NATIONAL BUREAU OF STANDARDS REPORT

5459

FACILITIES AVAILABLE AT THE NATIONAL BUREAU OF

STANDARDS FOR STRUCTURAL DETERMINATION OF ASPHALTS

by

Shigeru Ishihara

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended b\ Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

development of standard practices, codes, and specifications. The work includes basic and applied

research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

for other Government Agencies, particularly the Department of Defense and the Atomic Energy

Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the back cover.

Reports and Publications

The results of -the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project or program. Published papers appear either in the Bureau’s own serieb of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three monthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

complete papers reporting technical investigations; the Technical News Bulletin, which presents

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Information on the Bureau’s publications can be found in NBS Circular 160, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office, Washington 25, D. C.

Inquiries regarding the Bureau’s reports should he addressed to the Office of Technical Information, National Bureau of Standards, Washington 25, D. C.
NATS ON AL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1004-11-1017 September 13 9 1957 5459

FACILITIES AVAILABLE AT THE NATIONAL BUREAU OF

STANDARDS FOR STRUCTURAL DETERMINATION OF ASPHALTS

by

Shigeru Ishihara

Research Associate

Asphalt Roofing Industry Bureau

Floor 9 Roof and Wall Coverings Section

Building Technology Division

Jointly Sponsored by

Asphalt Roofing Industry Bureau

the Office of the Director, Natii Standards and Technology (NIST) il|1 permission is not needed,

however, by the Government ap October 9 ^01^ ''pared if that agency wishes

to reproduce additional copies

and

National Bureau of Standards

IMPORTANT NOTICE

NATIONAL BUREAU OF STAN

intended for use within the Go

to additional evaluation and rev

listing of this Report, either in Director Ol tne i\auonai institute ui „ j s Obtained in writing trom

U. S. DEPARTMENT OF COMMERCE
V
FACILITIES AVAILABLE AT THE NATIONAL BUREAU OF

STANDARDS FOR STRUCTURAL DETERMINATION OF ASPHALTS

by

Shigeru Ishihara

INTRODUCTION

This report is presented to the members of the Asphalt

Roofing Industry Bureau in answer to the request made in

the committee meeting of June 1957= A survey of the methods

and equipment used in the determination of the physical structure present in systems composed of organic compounds has

been conducted and herein are brief descriptions of methods

and instruments which may be applicable for study with

asphalt s o The first five sections are the areas of study where the

survey showed promise of positive evaluation in measuring the

structure of asphalt in entirety. Sections 6, 7 ? and 9 are

brief descriptions of techniques that have been employed on

pure compounds and further developments for complex mixtures

are desirable. Section 8, on use of the electron microscope,

has been mentioned, but at the present time there is no fulltime electron microscopist on the Bureau staff.

Many methods of structural determination of organic compounds were not included because the techniques developed to

date were not applicable for exploratory work with the entire

asphalt o Among these methods ares (1) nuclear magnetic resonance; (2) paramagnetic resonance; (3) direct measurement of

the dynamic bulk modulus; (4.) far-infrared analysis, and (5)

mass spectrophotome trie analysis.

1. THERMAL EXPANSION STUDY

Thermal expansion of high molecular weight organic compounds exhibits features quite different from the usual behavior of simple organic compounds. The volume-temperature

curve is characterized by the presence of a temperature, or

a range of temperatures, which separates the curve into two

portions corresponding to markedly different coefficients of

thermal expansion (l).l/ This temperature is known as the

1 /Numbers

paper.

in parentheses refer to references at the end of this
.

.
2

second-order transition temperature 0 As the material is

gradually heated past this temperature, there appears to be

a phase change, without apparent latent heat, resulting in

larger values of the coefficient of thermal expansion and in

changes in physical properties., The material softens and

acquires rubber-like elastic properties ( 2) „ On further

heating the material becomes completely amorphous or liquid

if, meanwhile, it does not decompose 0

L 0 A, Wood and N, Bekkedahl have made studies on unvulcanized rubber and found that this property was time

dependent., When amorphous rubber was maintained at any

constant temperature between -50°C and +209 C, changes in

volume were observed „ The rate of change of the volume

vs 0 temperature curve was somewhat like a probability

curve with a maximum rate near -25°C for unvulcanized

rubber (3)„

The volume change at constant temperature was attributed to crystallization of rubber and had been substantiated

by x-ray diffraction (4), heat capacity (5) 9 light absorption

(6), birefringence (7), and hardness measurements (6) 0 At

temperatures below - 50^0 the tendency of the molecules to

orient themselves is restricted by high viscosity; above

20°C this tendency is opposed by increased molecular motion,,

Jo D 0 Hoffman of the Dielectric Section at the National

Bureau of Standards and others have observed similar behavior

in thermal expansion in materials such as polyethylene and

Kel-Fiy, and have shown crystal-like structures associated

with these compound

s

0 At times volume-change measurements are more sensitive

than x-ray diffraction for detecting structural changes 0 X-ray diffraction methods often require crystal-like particles with more than 50 angstroms path length for detection,,

In the work with structure formation in Kel-F, J„ D„ Hoffman

was able to detect low degrees of crystallinity where x-ray

diffraction patterns showed nothing,,

2/Polychlorotrifluoroethylene

„
. *

.. /
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Many time-dependent properties of coating-grade asphalts

strongly indicate that some structural formation occurs during storage; for example, changes in softening point, degrees

of blister formation, penetration, bulk viscosity (8),

elongation with constant load, etc., have been observed.

If the thermal expansion study of asphalt gives us

positive results, i,e,, a volume-temperature-time relationship, information from' the data will give us our insight

on the proper approach for methods of studying structure

in asphalt.

The amount of time required for this study is dependent

on the time required for the change in physical properties.

Data on viscosity measurement indicated that up to 30 weeks

standing at room temperature are required for some road

asphalts before viscosities reach a steady value (8), In

one coating-grade asphalt, 400 hours elapsed before elongation at constant load approached a steady value (10), A

year's time is a reasonable period for this work, since

specimens must be subjected to various temperatures for

various lengths of time. Once test specimens are prepared,

the work required to gather data would be a matter of a few

minutes each day.

The estimated cost of balance, controlled temperature

bath, and density accessories is $1,200 ( 1957 )°

2, ELASTIC MODULI DETERMINATION BY SONIC METHOD

1 The bu^Lk, shear, and Young's moduli of a material have

always been important properties to be considered by structural engineers and architects. These elastic moduli result

from measuring deformation under compre ssional , shear, and

linear stresses. Sonic methods for determination of elastic

moduli have been used for 18 years and have certain advantages

over static methods. These dynamic moduli are obtained with

minute alternating stresses below the elastic limit of the

material and do not give rise to complex "creep" effects or

elastic hysteresis. Also, these minute stresses in no way

affect the specimen; hence, repeated tests can be made on

the same specimen.

- 4 -

The velocity of sound in a medium is related to the

density and elastic moduli of the material,. It is also

related to the fundamental resonating frequency of sound

waves and dimensions of the material. The apparatus used

for this study measures the fundamental resonant frequency

to determine elastic moduli of a substance. Briefly, vibrations are induced in the specimen by an electromagnetic

driver. At resonance the reinforced amplitude of vibration

is detected by a crystal pickup and, together with an audio

signal of the same frequency, produces a .Lissajou pattern

on an oscilloscope,

Sam Spinner, et, al, 9 determined Young’s modulus of

glasses and concrete (9)» In concrete, correlation between

resonant frequency and both the compre ssional and flexural

strength of the material was found.

Sonic equipment is available at the National Bureau

of Standards for exploratory work in asphalts in the Glass

and Concreting Materials Sections, Although this method

is useful in studies of glass and concrete at room temperature, non-rigid and viscoelastic materials such as coatinggrade asphalts may require different ambient conditions because dimensional stability of the specimen is an important

property for accurate and informative measurements. On the

other hand , this study may lead to interesting and empirical

relationships between apparent elastic moduli and various

physical characteristics of asphalt.

Allowing two months to develop a procedure for determining elastic moduli of asphalts, a minimum of one year

is estimated for comprehensive work on the project. If

the fragments of information gotten in the developmental

state show definite promise, equipment should be bought.

The cost, which includes oscilloscope, amplifier, signal

generator, crystal pickup and frequency counter will be

about $2000,00 (1957 price).

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-

3 . DIFFERENTIAL THERMAL ANALYSIS

In all substances 9 changes in phase and chemical reactions

are accompanied by energy changes which generally manifest themselves as heat energy 0 Some produce, heat and are called

exothermic; some require heat for the change and are called

endpthermic, The phase change which applies to asphalt is

the transition from ’’structured" to "liquid" state 0 Differential thermal analyzer is the apparatus used for detecting

phase change So

The method of Differential Thermal Analysis (DTA) has

reached the prominence of other techniques such as x-ray

diffraction, microscopes,, etc D as a helpful research and

control tool (11) „ This impetus is attributed to rapid

advances in the field of electronics 0 A differential thermal analyzer is composed of three

major components? a sample holder 9 a controlled source of

he at 5 and a device for the measurement of heat generated or

absorbed o Two substances, one inert material, such as aluminum oxide or Nujol, and the other, the specimen, are heated

at a constant rate in a well-designed furnace 0 When the

specimen undergoes a phase change, the analyzer detects the

heat generated or absorbed by measuring the thermocouple

voltages induced by the temperature difference between the

sample and the reference, A difference of one microvolt

can be amplified electronically and recorded automatically,

H„ S„ Kissinger, E„ S, Newman and others of the Constitution and Microstructure and Concreting Materials Sections

of the National Bureau of Standards have made studies on

numerous products such as plasters, alloys, metals, crystals,

and glass (12), Others have made studies on greases and

soaps ( 13 )o

With the advice and assistance of H„ E, Kissinger, a few exploratory runs were made on two asphalts, Midcontinent200 and California-200, Differences were observed in the

differential heating and cooling curves of the two asphalts.

The California-200 heated erratically while Midcontinent-200

heated uniformly when Nujol was used as a reference material.
'

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.

.
o

The asphalts were cast Into glass vials containing a chromelalumel thermocouple,, Allowing sufficient time for cooling,

differential heating and cooling curves were made with Nujol

as the inert reference „ Results indicated that 3 or 4 months

time of intensive investigation in technique would be necessary

before reliable and reproducible results could be made for

e valuation

o

The DTA is available commercially at prices ranging

from $2, GOO to $6 5 OOG (1957 price),,

Evaluation in this work is necessarily empirical unless

each component contributing toward temperature changes is

studied separately „ Manifested In the measurements are

specific heats, latent heat, chemical reaction, heats of

vaporization, conductivity, and various factors such as

sample size, sample geometry, rate of heating, noise level

of amplifiers, stability of potentiometer, etc„ (l6)„

4 0 X-RAY SHADOW MICROSCOPE STUDY

The x-ray microscope study applied to asphalt provides

a direct means of "seeing"8 structure formation if the structure size is large enough and if the structure has x-ray

absorption coefficients different from those of the bulk

of the asphalt e The General Electric shadow microscope operates on the

principle of using a point source of x-rays and casting an

x-ray shadow of the specimen on a fluorescent screen or

camera. The x-ray microscope has the advantage of viewing

thru material opaque to visible light,, Also the specimen

is not subjected to electron beams or vacuum This cannot

be done with, electron microscopes,, In metallurgy, it is

used for identification of Inclusions, study of grain

boundary precipitations, structure study of various layers

of electroplated coatings, etc„ In chemistry, It is used

for structure studies of organic oils and coatings, studies

of film changes due to "weathering’8 , and penetration of dyes

and adhesiveso Magnifications up to .1500 diameters are

possible. This study can be informative and can be made in

conjunction with a thermal expansion study,,

- 7

The Metal Physics Section at the National Bureau of

Standards has recently installed a General Electric x-ray

microscope o It will be used for studies in metals and alloys.

With asphalts 9 thin films can be etched on the surfaces with

ethyl ether or naphtha to observe structures (17)»

Three month's time should be sufficient to develop a technique for observing structures with this method.

The actual cost of services for the use of the x-ray

microscope has not been quoted , because the time required

by skilled technicians for this study is hard to determine,

A reasonable figure would be around $10,00 per photograph,

5, PARTICLE SIZE DETERMINATION BY THE METHOD

OF LOW-ANGLE X-RAY SCATTERING

A low-angle x-ray scattering apparatus is being developed

by A, S, Posner of the Dental Research Section, In principle,

the scattering of x-rays is dependent on the size and shape

of the particles. The smaller the lattice spacing, the larger

is the angle of x-ray scattering. For larger spacing, such

as those of higher molecular weight biological compounds,

the angle of x-ray scattering is of the order of 2 minutes

(18), The magnitudes of these scattered angles in low- angle

x-ray scattering studies is too small to be measured by conventional x-ray diffraction methods.

The intensity spectrum of the scattered x-rays is

mathematically treated to give us information on the size

and shape of the physical structures present in solids or

solutions. By this method structures of different varieties

of carbon and age hardening of alloys have been studied (18),

The instrument is designed to measure particle sizes

of 10 A to 1000 A, The instrument is expected to be completed by Fall 1957,

Unless a few samples of asphalts are subjected to low-angle

x-ray analysis, no evaluation can be made which will tell

whether this method is applicable or not. It has been made

- 8 -

clear that the cost of extended use of this technique 5 which

requires highly skilled technicians for correct interpretation would include considerable overhead „ The actual cost

has not oeen quoted 0

6 0 MOLECULAR WEIGHT DISTRIBUTION STUDY

In this study, substances in dilute solution are placed

in an uliracentrifuge at 65 9 000 rpm 0 The materials in solution will distribute themselves along the radius of rotation

according to their particle weight,. Optical means 9 such as

light transmission and index of refraction are used for

measuring the extent of sedimentation,, For a monodisperse

substance 9 a sharp boundary is found in the solution-solvent

system., while a diffuse boundary indicates the presence of

a polydisperse substance „ The molecular weight or particle

weight can be determined by the rate of shift of the boundary

and the distribution curve of the molecular weight can be

found from its diffuseness (l4) 0 In a complex system such as asphalt where countless

numbers of compounds are present 9 a proper procedure for

measuring "'structure"’ is difficult to fore see 0 In order to apply this technique to structural determination of whole asphalt , it must first be established

that "structured" asphalt is not adversely affected when

it is dispersed in a solvent,,

S 0 G 0 Weissbergj who has done work on plasma volume

expanders and polystyrene 9 recommends study of a more

simplified fraction of asphalt 9 rather than the total

asphalt, to greatly reduce the task in establishing a proper

procedure and to improve the chances of getting correct and

positive result So

The time and cost required in this study are very difficult to estimate o Many variables such as viscosities, concentration, solvent interaction, particle shape, stability of

"structured" asphalt in dispersion, etc B

9

must be considered

and accounted for 0 The equipment necessary is subject to

these variable So
, *

'
- 9

-

This study should be considered a long-term project

even in the developmental state 9 because the method is

tedious and time -consuming » Furthermore 9 development in

technique has not reached a point where accurate and reliable

results are obtainable with any assurance 0

7o DIELECTRIC STUDY

A compound is said to have dielectric properties when

the center of negative charges does not coincide with the

center of positive charges 0 The extent of displacement of

the charges is manifested in the dielectric constant and

measured almost entirely by the ratio of capacity of a

condensor with and without the medium,, The dielectric constants of almost all petroleum products are in the range of

values 2 o 0 to 2,9 (15) » Many factors cause changes in the

dielectric constant 9 one of which is a structural formation,,

Information on dielectric changes would be desirable

in any study of changes in physical structure „ Unfortunately 9 the precision of the measurement on relatively non-polar

materials is limited and small changes are difficult to

detect and reproduce „ Dimensional stability is another

desirable feature in accurate dielectric studies,,

Literature study and consultation with experts indicated that considerable development in technique and instrumentation is needed to interpret the results obtained

for such a complex and non-polar material as asphalt

„

Both on a theoretical and practical basis 9 dielectric

studies should be considered a long-term project,, From a theoretical standpoint 9 the opinion is that there would be

very little change in dielectric properties of asphalts,,

Mathematical relationships between dielectric constant and

index of refraction, polarization, etc„ 9 indicate that the

effect of the change in the index of refraction on the dielectric constant of asphalt would be so overwhelming that

it would mask the changes contributed by structure s„

Estimate of cost and time involved cannot be determined

unless a few exploratory runs are made on asphalts,,
>*

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8 0 ELECTRON MICROSCOPE STUDY

When a particle to be observed under a microscope is

of the order of the wave length of the light waves used for

observation^, considerable loss in resolution and intensity

(due to diffraction and reflection) of the image is experienced, In the electron microscope a beam of electrons is

focused on the sample and either the scattered rays or the

passing beam of electrons is focused on the image screen.

Magnification up to ^ 0^000 diameters or higher is possible

with this instrument. It is with this instrument that larger

molecules have been first observed.

There are two objectionable features when asphalt is

observed with this instrument. The specimen must be stable

to electron bombardment and thin sections of asphalts at

very high vacuum must be used. If the material is unstable

under these conditions 9 considerable work in the development

of technique and in the maintenance of the expensive instrument is to be expected.

Estimate of cost and time involved cannot be determined

unless a few exploratory runs are made on asphalt,

9, METHOD OF INFRARED ANALYSIS

Infrared absorption spectra have long been recognized as

a convenient means for studying the structure of organic

molecules. The interpretations of the spectra are based

on the energy interactions of the molecule and the Infrared

radiation. This radiation gives rise to vibrations of the

constituent atoms and molecular rotations. For simple or

highly symmetrical molecules^ the determination of the normal

modes of vibration (in effect^ the normal modes of vibrations

are the varieties of vibration possible without affecting

the position of the center of mass of the molecules) and the

calculation of the absorption frequency are relatively simple

and straightforward. For more complicated organic compounds

the computations become increasingly difficult because with

each additional atom the normal modes of vibration are increased by three. However 9 some useful information can be

gotten by empirically comparing the spectra with those obtained for simpler compounds with known structure.
.
- 11

The study of structural formation is best accomplished

by observing the changes in the absorption spectrum of either

thin films or KBr pelleted samples of powdered asphalt * The

interpretation of these changes must be substantiated by controlled and comparative methods.,

The Building Technology Division will have the use of

an infrared spectrophotometer in the near future 0 This

spectrophotometer is a dual-beam, automatic-recording type

in the range 2-15 microns 0 Three month's time should be sufficient to develop a technique for this study* If the results are positive, this

study may develop into a new method of measuring different

types of structural formation in asphalts*

The cost of equipment will be merely the cost of

accessories such as KBr powder, specimen die, NaCl cells,

etc*, which are necessary for almost all infrared study.

The cost will be about $500,00*

12

10 o REFERENCES

(1) Ro F 0 Boyer and R 0 S 0 Spencer, J, Applied Phys, 1£, 398,

(1944),

(2) 0 o S 0 Parks, et 0 al D , Physics 193 9 (1934)„

(3) Bo A 0 Wood and N 0 Bekkedahl, J, Applied Phys 0 17 0 362,

(1946)o

(4) S 0 Do Gehman, "The Contribution of X-Ray Research to

Knowledge of Rubber", Chem 0 Rev 0 26, 203, (1940) o

(5) NX Bekkedahl and H 0 Matheson, n Heat Capacity, Entropy,

and Free Energy of Rubber Hydrocarbon”, Rubber Cherru

Techo 2s 264, ( 1936)0

(6) Ao van Rossem and J Q Lotichius, "The Freezing of Raw

Rubber”, Kautschuk J2 , 2, (1929)°

(7) Wo H. Smith and C 0 P, Saylor, "Optical and Dimensional

Changes Which Accompany the Freezing and Melting of Hevea

Rubber”, Rubber Chem 0 Techo 12, 18, (1939)=

(8) Van Ort, "Asphalt Aging in Dark", Ind 0 Eng, ChemQ 49

»

1197 (1956)o

(9) So Spinner, "Elastic Moduli of Glasses by a Dynamic

Method", Jo Am 0 Ceramic Soc 0 229 (1954),

(10) Ao Bo Brown, J 0 WD Sparks, and F, M Q Smith, "Stearic

Hardening of Asphalts", Paper presented before A 0 C,S 0 Symposium on Bituminous Materials at Dallas, Texas

(1956)o To be published in Proceedings A 0 A 0 PoT 0 (1957)o

(11) Jo A 0 Pask, "Differential Thermal Analysis Methods and

Techniques", Bull, Amer, Cer, Soc, 168 (1954)o

(12) L 0 So Wells, et 0 al, , "Investigation of Failures of

White-Coat Plaster", N 0 B 0 S 0 Building Materials and

Structures Report 121 (1951)°
*'

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(13) Mo Jo Void ? et 0 al 0? "Phase State and Thermal Transitions

of Greases" 5 Ind „ Engo Chem, 4,1, 2539 (1949)

(14) R 0 Houwink, "Elastomers and Elastomer s", Elsevier's

Polymer Series, 452 (1950)° Published by Elsevier

Book Company, New York,

(15) A o A 0 Maryott and E„ R 0 Smith, "Table of Dielectric

Constants of Pure Liquids", N o B 0 S o Circular 514 (1951)°

(lb) Ro Co Mackenzie and K 0 R 0 Farquharson, "Standardisation

of Differential Thermal Analysis Technique", C 0 R 0 XIX

Session Congr 0 Geolo Into (Alger), 18, 183-200 (1952)o

(17) H° No Traxler and C Q E 0 Coombs, "Development of Internal

Structure in Asphalts with Time", ASTM Proceedings, Vol 0 Part II, 549 (1937)°

(18) A, Guinier and G, Fournet, "Small-Angle Scattering

of X-Rays", Published by -John Wiley and Sons, Inc 0 , (1955)°
'
U. S. DEPARTMENT OF COMMERCE

Sinclair \\ <-< ks. Secretary

NATIONAL BUREAU Ol STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its headquarters in Washington,

D. C., and its major field laboratories in Boulder, Colorado, is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section carries out spe- cialized research, development, and engineering in the field indicated by its title. A brief

description of the activities, and of the resultant reports and publications, appears on the

inside front cover of this report.

WASHINGTON, D. C.

Electricity and Electronics. Resistance and Reactance. Electron Tubes. Electrical Instruments. Magnetic Measurements. Dielectrics. Engineering Electronics. Electronic Instrumentation.

Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

Technology. Length. Engineering Metrology.

Heat and Power. Temperature Physics. Thermodynamics. Cryogenic Physics. Rheology

and Lubrication, Engine Fuels.

Atomic and Radiation Physics. Spectroscopy. Radiometry. Mass Spectrometry. Solid State Physics. Electron Physics. Atomic Physics. Nuclear Physics. Radioactivity. X-rays. Betatron. Nucleonic Instrumentation. Radiological Equipment. AEC Radiation Instruments,

Chemistry. Organic Coatings. Surface Chemistry. Organic Chemistry. Analytical Chemistry.

Inorganic Chemistry. Electrodeposition. Gas Chemistry. Physical Chemistry. Thermochemistry. Spectrochemistry. Pure Substances.

Mechanics. Sound. Mechanical Instruments. Fluid Mechanics. Engineering Mechanics.

Mass and Scale. Capacity, Density, and Fluid Meters. Combustion Controls.

Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure. Organic Plastics. Dental Research.

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion.

Metal Physics.

Mineral Products. Engineering Ceramics. Glass. Refractories. Enameled Metals. Concreting

Materials. Constitution and Microstructure

Building Technology, Structural Engineering i* ire Protection. Heating and Air Conditioning. Floor, Roof, and Wail Coverings. Codes and Specifications.

Applied Mathematics. Numerical Analysis Computation. Statistical Engineering Mathematical Physics.

Data Processing Systems. SEAC Engineering Croup. Components and Techniques. Digital

Circuitry. Digital Systems. Analogue Systems. Application Engineering.

e Office of Basic Instrumentation * Office ol Weights and Measures

BOULDER, COLORADO

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials.

Gas Liquefaction.

Radio Propagation Physics. Upper Atmosphere Research. Ionospheric Research. Regular

Propagation Services. Sun-Earth Relationships.

Radio Propagation Engineering, Data Reduction Instrumentation. Modulation Systems.

Navigation Systems. Radio Noise. Tropospheric Measurements. Tropospheric Analysis. Radio

Systems Application Engineering.

Radio Standards. Radio Frequencies. Microwave Frequencies. High Frequency Electrical

Standards. Radio Broadcast Service. High Frequency Impedance Standards. Calibration

Center. Microwave Physics. Microwave Circuit Standards.