

for seven Federal agencies and the District of Columbia. Fire hazards of

four packaged materials packed for transport in the mails were investigated

for the Post Office Department. Combustibility of insulation and similar

materials was determined on 12 lots of materials submitted by five Federal

agencies. The hazard of cellulose nitrate film in partly decomposed condition was evaluated for the National Archives, and the fire hazard of a plastic

reflector for a fluorescent light fixture was determined for the Public

Buildings Administration.

Electronics

Various types of electronic equipment and components were tested and

calibrated for other Government agencies. An example is the testing of

electron tubes. Specially designed, highly accurate, and extremely flexible

equipment has been installed for measuring the characteristics of a wide

variety of tubes, ranging in size from subminiature types to large power

tubes and ranging in frequency from direct-current to microwave. Typical

of the tests conducted during the year were (1) determinations of the

conformance of tubes to specifications, (2) evaluation of the suitability of

tubes for special circuit applications, (3) examination and evaluation of

tubes in electronic equipment which had failed or deteriorated, (4) meas- urement of the static curves of vacuum tubes in the positive grid region, (5)

measurement of characteristics of tubes operating under nonstandard conditions, (6) evaluation of sample tubes which had been subjected to highimpact shocks and to conditions of extreme vibration, and (7) evaluation

of foreign-made tubes and determination of their characteristics.

Radio Propagation

Instruments and devices tested included attenuators, bridges, diathermy

generators, field-intensity meters, a modulation monitor, multimeters, a phase modulator, quartz-crystal oscillators, radio receivers, standard resistors, transmitters, vacuum-tube voltmeters, voltage generators, and wattmeters. In the frequency band below 300 kilocycles, calibrations and tests were made on 78 items of 18 types for three manufacturers, six radio consultants, five radio stations, and 11 Government agencies. In the microwave region, 16 frequency meters and 10 attenuators were calibrated.

Standard frequencies and standard time signals were broadcast continuously

from the Bureau's radio station WWV for use in the calibration and test of frequency and time standards by the armed services, research laboratories

and various industries. The new experimental standard frequency station, WWVH, established last year on the island of Maui, T. H., was found

to be of great potential value. Technical broadcast services of both sta- tions were improved by the addition of time announcements in voice each

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five minutes, 600-cycle modulation, and a more effective warning system for

radio propagation disturbances.

17. Technical Services and Cooperation

The Bureau's consulting and advisory activities for other Government

agencies arise from the broad scope of its program in the physical sciences

and mathematics, its wide range of facilities, and expert staff. Since other

branches of the Government as well as industry rely on the Bureau for

extensive calibration and test work, the Bureau has taken a leading part

in the development of improved methods for testing materials and equipment, in determining the physical properties and physical constants of an immense variety of materials, and in the study of technical processes. As

a result, members of the Bureau staff are called upon by Federal agencies

to act as consultants in a great number of fields; where experimental work

is required, the necessary facilities are usually available at the Bureau.

The Bureau provides calibration services not only to the Federal Government but to State and municipal governments, universities, industry, and

private laboratories. In addition, the Bureau offers a program of assistance

to State and local departments of weights and measures, coordinating their

efforts and advising them on technical matters. The Bureau also cooperates

extensively with technical and trade groups, on a national basis, where the

interests of the Government are involved. Such cooperation is not only

of value to the Government but provides a means of disseminating the results of Bureau work to the Nation in a direct fashion.

The National Bureau of Standards is the technical spokesman for the

United States on international agreements relating to the development and

establishment of international scientific standards and the establishment of

values for scientific constants. It is thus active in such groups as the Inter- national Union of Chemistry, International Telecommunications Union,

International Committee on Weights and Measures, International Scientific

Radio Union, International Commission on Illumination, and International

Commission for Uniform Methods of Sugar Analysis. Another phase of

international cooperation involves a program whereby scientists or diplomatic representatives from other countries are accepted at the Bureau as guest workers or visitors. Both aspects, which are important to the United

States in terms of commerce and trade as well as the international policies

of the Government, are coordinated on the diplomatic level by the State

Department.

Advisory Services

Advisory and consulting services are rendered to all agencies of the Federal Government, as well as many State and municipal governments.

Agencies assisted during the year included the Departments of the Army,

Navy, and Air Force; State Department; Department of Agriculture; Post

99
Office Department; Atomic Energy Commission; Federal Communications

Commission; Civil Aeronautics Board; Federal Trade Commission; Interstate Commerce Commission; Library of Congress; U. S. Capitol; Joint

Chiefs of Staff; Veterans' Administration; Food and Drug Administration;

Smithsonian Institution; Weather Bureau; Rural Electrification Administration; National Research Council; Central Intelligence Agency; Coast

and Geodetic Survey; Federal Bureau of Investigation; National Advisory

Committee for Aeronautics; Munitions Board; District of Columbia; Federal Housing Administration; Housing and Home Finance Agency; U. S. Maritime Commission; Office of Rubber Reserve; Public Roads Administration; Federal Prison Industries; Bureau of the Mint; Panama Canal;

U. S. Tariff Commission; Bureau of Indian Affairs; U. S. Bureau of

Mines; Social Security Administration; Bureau of Foreign and Domestic

Commerce; Civil Aeronautics Administration; Bureau of Federal Supply;

U. S. Coast Guard; Public Health Service; Public Buildings Administration.

Continuous and more extensive work is undertaken through various

scientific and technical committees. The Bureau is represented on numerous committees, panels, and commissions of other Government agencies.

These include the Research and Development Board of the National Military Establishment, the Federal Interdepartmental Safety Council, the

Federal Fire Council, the Interdepartmental Radio Advisory Committee,

the National Conference on Weights and Measures, the National Advisory

Committee for Aeronautics, the Interdepartmental Committee on Photographic Papers and Films, the Interdepartmental Screw Thread Committee,

the Joint Committee on Unification of Building Codes, and a number of

similar groups.

Federal Specifications

An important phase of the Bureau's work consists in cooperation with

the Federal Specifications Board and other standardizing agencies in the

development and improvement of specifications. To avoid duplication of

effort in Government procurement, the Federal Specifications Board compiles and adopts specifications for the purchase of supplies by the Federal

Government. These specifications result in purchase economies by establishing criteria which guarantee quality and by providing an opportunity

for all business to compete for Federal trade through the bid system.

Under the chairmanship of the Director of the National Bureau of Standards and in cooperation with the Bureau of Federal Supply, the Board

discharges its functions through 76 technical committees. A total of 116

positions on these committees, including 23 chairmanships, are filled by

specialists of the Bureau's staff. Considerable experimental investigation

is carried on at the Bureau in the development of test methods, which are

so often indispensable before a specification can be framed or applied.

Other laboratory studies become necessary in connection with the continual

100
revision of the specifications to keep them abreast of industrial practice

and the changing needs of the Government. More than 2,000 Federal

specifications are now in effect.

Radio Propagation

The Bureau was consulted by other Government agencies on a wide

variety of problems in the radio field. For example, the Office of the

Surgeon General, U. S. Army, was assisted in the development of methods

to modify diathermy equipment so that it might be used in compliance with

new FCC regulations soon to go into effect. Consultative and test services were performed for the Federal Bureau of Investigation in connection with

a large order of FM transmitters and receivers. Field-intensity instrument

standardization was discussed with members of the staff of the Federal

Communications Commission. Assistance was given the Los Alamos Scientific Laboratory in planning improvement of its timing equipment.

Several proposed specifications and amendments for electronic components

were reviewed for the Armed Services Electro Standards Agency. Consultative services on voltage and impedance measurements were given 14

representatives of governmental and other laboratories. Information, advice, and design details on microwave equipment were furnished to other

Government agencies, including the Naval Research Laboratory, Air Materiel Command, and the Naval Ordnance Laboratory; to a number of

foreign institutions; and to numerous industrial, engineering, and educational institutions in this country.

Building Technology

As in previous years, the Bureau provided assistance to other Government

agencies on a wide range of technical problems relating to building construction and to fire and other hazards to life and property. Typical subjects were the probable origin of a destructive explosion during a fire in a Government building, deterioration of safety devices for elevators in Government

buildings, explosibility of ammonium nitrate, electrical hazards of electronic

computing machines, hazards of dangerous cargoes on military aircraft,

shipping hazards of television tubes, the design of chimneys for draft,

methods of measuring thermal conductivities of building materials, methods

of rating heating equipment for buildings, and performance characteristics

of refrigeration and air conditioning equipment.

The National Resources Board was given information on fire protection

needed for stock piles of strategic materials. Frequent requests were re- ceived from the Federal Housing Administration for opinions concerning

the acceptability of new materials and new construction methods. The

Post Office Department, the Treasury Department, the Departments of

War and Navy, the Public Buildings Administration, the Architect for the

White House, the National Institutes of Health, and other agencies were also

101
given information and advice on safeguards against fire and fire protection measures.

X-ray Problems

The Veterans' Administration was assisted in the preparation of a manual

for the guidance of its X-ray personnel. The Bureau also analyzed the

plans for a number of Veterans' Administration hospital X-ray departments

to determine their requirements for protective barriers and provided consultative assistance in the preparation of specifications for medical X-ray

equipment for purchase by the Veterans' Administration and other Government agencies. Assistance was given the Public Health Service in the

preparation of a manual for the guidance of architects and others concerning

protective barriers for hospital X-ray installations. In its capacity as technical consultant on radiographic equipment to the Surgeon General, U. S. Army, the Bureau participated on the Panel on Radiology of the Armed

Forces Field Medical Materiel Group.

Failure of Airplane Propellers

The Civil Aeronautics Board sought the advice of the Bureau concerning

the failure of propeller blades as a cause of airplane accidents. In order to add rigidity to the hollow metal propellers, rubber compounds are often

vulcanized in place inside the blades to fill completely the inside space.

Examination of the rubber compound inside a failed blade revealed that

the compound had been overcured to the point that it had become brittle

and that the vibration of the propeller had caused the compound to disintegrate and change position inside the blade. The same rubber compound,

when cured at a lower temperature, produced a much stronger, tougher,

and less brittle product.

Portable Electric Hot-Water Heaters

At the request of the Post Office Department and the Federal Trade

Commission, the performance of small electric hot-water heaters of the

"clamp-on" type was studied. It was found that several models of these

devices were serious hazards. As the heating coil was bare and in contact

with the water, they might easily have caused a fatal electric shock.

Rubber Technology

The Committee on Specifications for Government Synthetic Rubbers,

Office of Rubber Reserve, was assisted in the development of a complete

solution method for determing fatty acid and soap in synthetic rubbers, a method for determining Mooney viscosity of the polymer in GR-S rubber

latices, and recipes for the evaluation of GR-I and GR-S black synthetic

rubbers. Assistance was also given to the Office of Rubber Reserve in its educational program in the rubber industry on the merits of the strain test developed recently by the Bureau for the evaluation of rubber.

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Automotive Tire Tests

The Bureau assisted in the application of modern statistical methods to the design of a comprehensive road test on the tread wear of tires and to

analysis of the results. The test was conducted by the Government Tire

Test Fleet at San Antonio, Tex., operated by the Copolymer Corporation,

and was planned in conjunction with the polymer development work of the

Office of Rubber Reserve. Five tires of each of 42 types were tested. In

addition to the customary skid depth measurements, weight-loss determinations were made according to a method previously developed at the Bureau.

The introduction of the statistical design and of the more precise weighing

method resulted in a saving of approximately 65 percent in the cost of the

test. In addition to a comparison of types of tires, this procedure yielded

information not usually obtained by the customary method.

Codes and Specifications

The results of a large part of the research and testing carried on by

the Bureau have a direct bearing on the development of technical requirements designed to assure safe working and living conditions. Through

membership on numerous committees of national standardizing bodies, the

Bureau has been able to put these results before qualified persons for interpretation and practical use. It thus provides a central source of information to which Federal, State, and municipal authorities, as well as industrial

and trade associations, can turn when dealing with problems of safety or with building and plumbing codes. Similarly, the Bureau has participated

in the development of numerous national standards and specifications that are universally used as basis for intelligent purchase of commodities.

During the year, representatives of the Bureau took an active part in

work on revision of the National Electrical Code, the National Electrical

Safety Code, the Code for Protection Against Lightning, the American

Standard Elevator Safety Code, and other codes in the safety field. Other

work in process was concerned with codes for mechanical refrigeration,

electrical equipment in coal mines, electrical raceways, wood poles and

cross-arms, and plumbing systems.

Weights and Measures

While the National Bureau of Standards is the custodian of the Nation's

standards of length and mass, the Congress has left to the control of the individual States the regulation of commercial weighing and measuring

devices and operations. As the Bureau has no regulatory authority over

the weights and measures activities of the States, it functions only in an

advisory and coordinating capacity in this field. The translation of the basic standards of length and mass and of the derived standards of capacity to the channels of industry and trade is a matter

of great economic importance to the producing, manufacturing, processing,

and distributing agencies in this country and to all purchasers of commodi103
ties. To aid in this work, the Bureau established late in 1947 an Office of

Weights and Measures whose over-all function is to promote the extension,

raise the standard of efficiency and coverage, and increase the degree of

uniformity of State weights and measures supervision throughout the United

States. A definite program of assistance to State and local departments of

weights and measures as well as to business and industry has been set up

and successfully pursued.

A large part of the activity of the Office of Weights and Measures consists of consultative services rendered through correspondence; through

visits to the office by representatives of Federal agencies, business and manufacturing concerns, and weights and measures officials ; and through visits of

members of the office to weights and measures officials in their own jurisdiction. The field of inquiries is broad, embracing the drafting of new

legislation; the interpretation of laws, specifications, tolerances, and regulations; the design of testing equipment ; methods of test of commercial equipment; the reporting of activities in different weights and measures jurisdictions; problems of and plans for weights and measures administration;

planning and conducting weights and measures conferences; training schools

for State departments; and other similar problems.

A major medium of cooperation with weights and measures officials,

manufacturers of weighing and measuring devices, and associated interests

is the National Conference on Weights and Measures. The thirty-fifth

meeting of this organization was held in Washington in May 1950 under

the sponsorship of the National Bureau of Standards. The official registration of 292 included 143 weights and measures officials from 34 States,

the District of Columbia, and Puerto Rico; 123 representatives of business

and industry; and 24 persons from Federal agencies.

Actions of the Conference included tentative approval of a model weighmaster bill, which establishes the office of "licensed public weighmaster"

;

amendment of the textile section of the model State law to govern the

marking and sale of textile products by weight or measure; changes in the

codes of specifications, tolerances, and regulations for commercial weighing and measuring devices (NBS Handbook H44) ; and recommended

methods of sale for liquefied petroleum gas. A special committee was

formed to investigate, in cooperation with railroad authorities, the testing

of railway track scales by the States.

Research Associate Program

The research associate plan is an arrangement under which technical,

industrial, and commercial organizations can support work at the Bureau

on projects which are of special interest to them, yet of sufficient general

interest to justify use of Government facilities. Research associate projects must not only be of value to all groups concerned in the particular

field and to the Federal Government, but must also be important from the

standpoint of the Nation's sum total of technologic knowledge. While the

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arrangement is preferably made with an association or group representing a major part of the industry concerned, projects may be undertaken in co- operation with single companies or individuals when the results may be

expected to be of value to the general public. In any case, the results become a part of the public domain and are published by the Bureau. Research workers acceptable to both parties are either assigned by the Bureau

or employed by the supporting organization, which pays their salaries and

other expenses incident to the project.

Since the research associate plan was established in 1920, more than 175

organizations and individuals have supported cooperative research at the

Bureau. Many of the projects have been extremely specific and therefore

of relatively short duration. Others, such as that supported by the Portland Cement Association, have been directed toward fundamental research

in the field; this project has been active since 1924.

At the close of the fiscal year 13 groups were supporting 62 research

associates at the Bureau. Cooperative projects were under way on dental

materials, fuels, electron tubes, commercial adsorbents, electrodeposition, corn products, cement, concrete, standards for X-ray diffraction analysis,

chinaware, porcelain enamel, and asphalt roofing.

Scientific and Technical Groups

Through active participation in the projects of professional societies and

standardizing bodies, the Bureau plays an important part in the development of test methods and criteria, in the application of scientific discoveries,

and in fundamental research programs of a national nature. It thus aids

in developing and improving engineering standards, purchase specifications,

and building and safety codes. Bureau staff members now hold approximately 1,600 positions on committees of over 100 national groups such as the Acoustical Society of America, American Society for Testing Materials,

American Standards Association, American Society of Textile Chemists

and Colorists, American Ceramic Society, American Concrete Institute,

American Geophysical Union, American Institute of Electrical Engineers,

American Leather Chemists' Association, American Society of Heating and

Ventilating Engineers, American Society of Mechanical Engineers, Institute

of Radio Engineers, Institute of the Aeronautical Sciences, Instrument

Society of America, National Fire Protection Association, Optical Society

of America, Society of Automotive Engineers, Society of Plastic Industry,

and Society for Experimental Stress Analysis.

The Bureau was also active in about 30 international scientific and technical bodies such as the International Union of Chemistry, International

Union of Pure and Applied Physics, International Telecommunications

Union, International Committee on Weights and Measures, International

Commission on Illumination, International Scientific Radio Union, and

International Commission for Uniform Methods of Sugar Analysis. These

international societies deal largely with the establishment and maintenance

105
of international scientific standards and the establishment of values for

such quantities as scientific constants. The Bureau's participation in their

programs is important to the United States in terms of both international

trade and diplomatic policy.

Office of International Relations

Scientists and engineers from other countries are permitted to participate

in certain normal work of the Bureau as guest workers. The program is conducted under procedures of the Department of Commerce and the

Department of State, in accord with such legislation as the Fulbright Act

(Public Law 584, 79th Cong.) and the Smith-Mundt bill (Public Law 402,

80th Cong.). The Bureau's Office of International Relations makes ar- rangements for foreign scientists to be accorded guest privileges at the

Bureau; receives official visitors from abroad; correlates Bureau activities

with those of other Federal committees handling international relations,

and assists the Bureau in its own representation abroad at international

meetings. Such a program not only strengthens the relations of this country

with other nations but also permits the Bureau to keep more closely in

touch with foreign developments and provides it with additional expert

temporary staff associates.

During the fiscal year, a total of 636 persons from other countries were

visitors or guests of the Bureau. Among them were 17 directors of foreign

research institutions analogous to the National Bureau of Standards, 46

directors of specialized research institutions, 107 research scientists and

engineers, 58 university professors, 25 government officials, 116 industrial

engineers, and 12 delegations consisting of 165 persons. In addition, 29

scientists and engineers were accepted for programs ranging from three to twelve months, as well as 13 trainees sponsored and supported by the Department of State and 35 technical students of graduate level.

E. U. Condon,

Director, National Bureau of Standards.

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SCIENTIFIC AND TECHNICAL DIVISIONS AND

SECTIONS 1

ELECTRICITY

Resistance Measurements

Inductance and Capacitance

Electrical Instruments

Magnetic Measurements

Electrochemistry

OPTICS AND; METROLOGY

Photometry and Colorimetry

Optical Instruments

Photographic Technology

Length

Gages

HEAT AND POWER

Temperature Measurements

Thermodynamics

Cryogenics

Engines and Lubrication

Engine Fuels

Combustion

ATOMIC AND RADIATION PHYSICS

ATOMIC PHYSICS

Spectroscopy

Radiometry

Mass Spectrometry

Physical Electronics

Electron Physics

Atomic Physics

Neutron Measurements

J As of July 1, 1950.

107
ATOMIC AND RADIATION PHYSICS—Continued

RADIATION PHYSICS

Nuclear Physics

Radioactivity

X-rays

Betatron

Nucleonic Instrumentation

Radiological Equipment

CHEMISTRY

Organic Coatings

Surface Chemistry

Organic Chemistry

Analytical Chemistry

Inorganic Chemistry

Electrodeposition

Gas Chemistry

Physical Chemistry

Thermochemistry

Spectrochemistry

Pure Substances

MECHANICS

Sound

Mechanical Instruments

Aerodynamics

Engineering Mechanics

Hydraulics

Mass

Capacity, Density, and Fluid Meters

ORGANIC AND FIBROUS MATERIALS

Rubber

Textiles

Paper

Leather

Testing and Specifications

Organic Plastics

Dental Materials

108
METALLURGY

Thermal Metallurgy

Chemical Metallurgy

Mechanical Metallurgy

Corrosion

MINERAL PRODUCTS

Porcelain and Pottery

Glass

Refractories

Enameled Metals

Building Stone

Concreting Materials

Constitution and Microstructure

Chemistry of Mineral Products

BUILDING TECHNOLOGY

Structural Engineering

Fire Protection

Heating and Air Conditioning

Exterior and Interior Coverings

Codes and Specifications

APPLIED MATHEMATICS

Numerical Analysis

Computation

Statistical Engineering

Machine Development

ELECTRONICS

Engineering Electronics

Electron Tubes

Electronic Computers

ORDNANCE DEVELOPMENT

Mechanical Research and Development

Electromechanical Fuzes

Technical Services

Missile Fuzes—

I

Missile Fuzes—II

Projectile Fuzes

Ordnance Components

Ordnance Tests
CENTRAL RADIO PROPAGATION LABORATORY

IONOSPHERIC RESEARCH

Upper Atmosphere Research

Ionospheric Research

SYSTEMS RESEARCH

Regular Propagation Services

Frequency Utilization Research

Tropospheric Propagation Research

MEASUREMENT^STANDARDS

High-Frequency Standards

Microwave Standards

MISSILE DEVELOPMENT

Missile Engineering

Missile Dynamics

Missile Intelligence

Missile Instrumentation

Technical Service

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