x>ureau or standards

:ary, N.W. Bldg

4 1965

lACICICiiuc uuurx HUl iu uv/

taken from the library.

NBS

ecknical ^lote 273

ANALYSIS AND PURIFICATION SECTION:

SUMMARY OF ACTIVITIES

JULY 1964 TO JUNE 1965

EDITED BY JOHN K. TAYLOR

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NATIONAL BUREAU OF STANDARDS

Technical Note 273

ISSUED OCTOBER 1, 1965

ANALYSIS AND PURIFICATION SECTION:

SUMMARY OF ACTIVITIES

JULY 1964 TO JUNE 1965

Edited by John K. Taylor

Analysis and Purification Section

Analytical Chemistry Division

Institute for Materials Research

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, Government Printing Office

Washington, D.C., 20402 - Price 50 cents
FOREWORD

The Analytical Chemistry Division was established as a separate division at the National Bureau

of Standards on September 1, 1963* and became part

of the Institute for Materials Research in the

February 1, 1964, reorganization. It consists at

present of seven sections and about 85 technical

personnel encompassing some 30 different analytical

competences from activation analysis and atomic

absorption to vacuum fusion and x-ray spectroscopy.

These competences, and in turn the sections which

they comprise, are charged with research at the

forefront of analysis as well as awareness of the

practical sample, be it standard reference material

or service analysis. In addition, it is their

responsibility to inform others of their efforts.

Formal publication in scientific periodicals

is highly important, m addition, however, it has

been my experience that informal, annual summaries

of progress describing efforts of the past year can

be very valuable in disseminating information. At

the National Bureau of Standards, such publications

fit logically into the category of Technical Note.

In 1965 we plan to issue these summaries for all of

our sections. The following is the first annual

report on progress of the Analysis and Purification

Section.

W. Wayne Meinke, Chief

Analytical Chemistry Division

ii
PREFACE

The Analysis and Purification Section of the Analytical

Chemistry Division is engaged in two distinct yet complementary program areas.. The first consists of research in six

competence areas of analytical chemistry; namely, mass spectrometry gas analysis, polarography, coulometry, microchemistry,

stoichiometry, and cryoscopy. The second encompasses projects

in purification of research materials and may be classified

as follows: distillation, ultrapure reagents, light-element

purification, and other techniques.

In support of the scientific philosophy of the Analytical

Chemistry Division, the section's total program has two objectives: (1) to provide analytical measurements of the highest

reliability to the various research programs of the National

Bureau of Standards and to the Standard Reference Materials

Program, and (2) to develop new and improved methods of

chemical analysis applicable to wide areas of materials

research. The purification projects contribute directly to

materials research by providing research materials for use

by other investigators at NBS. At the same time, improved

methods of purification are actively investigated.

This first annual summary primarily describes activities

undertaken or completed during the period July 1, 1964, to

June 30, 1965. Because this is an initial report, the research

facilities of the section are described briefly to indicate

its research and service capability. In addition, summaries

of recent accomplishments of several programs are included

where they will provide background material to illustrate the

scope of the programs.

In order to specify adequately the procedures, it has

been necessary occasionally to identify commercial materials

and equipment in this report. In no case does such identification imply recommendation or endorsement by the National

Bureau of Standards, nor does it imply that the material or

equipment identified is necessarily the best available for

the purpose.

John K. Taylor, Chief

Analysis and Purification Section

iii
TABLE OF CONTENTS

1. ANALYTICAL PROGRAMS

PAGE

Mass Spectrometric Gas Analysis . 1

Instrumentation , o » « 1

Research and Development .«••••.••• 6

Analyses 7

Polarographic Analysis „...<, 8

Introduction . „ c 8

Facilities . 8

Research and Development 9

Coulometric Analysis 14

Introduction 14

Facilities 14

Research Activities ••••••••••., 16

Analysis of Samples 18

Microchemical Analysis 20

Scope and Program <,„.... 20

Facilities . . . . «... 20

Analytical Activities 22

Stoichiometry ..» „ 25

Introduction e 25

Research and Development . . . e 25

Cryoscopic Analysis 29

Introduction ..» 29

Thermometric Cryometry 29

Calorimetry ...... c 31

Supporting Services .„.,... 35

iv
PAGE

2. PURIFICATION PROGRAMS . . . • 36

Distillation 36

Introduction „ 36

Facilities . „ 36

Research and Development . 43

Purification Activities ........... 44

Ultrapure Reagents 45

Scope 45

Facilities . . . 45

Research and Development ..... 46

Preparation of Specific Reagents 46

Use of Ultrapure Reagents 50

Light -Element Purification ..... 51

Scope 51

Facilities 51

Evaluation of Performance 64

Other Purification Techniques ..••••••• 68

3. PERSONNEL AND ACTIVITIES 69

Personnel Listing ..... 69

Publications <».... 70

Talks 71

Committee Activities ....... 72

4. REFERENCES . 73
LIST OF FIGURES

FIGURE NO. PAGE

1. Analytical mass spectrometer 1

2. Schematic diagram of inlet system 2

3. Septum holder for direct injection of liquid

samples 3

4. Device with furnace for introduction of solid

and liquid samples of low volatility 3

5. Device for introduction of samples contained

in ampoules and sealed tubes 4

6. Block for direct connection to gas cylinder and

for samples in glass tubes and ampoules .... 5

7. General view of polarographic laboratory 9

8. Equipment used in constant -current coulometric

titrations 15

9. Coulometric cell and associated equipment .... 15

10. Apparatus for transfer of samples for coulometric

analysis 17

11. General view of microchemical laboratory 21

12. Microcell for e lee trogravime trie determination

of copper 27

13. Thermometric cryometer 30

14. Adiabatic calorimeter for volatile materials ... 32

15. Calorimeter vessel attached to vacuum system ... 33

16. Temperature controls and measurement station

for adiabatic calorimeter 34

17. Small still equipment in the distillation

laboratory 38

18. Three -meter packed stills 38

19. Automatic pressure regulator 39

vi
LIST OF FIGURES (CONT'D)

FIGURE NO. PAGE

20. Details of vaporizer for still 40

21. Rotating fraction collector .... 4l

22. Sliding fraction collector 42

23. Efficiencies of packed still columns ....... 43

24. Stills used for preparation of ultrapure

reagents ..... 47

25. Extractor for purification of silica gel 49

26. Quartz container for dispensing purified

reagents 50

27. Physical arrangement of the major facilities

for light-element purification 52

28. Three -compartmental assembly for high-temperature

experiments with toxic materials 53

29. Cabinet area of assembly for low-temperature

trap, absorption tube, and fore -pump 54

30. Three-zone furnace, automatically controlled,

for high-temperature phase separations 55

31. Front and back views of electronic units for

automatically controlling and recording

temperatures in the three-zone furnace 56

32. Controlled -atmosphere glove box 58

33. Phase purification and thermal analysis cell ... 59

34. Assembled cell for use at 1000°C in phase

purification 60

35. Disassembled cell for use at 1000°C in phase

purification 61

36. Rupture-disk ampoule 62

37. Manifold used to fill rupture -disk ampoule .... 63

38. Platinum-lined Morey pressure bomb and parts ... 64

vii
ANALYSIS AND PURIFICATION SECTION: SUMMARY OF ACTIVITIES

JULY 1964 TO JUNE 1965

Edited by John K. Taylor

ABSTRACT

This report describes the scientific programs and

research activities of the Analysis and Purification Section

of the Analytical Chemistry Division of the NBS Institute

for Materials Research. Analytical research areas include:

gas analysis by mass spectrometry, polarography, coulometry,

microchemistry, stoichiometry, and cryoscopy. Research in

methods of purification is concerned with distillation, hightemperature phase separations, and the ultra purification of

chemical reagents. The facilities and general objectives of

all programs are discussed. Research accomplishments described

in some detail include: modification of mass spectrometer

inlet systems to facilitate analytical sampling, polarographic

analysis of lead alloys, coulometric calibration of microvolumetric apparatus, precise analysis of copper in small

samples, development of apparatus for the purification of

inorganic fluorides by high-temperature phase separations,

and development of an adiabatic calorimeter for determination

of purity of volatile substances.

viii
1 # ANALYTICAL PROGRAMS

A. Mass Spectrometric Gas Analysis

The major interest in this laboratory is in the development

and application of methods of gas analysis utilizing the mass

spectrometer. Other instruments are available for use in conjunction with, or independent of, the mass spectrometer. The

basic mass spectrometer has been extensively modified to facilitate the gas analysis function.

1. Instrumentation

The mass spectrometer most often used (see figure 1) is a

Consolidated Electrodynamics Corporation Model 21-103C. This

is a 180° magnetically focused instrument with electrostatic

scanning. It is designed for the analysis of gases and highly

volatile liquids, but the addition of a heated inlet system

allows the analysis of less volatile liquids and solids. Samples of widely ranging chemical types and in any physical form

are submitted for analysis. This variety of sample type as well

as the variety of sample containers requires a sample handling

2 q.

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Figure 2, Schematic diagram of inlet system,

inlet system of considerable versatility. The original system

has, therefore, been extensively modified to facilitate the

analysis of all samples. A schematic diagram of the inlet

system showing the arrangement of valves and inlet ports is

shown in figure 2. Liquid samples of low volatility can be

injected directly with a hypodermic syringe through the septum

holder shown in figure 3* which is attached at (c) in figure 2.

This holder was machined from a commercially available 12/30

taper, stainless steel outer joint. The threaded end was turned

flat after the threads were cut to provide a seat for the rubber

septum. The cap was machined from 3/^ inch stainless stock and

can easily be finger tightened to provide adequate sealing. A

furnace (see figure 4) is used to heat the entire assembly when

samples of low volatility are injected. The furnace was built

from a short length of brass tubing covered with glass cloth.

The nichrome windings are held in place by a layer of asbestos.

The thermocouple allows the temperature to be measured and

adjusted to a value approximately that of the inlet system.
FURNACE

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Figure 4. Device with furnace for introduction of solid and

liquid samples of low volatility.
Samples of high viscosity and solid samples are admitted

to the inlet system by the device shown in figures 4 and 5.

Samples are placed in short lengths of capillary tubing and

are then placed in the cool end of the glass tube. The tube

is evacuated. The sample in the capillary tube is then moved

forward with the magnet into the portion of the tube heated by

the furnace where it i's vaporized. In some cases, it may be

desirable to seal the sample in a tube before evacuating to

prevent loss of volatile components. These sealed capillaries

are placed in short lengths of clean 1/4 inch copper tubing

(figure 5A) which are attached to the inlet system at the

stainless steel block shown in figure 6. This block is attached

to the inlet system at (a). The copper tube containing the

sealed capillary is evacuated after which the capillary is

broken by bending the copper tubing. Ampoules or other large

glass containers are treated in a similar manner using the

device shown in figure 5B. Larger diameter tubing is connected

to 1/4 inch tubing with reducing unions using either hard or

soft solder. The sample tubes are broken by gently squeezing

the large diameter tubing with a small C -clamp.

^

1/4" CONNECTION

1/4" COPPER TUBING

SEALED GLASS SAMPLE TUBES

B.

Figure 5. Device for introduction of samples contained in

ampoules and sealed tubes.
TO MANOMETER AND

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STAINLESS SCREEN

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CONNECTOR

12/3 STAINLESS

SOCKET

12/30 STAINLESS

TAPER

TO SPECTROMETER

Figure 6. Block for direct connection to gas cylinder and

for samples in glass tubes and ampoules.

Gases contained in flasks equipped with stopcocks or

breakseals are attached to the inlet at (c) of figure 2. Those

contained in lecture bottles or larger cylinders are attached

to the 0-seal connector of the stainless steel block shown in

figure 6. Metal tubing is used for connecting cylinders to the

system and the entire system can be evacuated as far as the

cylinder valve. The manometer allows the measurement of sample

pressure when the pressure is below one atmosphere. The mercury

bubbler allows a slow flow of gas through this portion of the

system thus eliminating contamination from small atmospheric

leaks.

The outlet from the column of a gas chromatograph is connected to the inlet system at (b). Suitable valving has been

provided to allow the condensation of compounds separated

chromatographically for subsequent vaporization and admission

to the inlet system.
A high -capacity mechanical vacuum pump has been connected

to the inlet at (b) to allow very rapid pump-down of the inlet

system and reservoir. In addition, it prevents excess contamination of the inlet diffusion pump, thus reducing the number

of periodic shutdowns for pump cleaning. Also, the pump serves

as a ready source of vacuum for the operation of a McLeod gage

connected at (c) of figure 2. This gage is used to extend the

range of pressure measurement in the reservoir from 0-500 \i to

to 0-10 mm.

The original vacuum system used to exhaust the ionization

region consisted of a two-stage mercury diffusion pump with

associated cold traps. This was replaced with a 15 1/s ion

pump which resulted in a considerable saving in maintenance

time and expenditures for refrigerants.

The original two -stage mercury pump is now used in parallel

with the ion pump for the analysis of rare gases and in research

on high-pressure mass spectrometry, both cases where the ion

pump is inadequate. In addition, the availability of a second

pumping system which can be activated in a short time has considerably decreased time lost during certain maintenance operations.

Minor changes in the electronics have been made to facilitate analyses. The only major change is the addition of a circuit to control and measure the ionization potential in the

region from about 7 volts to 40 volts. The original available

range of ionization potentials was from 50 volts to 100 volts.

The circuit added is essentially that reported by H. E. Lumpkin

[1] with minor changes.

In addition to the mass spectrometer, there is other equipment available for specialized gas analysis problems. An

apparatus has been constructed for the accurate preparation of

gas mixtures at pressures ranging from below one atmosphere to

over a hundred atmospheres and. with concentration of components

as low as a part per million. These mixtures are used within

the laboratory in research on analytical methods and for calibrating gas analysis instruments. Preparation of gas mixtures

for other groups has been undertaken when such mixtures have

not been readily available elsewhere.

2. Research and Development

The current research is concerned with a method of highpressure mass spectrometry which will allow the determination

of trace quantities (<0.01 mole percent) of components in

gas mixtures.
At present it is necessary to concentrate impurities by

physical methods if they are present at concentrations below

the 0.01 mole percent level. This procedure is not only timeconsuming, but because of the nature of the treatment, it

introduces the possibility of seriously altering the composition of the sample.

The method under investigation consists of using sample

pressures as much as two orders of magnitude greater than in

normal routine operations. An evaluation is in progress of the

change in nature of the spectra obtained at the higher pressures

and of the effect of the changes on analytical problems.

The technique has been experimentally applied to several

service problems with encouraging results, and it is expected

that the technique will soon be applicable on a routine basis

to any analysis requiring the detection of trace quantities of

gases.

3. Analyses

In general, the major effort of the group concerns the

qualitative and quantitative analysis of gas mixtures. These

mixtures may range in complexity from relatively pure gases

with one or two minor components to mixtures as complicated as

pyrolysis products containing dozens of components. Simple

mixtures with components at concentrations above 0.01 mole percent are quickly and easily analyzed. More complex mixtures

with the same concentrations can be analyzed by employing

specialized techniques such as fractional distillation, preseparation by gas chromatography, and low ionization potential.

Requests for isotope abundance measurements are quite

frequent. While the mass spectrometer employed here is not

specifically designed for isotope-ratio measurements, such

measurements can be done quickly and easily for a number of

elements. The elements hydrogen, helium, boron, carbon,

nitrogen, oxygen, and chlorine and their isotopes have been

studied. Gas mixtures can be prepared and analyzed for components present at concentrations greater than 0.01 mole percent.

(E. E. Hughes and w. D. Dorko)
B. Polarographlc Analysis

1. Introduction

Polarographlc measurement Is one of the most versatile

analytical techniques that has appeared In the last 40 years.

In principle, any material that is capable of electro-oxidation

or -reduction and that can be dissolved in an aqueous or

partially aqueous solvent can be polarographically determined.

In many cases, the electrode process is sufficiently selective

to tolerate the presence of constituents that would interfere

in less selective methods. Otherwise, conventional separation

techniques may be employed prior to the polarographlc measurement. The high sensitivity of polarography when coupled with

preconcentration procedures makes possible determinations at

the nanogram level.

2. Facilities

The laboratory is we 11 -equipped with both conventional and

modified polarographlc equipment.

Instruments covering the conventional range of polarography;

namely, 10 "^ to 10~-> M, are the Sargent Model XXI and the

Sargent Model XV polarographs . The latter has accessory equipment consisting of a linear residual -current compensator and

microrange extender to increase current sensitivity. The Oak

Ridge Model Q1988A controlled potential and derivative polaroscan, shown in figure 7(b), lowers the sensitivity limit to at

least 10"D

M. The controlled -potential mode of operation

overcomes dTfficulties caused by large cell resistance; the

derivative network allows increased resolution between closely

occurring reductions.

The Sargent fast-sweep polarograph, shown in figure 7(c), for use with the hanging-drop electrode, further lowers the

sensitivity limit to 10~9 m. By plating for a definite length

of time into the very smalT volume of a mercury drop, a considerable concentration enhancement may be achieved. The current

may then be measured as the reduced material is anodically

stripped, resulting in significantly increased sensitivity.

qhnm^

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vls differential Cathode -Ray Polarotrace Model Al66o, shown in figure 7(a , possesses normal, derivative, comparative

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tions down to 5xl0~8 M may be determined, preceding reductions

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be ^ierated, aid peaks differing by 40 mV may be resolved, m the twin cell mode of operation and by use of accurately known standards? precis^n I

8
Figure 7. General view of polarographic laboratory.

of 5 parts In 10,000 may be obtained, which represents a 50-

to 100 -fold increase in precision over that obtainable by conventional polarography. By use of the reverse sweep, an

amalgam electrode is formed during a 5-second delay period,

which is then subjected to anodic stripping during the 2-second

reverse voltage scan. This mode of operation permits the deter^

mination of reversibly reduced constituents in the presence of

an irreversible reduction at the same peak potential.

3. Research and Development

Polarography has been especially suitable for a number of

analyses connected with the certification of standard reference

materials and with the analytical sample responsibilities of

the section. In some cases, methods already reported in the

literature were useful with few modifications, while in others,

major development was necessary/ Examples are mentioned only

briefly. However, upon request, the section would be glad to

furnish full details of all methods used or developed.

a. Standard Reference Materials . Polarographic

methods for the determination of a number of elements in standard reference materials have proved highly advantageous, in

particular for the analyses of cartridge brass standards for

cadmium and tellurium and of white cast iron standards for

lead, bismuth, and tellurium.
Cadmium was determined in approximately 1-gram brass samples in 0.1 N hydrochloric acid supporting electrolyte after

removal of arsenic, tin, antimony, and copper by fuming with

a hydrobromic acid -bromine mixture and electrolysis.

Lead and bismuth in the white cast irons were easily determined simultaneously by a method originally developed by

Rooney [2], Most of the iron was removed by an isobutyl acetate

extraction of 1/5 or 2/5 aliquot s of a hydrochloric acid solution of a 1-gram sample. After evaporation of the aqueous

layer to dryness and dissolution of the residue in dilute

hydrochloric acid, the residual iron was reduced with hydrazine

hydrochloride. Ammonium hydroxide, sodium tartrate, and

potassium cyanide were added, and lead and bismuth were extracted

as the carbamate complexes with chloroform. The extracts were

evaporated to dryness, and organic material was destroyed by

evaporation with nitric and perchloric acids. The residue was

dissolved in a supporting electrolyte of dilute nitric acid and

sodium tartrate at a final pH of 4.5.

The determination of trace or greater amounts of tellurium

in cartridge brass and white cast iron was conveniently done

by cathode-ray polarography. Tellurium is separated from the

cartridge brass by ammonium hydroxide precipitation using an

iron carrier and determined with a cathode-ray polarograph in

1.5 M phosphoric acid. The results by forward scan are linear

between about o 05 and 0.7 to 1 ppm of tellurium in the final

solution. Above this range, nonlinear peak currents are obtained, but by use of the reverse-scan mode of operation, the

region of linearity may be extended to about 5 ppm. Tellurium

is separated from the white cast irons by precipitation with

sulfur dioxide using a selenium carrier and determined with a cathode-ray polarograph in 1.5 M phosphoric acid.

This work was described in a talk presented at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy

March 1, 1965^ and is being submitted for publication.

Antimony was also determined in the cast irons; however,

the results obtained were not as satisfactory. The method of

determination depended upon the amounts of antimony present.

If the antimony content was greater than 0.1 percent, an aliquot equivalent to 100 mg of sample was reduced polarographically in a perchloric acid -hydrochloric acid supporting

electrolyte after reduction of iron with ascorbic acid. Antimony

in concentrations which were less than 0.1 percent was converted

to the pentavalent state and extracted from a hydrochloric

citric -oxalic acid solution with ethyl acetate. After destruction of the organic material, antimony was reduced with sulfur

10
dioxide and determined in a sulfuric -hydrochloric acid supporting electrolyte. Although the precision of the results is

generally good, further modification of the procedure is needed

to increase the accuracy. A systematic study of methods of

separation and investigation of other sources of error would

undoubtedly result in an improved method. Among the possible

sources of error are: incomplete antimony recovery of the

large residues from some of the samples; loss of antimony

through volatility; incomplete reduction of antimony to the

trivalent state and incomplete oxidation to the pentavalent

state at various steps of the procedure where it is required

to be in a given oxidation state; and incomplete separation of

antimony from some of the alloying elements of the cast iron.

b. Lead -Base Alloys . Nuclear magnetic resonance

studies made by the NBS Metallurgy Division of alloys of

lead with bismuth, indium, thallium, or cadmium to obtain

information of their electronic structure necessitated the

development of simple yet rapid methods for the chemical analysis of these materials, preferably requiring no prior separations. In general, 0.1 to 0.2 g samples were used for the

analysis of the lead alloys. Smaller samples would have been

adequate except for possible sample inhomogeneity.

In a series of lead -thallium alloys, the thallium composition varied from 1 to 76 percent. In some cases, both the lead

and thallium content was needed as an indication of oxidation

of the alloy. It was possible to determine both constituents

directly in a 1 M potassium hydroxide supporting electrolyte

measuring the thallium peak at -0.4 V and the lead peak at

-0.7 V. The lead -bismuth alloys, ranging from 1 to 21 percent

of bismuth, were analyzed in a sodium tartrate supporting

electrolyte whose pH had been adjusted to 4.4. Lead could also

be determined simultaneously if necessary.

For the determination of about 2 percent cadmium in a

lead-cadmium alloy, lead was precipitated as sulfate, and aliquots taken from this solution were measured polarographically

in an ammonia -ammonium sulfate supporting electrolyte.

The lead -indium alloys contained from about 0.005 to

23 percent indium. In these, lead was precipitated as sulfate,

but not removed by filtration since its presence as sulfate

did not interfere in the subsequent polarography of indium.

The indium was determined in a supporting electrolyte which was

0.9 M in sulfuric acid and 1 M in potassium chloride. Both

bismuth and indium could be determined simultaneously, in a

similar way, in a ternary alloy containing about 1.2 percent

bismuth and 0.7 percent indium. Bismuth was reduced at -0.1 V

and indium at -0.7 V in a supporting electrolyte which was

0.9 M in sulfuric acid and 0.1 M in potassium chloride.

11
c. Miscellaneous . The rapidity of many polarographic determinations nas resulted in the quick solution of

many analytical problems encountered as a part of the analytical sample responsibilities of the section. Determinations

of cadmium in several p -glucoheptonate cadmium bromide or

chloride salts were made in a total elapsed time of approximately 10 minutes. The samples were dissolved in 0.1 N

hydrochloric acid and measured polarographically at -077 V.

Cadmium was also easily determined in some cadmium

chloride/potassium chloride-fused salts in a potassium chloride supporting electrolyte. The fused mixtures ranged in

composition from 45 to 59 percent cadmium.

The synthesis of some metal organic phenanthroline compounds by the NBS Inorganic Materials Division in order to

study their structure and properties required the determination of copper and zinc as well as carbon, hydrogen, and

nitrogen. Generally, only a few milligrams of sample were

available for all the determinations. Copper and zinc were

easily measured simultaneously in an ammonium hydroxide/ammonium chloride supporting electrolyte.

Lead was determined simply and quickly in samples of tin

pipe to be used for distilled water lines at the new Gaithersburg facilities. After dissolution and volatilization of the

tin with hydrobromic acid and bromine, lead was determined in

0.1 M hydrochloric acid.

The mother liquor remaining after growth of ammonium dihydrogen phosphate single crystals was submitted for determination of trace amounts of arsenic. After reduction of As(v) to

As (III) with hydrazine sulfate, arsenic was measured polarographically at -0.9 V in 1 N sulfuric acid. The polarographic

sensitivity of this method Ts about 0.01 ppm in the final

solution, corresponding to a limit of detection of 1 ppm in

the 5 -ml sample available for analysis.

At the request of the Bureau of Sport Fisheries and

Wildlife, periodic analyses were made of copper and zinc in

the local water supply to evaluate its suitability for use in

the proposed National Aquarium. One hundred to 500-ml samples

were filtered, the organic material in the water destroyed by

acid treatment, and evaporated to dryness. The residues were

dissolved in dilute hydrochloric acid and the solutions made

ammoniacal. Copper and zinc were determined simultaneously

on the cathode -ray polarograph from peaks appearing at -0.4 V

and -1.2 V, respectively. By use of the sample sizes indicated,

the method was applicable down to at least 5 ppb of copper and

zinc.

12
A program of the NBS Metallurgy Division on defects

and dislocations in metal single crystals required the determination of aluminum present in high-purity tin. The method

used was similar to one developed by Rooney [3] for the determination of aluminum in cast irons. The tin matrix, which

would interfere with the subsequent steps, was easily eliminated by evaporation with hydrobromic acid and bromine. When

heated with the diorthohydroxyazo dye, Solochrome Violet RS,

at a pH of 4.5 in a sodium acetate buffer, aluminum forms a

complex which is readily reduced polarographically. Investigation of the sensitivity under these conditions showed that

a linear calibration curve for aluminum could be obtained down

to a final concentration of at least 0.02 ppm in the solutions

measured. If a 1-ml final volume is used, this would represent

20 nanograms of aluminum. At these low concentrations, however, the aluminum blank derived from containers, the atmosphere,

and the reagents used was found to be of the order of 0.015 ppm.

Container blanks were minimized by the use of quartz and polyethylene. The use of redistilled bromine and hydrobromic acid

resulted in no significant lowering of the 0.005 ppm blank from

this source. The aluminum content of the high-purity tin

samples had been expected to be in the 10 -ppm range, but by use

of this method, was found to be less than 0.2 ppm.

Investigation by the Harry Diamond Laboratories of the

resistivity of some thin films of antimony and bismuth for

possible applications such as electronic components required

the analysis of very small samples. The films were formed by

the evaporation of mixed powders in vacuum onto a coated glass

plate. Since in some cases only as much as 0.3 mg of film was

available for analysis, it seemed advisable to determine both

the antimony and bismuth simultaneously if a supporting electrolyte could be found which would give well-defined waves for

both. Investigation of conditions showed that both elements

could be determined in a sulfuric -hydrochloric acid supporting

electrolyte if the antimony were first reduced to the trivalent

state with sulfur dioxide. The samples in question ranged from

4 to 70 percent of bismuth; however, the method developed is

applicable to the range of 1 to 100 percent of bismuth.

(E. J. Maienthal)

13
C. Coulometric Analysis

1. Introduction

Coulornetry depends upon quantitative electrolysis in which

Faraday's laws of electrolysis are applied to chemical analysis.

Accordingly, a coulometric analysis consists essentially of

titrating with electrons. Although the electrochemical equivalency was quantitatively known for more than a century, its

application to chemical analysis has been a development of the

last 25 years and indeed largely of the last decade.

Coulometric analysis was first introduced into the program

of the Analytical Chemistry Division in 1957. while most analysts prior to that time and even today have applied this

technique to trace determinations or to determinations of ordinary analytical accuracy, the KBS has pioneered to develop

apparatus, techniques, and procedures that provide assays of

the highest precision and accuracy. Such determinations are

based upon physical measurements which are easily made with

high precision and accuracy. Moreover, the absolute nature of

coulometric measurements is especially attractive since it minimizes the need for chemical standards in many cases.

The program since its initiation has been concerned largely

with the exploitation of constant -current coulornetry, and methods

precise and accurate to a few parts per one hundred thousand

have been developed for acidimetry and alkalimetry [4], for

argentimetric titrations of halides [5], and for electroreductior

of potassium dichromate [6], A highly precise coulometer for

integration of the current in controlled -potential electrolysis l7 ] has also been developed and described.

2. Facilities

High-precision constant -current coulornetry is done with

apparatus developed in this laboratory and shown in figure 8

and figure 9. The current is measured by comparison of the

voltage of a saturated standard cell with the voltage drop

produced across a standard resistor. The source of the current

is a solid-state, constant -current supply that maintains it at

a selected level to within a few parts in a million over a period of 8 hours. The output is monitored manually and is

adjusted occasionally to compensate for drift. The time of

electrolysis is measured with a quartz-crystal controlled time

interval meter. This timer is calibrated with reference to

Station WW to provide time -interval measurements reliable to

a part in a million.

14
Figure 8. Equipment used in constant -current coulometric

titrations

.

Figure 9. Coulometric cell and associated equipment.

15
Measurements of mass are made on a microbalance so that

a one-gram sample can be weighed to within a few micrograms.

A calibrated mass is used in a substitution technique while

repetitive weighings are made in a sequence designed to provide

an average value of requisite precision.

The coulometric cell for high-precis ion analysis was

designed in the early work [4] and is used with electrodes

and end -point detectors suitable to a given determination.

Coulometric end points are determined in several ways,

potentiometrically, amperome trieally, or colorimetrically as

the case may require.

For constant -current coulometric determinations where

precision of a few parts in ten thousand is satisfactory, a commercially available constant -current supply is used incorporating a syncronous clock as timer. The latter is driven

by a tuning-fork regulated power supply.

The section has a commercial model of the Oak Ridge

Model Q2005 controlled -potential titrator.

3, Summary of Research

a. Determination of Uranium. A method of high precision has been aeveiopea ror "cne assay of uranium in metal or

in its compounds such as black oxide (TJ0O3). It consists in

the reduction of uranium(VI) to uranium^IV) by coulometrically

generated titanium(lll) . The electroreduction takes place in

a 1 M titanyl solution in a 9 M solution of sulfuric acid at

a current density of 2.5 mA/cm

,

" Under these conditions,

titanium(iv) is reduced to titanium(lll} with essentially

100 percent current efficiency. The initial electrode reaction

consists in the direct reduction of uranium. As the uranyl ion

is depleted, electroreduction of titanium becomes the principal

reaction, but the titanous ion in turn acts as reductant for

the uranyl ion in the bulk of the solution.

Because the kinetics of the chemical reduction of uranium

are unfavorable, it is necessary to overt itrate, to wait a sufficient period of time, and to determine amperometrically the

amount of excess titanium(III) produced.

Pull details of the method were disclosed at the EURATOM

Conference on High -Precision Analysis of Substances of Interest

to Nuclear Chemistry, January 18-22, 1965 [8] , and will be published in the near future. In summary, analyses of uranium

dingot metal and of standard oxide (U0O3) have shown an accuracy

of ±0.004 relative percent. J

16
Rubber Sept

Polyethylene Tubing

Figure 10. Apparatus for transfer of samples for coulometric

analysis.

b. Liquid -Sampling Apparatus . Weighing considerations make a solid sample prereraoie wnerever possible, in

many cases, however, liquids or solutions must be analyzed

either because of the nature of the sample or because chemical

processing may be required prior to coulometric determination.

The apparatus shown in figure 10 was developed to provide for

quantitative transfer of liquids to the coulometric cell. A

125 -ml Erlenmeyer flask, covered with a rubber septum, contains

a sample which has been weighed by the technique described by

Murphy in section E, page 25, of this report, or a solution

resulting from chemical operations in situ . Two polyethylene

tubes are inserted in appropriate holes in the septum as shown

in the figure. The drawn-out tube serves to deliver the solution to the titration cell.

m use, tube B enters the cell through a suitable opening

in the cover, and its tip is immersed in the electrolyte.

Pressure is applied to tube A to transfer most of tjie contents

of the flask to the cell where it is electrolyzed. At or near

17
the end point, suction is applied to A to return some electrolyte to the flask for rinsing which can be accomplished without

disturbing tube B due to the flexibility of the connections.

The rinsings are then returned for further electrolysis. The

process is repeated, if necessary, before determining the final

end point.

The apparatus also may be used to transfer solutions from

a beaker to the cell for example. In this case, tube B is

immersed in the beaker and suction is used to transfer the

sample to the flask. The flask should be tipped to expose outlet C lest bubbling of air through the flask contents cause

undesirable splashing on the upper parts of the vessel. The

sample is then transferred to the cell as before. To minimize

undue dilution of the sample by rinsing, it may be desirable

to withdraw some of the cell electrolyte at the end point,

transfer it to the beaker for rinsing, and return it to the

cell for the final end -point determination.

c. Coulometric Calibration . A precise method has

been developed for the calibration of microvolume trie ware by

a coulometric titration procedure. The volumetric equipment

is caused to deliver an accurately prepared normal solution of

potassium dichromate into a coulometric cell where it is titrated using the precise method described earlier [6]. Calibrations at the 100- nl level may be made with an accuracy of

0.1 percent while volumes as small as 1 nl can be calibrated

to 3 percent. Such calibrations are less difficult and more

reliable than by gravimetry. Moreover, using the recommended

technique of immersion of delivery tip, the method simulates

the actual way in which such apparatus is ordinarily used.

The method was described at the 1965 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy [9] and

has been prepared for publication.

4. Analysis of Samples

The highly precise methods of coulometric analysis developed in this section have found considerable use in analytical

determinations of research samples for other sections. For

example, the NBS Electrochemical Analysis Section has been

engaged in isopiestic studies of solutions of calcium chloride

and magnesium chloride. Reference solutions of this kind

have been titrated with coulometrically generated silver [5].

Standard deviations of 0.01 relative percent are easily obtained on 1-gram samples of these solutions.

18
The method developed for the determination of uranium is

being used to analyze uranium oxide (U3O8) for use as a standard reference material and to the assay of oxides of uranium

for use in the preparation of isotopic abundance standards by

the oxide dilution technique. Samples of approximately 0.5 g

are analyzed after controlled ignition. Results obtained to

date show a standard deviation of about 0.02 percent which is

about double the value expected for samples of this size. The

uncertainty reflects both analytical error and deviations from

reproducible composition. More work is in progress to clarify

this problem.

The high precision obtainable with small samples has made

coulometry the method of choice for the assay of solutions of

bromide and chloride for use in atomic weight determinations

(see section E> page 26). In the case of bromides, samples

of 2.5 meq were available for analysis in groups of four. The

analytical uncertainty which included errors due to titration

and sampling amounted to 0.007 percent in the concentration

of the reference solutions. For the chlorides, samples of

approximately 1 meq were provided, again in groups of four.

The analytical uncertainty in this case was 0.02 percent.

(G. Marinenko)

19
D. Microchemical Analysis

1. Scope and Program

Microchemical analysis has been a valuable and much used

tool in the research laboratory for many years because of its

economical use of small samples and its relatively rapid

determinations. Microchemical analysis in this section is

concerned with the determination of major and minor constituents using samples of only a few milligrams. It includes both

organic and inorganic materials. While the major emphasis has

been on organic materials, there has been an increasing amount

of inorganic work, especially with smaller samples.

The direction of the program is toward the analysis of

even smaller samples (one mg or less). This is to be done

through the development of more reliable and sentitive methods

especially through the incorporation of instrumental approaches

into the traditional elemental methods.

There has been a microchemical laboratory at NBS for

approximately 30 years, and it has grown as the field has grown

from the methods of Pregl and Emich to modern instrumental

methods. The equipment in use is described below. Most of it

is housed in one laboratory. A general view of one section of

the laboratory is shown in figure 11. A second laboratory is

used for wet chemical operations such as solution, heating,

and fuming.

2. Microchemical Facilities

Three microchemical balances are in use. There is a Mettler M-5 microbalance and a noncommercial balance designed

and constructed by Dr. A. H. Corwin of Johns Hopkins

University. Both of these have a capacity of 20 grams and a sensitivity approaching 1 p.g. In addition, there is a Cahn

electrobalance, which has a number of ranges. In the most

sensitive range, 1 mg can be read to 0.1 fig.

The determination of carbon and hydrogen is the analysis

most frequently performed. A coleman carbon-hydrogen analyzer

is used for most determinations of this kind. This is a semiautomated combustion apparatus in which the sample and absorption tubes are weighed, but all the other operations are

automatic. The time required for a determination is about

20 minutes.

20
Figure 11. General view of microchemical laboratory.

A Sargent carbon and hydrogen combustion apparatus is used

for materials which have special requirements of temperature,

time, or tube packing. This apparatus is used for the combustion of liquid samples, especially those with high vapor pressures. Samples containing the alkali metals are burned in this

apparatus because a flux is needed to prevent the formation of

carbonates. In determining carbon and hydrogen in fluorine

containing compounds, magnesium oxide is added to the tube

packing to remove the fluorine. The reaction is more efficient

if the magnesium oxide can be kept hot continuously as it is in

the Sargent apparatus. Each determination requires about 1

hour.

A Coleman nitrogen analyzer is used for most determinations

of nitrogen. This is an automated instrument for the rapid

determination of nitrogen by the micro-Dumas method. The

weighed sample is placed in a combustion tube which is then

attached to the apparatus. All manipulations are performed

automatically as the instrument goes through an operating cycle

of purge, combustion, and sweep. All gases except nitrogen are

absorbed in an absorption vessel containing concentrated potassium hydroxide solution. The volume of nitrogen gas remaining

is measured in a stainless steel syringe linked to a digital

counter. Each determination requires 10 minutes compared with

1 hour for the Pregl method. The Kjeldahl method is used for

some materials, especially for those materials low "in nitrogen.

The ammonia formed is determined by titration or if present in

microgram amounts, photometrically.

21
For most determinations of sulfur and halogens, the oxygen

flask method is used for combustion followed by titration with

a suitable 0.01 N reagent solution. Occasionally, the Carius

sealed -tube or tEe catalytic combust ion-tube methods are used

followed by gravimetric determination. A Cotlove-type coulometric titrator is used to determine small amounts of chloride

or bromide (1 to 500 ppm) . Fluorine when present below about

30 percent can be determined using the oxygen flask combustion.

Larger amounts are determined by titration with thorium nitrate

solution. Smaller amounts are determined spectrophotometrically.

Above 30 percent fluorine and especially in the perfluoro

polymers, two problems arise: there is incomplete decomposition of the sample and the accurate determination of relatively

large amounts of fluorine is difficult. Solution of these

problems is among our aims.

A variety of methods are available for the determination

of other elements and functional groups. Alkali metals and

alkaline earth metals are usually determined by flame photometry

although they can also be determined gravimetrically. Some

metals such as copper, silver, zinc, and cadmium are determined

by electrodeposition on small, weighed electrodes. Other elements such as iron, silicon, chromium, and phosphorus are

determined photometrically although phosphorus is often weighed

as ammonium phosphomolybdate after the destruction of organic

material by Kjeldahl digestion.

3. Analytical Activities

A large part of the work involves elemental analyses of

organic materials or compounds for other laboratories at NBS or

for other government agencies. While these are mostly determinations of carbon, hydrogen, nitrogen, sulfur, and halogens,

quite a few are of an unusual nature involving special handling

or the development or modification of a method. An example is

the analysis for small amounts (20-80 \l g) of chloride in polymers

where the chloride is in a terminal position and an accurate

analysis is needed for estimating the molecular weight. The

chloride is determined after combustion by a careful titration

with dilute standard mercuric nitrate solution. As another

example, mercury in organic compounds is determined by burning

the sample in a combustion tube and collecting and weighing the

volatilized mercury on gold foil. Silicon in organic compounds

is oxidized by a sodium peroxide fusion in a micro-Parr bomb,

followed by conversion to yellow silicomolybdic acid which is

measured photometrically. Trace amounts of chloride and iodide

have been determined in photographic films and solutions. After

removal of bromide and iodide, chloride is found turbimetrieally.

Iodide is oxidized to iodate with sodium hypochlorite and then

determined polarographically.

22
Certification analyses were made for the new cystine microchemical standard No. l43b which had been prepared by Delmo

Enagonio of this Division. The purity of the cystine was evaluated by several microanalyses comparing this material with a

previously issued standard reference material sample of cystine.

The results of these analyses indicate no significant difference between the two samples. Cystine is used as a microchemical standard for carbon, hydrogen, nitrogen, and sulfur.

Another type of micro sample frequently received ror

analysis is the unexpected deposit or corrosion product found

on parts of equipment, often after there has been a failure.

Identification of the product might aid in determining the

cause of the failure. A number of burned portions of aircraft

have been examined to attempt to determine the source of the

combustion products. This is of special importance in determining whether a fire occurred before or after a crash. Residues on engine parts have also been investigated. The material

on the outside shell of a small electrical capacitor from a

space missile was identified as electrolyte which had seeped

through a tiny failure. Identification of the corrosion product on a naval mine which had been in the Caribbean Sea for

some time indicated that the part should have been of a different metal. Analyses have also been made of the solid combustion products often found in the fluorine oxidation bombs

used in calorimetric measurements.

A number of analyses have been concerned with determination of trace impurities in water. Samples of water have been

received from the future National Aquarium where the interest

is in the part -per -mil lion amounts of copper and zinc which

are injurious to fish. Waste water from the National Airport

has been analyzed to aid them in planning a water treatment

plant. Reactor pool water from the Harry Diamond Laboratories

was analyzed periodically for traces of sodium, potassium,

chloride, mercury, aluminum, iron, rare earths, and solids to

determine if the water purification system was working correctly. Drinking water from a government station in the Arctic

was analyzed to determine the reason for its nonpotability; an

excessive content of magnesium sulfate was found.

A number of unusual materials such as lithium hydride,

lithium nitride, aluminum carbide, beryllium carbide, and

boron carbide have been analyzed for the NBS Heat Measurement

Section. This section, in determining calorific values,

requires well-characterized materials if these results are to

be meaningful, with most of these materials, the most meaningful is determination of the amount of gas evolved by acid

treatment. Larger samples (200-300 mg) are used for these

analyses.

23
In the case of beryllium carbide, it was found that the

material was far different from the analysis supplied by the

producers. In this analysis, which is typical of the group,

beryllium carbide is dissolved in hydrochloric acid in a

closed system. One mole of methane is formed from each mole

of beryllium carbide present. The methane is swept through a drying column with air and then burned in a combustion tube

packed with copper oxide. The carbon dioxide and water are

weighed, the weight of carbon dioxide indicating the amount

of methane formed and the amount of beryllium carbide originally present. Any excess of water over that which came from

the methane is a measure of the amount of metallic beryllium

in the sample. Free carbon remains undissolved in the solution and is filtered and weighed. Total carbon determined by

combustion in an induction furnace and total beryllium determined gravimetrically give corroborative information of the

beryllium carbide purity and make possible a calculation of

the beryllium oxide present in the sample.

During the past year, the section has worked with J. C.

Davis of the NBS Mechanical Systems Section in investigating the composition of antifreeze solutions used in the snow

melting systems for aprons of aircraft hangars. Corrosion

problems had arisen at a number of Air Force bases, but not

at others. The investigation concerned the amounts and types

of corrosion inhibitors present in the antifreeze solutions,

especially those which showed the best inhibiting action. As

a result of these analyses, specification have been developed

to insure that the materials used will be satisfactory with

respect to their corrosive action.

(R. A. Paulson and R. J. Hall)

24
E. Stolchiometry

1. Introduction

The composition of a chemical compound depends not only

upon the impurities present , but also upon the stolchiometry;

that is, the degree to which the compound conforms to the law

of constant proportions. It is well known that deviations

from ideal composition, nonstoichiometry, occur in many compounds. The degree of this departure from stoichiometry is

often best detected physically by such methods as x-ray analysis. However, in many compounds, these deviations can be

detected by precise chemical analysis as in TIOq y-TiO-, 27^

uo3.0~uo2 67; and FeQ gcO-Fe gt-0 (stoichiometric FeO probably

does not exist). ' °

Since there is the possibility of departure from ideal

composition, stoichiometric considerations are necessary wherever highly precise chemical analyses are undertaken. Work in

this section has been concerned with developing precise and

accurate methods of analysis for the chemical elements to

verify the stoichiometry of a compound to about 0.01 percent.

Emphasis has been given to the Division's program for the mass

spectrometric determination of atomic weights in which it is

necessary to quantitatively blend the separated isotopes of an

element with a precision of about 0.01 percent. Since the

amounts of separated isotopes available for this use ordinarily

are relatively small, the methods developed for their determination should require only small samples.

It is anticipated that future work will be focused on

stoichiometric compounds usable for this program, but attention will also be given to stoichiometric problems arising

elsewhere within the Bureau.

2. Research and Development

a. Precise and Accurate Sampling of Solutions . Mixtures of separated isotopes for calibration of mass spec- trometers may be prepared by blending weighed amounts of each

isotope in elemental form of known purity or in combined form

of known purity and stoichiometry. They may also be prepared

by mixing weighed portions of solutions whose concentrations

are accurately known. The method of mixing weighed portions

of solutions has the advantage of eliminating problems concerned with the homogeneity and the weighing form of the

sample of separated isotope (hydrolysis, hydration, etc.).

The problem of purity is also considerably reduced since it

is not necessary to know the concentration of all the impurities present, but only the concentration of those impurities which would react chemically in the same manner as the element

being' studied.

25
The following method has been developed for the precise

and accurate sampling of solutions. A solution of the material to be analyzed is placed in a 100-ml volumetric flask whose

neck has been cut off so that only about 1 cm remains. The

solution is diluted to about 65 ml and thoroughly mixed by

swirling the flask for several minutes. The flask is sealed

with a rubber septum and allowed to stand overnight in the

case of a semi -microba lance to insure thermal equilibrium.

The flask and contents are then weighed on the balance to

±0.02 mg. Samples are taken from the flask by inserting a

platinum or stainless steel needle attached to a glass hypodermic syringe through the rubber septum, withdrawing the

desired amount of solution, and transferring it to a suitable

container. A second needle which just punctures the septum

serves as a vent. The syringe and needle are washed with distilled water and the washings combined with the bulk of the

sample. The weight of the sample withdrawn is determined from

the weight of the flask before and after the withdrawal of

solution.

This system of aliquoting solutions is used to take advantage of the precision and sensitivity of a semi-microbalance.

To do this, it is necessary not to exceed the 100-gram capacity of the balance. A glass weignr Duret could not be used

because of its excessive weight. On the other hand, the cutoff, 100-ml volumetric flask, stopper, and 65 ml of solution

weighed less than 100 g. Five to 10 grams of solution can be

weighed to better than 1 part in 100,000 by this procedure.

b. Precise Methods of Analysis . Precise methods of

analysis have Deen developed ror zne following elements.

(1) Chlorine . The chloride -ion concentration

in solutions of sodium chloride containing negligible amounts

of other halides and pseud o -ha 1 ides has been determined by

constant -current coulometric titration with silver ions generated at a silver anode. The end point was determined ampero- metrically. Samples containing approximately 1 milliequivalent

of chloride ion were analyzed with a standard deviation of

about 0.02 percent. The results of this work were applied to

the mass spectrometric determination of the atomic weight of

chlorine [10 ].

. . . ., (?) Bromine . The bromide -ion content of solu- t

i

onLof Pu?Hled soaium bromide containing negligible amounts of other halides and pseudo-halides has been determined by constant-current coulometric titration with electrogenerated silver ions in a manner similar to that described for chloride ion. Samples containing about 2 milliequivalents of bromide ion were analyzed with a standard deviation of about 0.01 per- cent The results of this work were applied to the mass spec- trometric determination of the atomic weight of bromine 111".

26
It is usually necessary to chemically purify the separated isotopes to insure removal of those elements that would

interfere with the mass spectrometric measurements or with

the analytical method. The bromine isotopes (as NaBr) were

purified by a method developed previously in this section,

based on the preferential oxidation of bromide to bromine

with dilute nitric acid [12], This purification was necessary to insure the removal of the other ha 1 ides, iodide, and

chloride, and the pseudo-halides, cyanide, and thiocyanate

which would react with silver to form insoluble compounds and

cause the determination of bromide to be in error. About

0.1 percent of chloride ion was found to be originally present in the separated bromine isotopes, which would have caused

an error of 0.2 percent in the bromide determination if it

had not been removed. The purification procedure reduced the

chloride concentration to less than 0.001 percent.

(3) Copper . A method requiring small samples

has been developed for the precise assay of metallic copper

and its solutions. The method is based on the electro

deposition of the copper onto a small platinum electrode. The

gauze cylinder of this electrode is 1.5-cm high and 2 -cm in

diameter, and weighs about 1 gram. A 6-dram vial serves as

the electrolysis cell. The assembly is shown in figure 12.

Figure 12. Microcell for

electrogravimetric determination of copper.

27
The copper remaining in the electrolyte after electrolysis is

determined spectrophotometrically with sodium diethyldithiocarbamate. Using high-purity copper as a reference material,

it has been shown that samples containing 0.10 to 0.25 grams

of copper can be assayed with a standard deviation of 0.007

percent. The results of this work have been published in

Analytical Chemistry [13] and have been applied to the mass

spectrometric determination of the atomic weight of copper Ll4l

(4) Chromium . A precise method for the

determination of chromium has been developed. In this

method, trivalent chromium is oxidized to hexavalent chromium

by hydrogen peroxide in alkaline solution and the excess

oxidant is destroyed. The hexavalent chromium is then determined by constant -current coulometric titration with ferrous

ions generated at a platinum cathode by electroreduction of

ferric ion. The end point is determined amperometrically.

The accuracy and precision of this method was determined

by applying the procedure to NBS standard reference material

136b, potassium dichromate. This material has been shown to

be 99.977 percent KoCr2 7[6] based on oxidizing power. Four

solutions of this material were prepared on a weight basis,

and the concentration of each solution was calculated as

milliequivalents of chromium per gram of solution. Four to

six samples were withdrawn from each solution and the chromium

in each sample was partially reduced with hydrogen peroxide

in acid solution to simulate the conditions of the separated

isotope solutions. The chromium in each sample was determined

as described and the results were compared to the amounts

known to be present.

Data resulting from these analyses showed that: (a) the

average concentration of chromium for each set as determined

by this method agreed to within 0.002 percent with the calculated concentration, and (b) the standard deviation of an

individual determination (20 degrees of freedom) is calculated

to be 0.010 percent for a solution containing 1.0 meq Cr g solution. The excellent agreement between the average for

each set and calculated amount of chromium also proved that

the oxidation of trivalent chromium to hexavalent chromium by

hydrogen peroxide in alkaline solution is quantitative and

that the excess hydrogen peroxide is completely destroyed.

The procedure developed by this work is being applied to

the mass spectrometric determination of the atomic weight of

chromium which is now in progress.

(T. J. Murphy)

28
F. Cryoscopic Analysis

1. Introduction

The study of the change In temperature as a function of

the change In ratio of the solid phase to the liquid phase

in ideal or nearly ideal solutions is called cryoscopy. This

temperature change is directly dependent on the initial purity

of the system, consequently crysocopy can be used as a highly

sensitive tool for determining concentrations of impurity in

these materials. Basic principles involved in estimation of

purity by the cryoscopic method have been described in detail

by Glasgow, Streiff, and Rossini [15 L

The basic difference between the three most widely used

cryroscopic techniques is the fashion in which the liquid - solid ratio is determined. In dilatometry, the ratio is

observed as a function of volume; in the thermometric method

(time -temperature freezing), the ratio is determined as a function of time; and in adiabatic calorimetry, the ratio is

measured as a function of heat content. All of these methods

are useful in obtaining precise and accurate determinations

of purity if the heat of fusion of the material is known.

The thermometric method has been used extensively for

years at NBS for determinations of purity in the range 99.0

mole percent up to 99.999 mole percent for many materials,

an adiabatic calorimeter has recently been constructed and is

presently undergoing final test. It will be used to further

augment the Division's capabilities in the field of cryoscopy.

2. Thermometric (Time -Temperature) Cryometry

The thermometric system used at NBS consists of a glass

sample container with a noble metal reciprocating stirrer.

The detecting and measuring portion of the system is a platinum

resistance thermometer, a d-c resistance bridge, and an automatic temperature recording system made up of a high-gain d-c

amplifier and a potentiometric recorder. The cryometric cell

is described in detail by Glasgow and Tenenbaum [l6], and the

measuring system is described by Ross and Dixon [17L

This cell can be operated as a closed system, open to

normal atmospheric conditions, or under controlled atmospheric

conditions. Since the closed system is constructed of glass

and noble metals, it is useful in determining the purity of

many substances which are toxic, reactive with air, or hygroscopic. If normal atmospheric conditions can be tolerated,

29
Figure 13. Thermometric

cryometer and equipment

for recording timetemperature cooling and

melting curves.

the open system is easier and faster to operate than the

closed system. The general temperature range of the equipment will accommodate substances which freeze between 150"K

and approximately 350°K. The amount of sample required for

a determination is about 50 ml. The time required to complete

a single analysis varies from one-half to one day depending

on the freezing temperature and whether open or closed system

conditions are used. Figure 13 shows the time -temperature

cryometer as it is normally operated.

The purity of highly purified samples of benzene, carbon

tetrachloride, titanium tetrachloride, hydrogen chloride,

dimethylphth late, dichlorostyrene, isopropyl alcohol, and isomers of dichloroethylbenzene have been determined with this

apparatus. The purity values of the presently available NBS

standard reference materials of hydrocarbons were obtained

by this method. Examples of more recent results and comparisons of this method against the other cryoscopic techniques

have been published [18,19].

30
3. Calorimetry

The National Bureau of Standards extensive and expanding program of evaluating research and reference materials

demands that prime consideration be given to estimation of

the total purity. The best known instrument, which uses

physical methods of analysis, for determining the total purity

of a material is the high -precis ion adiabatic calorimeter.

Moreover, the calorimeter is a versatile tool, not limited

strictly to analytical uses. This allows it to play a major

role in producing information on physical constants and properties of research materials.

Since apparatus of this type is normally not commercially available, a program was initiated to design and construct a high-precision adiabatic calorimeter with special

emphasis directed to extending the capabilities of the

Division in evaluating the purity of materials. In general,

the reliability of this type of apparatus is determined by

its ability to ascertain true equilibrium temperatures and

maintain precise adiabatic conditions. Accordingly, much

effort has been devoted to the design and the construction of

a sample container to achieve thermal equilibrium conditions.

Fully automatic temperature control units are employed to

obtain precise adiabatic control.

Figure 14 is a cross-section sketch of the calorimeter

construction. The sample container, valves, and filling

assembly are made of platinum, iridium, and gold to minimize

heat transfer problems and to provide a surface which is inert

to a broad range of materials, perforated disk-type vanes of

platinum are horizontally attached from a central re-entrant

well to help prevent segregation of impurity during analysis.

The sample container is suspended in the calorimeter by a thin-walled platinum tube containing a needle valve to allow

sealing of the sample container. This prevents vaporization

of material into the filling tube during analysis. The central re-entrant well contains a platinum resistance therometer

and a non- inductively wire wound heater.

A copper shield surrounds the sample container. Electronic

equipment controls the shield heaters so that the temperature

can be automatically maintained the same as that of the sample

container. Thermocouples between the shield and the sample

container control operations of the electronic equipment. The

space surrounding the shield and sample container is maintained

at a pressure of approximately 10"b mm mercury.

31
Volve Packing

9- —+ To High Vacuum and Samples

Leads to Terminal Box

Q^ To High Vacuum

Thin-wall Platinum Tube

Valve Seat

Leads with Heaters

Tempering Ring

Shield with Heaters

Thermocouples

Vacuum Jacket

Calorimeter Heoter

Thermometer

I 2

I i . i i i_ Inches

Scale

Figure 14. Adiabatic calorimeter for volatile materials.

32
Figure 15. Calorimeter

vessel attached to vacuum

system.

The temperature control units operate from an amplified

signal to an indicating potent iometrie recorder with a control

setting device. A control unit which automatically produces

an output current proportional to the input requirements of

the process completes the system. Direct current is used to

avoid electronic interference that is normally associated with

the use of alternating current. The temperature of the sample

is measured with a platinum resistance thermometer and a

Mueller G-3 bridge. Electrical input energy is determined

from measurements taken with a six-dial, triple range potentiometer which provides precise measurements of voltages between

the limits of zero and 1.6 volts. The time interval of heating

is obtained by using NBS standard time frequencies and a gated

electronic counter. The rise of the electrical input signal

at the beginning of the heating interval starts the counter

and the fall of the signal at the end of the interval stops

the counter, a highly sensitive microvoltmeter is used as the

detector for the bridge and potentiometer. A low pass filter

is used to eliminate line interference to the detector from

rectified d-c sources used to supply power to the main and

shield heaters.

The calorimeter is mounted in a stationary position and

is limited to the assaying of materials which can be introduced and removed by distillation. The temperature range of

the system was designed for determining purity of materials

which melt from 90°K to approximately 375 K.

33
Figure l6. Temperature

controls and measurement

station for adiabatic

calorimeter.

Three days to one week are required for the completion of

a single analysis. Approximately 50 ml of sample is required,

but the method is nondestructive and the material can be reclaimed. All the data needed for a purity determination can

be obtained from one experiment.

Construction of the apparatus has been completed and the

system is presently undergoing performance testing and calibration.

Since analyses have not been made with this equipment,

no claims can be made regarding the precision and accuracy of

its measurements. However, it is anticipated that a subsequent report will show that the analytical capability of this

Division to estimate concentrations of impurities in the partsper-million range by cryoscopic methods has been improved by

an order of magnitude.

(H. D. Dixon)

34
G. Supporting Techniques

In the recent past, research projects have been active

in the competences of gas chromatography, nuclear magnetic

resonance spectroscopy, and infrared spectroscopy. While

these programs are inactive at the present, the section has

modern equipment of -this kind and possesses considerable

experience in its use in analytical applications. Thus, infrared and nuclear magnetic resonance spectra are prepared for

other research groups. Gas chromatography finds extensive use

both in the analysis of research samples and in monitoring

purification processes and in evaluating the purity of the

purified material.

The section also uses the above techniques in conjunction

with other analytical competences. Thus, gas chromatography

may be used as a preconcentration or preseparation technique

to facilitate a later analysis by mass spectrometry. Infrared

spectrometry is likewise used to identify fractions from gas

chromatographic measurements.

In addition to providing analytical services with these

techniques, the section maintains the equipment and makes it

available to qualified users in other sections of the Bureau.

This arrangement is especially advantageous to those chemists

who have only occasional need for specialized equipment, but

who are skilled in its use and are willing to devote the time

necessary to make their own measurements and interpret the

data.

(J. K. Taylor)

35
2. PURIFICATION PROGRAMS

A. Distillation

1. Introduction

The laboratory provides facilities for purification of

research quantities of materials that are needed by the personnel of the Bureau of Standards. The distillation laboratory

will attempt to purify any material whose vapor differs in

composition from the liquid or solid phase. Since no one type

of still is adapted to all the needs which arise, a variety

of types have been set up hoping to anticipate the most likely

requests. This is not always possible so that additions or

modifications to the equipment must be made from time to time.

Not only is the requirement for equipment unpredictable, but

the workload varies so that automation is desirable to avoid

variation in the requirement for personnel. Accordingly, the

equipment has been designed and constructed in this laboratory

to operate continuously for long periods of time with as little

attention as possible.

2

Facilities

The types of stills which are now available are cataloged

in table 1. The small stills are equipped with reflux controls,

but samples of distillate are removed manually because the

tubes which connect the sample receivers in automated collectors

can lead to mixing through the vapors. However, distillate

collects so slowly that personal attention is not an undue

burden. Larger stills are equipped for the control -of the rate

of boil-up, reflux rate, and automatic collection of fractions

in a closed system.

Figures 17 and 1J show some of the equipment in the distillation laboratory. On the left of (A), figure 17, is a cylinder which protects a large glass Dewar container for

refrigerants such as solid carbon dioxide or liquid nitrogen.

A pump circulates a cryostatic liquid through the refrigerant

and thence to the head of the still for distillation of lowboiling materials. Solid carbon dioxide sufficient for 24 hours

of operation can be placed in the Dewar, and by throttling the

flow of the cryostatic liquid, the head of a small still can

be cooled to any desired temperature as low as -50°C for long

periods. By using liquid nitrogen, a temperature of -130°C

can be reached. The consumption rate of liquid nitrogen is

about 2 liters per hour.

36
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37
Figure 17. Small still equipment in the distillation service

laboratory. (A) and (c) microspinning band stills with

equipment for regulating temperature and pressure; (B) microconcentric tube still; (D) macroconcentric tube still.

Figure 18. Three -meter by

25-mm packed stills with

boil-up and take-off controls and closed-system

fraction collectors.

38
Below the cylinder In figure 17 is a pressure control

unit. Each still is regulated individually by one of these

units. A detail of the control is shown in figure 19.

At the bottoms of the stills shown in figure 18 are the

vaporizers. Details are shown in figure 20. The vaporizers

are relatively safe for flammable materials because the heaters

are enclosed In metal. Vapor from the flask rises through the

large tube, passes horizontally to the left, and Is emitted

from orifice E to rise up the still column. Liquid returning

from the column passes down through F and H and enters the

flask at the side. If valve H is closed by a hand-operated

permanent magnet, the column will fill with liquid for

"preflooding. " The wells D and G are for the insertion of

thermistors to detect the rate of flow of vapor and to actuate

a correcting mechanism to keep flow constant.

Figure 19. Pressure regulator. (A) ballast; (b) manostat;

(C) vacuum control valve; (D) relay (lower case letters

are detailed points of construction).

39
B— %

Figure 20. Vaporizer for still. (A) to column of still;

(B) polyfluoroethylene gasketed spherical joint; (t^ to

bfi) detailed points of construction: (c) closure for

filling tube; (c-, to eg) details (D) and (G) thermistor

wells; (E) vapor nozzle; (F) bulb for measuring the

returning liquid (H) valve; (J) through (P) details of

heater and shield.

The metal frames at the left of each still support automatic fraction collectors. These units are independent of

the stills and can be dismantled for cleaning. Two designs

have been used. Figure 21 shows a rotary design with the

photocell and preliminary receiver containing a glass float

which actuates the collector. The units have 12 receivers

which are inverted-cap bottles. Filled bottles can be replaced without disturbing the operation of the stills at

reduced pressure and the bottles can be filled with inert gas

before removal if desired. The collectors which are shown in

the photograph (see figure 18) have sliding distributors, the

details of which are shown in figure 22.

All the stills are assembled in units with tapered and

spherical joints for ease of cleaning and repairing. Special

polyfluoroethylene gaskets are used in place of greases.

40
?TOQ

A photocell B cork support C gloss bulb blackened within D pressure equalizer EF to head of still G receiver

Q, light weigt glass f loot H solenoid valve

h| magnet

h2 armature in gloss

h 3

"lock open" plunger

J slow- leok valve

K teflon gasketed joint L teflon lined stopcock M distributor m, adjustable stops

FRACTION COLLECTOR

m2 iron armature in glass mj permanent magnet

m4 6watt,l0rpm motor m5 bearing for funnel mg spring pressing motor m7

drain from funnel mo rotating disc ~ 9 bearing for disc metol frgme

metal cylinder

> wire ties

i springs

i stirrup 2 slotted disc tapered joint reservoir

teflon gasket

delayed action reloy

Scale k-i'ii r

( hot 110 volts to signal rj neutral 110 volts S rhicroswitch T inverted stopper

bottles

N

Figure 21. Rotating fraction collector. (A) through

(T) detailed points of construction.

41
Igure 22o Sliding fraction collector, (a, to Apj.) detailed

points of construction of general assembly; (Bt To B3) details

of packing glands; (A-,4), {C-y) , and (c 2

) details of sliding

sleeve; (D^ to D^) details of supporting frame.

Figure 23 shows the behavior of a 3-meter still packed

with closely wound spirals about 2x2 mm. The graph shows

that the effectiveness of separation (expressed in numbers

of theoretical plates) increases gradually for about 50 to

75 hours after the column is filled with liquid distillate

and drained (pref looded) . Also, it shows that there is an

optimum rate at which the column can be operated. For the

mixture of n-heptane and 2,2,4 trimethylpentane which was

used for the test, the optimum boil-up and through-put were

15 and 8 ml/min, respectively. The efficiency under these

conditions reached about 220 theoretical plates. Expressed

less technically, such a still can produce a mixture containing 97 percent n-heptane (bp 98°C) from a mixture with

2,2,4 trimethylpentane (bp 101°C) containing only 3 percent

n-heptane.

42
300 -

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D

50 100 150 2'66

HOURS AFTER PREFLOODING

AVERAGE BOIL-UP AND THROUGH-PUT RATES,ML/MIN

© 30,15 • |0,6

O 15,8 Q 7, 1.5

Figure 23. Efficiencies of 300-cm packed still columns

at varying rates.

3. Research and Development

Stills which are equivalent to more than 200 theoretical

plates are highly desirable but are not common. The simplest

way to increase the total separating power is to increase the

length of a column, but the improvement becomes smaller as the

length is increased. It has long been known that a given column can sometimes be made more effective by using techniques

other than simple rectification. For example, if a relatively

nonvolatile liquid in which some constituents of a mixture are

more soluble than others is flowed down a column during a rectification, the separation may be enhanced. The technique is

termed extractive distillation and is somewhat analogous to

gas-liquid chromatography (glc). To study the possibilities

of extractive distillation further than has already been done,

the effect of various extractive agents on the separation of

test mixtures has been undertaken. The immediate purpose is

to isolate a mixture of 2-methylhexane and 2,3-dimethylpentane

43
from an inexpensive source such as the heptane -cut of petroleum.

This mixture is a good combination for testing stills of more

than 300 plates. However, the long-range purpose is to develop

a quick method of evaluating agents for extractive distillation

and improving the technique of using them with laboratory stills.

A micro spinning-band column has been modified to permit the

continuous introduction of extractive agent at the top and removal at the bottom. The results are studied by glc examination of the distillate. This can be done without the complete

removal of the extractive agent from the material. The effectiveness of an extractive agent for separating a given mixture

can be evaluated in less than 24 hours in this way.

4. Purification Activities

The demand for purification by distillation at the NBS is

somewhat irregular. With the equipment which has been described

and a personnel of two, there is almost always a small backlog

of requests. Over a number of years, requests have been most

frequently for lots of 50 to 100 ml of material and boiling

points of the material are most often between 50° and 100°C.

More organic than inorganic samples are received.

Materials Distilled, June 1964 to June 1965

Name bp, °C mp, °C

Durene ^6760 + 79.3

Methanol 64 ' 776o - 97

Nitroe thane ll4 - 876i - 90

Glycerol 2 90

76o + 17.9

c is-Decahydronaphthalene 193.3760 + 51

trans -Dec ahydronaphtha lene 185 ' 3

760

- 32

Benzophenone 3°5-V6o + 48.5

Thujaplicin oil 140 - 150 14-15

+ 70

Bromine 58.8 " - 7.2

Hydrobromic acid (aqueous) 126

1,1 dime thy leyclohexane 175

(R. T. Leslie and E. C. Kuehner)

44
B. Ultrapure Reagents

1. Scope

Recent advances in trace analysis have created an urgent

need for reagents of -special high purity because the amount of

an impurity sought in a sample is often less than that present

in the best grades of reagents normally available. As a result

of this urgent need for ultrapurification of reagents to reduce

the intolerably high blank corrections, this project was initiated in December 1964. It will eventually include the ultrapurification of many of the reagents and related materials

required in the trace analysis activity of the Division, but

at present, water, sodium hydroxide, hydrochloric acid, nitric

acid, sulfuric acid, and aqueous ammonia have been selected for

intensive study with priority being given to water and acids.

The satisfactory storage to prevent deterioration or contamination of the ultrapure reagents by the container is another

important problem which is being investigated. This includes

a systematic study of various materials from which containers

may be fabricated, especially with reference to trace analysis

application.

2. Facilities

The methods available for preparing specially purified

reagents include distillation, crystallization, zone refining,

extraction, and preparative chromatography. However, contaminants introduced into the reagents from apparatus used by

these methods are no longer considered negligible and require

modifications in techniques. Apparatus and labware require

special cleaning techniques or must be constructed from special material to prevent contamination. For example, in the

distillation of reagents for the removal of trace metals, a

glass still may actually contaminate the distillate by leaching metallic elements from the glass used in its manufacture.

Since these metals are more readily leached out by certain

acids, it is especially important that the material used in

construction of a still f^or this purpose contain minimum

amounts of metallic elements. Because quartz contains less

than a tenth as much metallic elements as glass, three of the

stills in operation are made of quartz.

When the purification of a reagent or related material is

not effective or feasible by the above methods, synthesis will

be carried out from reactants which are specially purified.

45
3» Research and Development

Since the initiation of this project, the emphasis has

been on preparing and supplying a few of the most -needed ultra

pure reagents and little time has been spent in pure research.

Most of the techniques and methods utilized in the preparation

of reagents were obtained from literature search and past experiences. Some preliminary research has been started on zone

refining of solid sodium hydroxide. The problem of the best

container for storing ultrapure reagents will require considerable research and testing. Preliminary work is in progress in

preparing ultrapure reagents to be characterized and stored in

a number of types of containers.

4. Preparation of Specific Reagents

a. Water . Although water is not a reagent in the

strictest sense, ru plays an important role in the preparation

of proper reagent concentrations. It is, therefore, important

that the water used to make up the reagents or used in any

other capacity of trace analysis is ultrapurified

The ordinary distilled water for the Analytical Division

staff members located in the Chemistry Building is supplied by

a special Barnstead steam-heated still. The evaporator is

stainless steel, and the condenser is tinned copper. The still

is capable of producing 40 gallons per hour, but is operated

at one-fourth that rate to produce water having a conductivity

of approximately 4.5x10-7 mho. The total metal content in the

distillate has not been determined quantitatively; however, an

analysis for copper showed 1.5 ppb in water directly from the

still and 8.5 ppb in water standing in the storage tanks for

2 weeks. This distilled water does not give a positive result

for metals when shaken with chloroformic solution of dithizone

unless the impurities are concentrated by a factor of ten by

removal of water.

A one-meter, quartz still, shown on the left in figure 24,

randomly packed with 4-mm quartz Raschig rings was used for the

ultrapurification of ordinary distilled water. This quartz

batch still was charged with two liters of the water, and the

distillate was collected in three fractions in which only the

largest middle fraction was saved. The 50 ml of water allowed

to remain in the pot gave a positive test with dithizone

chloroform solution. The pot was then rinsed with a few portions of the middle fraction and charged with the remainder.

When this fraction was again distilled in the same manner, no

color change was observed when the 50 ml of water remaining in

the pot was shaken with dithizone -chloroform solution. This

indicated that most of the trace metals were removed by a single

distillation in the quartz still having about eight theoretical

plates. This test has a sensitivity of about 10 ppb. The

46
Figure 24. Stills used for preparation of ultrapure reagents.

quartz still described above is being used for the ultrapurification of water until the installation of a continuous distillation quartz still is completed in the proximity of the Barns

Barnstead water still. The continuous quartz still will be

capable of producing water at the rate of 400 ml per hour which

would be sufficient to meet the present demands for specially

prepared water. This still would then free the quartz batch

still and make it available for the distillation of other reagents.

b. Nitric Acid . A one-meter, all-quartz still

(center still in rigure 'dh) which is randomly packed with 4x4-mm

quartz Raschig rings is used for the distillation of nitric

acid. The still column is lagged with foamed styrene to prevent heat loss and has an estimated efficiency of about eight

theoretical plates. The effectiveness of the still in removing

trace metals from the reagent under a normal operating procedure was determined. The still pot was charged with 1500 ml

and allowed to distill off to dryness at a slightly reduced

pressure provided by a water aspirator. The middle fraction

containing approximately 1000 ml was collected in a quartz

47
flask for a second distillation. The still pot was rinsed with

50 ml of specially purified water, and the mixture was shaken

with a few drops of chloroformic dithizone solution. A definite color change from blue to pink confirmed the removal of

metals in the parts-per-million range. The middle fraction

was distilled in a similar manner and the dry pot again rinsed

with specially purified water and tested with dithizone. The

test revealed only a few parts per billion of metal in the

residue and indicates that a single carefully controlled distillation removes most of the trace metals in the reagent grade

nitric acid, and a second distillation should produce nitric

acid of ultrapurity.

c. Sulfuric Acid . Reagent grade sulfuric acid is

distilled in a 60-cm quartz still which is randomly packed with

4x4-mm quartz Raschig rings and lagged with glass wool insulation. Distillation is carried out at reduced pressure provided

by an aspirator which serves to remove the initial surge of

SOo gas released until the azeotrope of H2

S0i| and water is

reached and allows the distillation to proceed at a lower vaporizer temperature. The distillate is collected in three

fractions in which the first and last are discarded. The middle fractions from two such distillations are combined and

redistilled. The middle fraction from the redistillation is

collected in a quartz flask and transferred to a 2-liter quartz

container for storing and dispensing.

d. Hydrochloric Acid . At present, specially purified hydrochloric aclasis prepared by saturating ultrapurif led

water with hydrogen chloride gas from a cylinder. The hydrogen

chloride gas is first scrubbed by bubbling it through concentrated reagent grade hydrochloric acid before dissolving it in

the purified water in a quartz flask.

e. Silica Gel . Silica gel has been included as a material related to reagents since it plays an important role

both in purification and in chemical analysis. Metals, especially uranium, were found to be an interferring impurity in

a silica gel used in thin-layer chromatography by another section in the Division. A small amount of silica gel was extracted

with nitric acid in a Soxhlet extractor in which the gel was

contained in three small sintered glass bottom crucibles suspended in a Teflon harness above the siphon drain of the

extractor. Nitric acid dripped off the condenser into the top

crucible, filtered through the silica gel and glass frit into

the crucible below, and eventually reached the lower part of

the extractor where it accumulated to a certain level before

it siphoned over into the vaporizer. The extraction was allowed

to run continuously for 7 days after which the nitric acid was

replaced with distilled water. The silica gel was then extracted

with distilled water for 2 more days. No quantitative results

48
on the purity of the silica gel were obtained. However, extraction decreased the impurities by several orders of magnitude to

a level where the silica gel was satisfactory for the particular

separation by thin-layer chromatography.

Because of the limited capacity of this apparatus, a larger

extractor having a -50-g capacity was constructed as shown in

figure 25. Condensate from the distillation of nitric acid is

forced up through the lower fritted disk and silica gel by

hydrostatic pressure. The acid then passes through the upper

fritted disk taking along any impurity dissolved in the acid

while the silica gel remains in the funnels. Using this apparatus, a 50-g sample of silica gel was extracted with HNOo for

3 days and then washed with several portions of specially distilled water. Quantitative determination of the purity of the

gel has not been completed; however, preliminary results indicate a considerable decrease of impurities.

rp*- Cooling Water

\z Water Exit Condenser

Glass Funnelswith 90 mm

fine fritted disc

Silica gel

Heating Tape

Liter Vaporizer

HNO3

Heater

Figure 25. Extractor for purification of silica gel.

49
Taper Joint

~4mm I.D.

Taper Joint

2 Liter Flask

Figure 26. Quartz container for dispensing purified reagents.

5. Use of Ultrapure Reagents

The preparation and distribution of ultrapurified reagents

is only beginning to gain momentum since much time has been

spent earlier to procure and install the necessary apparatus.

In addition to the 50 grams of silica gel previously mentioned,

a total of 8 liters of specially purified water and a liter

each of ultrapurified nitric acid and sulfuric acid have been

provided to staff members of the Division. Also, there is

maintained a reserve of two liters each of ultrapurif ied nitric

acid, sulfuric acid, and water. These reagents are stored in

and dispensed from two-liter quartz flasks. A sketch of one

of them is shown in figure 26.

(E. Q. Kuehner)

50
C. Light -Element Purification

1, Scope

The establishment of accurate values of the physical and

thermodynamic properties of solids is often limited by the

inability to obtain material that is of high-chemical purity

and that is also well-characterized as to its physical state.

When such material is not available, large uncertainties are

introduced even though compositional determinations are made

by the very best analytical procedures and very precise measurements are made of their physical and thermodynamic properties.

Generally, inorganic substances are polymorphic, and the solid

form of the material can exist in several different crystalline

states. In this case, the material to be measured, in addition

to a high-chemical purity, must be a solid consisting of only

one of the polymorphic forms. Inorganic fluorides are a class

of such polymorphic solids of which beryllium fluoride, BePo,

was of particular interest at NBS for the ARPA light -elements

program.

The main objective of this research was the development of

new apparatus, new procedures, and new techniques for physicochemical phase separations, for chemical purification, and

physical-state preparation of pure polymorphs (chemically pure

and in one crystalline form) of inorganic fluorides with particular emphasis on beryllium fluoride, BeF2

. A second very

important objective in the planning was the devising of techniques and procedures for the safe handling or inorganic fluorides such as BeF2 and exclusion of moisture in these processes

because of their extreme toxicity at elevated temperatures and

their reaction with moisture at ordinary temperatures.

2. Facilities

In January 1962, plans were made to equip a laboratory with

facilities for performing phase separations uo to 1000°C, whereby

inorganic fluorides such as beryllium fluoride could be both

chemically purified and prepared as a crystalline product consisting of only one of several possible crystalline forms. A

recent photograph (figure 27) shows the physical arrangement of

the major facilities in the laboratory. These facilities consist of the following units: Experimental assembly for toxic

materials; furnace and temperature control; controlled -atmosphere

dry box; special cell for phase purifications; apparatus for the

hydrofluorothermal process; and helium leak detector.

51
Figure 27. Physical arrangement of the major facilities

for light-element purification.

a. Experimental Assembly for Toxic Materials . For safety in phase purifications up to iouuwc or nigniy toxic

materials, such as BeF2

, the experimental assembly for closedsystem operation has been installed in a three -compartmenta

1

manner as shown in the photograph (figure 28).

The high-temperature part of the assembly is in a highexhaust hood which serves as a separate compartment. The

hood is equipped with absolute filters and a 10-foot exhaust

pipe on the roof of the building. The hood contained the furnace, the thermocouple leads for recording and controlling the

temperatures of three furnace zones, an excess-temperature

thermocouple lead for cutting off power to the furnace, three

power lines to furnace zones, the experimental vessel, and

the upper part of a vacuum manifold of Monel containing a nickel-Monel trap in which by-products that are solids at

room temperature are collected.

52
Figure 28. Three -compartmenta 1 assembly for high-temperature

experiments with toxic materials.

53
Figure 29. Cabinet area of assembly for low-temperature

trap, absorption tube, and fore -pump.

Services for the special cell for phase separations built

into the hood proper include: coolant lines to two heatexchange probes to the cell for condensation of vapors and for

nucleation of crystals, six thermocouples for thermal analysis

of phase processes in the cell, and two lines for evacuation and

pressure control of double -walled, Inc one 1 -nickel spaces of

cell.

Another compartment is the cabinet under the hood, in

which are located the lower part of the vacuum manifold of

Monel (see figure 29), a nickel -Monel trap for liquid and gases,

a Monel cylinder for transfer and removal of the trapped liquid and gas, an absorption tube of Monel (for HF vapors with

fluorides), and an oil mechanical pump. This cabinet has

louvers on the doors, forced ventilation by a small blower

into a pipe opening near the exhaust outlet of the hood, and

a discharge pipe for the exhaust from the mechanical pump into

this same exhaust area of the hood.

54
A bench area at room tempera ture, adjacent to the hood,

is the third compartmental area on which are located the following: the mercury diffusion pump of glass and the accessories (glass traps and McLeod vacuum gage) for the high-vacuum

system proper; a system for evacuation and pressure control of

the nickel-Inconel spaces of the body and well of the cell;

and a thermocouple assembly with a potentiometer for thermal

measurements of six areas of the cell.

Figure 30. Three-zone furnace, automatically controlled,

for high-temperature phase separations.

b. Furnace and Temperature Control . A three-zone

furnace (figure 30 J and a panel cabinet (figure 31) with

instrumentation for automatically controlling and recording

temperatures as emf of three furnace zones was custom fabricated according to our specifications.

The furnace is of the split-tube type with hinges and a

special closing fixture and guide to permit vertical or horizontal operation. The diameter of the shell is 12 3/4-inches.

55
Figure 31. Front and back views of electronic units for

automatically controlling and recording temperatures in

the three -zone furnace.

56
The over-all length is 15 1/2-inches with end transite cover

plates, l/2-inch thick, and end vestibules, 1 l/4-inches in

length. A type 330 stainless steel liner (2.47-in. i.d. and

2.86-in. o.d.) 14 l/4-inches long fits into the heat chamber.

It is held concentric to the heat chamber by the end vestibules and is easily removed. The heat chamber is 12 inches in

length and 3 3/4-inches in diameter. It is divided into three

electrically heated zones of 4 inches each, which are independently heated with separate power lines to each section.

Six chrome 1 -a lumel thermocouples are located in the heating

elements of the furnace chamber; one in each end zone and

four in the center zone. Five of these are used for temperature control and recording. The sixth is used for the overtemperature protection instrument that automatically cuts off

power to these zones if the temperature exceeds a predetermined

set value.

Thermocouple lead wires from the panel cabinet in a rubber covered cable terminate in a junction box located outside

the hood. The six thermocouple leads from the furnace are

connected to this box. The electric power cords to each of

the three furnace zones are connected to separate power outlets that are located outside the hooded area. The current

to these outlets is controlled from the panel cabinet by the

emf of the thermocouple in the furnace zone.

Three recorders are used to control and record temperatures as emf for the three furnace zones. The electronic

assembly in the panel in addition to the recorders includes

three control units, three magnetic amplifiers and selfsaturating reactors, one control circuit transformer, one constant voltage transformer, one over -temperature protection

instrument, and one main cut-off contactor.

c. Controlled -Atmosphere Dry Box . A controlled

atmosphere dry box witn a glove panel ana accessories for

maintaining a dry, inert atmosphere is used in experimentation

with hygroscopic substances, such as BeF2

. The controlled

atmosphere is used in processes involving the filling and

removal of material into or from the experimental vessel.

The glove box (figure 32) is basically a commercial model

with the exception that, in addition to the interchange compartment on one end, there is also a swinging door panel on the

other end which is used for inserting large experimental vessels.

Main alterations in the box include the following: a

well for the special cell so that it may be assembled or disassembled in a vertical position; a line, gauge, and vacuum

57
Figure 32. Controlled -atmosphere glove box.

pump for the evacuation and subsequent filling of the interlock compartment with an oxygen-free, moisture-free gas such

as nitrogen; metal drying tubes packed with molecular sieves

which may be reactivated in place; a line to discharge the

pressure release from the circulating pump into the box rather

than into the room; two manifold lines which connect the

valves to a gas inlet system through a pressure gauge or a

gas outlet system that is connected through one union coupling

to a line to the hood such that all gases are vented to the

hood; and a dew-point device for sensing the moisture content

of the box.

d. Special Cell for Phase Purification . A crosssectional drawing of the special cell, that was designed and

constructed at NBS, for use to 1000°C in phase purifications

and thermal analysis for the preparation of pure crystalline

polymorphs of polymorphic inorganic fluorides is shown in

figure 33. The numbers in the figure refer to the disassembly

58
Figure 33. Phase purif ication and thermal analysis cell

59
Figure 34. Assembled cell for use at 1000°C In phase

purification.

parts, the lower case letters to welds, and the capital letters to details of other parts. Photographs of the assembled

and disassembled cell are shown in figures 34 and 35. Figure 34 also shows two heat-exchange probes that are used for

the removal of heat at re-entrant coolant well, B, and at

protrusion, M, of the cell for crystal nucleation. Figure 35

shows the tool for removing vessel 6 by interlocking into

grooves J.

60
The cell is provided with removable containers at the

bottom, lower center, and top of the cell in which the products

as solids can be removed after phase separations involving

distillation, crystallization, sublimation, and preferential

decomposition. These operations are performed in a hooded

area with the cell placed in a vertical position in a threezone control furnace whose temperatures are automatically

controlled and recorded by remote electronic controls. A

closed stopcock at A protects the contents of the cell after

pre treatment or phase separations. Disassembly of the cell

for filling or product removal is performed in the dry box.

*

m

3>

u

Figure 35. Disassembled cell for use at 1000°C in phase

separations.

61
fp^

!i

l'-

llIt

II /

A. Platinum tube 1/8 Inch o.d.,

0.010 inch wall

B. Platinum-iridium body (90$

Pt-10$ Ir alloy)

C. Platinum-iridium ring (90$

Pt-10$ Ir alloy)

D. Platinum disk, foil 0.001

inch thick soldered to B

and C

E. Position where tube is cut

off after filling with HP

and closing tube with pliers

Figure 36. Rupture-disk ampoule.

62
e. Apparatus for the Hydrofluorothermal Process . A cross-sectional drawing or the rupture -disk ampoule for the

anhydrous addition of hydrogen fluoride to a closed bomb Is

shown in figure 36. This ampoule was designed for use in the

development of a method for the hydrofluorothermal growth of

BeF2 crystals under HP pressure similar to the hydrothermal

growth of quartz from SiOp. Photographs of the manifold used

to fill the ampoule and the platinum-lined Morey bomb and

parts are shown in figures 37 and 38.

9" %j|

Figure 37. Manifold used to fill rupture-disk ampoule.

63
Figure 38. Platinum-lined Morey pressure bomb and parts

f . Helium Leak Detector . The mass spectrometer

leak detector is capable of detecting one part of helium in

10 million parts of air or leaks of 10"10 cc per second.

Metal parts and assemblies in this research are tested for

tightness with this detector.

3. Evaluation of Performance

a. Experimental Assembly for Toxic Materials . The three -compartmental arrangement of the experimental assembly has been used successfully in filling ampoules with HF gas

for the hyd rof luorothermal process and in performing phase

separations to 1000°C with BeFp in the special cell.

64
The above compartmental arrangement of the experimental

assembly has the following advantages. The separation of the

most hazardous, high-temperature part of the apparatus from

the others minimizes danger in that only a few operations at

most or none at all are required in this area during an experiment; whereas, in the cabinet area, frequent attention is

required in the refrigeration with liquid nitrogen of the trap

for liquid and gas and in the transfer of the trap contents to

a cylinder. Also in the case of a failure in the experimental

vessel at the high temperature, the vacuum manifold in the

hood can be isolated from the vacuum system by closing a valve

in the cabinet area. The location in another area of the

glass system that was available for producing and measuring a high vacuum, facilitates the much more frequent attention to

this part of the system. Further, it separates the glass parts

containing mercury in the diffusion pump and in the McLeod gage

from the all-metal system within the hood and cabinet areas,

thus minimizing breakage and enhancing safety.

In setting up a laboratory for high-temperature research

with toxic materials, alterations were made in an existing

hood to achieve the above separations of the apparatus assembly into three areas. However, commercially available hoods

designed on this principal would appear to be of a great

advantage to other workers performing experiments with toxic

materials at high temperatures under high-vacuum and controlled

pressure conditions.

Description and drawings of the trap, the ultrahigh vacuum

couplings of Monel, and the high-temperature valve of nickel

and Monel, which are used in the manifold, have been reported

[20], A description of the high-temperature valve will be

prepared for formal publication [21],

b. Furnace and Temperature Control . The custom

design and automatically controlled tnree-zone furnace [22 ] has performed well in establishing and reproducing varied heat

environments that are required to achieve the experimental

heat conditions in the furnace for performing different types

of phase separations to 1000°C in the special cell.

The thermocouples for controlling and recording the temperatures of the three furnace zones are arranged so that each

zone may be operated independently or with either end zone as

a slave to the center zone. Temperature control with this

system was such that the band width on the strip chart of the

recorder for the center zone was constant to within several

hundredths of a degree in the range of 500 to 1000°C when the

end zones were operated as slaves to the center zone.

t
c. Controlled -Atmosphere Dry Box , The modified

glove box, described under facilities, has been operated under

a good anhydrous atmosphere as sensed by dew-point readings

below -8o°C, and in some cases after long periods (one week),

below -165 C.

The balloon inflation and deflation technique allows the

air in the main portion of the box to be displaced and filled

with a controlled atmosphere such as nitrogen. The interlock

compartment can also be conditioned to a controlled atmosphere*

by provisions made for its evacuation and subsequent filling

with a dry gas.

The special panel door allows large objects such as a

vacuum desiccator or the special cell to be placed in the box

without any panel disassembly. The well, built in the bottom 1 of the glove box, allows the special cell to be housed in a vertical position for its assembly or disassembly during fillings or product removals.

d

.

Special Cell for Phase Purifications . The

fabrication of the inner system of the cell for resistance to

chemical attack, the machine design for optimum heli-arc welds

with no crevices for a noncorrosive surface and a vacuumtight seal, and the provisions for thermal analysis and for the

detection of temperatures for phase separations and polymorph

formation have been tested to be quite satisfactory in operations of the cell to 1000°C with BeF2

. Details of the cell

fabrication, cell design, thermal analysis during phase purifications, and the varied phase separations involving distillation, crystallization, sublimation, and preferential

decomposition will be described in a formal publication [23];

for other reports see [24, 25, 26],

In the program for the chemical purification and chemical

analysis of BeF2> and its preparation as a pure crystalline

solid of only one of the polymorphic forms, the following

tasks have been achieved by phase separations in the special

cell: (1) a more accurate analysis of the BeO content in the

original sample of BeFQ through analysis for BeO in the residue portion after distillation [27]; (2) chemical purification

of BeFp by distillation in vacuo to remove volatile impurities

to concentrate BeO in residue, and to condense BeF^ vapors as

a glassy solid of high-chemical purity [28]; and (3) the preparation of BeFp in vacuo and collection of its vapor product

as a well-defined, crystalline solid, which after cooling and

removal at room temperature in a dry box, was identified as a single polymorphic species, alpha (low temperature), quartzlike, hexagonal form of BeF2 [28],

66
The pure crystalline polymorph of BeF described above

fulfills the material requirements of a high-purity, welldefined, crystalline solid sought for in the establishment of

very reliable physical and thermodynamic properties for BeFp

in the ARPA light -elements program. The amount on hand, however, is small with the major portion of the distillate obtained

as a glassy solid. However, different temperature conditions

for the condensation of the vapors would be expected to enhance

the yield of the major portion of the distillate as the crystalline product and thus offers a good method for producing

the large quantity (150 g) of a pure crystalline polymorph of

BeFp. The glassy BeF

p

of high-chemical purity and free of

gaseous or other inclusions is also very useful for other

aspects of the program such as determination of the vapor

pressure and heat of fusion. Another possible use for this

material would be as a chemical standard for beryllium and/or

fluorine.

e. Apparatus for Hydrof luorothermal Process . A

major bottleneck in the development of this process has been

the anhydrous addition of . HF to a closed bomb. The technique

for this addition from a rupture -disk ampoule (figure 36) was

perfected. The manifold used for the transfer of gaseous HF

from the cylinder to the ampoule is shown in figure 37 and

the bomb parts are shown in figure 38. A short formal publication of this technique is planned [29]: for other reports

see [30, 31].

(A. R. Glasgow, Jr.)

67
D. Other Purification Techniques

In the past, considerable use has been made of a variety

of physical methods for separating materials. Liquid-liquid

extraction, especially with low-boiling solvents (below C)

which are easily removed, and solid -liquid absorption (chromatography), using low-boiling elutants, have been used.

Adduct and clathrate formation have been applied occasionally.

Low -temperature solubility differences have also been found

to be useful (for example, a cold solution of hydrocarbons in

liquid propane partially precipitates when poured into liquid

methane). Any of these methods can be reactivated if their

use is indicated.

Currently the section is prepared to purify some materials by multiple zone melting of solids, very slow freezing

of liquids (directional freezing), or preparative gas-liquid

chromatography.

Quantities of about 10 g or less of materials which melt

between about 50° and 150°C can be zone melted in sealed

tubes by external resistance heaters which traverse the tube

automatically. Quantities of 0.5 to 1.5 liters of materials

which freeze between about +50° to -150° can be purified by

directional freezing. The freezing is done by very slow cooling in a spherical, vacuum- jacketed container of glass which

is submerged in a bath slightly cooler than the freezing point

of the material. The liquid phase is stirred during the

freezing by swirling the entire apparatus in the bath, first

in one direction and then in the opposite direction, for about

10 revolutions at the rate of about 30 revolutions per minute.

A thermocouple and a resistance thermometer placed in a well

which is located in the axis of rotation permits recording of

the temperature.

A gas-liquid chromatograph with a column 5/3-inch in

diameter by 12 to 60-feet long is available for some separations on a macro scale by this method. In its present

state, the apparatus Is most suited to separating materials

which boil below 100°C. Automatic injection of samples and

programed collection of product can be arranged, but hand

injection of about 2-ml samples and personal attention to the

collection of product has been used for most separations.

(R. T. Leslie)

68
3. PERSONNEL AND ACTIVITIES

A. Personnel Listing

John K. Taylor, Section Chief

Elaine H. Beale, Secretary

CHEMICAL ANALYSIS

Mass Spectrometric Gas Analysis —

Ernest E. Hughes, William D. Dorko

Polarography —

E. June Maienthal

Coulometry —

George Marinenko

Microchemistry —

Rolf A. Paulson, Robert J. Hall

Stoichiometry —

Thomas J. Murphy

Cryoscopy —

Herbert D. Dixon

PURIFICATION

Distillation —

Robert T. Leslie

|uitrapure Reagents —

Edwin C. Kuehner

j Light -Element Purification —

Augustus R. Glasgow, Jr.

69
B# Publications

1. E. J. Malenthal and J. K. Taylor , Separation and

determination of zirconium In zirconia-yttria mixtures by

precipitation with cupferron, Anal. Chem. 36_, 1286 (1964).

2. H. R. Finegold , NMR studies of asymmetric ethanic

rotators: 1 , 2 -d Isub s t ituted propanes, J. Chem. Phys. 4l,

18Q8 (1964). —

3. W. R. Shields, T. J. Murphy , E. L. Garner, Absolute

lsotopic abundance ratio and the atomic weight of a reference

sample of copper, J. Research NBS 68a , 589 (1964).

4. E. J. Catanzaro, T. J. Murphy , E. L. Garner, w. R.

Shields, Absolute lsotopic abundance ratio and the atomic

weight of bromine, J. Research NBS 68a , 593 (1964).

5. R. A. Durst and J. K. Taylor , Near infrared spectrophotometric method for the determinaTTon of hydration numbers,

J. Research NBSJ58A, 625 (1964).

6. W. R. Shields, S. S. Goldich, E. L. Garner, T. J.

Murphy , Natural variations in the abundance ratio and the

atomic weight of copper, J. Geophys. Res. 70, 479 (1965).

7. J. K. Taylor and G. Marinenko , High-precision coulometric analysis with special reference to the determination of

uranium, Proc. Conf. High-Precis ion Anal. Substances of Interes

to Nuclear Energy, p. 147, EURATOM, Bureau Central de Me sure

s

Nuclaires, Brussels (January 18-22, 1965).

8. Jo K. Taylor, Moderation in instrumentation, Sci.

Teacher 32, 37 (19&5).

9. T. J. Murphy and J. K. Taylor , Precise assay of

copper using small samples, Anal. Chem. 37, 929 (1965).

10. E. L. Weise, R. W. Burke, J. K. Taylor , Gas chromatographic determination of the moisture content of grain,

Humidity and Moisture , Vol. 4, p. 3-6, Reinhold, N.Y., 1965.

11. R. T. Leslie and E. C. Kuehner , Distillation analysis

Encyclopedia of Chemistry , Reinhold, N.Y. — In Press

12. E. C. Kuehner and R. T. Leslie , Sublimation,

Encyclopedia of Industrial Analysis , InTerscience, N.Y. — In

Press " "

13. J. K. Taylor , Density and specific gravity, Encyclo- . pedia of Industrial Analysis , Intersciences, N.Y. -- In Press

70
14. A. T. Horton, A. R. Glasgow , Equipment for single - crystal growth from the melt suitable for substance with a

low melting point, J. Research NBS (Phys & Chem) --In Press

15. J. K. Taylor, E. J. Maienthal, and G. Marinenko , Electrochemical methods, Trace Analysis , Intersciences, N.Y. --

In Press

16. R. T. Leslie , Distillation as a tool for purification

of research quantities of materials, Ann. N.Y. Acad. Sci. --

In Press

C. Talks

1. A. R. Glasgow, Jr. , "Rupture -Disk Ampoule for

Anhydrous Addition of HF to a Closed Bomb," 19th Annual Calorimetry Conf., NBS-Naval Med. Res., Washington, October 1964.

2. A . R . Gla sgow , Jr, "Thermal Analysis in Phase Purifications of Polymorphic Solids," Anachem Conf., Detroit,

October, 1964.

3. J. K. Taylor, "Electrical Measurements and Chemical

Analysis," Science Club, Rollingcrest JHS, December 1964.

4. J. K. Taylor and G. Marinenko , "High-Precision

Coulometric Analysis with Special Reference to the Determination of Uranium," EURATOM Conf., Brussels, January 1965.

5. J. K. Taylor , "Standards of Measurement," American

Univ. Teachers Institute, February 1965.

6. G. Marinenko and J. K. Taylor , "Coulometric Calibration of Microvolumetric Apparatus, " Pittsburgh Conf. on Anal.

Chem. and Appl. Spectroscopy, Pittsburgh, March 1965.

7. E. J. Maienthal and J. K. Taylor , "Determination of

Tellurium in Spectrographic Cartridge Brass and white Cast

Iron Standards by Cathode-Ray Polarography, " Pittsburgh Conf.

on Anal. Chem. and Appl. Spectroscopy, Pittsburgh, March 1965.

8. R. T. Leslie , "Distillation as a Tool for Purifica-

.: tion of Research Quantities of Material," Conf. on Purification 1 of Materials, N.Y. Acad. Sciences, N.Y., May 1965.

9. E. E. Hughes and w. D. Dorko , "High-Pressure Mass

Spectrometry ror Trace Analysis with an Analytical Mass Spectrometer," Am. Chem. Soc. Meeting -in-Miniature, Baltimore-

! Washington Section, Univ. Md . , College Park, May 1965.

II 10. G. Marinenko and J. K. Taylor , "Precise Analysis of

^Uranium by Constant -Current Coulometry, " Am. Chem. Soc.

Meeting-in-Miniature, Baltimore -Washington Section, Univ. Md

;College Park, May 1965.

71
D. Committee Activities

J. K. Taylor

Service Analysis Coordinator, Analytical Chemistry Division

Member, Analytical Standards Committee

Chairman, Panel on Chemistry, Civil Service Board of Examiners

Vice-chairman, Civil Service Board of Examiners

Member, Review Board, Science Book List, American Association

for the Advancement of Science

President-Elect, Washington Academy of Sciences (WAS)

Chairman, Committee on Science Education, WAS

Member, Joint Board on Science Education

Director of Science Projects

Elected member, Council of the American Chemical Society (ACS ) Member, Canvassing Committee for the ACS Award in Pure Chemistry

Member, Advisory Board, Analytical Chemistry, journal of the ACS

Secretary-Treasurer, ACS Division of Analytical Chemistry

Chairman, Analytical Topical Group, Chemical Society of Washington

Member, Board of Managers, Chemical Society of Washington

Member, Professional Relations Committee, Chemical Society of

Washington

Chairman, Publicity Committee, Electrochemical Society

Session Chairman, 1965 Eastern Analytical Symposium

E. C. Kuehner

Coordinator, Ultrapure Reagents Committee, Analytical Chemistry

Division

E. June Maienthal

NBS Reporter for Capital Chemist , chemical Society of Washington

Elected member, Board of Managers, Chemical Society of Washlngtoi

T. J. Murphy

Member, Civil Service Board of Examiners

Member, Committee on Meeting Arrangements, Chemical Society of

Washington

R. A. Paulson

Member, Service Analysis Committee, Analytical Chemistry Divisioi

Collaborator on the Committee for Study of Microchemical Methods

Association of Official Agricultural Chemists

72
4. REFERENCES

[I] H.E. Lumpkin, Anal, Chem. 30, 321 (1958).

[2] R.C. Rooney, Analyst 83, 83 (1958).

[3] R.C. Rooney, Analyst 83, 546 (1958).

[4] J.K. Taylor, S.W. Smith, J. Res. NBS 63A, 153 (1959).

[5] G. Marinenko, J.K. Taylor, J. Res. NBS 67A, 31 (1963).

[6] G. Marinenko, J.K. Taylor, J. Res. NBS 67A, 453 (1963).

[7] S.W. Smith, J.K. Taylor, J. Res. NBS 63c, 65 (1959).

[8] J.K. Taylor, G. Marinenko, Proc. Conf. High-Precision

Anal. Substances of interest to Nuclear Energy,

EURATOM, Bureau Central de Mesures Nuclaires, Brussels,

Belgium, p. l47-l6l (1965).

[9] G. Marinenko, J.K. Taylor, Pittsburgh Cohf . on Anal. Chem.

& Appl. Spectroscopy, Pittsburgh, March 1965.

[10] W.R. Shields, T.J. Murphy, E.L. Garner, V. H. Dibeler,

J. Am. Chem. Soc. 84, 1519 (1962).

[II] E.J. Catanzaro, T.J. Murphy. E.L. Garner, W.R. Shields,

J. Res. NBS 68a, 593 (19o4).

[12] T.J. Murphy, W.S. Clabaugh, R. Gilchrist, J. Res. NBS 53,

13 (1954). —

[13] T.J. Murphy, J.K. Taylor, Anal. Chem. 37, 929 (1965).

[14] W.R. Shields, T.J. Murphy, E.L. Garner, J. Res. NBS 68a,

589 (1964).

[15] A.R. Glasgow, Jr., A.J. Streiff, F.D. Rossini, J. Res.

NBS 35, 355 (1945).

A.R. Glasgow, Jr., M. Tenenbaum, Anal. Chem. 28, 1907 (1956)

G.S. Ross, H.D. Dixon, J. Res. NBS 65C, 271 (i960).

A.R. Glasgow, Jr., et al, Anal. Chim. Acta 17, 54 (1957);

reprinted in W.M. Smit, purity Control by Thermal

Analysis, p. 54-79, Elsevier Put). Co., Amsterdam, 1957.

73
[19] G.S. Ross, H.D. Dixon, J. Res. NBS 67A, 247 (i960).

[20] A.R. Glasgow, Jr., NBS Rept. 8l86 , Chapter 8 (1964).

[21] A.R. Glasgow, Jr., High-temperature valve for use with

fluorides, Anal. Chem. Aids for the Analyst . To be

prepared for publication.

[22] A.R. Glasgow, Jr., Design of automatically controlled,

high-temperature, three-zone furnace, J. Res. NBS

(Eng&mst). To be prepared for publication.

[23] A.R. Glasgow, Jr., Preparation of pure crystalline solids

by phase purifications at high temperatures, J. Res.

NBS (phys&Chem). To be prepared for publication.

[24] A # R Glasgow, Jr., Thermal analysis in phase purifications

of polymorphic solids, 12th Anachem Conf., Wayne State

Univ., Detroit, October 1964.

[25] A.R. Glasgow, Jr., NBS Tech. Note 251, p. 53 (Oct 1964);

NBS Tech. Note 260, p. 75 (May 1965).

[26] A R. Glasgow, Jr., NBS Rept. 8504, p. 73 (July 1964).

[27] Analysis by R. A. Paulson, National Bureau of Standards

[28] Microscopic and x-ray powder diffractometry examination

by Carl Robbins, National Bureau of Standards

[29] A.R. Glasgow, Jr., Rupture-disk ampoule for anhydrous

addition of HF to a closed bomb, Anal. Chem. Aids to

the Analyst . To be prepared for publication.

[30] A.R. Glasgow, Jr., Rupture-disk ampoule for anhydrous

addition of HF to a closed bomb, 19th Ann. Calorimetry

Conf., NBS & Naval Med. Center, Washington, Oct 1964.

.[31] A„Re Glasgow, Jr., NBS Tech. Note 251 , p. 10 (Oct 1964);

NBS Tech. Note 260, p. 23 (May 1965).

74


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WASHINGTON, D.C. 20230 U.S. OCPAKTMCMT '

OFFICIAL BUSINESS