ED STATES WENT OF MERCE

CATION

NBS TECHNICAL NOTE 585

Microchemical

Analysis Section:

Summary of Activities

July 1970 to June 1971

BBSS
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety.

The Bureau consists of the Institute for Basic Standards, the Institute for Materials

Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—Linac

Radiation2—Nuclear Radiation2—Applied Radiation2—Quantum Electronics3—

Electromagnetics3—Time and Frequency3—Laboratory Astrophysics3—Cryogenics3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies;

and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

Radiation—Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to pro- mote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes

and methods of test; and provides technical advice and services to Government agencies

upon request. The Institute also monitors NBS engineering standards activities and

provides liaison between NBS and national and international engineering standards

bodies. The Institute consists of the following divisions and offices: Engineering Standards Services—Weights and Measures—Invention and

Innovation—Product Evaluation Technology—Building Research—Electronic

Technology—Technical Analysis—Measurement Engineering—Office of Fire Programs.

THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition,

and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center

consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination

and accessibility of scientific information generated within NBS and other agencies of

the Federal Government; promotes the development of the National Standard Reference

Data System and a system of information analysis centers dealing with the broader

aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world,

and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

Publications—Library—Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

2 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.
UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

NBS TECHNICAL NOTE 585

ISSUED JANUARY 1972

Nat. Bur. Stand. (U.S.), Tech. Note 585, 77 pages (Jan. 1970)

CODEN: NBTNAE

Microchemica! Analysis Section:

Summary of Activities, July 1970 to June 1971

John K. Taylor, Editor

Microchemical Analysis Section

Analytical Chemistry Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

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, U.S. Government Printing Office, Washington, D.C, 20402.

(Order by SD Catalog No. C 13.46:585). Price 70 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 nine sections and about 100 technical personnel encompassing some 57 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 a highly

important output of our laboratories. In addition, however,

it has been our experience that informal, annual summaries of

progress describing efforts of the past year can be very valuable in disseminating information about our programs. A word

is perhaps in order about the philosophy of these yearly

progress reports. In any research program a large amount of

information is obtained and techniques developed which never

find their way into the literature. This includes the

"negative results" which are so disappointing and unspectacular but which can often save others considerable work. Of

importance also are the numerous small items which are often

explored in a few days and which are not important enough to

warrant publication—yet can be of great interest and use to

specialists in a given area. Finally there are the experimental techniques and procedures, the designs and modifications

of equipment, etc., which often require months to perfect and

yet all too often must be covered in only a line or two of a

journal article.

in
Thus our progress reports endeavor to present this information which we have struggled to obtain and which we feel

might be of some help to others. Certain areas which it

appears will not be treated fully in regular publications are

considered in some detail here. Other results which are

being written up for publication in the journal literature

are covered in a much more abbreviated form.

At the National Bureau of Standards publications such as

these fit logically into the category of a Technical Note.

In 1971 we plan to issue these summaries for all of our

sections. The following is the seventh annual report on

progress of the Microchemical Analysis Section.

W. Wayne Meinke , Chief

Analytical Chemistry Division

IV
PREFACE

This report summarizes the current program and recent

activities of the Microchemical Analysis Section of the

Analytical Chemistry Division. This Section has the primary

mission to contribute to the science and technology of the

analysis of small samples and its program includes both fundamental studies to improve the precision, accuracy and sensitivity of analytical techniques, and developmental research to

provide new and improved methods applicable to wide areas of

materials characterization. As a closely related activity,

the Section provides analytical measurements for various

research programs of the Bureau and develops and characterizes

Standard Reference Materials. Research projects are active in

the following areas: gas analysis; atmospheric pollution

anlaysis; and conventional microchemical analysis.

A major effort of the Section during the year has been

concerned with the analysis of Standard Reference Materials.

No effort has been spared to characterize these materials to

a high degree of reliability. The use of such materials not

only establishes benchmarks for industrial control but also

provides a sound basis for inter-laboratory comparisons and

for the intercomparison of measurement techniques and methodology. Such materials are regularly used in this laboratory

to verify the accuracy of analytical procedures . They are

referred to by an identification such as SRM l60b, for example,

A catalog containing full descriptions of these materials may

be obtained from the Office of Standard Reference Materials,

National Bureau of Standards, Washington, D. C. 2023^.

A number of analytical methods developed or modified for

the analysis of Standard Reference Materials as well as materials submitted by several NBS research projects are described

briefly. Space limitations have dictated only a brief description of methods in most cases. It is hoped that such descriptions will be understandable to an experienced analyst. Howv
ever, specific details of all work reported here will be made

available to anyone interested in such matters. Some of the

work discussed is a continuation of activities described in

previous reports. Copies of the latter are available upon

request in most cases.

In order to describe 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

is necessarily the best available for the purpose.

John K. Taylor, Chief

Microchemlcal Analysis Section

VI
TABLE OP CONTENTS

PAGE

1. INTRODUCTION 1

2. AIR POLLUTION MEASUREMENT STANDARDS 4

3. SULFUR DIOXIDE STANDARDS 6

A. Sulfur Dioxide Permeation Tubes 6

B. Sulfur Dioxide Standards for Source Analysis . 8

4 OZONE STANDARDS. .... 11

A. Design 13

B. Method - General 16

1. The Neutral Potassium Iodide Method. ... 17

2. Bergshoeff Method 18

3. Mast Ozone Meter 20

C. Results of Calibration 20

D. Stability 23

5. NITROGEN DIOXIDE STANDARDS 26

6. CARBON MONOXIDE STANDARDS 32

7. PARTICULATE STANDARDS 35

A. General Considerations 35

B. Feasibility Studies 36

C. Microchemical Investigations 37

1. General Appearance 37

2. Microscopic Examination 37

3. Chemical Analysis 39

8. MICROCHEMICAL ANALYSIS 4l

A. Residual and Distillate Fuel Oil SRM's . . . . 4l

B. Proposed Bovine Liver SRM 43

C. Metallo-Organic Chromium Compound SRM 1078b. . 44

D. O-Bromobenzoic Acid SRM 2142 45

E. Fluorine Content of Orchard Leaves SRM 1571. . 48

9. FIRE RESEARCH PROGRAM 51

.0. INTERNATIONAL GRANTS PROGRAM 56

A. Program at the Technion Israel Institute of

Technology 56

1. Trace Analysis by Anodic Stripping

Voltammetry 56

2. Spectrophotometric Studies at Optically

Transparent Electrodes 59

3. Anodic Stripping Voltammetry in Propylene

Carbonate 6l

B. Program at the University of Zagreb 62

VII
TABLE OF CONTENTS (CONT'D.)

PAGE

11. PERSONNEL AND ACTIVITIES 64

A. Personnel Listing 64

B. Publications 64

C. Talks 65

D. Committee Activities 65

12. REFERENCES 67

vm
LIST OP TABLES

TABLE NO. PAGE

1. Stability of sulfur dioxide mixtures 9

2. Comparisons of analytical concentrations with

mixing data 9

3. Summary of calibration analyses of twelve ozone

generators 21

4. Differences found between neutral potassium

iodide and the Bergshoeff method 22

5. Generator No. 6, change of ozone output with

time 24

6. Generator No. 9, change of ozone output with

time 25

7. Stability of carbon monoxide mixtures 33

8. Comparison of catalyst performance 34

9. Analysis of particulate material 39

10. Analysis of fuel oils 42

11. Volatility of fuel oil SRM's 43

12. Nitrogen content of bovine liver 44

13. Chromium content of SRM 1078b 46

14. Bromine content of 0-bromobenzoic acid,

SRM 2142 47

15. Fluorine content of orchard leaves,

SRM 1571 50

16. Fluorine content of SRM 1571, reported by

several laboratories 50

17. Toxic atmospheres associated with real fire

situations 51

IX
LIST OP FIGURES

FIGURE NO. PAGE

1. Ozone generators 12

2. Ozone generator showing principal features ... 14

3. Apparatus for ozone production and analysis . . 16

4. Analytical scheme for Bergshoeff's method. ... 19

5. Rates for commercial nitrogen dioxide

permeation tubes 26

6. Rates for nitrogen dioxide tubes containing a

drying agent 2 8

7- Device with very low permeation rate 30

8. Device with intermediate permeation rate .... 31

x
MICROCHEMICAL ANALYSIS SECTION: SUMMARY OF ACTIVITIES

July 1970 to June 1971

Edited by John K. Taylor

This report describes the scientific program of

the Microchemical Analysis Section of the Analytical

Chemistry Division of the National Bureau of Standards

,

Institute for Materials Research during July 1970 to

June 1971. General activities are reported in the

areas of air pollution measurement standards including

both gases and particulates, in the field of microchemical analysis, in fire research and In electrochemical analysis performed under an international

research grant program. A sulfur dioxide standard

reference material for use in monitoring ambient atmosphere, and the initial work on a similar standard for

stationery sources are described. Research activities

on potential standard reference materials for ozone,

nitrogen dioxide, and carbon monoxide are also

described.

Key words: Air pollution analysis; sulfur dioxide;

carbon monoxide; ozone; nitrogen dioxide;

fire research; microchemical analysis;

particulate analysis.

1. INTRODUCTION

The scope of activities of the Microchemical Analysis

Section has been changing during the past several years. The

competences within the Section have always included techniques with considerable analytical applicability. Accordingly,

the certification analysis of Standard Reference Materials

(SRM's) and the analysis of research materials for other NBS

programs has been a major activity. As a result, the Section's

program has shown a high degree of flexibility, responding

to both national needs and to the needs of the NBS research

{activity. A research program to provide improved measurement

capabilities has been a logical compliment to these analytical

activities. ]_
The growing concern in the United States about air

pollution has focused sharply the need for reliable

determination of trace constituents in the atmosphere. Not

only must such measurements be made more extensively than

ever before, but legal enforcement considerations demand a high degree of compatibility between measurements made by

different laboratories. The reliability required can only

be achieved by the development of a national system of

standard reference materials to which all measurements can

be traced.

In recognition of this need, the Air Programs Office of

EPA has sponsored a program at NBS for several years to

help support the research and development aspects, and the

NBS Office of Standard Reference Materials has devoted

considerable resources to production of SRM's as they are

developed. The Micro chemical Analysis Section has been the

main participant in this program. Accordingly, these

activities play a dominant role in this year's Progress

Report

.

The Section has also become involved in some other

activities closely related to the program mentioned above.

A survey to determine the composition of the atmosphere

encountered by fire fighters In burning buildings has been

completed. An extensive project to evaluate analytical

methodology and calibration procedures for measurement of

toxic materials in industrial atmospheres was initiated

under the sponsorship of the newly created National Institute

of Occupational Safety and Health. This program will not

be further described in the Report but will be deferred

until the following year, since its activities have

consisted in preliminary planning up to the present time.

Activities in the area of water pollution measurements have

also been initiated and it is expected that these will be

expanded.
The Section has continued to be active in classical

micro chemical analysis and these activities are reported.

The excellent work carried on at the Technion, Haifa,

Israel, by Professor Ariel and her students, under the

PL480 Program is also reported.

In light of the changing emphasis of the Section's

activities, and also to consolidate electroanalytical

programs, the Section's long established projects in

coulometry and polarography have been transferred to the

Electrochemical Analysis Section of this Division. Readers

who have been following the course of these activities will

find them reported in the Progress Report of that Section.

(John K. Taylor)
2. AIR POLLUTION MEASUREMENT STANDARDS

This Section has initiated a program to establish a compatible series of analytical reference standards for

air pollution measurements related to the National

Ambient Air Standards. Reference standards for sulfur

dioxide and hydrocarbon measurements have recently been

issued. Work on similar reference materials for use in

measurement of carbon monoxide, oxides of nitrogen, and

photochemical oxidants is now in progress and will be

discussed in suceeding chapters.

The system consists in maintaining a group of reference

materials or generators of specific pollutants, whose

compositions or operational characteristics are known to a

high degree of accuracy. The members of each group will be

systematically and periodically evaluated, using

state-of-the-art measurement techniques so that their

composition or performance can be reliably predicted at any

time. The reference standards will be intercompared, as

possible, to validate the compatibility of the system.

Standard Reference Materials or devices capable of

generating calibrants will be compared with these analytical

reference standards and distributed by the NBS Office of

Standard Reference Materials.

Initial emphasis is being placed on pollutants related

to ambient air measurements because of the air quality

standards that have been promulgated. The system will be

expanded to include emission levels, as well. Plans

are now being made to provide an entire series of standard

reference materials suitable for the calibration of

automotive emission measurements. Because emissions from

all sources must be introduced into a diffusion model to

interpret ambient air quanlity measurements, all of the

analyses must be compatible. This is not achievable at

present because of variations in measurement and calibration
procedures. The SRM's processed by NBS should make

compatible measurements possible.

The need for compatible standards for analytical

calibrations has been recognized by both government and

industry. The Air Programs Office of EPA has provided

substantial support to NBS in establishing the program and

sponsoring the research back-up it requires

.

(John K. Taylor)
3. SULFUR DIOXIDE STANDARDS

A. Sulfur Dioxide Permeation Tubes

A research project to evaluate the potential of

permeation tubes to provide reliable calibrations of sulfur

dioxide determinations at ambient levels was carried out

during fiscal year 1970. This program was sponsored by the

Air Programs Office of EPA and much of the results were

published in the Summary of Activities for 1969-70 [1].

In brief, this work demonstrated the feasibility of this

approach and established the basis for the calibration

procedures used.

A standard reference material consisting of a 10 cm sulfur

dioxide permeation tube was announced on December 1, 19 70 and

is available from the Office of Standard Reference Material

(SRM 1625) • These tubes have a typical S0

? permeation rate of

2 yg/min at 25 °C. Two additional standards in this series

will be available shortly. These consist of 5 cm and 2 cm

sulfur dioxide permeation tubes and are designated SRM 1626 and

SRM 1627 respectively. The typical permeation rates of these

tubes are 1.0 yg/min and 0.4 yg/min, respectively.

The permeation tubes in these series are individually

calibrated at three or more temperatures in the range between

20 and 30 °C. The primary calibration technique is by gravimetric determination of the weight loss due to S0 ? emission.

However, selected tubes are calibrated by coulometric measurement, as described by Scaringelli [2]. The measured rates are

computer fitted by the method of least squares to an equation

of the type log R = mt + b . The resulting equation is used to

calculate rates at 1-degree intervals between 20 and 30 °C.

The precision of measurement is estimated from the results

obtained on calibration of each lot, consisting of between 25

and 50 tubes. The calibration uncertainty for the 10 and 5 cm

tubes is approximately 0.5 percent at 25 °C and less than

1 percent at the higher and lower temperatures. The uncertainty

6
for the 2 cm tubes is about 1 percent at 25 °C and 2 percent at

either end of the temperature range.

The systematic errors concerned with the calibration

are considered negligible. Variations are minimized by

controlling the bath temperature to better than ± 0.01 °C

and the weighings are made with a microbalance at sufficiently

long time intervals that the uncertainty in weight losses is

probably less than 5 parts in 2000.

These tubes are used to produce known concentrations

of sulfur dioxide in air streams which are then used for

the calibration of instruments designed principally for

measuring ambient atmosphere concentrations of sulfur dioxide.

Apparatus and techniques for this purpose are described

in references [3] and [4] and should be consulted for

operational details. Because of the large temperature

coefficient of the permeation rate, approximately 9 percent

per degree celsius , the temperature must be maintained

constant and measured accurately to 0.1 °C to provide

concentrations consistent with the calibration uncertainty.

It is recommended that the tube temperature be held

constant during use and that desired concentration levels

be achieved by adjustment of the flow rate. If it is

necessary to vary the concentration by changing the tube

temperature, a suitable time interval must be allowed for

equilibrium of the permeation rate to be re-established.

For changes of 1 or 2 degrees celsius, a period of 3 hours

should suffice. For changes of 10 degrees or when removed

from low temperature storage, a period of 24 hours is

advisable

.

These tubes are stable and relatively rugged sources of

sulfur dioxide and when properly used, the calibration

should remain valid for the entire time that any visible

liquid sulfur dioxide remains in the tube. At room

temperature, the useful lifetime is about nine months but this

can be extended by storage of the tube at low temperature
between periods of use. However, they should be protected

from moisture during storage. On removal from low temperature

storage, the tubes should be equilibrated at the operating

temperature for at least 24 hours, before use as analytical

standards

.

B . Sulfur Dioxide Standards for Source Analysis

Analytical methods for the determination of high

concentrations of sulfur dioxide in emission sources require

calibration mixtures which cannot be conveniently produced,

using permeation tubes. Mixtures containing low concentrations of sulfur dioxide in air are not sufficiently stable

in ordinary gas cylinders to allow the use of such materials

as standards in the part per million concentration range. It

was anticipated that higher concentrations, 0.2 mole percent

for example, would be unstable to some extent but it was

hoped that the instability would be analytically harmless,

if not insignificant.

Mixtures at the 2000 ppm concentration level were prepared

in large cylinders and transferred to a number of small

cylinders. The ratio of sulfur dioxide to nitrogen was

determined mass spectrometrically both for the large cylinders

and for several of the small cylinders. After a period of two,

years, the sulfur dioxide content of the large cylinders was

compared to another group of small cylinders which had been

filled at the same time as the previous group of small cylinders.

The later analysis was performed by a chemical method involving

the oxidation and conversion of sulfur dioxide to sulfuric acid

with subsequent titration of the acid. The results (ratios)

shown in Table 1 indicate an initial small loss of sulfur

dioxide after transfer from the large cylinder to the small

cylinder, but no further significant loss after a period

of two years.

The apparent randomness of values presumably represents

different degrees of reaction of the sulfur dioxide within

8
the individual cylinders and indicates the necessity for

individual calibration of each small cylinder if these are

to serve as standard reference materials.

Table 1. Stability of sulfur dioxide mixtures.

Elapsed time after transferral

Cylinder Ratio of calculated to Ratio of calculated to

number measured concentration measured concentration

5 days 2 years

308 0.92

281 0.94

171 0.97

132 0.97

181 0.93

264 0.95

282 0.93

The question naturally arises as to the stability of the

gas in the large cylinder. Obviously, any reaction that might

occur in small cylinders could also take place in the large

cylinder, although surface-to-volume considerations might

influence the quantitative effects. Unfortunately, the mass

spectrometric method originally used did not enable the

determination of the absolute concentration of sulfur dioxide.

However, the contents of the large cylinders were analyzed,

titrimetrically , as described above, and these results, in

comparison with the mixing data are given in Table 2.

Table 2. Comparison of analytical concentration with mixing

data.

Concentration Concentration

based on based on

Cylinder mixing data analysis

number ppm ppm

2903180 2020 2050

H 22490 1954 2025
The analytically determined concentration was higher,

in each case, than that calculated from the measured partial

pressures of the constituents. Because the high values

cannot be explained on the basis of reaction with the

cylinder, it seems logical to conclude that calculation of

concentrations of S0

?

mixtures on the basis of mixing data

is not reliable. To confirm this postulate, a new mixture

of SOp-air was prepared, in which the components were weighed

and the partial pressures were measured after each addition.

In this case, the concentration by weight was 2096 ppm while

the pressure measurements indicated a concentration of 1900 ppm.

Evidently, concentrations based on pressure measurements are

too low.

The essential conclusion from all of the above is that

it should be possible to prepare samples of relatively high

concentrations of sulfur dioxide-in-air which after a short

period of ageing can be analyzed with a degree of confidence

that the results will remain valid for a period of at least

two years. Whether or not a method of pre-treatment could

be found that would preclude individual calibrations , needs

further investigation.

(E. E. Hughes)

10
4. OZONE STANDARDS

Photochemical oxidant is one of the most important

pollutants in urban air. Not only do such constituents have

deleterious effects on man and materials but they are the

precursors of smog which has both adverse physiological and

visibility effects . Until recently, total oxidants were determined in ambient

air for both pollution research and abatement measurements.

The advent of specific instrumental methods now makes possible

the determination of ozone, the principle photochemical

oxidant constituent, and this measurement has become a requirement in air pollution monitoring. This instrumentation

needs a source of known ozone concentration for its calibration. This can be provided by an ozone generator which in

turn is calibrated with the neutral potassium iodide method.

In order to provide a reliable calibration procedure,

and also to evaluate referee methods for photochemical

oxidants, NBS is engaged in a program to provide sources of

certified ozone output. This program involves not only the

determination of the ozone output of each generator, but a study of the parameters which could affect the output.

Hodgeson, Stevens, and Martin [5] have constructed a similar

ozone source and used it with a Nederbragt chemiluminescent

ozone detector and also in a two month field evaluation test

in Los Angeles. A number of assembled generators are shown

in Figure 1.

The problem of providing an atmosphere of known ozone

concentration for direct calibration of ozone analyzers is

a difficult one, primarily because of the nature of ozone.

Ozone is an extremely reactive oxidant, oxidizing most reducing

materials and many organic materials. Ozone is fairly stable

at ordinary temperatures but can easily decompose to normal

oxygen in contact with solids. Many surfaces promote this

change and as a result, only glass, quartz, Teflon and

11
I

Figure 1. Ozone generators

mylar can be used in the parts of the generating or detecting

system which are in direct contact with ozone. Because of its

^reactivity, it is very difficult if not impossible to

prepare and keep a volume of air of known ozone concentration

for any reasonable length of time. Such known concentrations

are not only necessary for calibrating instrumental ozone

monitors, but also for the study of the stoichiometry of

ozone reactions. While it has been assumed for a number of

years that there is a 1:1 reaction of ozone and iodine in

neutral KI buffer, it has only been in the last two or three

years that other methods [6,7,8] have substantiated this

because of their 1:1 reaction with ozone. There is at present

no "absolute" method available for the determination of ozone.

12
The neutral potassium iodide method in which ozone

reacts with a 1 or 2 percent KI solution in a phosphate

buffer of pH 6.8 has been designated the method of choice

[9]- This assumes the following reaction:

+ 3KI + H

2 = KI +2 + 2K0H

The KIo is usually determined by spectrophotometry by

comparison with known concentrations of iodine in potassium

iodide. It is not possible to prepare a container of gas of

known ozone concentration, and an alternative is to generate

ozone at a steady rate under reproducible conditions. This

can be accomplished by passing a known flow of clean dry air

through a quartz tube irradiated by ultraviolet light from a

low-pressure mercury lamp. The ozone output can be varied

by changing the UV intensity irradiating the air stream. The

air containing ozone passes to a sampling manifold where a

number of samples can be withdrawn simultaneously.

A. Design

The actual generator is shown in Figure 2. It consists

of an aluminum box containing the ozone source, a UV lamp,

and a quartz tube (length 38 cm, OD 2.5 cm) in which dry air

is irradiated as it flows through. Covering the lamp is a brass tube with two slots 0.16 cm wide and 180 ° apart,

running the length of the tube . The tube is placed so that

one slot is directly between the lamp and the irradiation tube.

Its purpose is to reduce light intensity and hence the ozone

output to an appropriate level. In addition, the inside of

the aluminum box is black anodized to reduce internal reflections. This generator provides four ranges of ozone concentrations which can be varied from zero to a maximum. This is

accomplished by two methods: First, the UV lamp, lamp base

and slotted brass tube are mounted on a circular plate which

can be rotated 180° giving two positions for the lamp. In

one position, the lamp is ^ 5 cm from the irradiation tube,

13
\- 10 cm -| ALUMINUM BOX

LAMP BUSHING

COLLAR J_

LAMP BASE

ROTATING END PLATE

MOVABLE SLEEVE

Figure 2. Ozone generator showing principal features.

in the other it is about 2.5 cm. Second., it was found that

the cross section of the UV lamps is not circular but

elliptical resulting in two positions of maximum intensity,

180° apart. This feature was utilized to give two additional

ranges . A pin was placed on the end of the lamp base bushing

and a collar was placed on the lamp base. A 90° cutout was

made in the collar in such a way that with the pin at one end.

of the cutout, a maximum output results. Rotating the lamp

base to position the pin at the other end of the cutout results

in a minimum output. These positions are very reproducible.

The four possible ranges produced by combinations of lamp

positions are

:

Distance between Range, ppm,

lamp & tube , cm Rotation at 5 1/min

1 2.5 max 0-0.8

2 2.5 min 0-0.2

3 5.0 max 0-0.25

4 5.0 min 0-0.04

14
The ranges are only approximate as there is a considerable difference in the output of the lamps . Each range can

be varied from zero to the maximum by a movable aluminum

sleeve which slides between the lamp and the brass tube.

This sleeve is marked in arbitrary units from to 100.

At zero, the UV lamp is completely covered and there is no

ozone formed. At 100, it is not covered at all and output

is at a maximum.

If the lamp intensity were uniform aZ ong the long axis,

then the output of ozone should be linear between and 100.

Analyses showed that between and 10 and 90 and 100 the

output tended to vary from linearity. Occasionally other

points would not fit the line as well as was desired. This

may be because of irregularities in the lamp along its

length. Because of the variations in roundness, it is

possible that there may also be longitudinal variations

which give effects which are difficult to separate from

normal analytical uncertainties.

The laboratory air supply at ^20 psi is passed through

a silica gel dryer to remove moisture and other impurities.

A large wad of glass wool is placed at the end of the drier

to remove large particles. The flow is regulated by a needle

valve and measured with a mass flow meter. Five 1/mln is the

usual air flow. This meter is easily read to about 0.5 percent

Copper tubing with a few short connections of tygon tubing are

used to move the air through the system to the generator. The

generator is connected to a sampling manifold by a spherical

glass joint and no reactive materials are in the system down

stream of the generator. There are seven outlets on the

sampling manifold. One is connected with teflon tubing to the

Mast meter, which continuously monitors the ozone. Other

outlets are used for sampling for the neutral potassium

iodide method. A schematic of the entire apparatus is

shown in Figure 3-

15
NEEDLE VALVE

DRY AIR SflPPLY -HgK- FlOW METER

MAST METER

OZONE GENERATOR

S1IPHHS Nillflll

F±&m?e 3- Apparatus tmsr <m,wm pipexdoitEltixsn and analysis,

B. Method - General

The ctry air passes through the generator and the flow

rate is monifeor^ed with the flow meter which in turn is checked

at least onee a day with a wet test meter. If the flow

deviates from 5 l/'min by more than 1 percent, it is adjusted,

with the needle valve. Closer adjustment is difficult. Two

outlets from the manifold are connected to absorbers with

flexible teflon tubing. If two absorption trains are in

operation, a maximum of 3-5 1/min will be drawn through them

leaving a reserve of 1.5 liters vented out of the manifold.

Two midget impingers in series are used to collect the

ozone . These are connected to a vacuum system through a

trap, wet test meter, and needle valve, with a three-liter

bottle as ballast. The usual sampling rate is 1.5 1/min.

The size of sample is determined by the ozone concentration

and by the method used. Two chemical methods were employed:

16
(1) the neutral potassium iodide method [10 ]' and (2) the

Bergshoeff variation of it [6], Between samplings, the

sampling system was connected through dummy impingers to

maintain equilibrium, in the system. Some details of the methods

are given below along with comments on their advantages and

disadvantages ~

1. The Neutral Potassium Iodide Method

The method- used is essentially that recommended by

the Intersociety Committee pL©]. Ten ml of the pH 6.8 potassium

iodide^ absorbing; solution are used in each of two absorbers.

The sample sizce varied from 30: 1 to 10 1 for the ozone range

used (0.03 to 0.25 ppm); . Mi the end of the sampling, each

solution was transferred to a 25 ml volumetric flask. Each

absorber and the connecting glassware were rinsed with buffer

solution which was also added to the flasks, after which the

flasks are filled to the mark and mixed. After 30 min,

absorbance readings were made, using a spectrophotometer, at

352 nm with 50 mm cells . A calibration curve was prepared

using iodine solutions of known concentration. The sampling

volume was corrected to 760 mm and 25 °C. Corrections were

also made for the water vapor picked up by the dry air in the

absorbers and wet test meter. One microequivalent of iodine

is equal to 12.72 ul of ozone. Under the conditions used here,

2.5 ul of ozone forms iodine with an absorbance of about 0.5.

The main problem with this method is the volatility of

the iodine and the ease with which it is lost. Higher ozone

concentrations at longer sampling times give results that

are slightly lower than expected. In general the volume of

sample is kept to a practical minimum. Some sensitivity in

measurement is sacrificed to avoid iodine losses. We use

25 ml volumetric flasks to obtain more accurately measured

solution volumes and 50 mm absorption cells to increase the

sensitivity. It is probably better than a measured 10 ml

volume in the absorber and 10 mm cells. We followed the

17
directions of waiting 30 minutes before measuring the absorbance. We confirmed earlier reports [10,11] that the iodine

intensity reached a maximum in about 30 minutes and then

decreased. Bergshoeff and others [6] have reported that

iodine is lost by adsorption on glass. This seems quite likely

to be appreciable where there is only 0.2 of a microequivalent

or less present.

2. Bergshoeff Method

Bergshoeff [6] suggested the addition of a small amount

of thiosulfate to neutral buffered potassium iodide. The

iodine which is formed by the ozone reacts immediately with

the thiosulfate and so cannot be lost by volatilization.

A measured amount of iodine, in excess of the amount needed

to react with all the thiosulfate even if no ozone is present,

is added after sampling, and the excess iodine is then

determined spectrophotometrically . Bergshoeff does not give

the values of the concentrations. He also uses a special

4-section absorber rather than impingers. We chose our

concentrations such that each 10 ml neutral KI absorbing

solution contained 0.80 microequivalents of thiosulfate. After

sampling and a 30 min wait, the absorbing solution was transferred to a 25 ml volumetric and 5 ml of 0.0002 N iodine

solution (1.0 microequivalent) is added. The absorbance is

measured at 352 nm using 20 mm cells. A blank (0.8 y equiv

thiosulfate + 1.0 u equiv I) must be measured with each sample.

The excess of iodine found in the sample is equivalent to the

ozone sampled. A calibration curve is prepared using 0.0002 N

iodine solution. Figure 4 is a graphic representation of the

procedure

.

In the blank the iodine reacts with an equivalent amount

of thiosulfate leaving an excess (CD) of 1 (in this case

0.2 yg) which is measured spectrophotometrically. In the

sample an amount of ozone (BC) reacts with KI forming iodine

which reacts with thiosulfate (BC) . When 1.0 microequivalent

18
SODIUM

THIOSULFATE

0.8 MICROEOUIVALENT

IODINE

1.0 MICROEOUIVALENT

OZONE

Figure 4. Analytical scheme for Bergshoeff's method.

of iodine (AD) is added, part, (AB) reacts with the remaining

thiosulfate leaving BD to be measured. Subtracting the blank

CD from this leaves the iodine equivalent to the ozone which

was sampled.

The advantage of this method is that there is no loss

of volatile iodine during the sampling making it possible

to sample for as long as one hour. Two absorbers in series

were used for sampling but usually 95 to 99 percent of the

total ozone was found in the first absorber. The lower

efficiency is associated with lower ozone concentrations. One

disadvantage of the method is that many pipetting operations

must be performed. Another is that 0.002 N iodine solution

changes rather rapidly and loses about 3 percent of its

strength in 3 hours. Accordingly, it is necessary to prepare

a new solution every 3 hours.

19
A modification of the Bergshoeff method has been tried.

The excess thiosulfate present after sampling is titrated

with 0.01 N iodine solution using starch as an indicator.

Two ml of 0.001 N thiosulfate is added to each impinger. The

titration is carried out in the impinger so no transferring

of liquid is necessary. A microburet with a capacity of

1 ml is used for the iodine solution. The method worked

very well for the higher concentrations but was not sufficiently

precise with low ozone concentrations, mainly because of

difficulty in determining the end point.

3 . Mast Ozone Meter

All of the chemical measurements of ozone were simultaneously compared with measurements using a Mast oxidant analyzer.

The average efficiency of the Mast analyzer was found to be

85 percent. The analyzer is satisfactory for quickly following

the output of the generator, and for setting the generator at

a desired concentration. There is a variation in the signal

of the Mast meter which may at times be as large as 0.5 mV

per hour which is equivalent to 0.005 ppm ozone. In the

Intersociety method on the continuous monitoring of oxidant [12],

it is stated that the hourly variation should not exceed

± 0.01 ppm.

C . Results of Calibration

Table 3 is a summary of the calibration of twelve generators, obtained by a least squares fit of the data. The

determinations were made at sleeve settings which would give

ozone concentrations of approximately 0.04, 0.08, 0.12 and

0.20 ppm. Ozone determinations were made at each setting by

both methods with at least four determinations for each setting

and at least 16 for each generator. The slope of the line of

concentration in ppm vs . sleeve setting is given in column 2

and the intercept is given in column 3- The predicted ozone

concentration for any setting is given by 0^ Cppm) = AX + B

where X indicates the sleeve setting.

20
Table 3. Summary of calibration analyses

generators

.

of twelve ozone

i

Generator

number

Slope Intercept

A B

Standard

deviation of

the slope

Standard

deviation of

the predicted

values (ppm)

Ends Middle

1 .00237 -.0136 .000042 .0018 .0011

2

i .00294 -.0101 .000069 .0025 .0018

3 .00241 -.0008 .000052 .0021 .0012

4 .00329 -.0126 .000069 .0024 .0015

5 .00297 -.0182 .000058 .0026 .0016

6 .00292 -.0182 .000086 .0030 .0018

7 .00209 -.0081 .000035 .0015 .0009

8 .00224 -.0167 .000044 .0018 .0012

9 .00229 -.0035 .000030 .0012 .0007

10 .00249 -.0128 .000048 .0018 .0012

11 .00259 -.0109 .000044 .0021 .0010

12 .00326 -.0240 .000057 .0019 .0011

The uncertainty of the predicted value of the ozone concentration for these generators is of special interest. In this

kind of fit, the uncertainty is greater at the ends and smaller

in the middle. The average of the standard deviation of the

ends of the line is given in column 5 while the standard

deviation in the center is given in column 6.

The results show a large variation both in the slope

and in the uncertainties. The variation in the slope is

undoubtedly due to differences in the UV lamps, especially

in the thickness and shape of the quartz envelope. These

variations were expected. An examination of the lamp output

using a photocell while seeking the maximum and minimum

positions had shown large differences in the lamps . The

irariations in the standard deviation of the predicted values

21
are probably due to the analytical method. It is possible

that there are some changes in the ozone output, due to

variations in lamp output or the flow through the irradiation

tube j but those would be very small compared with the uncertainties in the analytical method.

To check on the reproducibility of the method, 21

determinations were made at the same generator setting over

a period of three days . The standard deviation of a single

measurement was 0.004 ppm and the 95 percent confidence

limit for the mean was O.O896 ± .0017 ppm.

For most of the generators, a set of simultaneous

determinations were made by the two KI methods. As was

expected, the Bergshoeff method gave slightly higher

results. Averaged results are given in Table 4.

Table 4. Differences found between neutral potassium iodide

method and the Bergshoeff method.

Average

Ozone level Difference between methods

0.20 ppm .006 ppm

0.12 .003

0.08 .002

0.04 .001

These differences do not appear to be significant and

so the results were pooled in the calibration curve.

Early work showed that results deviated markedly from

a straight line near the ends of the lamp, that is with high

and low sleeve settings. This could be caused by a different

geometry of the position of lamp slot and tube, especially

at the low setting, where only the UV rays which are

perpendicular to the lamp and tube can produce ozone. It

could also be due to changes in the quartz lamp envelope

??

near either end.
D. Stability

In investigating the stability of the generators, we

have looked for both long and short term changes in the

output

.

Hodgeson, Stevens and Martin [5] found that the output

of their generator decayed about 15 percent in the first two

weeks of use. We were interested in whether this decay was

greatest during the first few hours of use, or was uniform

during the entire two weeks . Accordingly the ozone output

of most of the generators was measured during the first two

hours of use by both the neutral KI method and the Mast meter

and was again measured after 48 to 72 hours. Any change which

might have occured was hidden by an unexpectedly long warm-up

period. A generator would rise to about 80 percent of its

maximum output within 30 min after it was turned on and would

remain relatively constant for anywhere from 2 to 12 hours

before increasing. A lamp which has been off only an hour

will reach its maximum within 5 min, but for much longer than

that an overnight warm-up is the most satisfactory procedure.

This slow warm-up apparently is involved with the vaporization

of the mercury of the lamp. A UV lamp which had not been used

for several days was removed and gently heated in a flame. It

then reached about 95 percent of its maximum output within

a few minutes but required about two hours to reach the

maximum. This suggests that a warm-up of the entire box

may be involved. One generator was wrapped in heating tape

and the temperature raised while following the ozone output.

As the temperature increased within the box, the ozone output

decreased. With a rise of 15 °C within the box, there was

a 5 percent decrease in output

.

On the possibility that the voltage regulator or the

transformer might also need a warm-up period, they were

turned on overnight and then used with a cold lamp. This

resulted in a lower level of ozone production for several

hours. In addition the voltage on the lamp was measured.

23
This was found to reach a steady state within 15 min. For

most generators the voltage on the lamp was 410 volts. A few

were as high as 420 volts.

Mast analyzer readings appeared to indicate short term

(one or two hours) changes at times as high as 4 or 5 percent.

Such changes could not be verified by the neutral KI measurements as the normal variations in the method approached this

value. At other times the Mast meter would run for hours with

variations of less than one percent. It was also noticed

that the variations were relatively higher at high ozone

concentrations. It is believed that the short time changes

as indicated by the Mast meter are in fact variations within

the Mast meter and not variations occuring in the ozone

generator. The planned use of a chemi luminescent ozone meter

with its rapid response time should be helpful in determining

whether or not variations arise from the generators.

The long-time rate of decay of the generators is also of

special interest . Two of the generators have been in use for

extended periods of time. The ozone outputs for a selected

calibration point are shown in Tables 5 and 6. Both generators

show a similar decreased output with time. The decrease is

essentially linear and is about 1.3 percent per 100 hours in

each case.

Table 5. Generator Number 6. Change of ozone output with

time

.

Hours of use Ozone output, ppm

120 .200

144 .200

216 .200

500 .191

524 .194

548 .189

24
Table 6. Generator Number 9. Change of ozone output with

time

.

Hours of use Ozone output, ppm

120 .207

144 .210

265 .199

290 .191

314 .199

725 .190

773 .191

777 .186

821 .186

An earlier model of the ozone generator showed a decrease

of 18 percent in 1080 hours or a slightly higher decrease of

1.7 percent per 100 hours. In general the decrease of output

of a generator will be about 1.5 percent per 100 hours of use.

This decrease which has been noted by others is probably

caused by solarization of the quartz of the lamp envelope.

A number of factors were examined to determine if they

had any effect on the ozone output or analysis. Dry air was

used in the generator. Saturation of the incoming air with

water vapor decreased the ozone output by about 20 percent.

The quartz irradiation tube was rotated and moved back and

forth within the box. No change in ozone output was noted.

Thirty feet of smooth teflon tubing was used to carry

the ozone from the manifold to the Mast analyzer. After a few

minutes there was no difference in readings from that of

ozonized air carried through the usual three feet of tubing.

(R. A. Paulson, W. D. Kinard, E. E. Hughes)

25
5. NITROGEN DIOXIDE STANDARDS

Nitrogen dioxide permeation tubes have been studied in

great detail in order to assess their potential as standard

reference materials similar to the sulfur dioxide permeation

tube standards (SRM 1625 } 1626, 1627). However, many more

problems are associated with these devices and the ultimate

practicality has not yet been fully evaluated.

A number of commercially available nitrogen dioxide

permeation tubes were obtained. The permeation rates were

determined by a gravimetric method over the entire lifetime

of the tubes. The most significant result of this study is

the observation of a steadily declining rate with time. A

typical result from a single tube is shown in Figure 5.

This tube was maintained in a dry atmosphere at a fixed

temperature during the period in which the gravimetric

determination of the weight loss was performed.

20

TIME IN DAYS

Figure 5. Rates for commercial nitrogen dioxide

p e rme at I on tubes.

26
After the disappearance of the liquid phase of nitrogen

dioxide, a few small droplets of liquid were observed within

the tubes. The color of the vapor and liquid within the tube

suggested that the droplets were not nitrogen dioxide but

rather some other material. A small amount was removed and

was analyzed mass spectrometrically . The spectrum consisted

of a large peak due to water and smaller peaks due to nitrogen

dioxide, a spectrum similar to that obtained from fuming nitric

acid. The substance was probably nitric acid and dissolved

nitrogen dioxide. The quantity of water was considered to be

much greater than could have effused into the tube between the

time it was manufactured and the time when the last visible

amount of nitrogen dioxide disappeared. This suggested the

strong possibility that the water had been present in the

nitrogen dioxide with which the tube was originally charged.

Two solutions to the problem of declining rate were

suggested, either removal of the water from the nitrogen

dioxide before filling the tube , or inclusion of a drying

agent in the tube to remove water originally present and any

water which subsequently effused into the tube. Mechanical

problems associated with drying the nitrogen dioxide were

considered to be greater than those involved in including a drying agent within the tube and this approach was tried first.

A number of tubes were prepared in which a small amount

of phosphorous pentoxide was included in addition to the

nitrogen dioxide. The rates of these tubes were determined

gravimetrically during the entire period when a weight loss

was occuring. The results for a typical tube are shown in

Figure 6. It was presumed that the loss in weight was due

to nitrogen dioxide and the further presumption was made that

this technique would result in a tube sufficiently stable for

use as a standard reference material, Tubes of this type were

later used by several different groups in field studies and

some question arose as to the composition of the material

permeating through the tube. At present it appears that a

27
C/3

10 20 30

TIME IN DAYS

40 50

Figure 6. Rates for nitrogen dioxide tubes containing a

drying agent

.

portion of the vapor is nitric oxide. The amount effusing is

apparently constant for a tube, but quantities of 1 to 6 percent

have been estimated for different tubes. This aspect of the

problem is being studied further and a possible explanation

may be found in the total system which includes at least water,

nitrogen oxides, phosphorous pentoxide and phosphoric acid.

Phosphorous pentoxide is reported to react with nitrogen

tetroxide to give a compound of empirical formula, PpOr * 2NO

and oxygen [13, 1^]. The reaction is extremely slow at room

temperature and would not affect the rate of permeation of

nitrogen dioxide through Teflon. The compound, PpO,- • 2NO,

can, however, react with water to yield phosphoric acid and

nitric oxide.

28
While water appeared to be the principal reason for a

declining rate, other possibilities relating to changes in

the physical or chemical nature of the tube material were

considered. It had been observed early in the development

of these tubes that small blisters appeared on the surface

after a short period of time [15] • The blisters appear to be

a few micrometers in diameter and are found only on the outer

surface. Microscopic examination of cross sections of tube

material obtained from badly blistered tubes failed to disclose

evidence of any changes other than on the surface. A crude but

definitive experiment was performed which consisted of refilling

tubes which had shown a significant change in rate during one

lifetime. The rates after refilling were determined and

compared to those before. If the change in rates were due

either to a reaction between nitrogen dioxide and the tube

material or to a change In structure of the Teflon then the

rate after refilling should have been the same as the last

measured rate before refilling. This was not the case, however,

and the initial rates after refilling were approximately the

same as those which would have prevailed when the tubes were

originally filled.

Nitrogen dioxide permeates through Teflon tubing at an

undesirably fast rate. Permeation tubes constructed to

dimensions similar to sulfur dioxide permeation tubes produce

quantities of nitrogen dioxide that are inconveniently high

for dilution to ambient atmospheric levels. In practice, the

shortest tube which can be filled is 2 cm. Furthermore,

because of the high rate, the life of a tube is only two or

three months . Other devices were needed which would both

extend the life of the calibrant, as well as, produce smaller

quantities of nitrogen dioxide. A further requirement of

such devices is that the final rate be predictable to some

extent from the dimension of the component parts in order to

avoid the necessity of producing large numbers of devices to

satisfy the needs for a few rates. Two relatively simple

29
devices were designed and built both of which have been

preliminarily evaluated and both of which appear to be

satisfactory

.

The first, shown in Figure 7 consists of a disk of TFE

Teflon forced into the end of a glass tube. The last inch of

the tube is shrunk slightly around a carbon mandrel and the

end is heated to form a constricting lip. The disk is machined

for a snug fit in the larger diameter. The disk is then

forced into the constriction, while the tube is gently heated.

The tube is then partially filled with liquid nitrogen dioxide,

cooled, partially evacuated, and sealed. This device can be

constructed to yield rates of any value up to about 0.1 yg/min

.

Higher rates require a disk which is too thin to form a tight

seal to the glass

.

A second device with which rates between 0.1 yg/min

and the rates produced with 2 cm tubes, is shown in Figure 8.

Glass tubing of slightly larger diameter than the inner

diameter of the Teflon tubing is forced into a short length

of glass tubing. A plug is seated in the teflon and a

stainless steel or brass fitting is swaged around the tube.

The final rates can be controlled to some extent by controlling

the distance between the end plug and the glass tubing. The

tube is filled with nitrogen dioxide and sealed in the same

manner as previously described.

^TT '

I I'M' i /

I

|

I I

I I II

l\ cm-l

LIQUID

REDUCED DIAMETER

I h

TEFLON DISK

Figure 7. Device with very low permeation rate

30
STAINLESS STEEL FERRULE

TEFLON PLUG

j- 1 cm

-J

LIQUID TEFLON TUBE

Figure 8. Device with intermediate permeation rate

Some of these tubes have been fabricated with a small

amount of phosphorous pentoxide inside but the majority have

not been made in this way. These devices have potential

lifetimes of up to three years. If the initial charge of

nitrogen dioxide is relatively dry, then the effect of water

on the rate will be insignificant for a rather long period.

The amount of water which will effuse into a tube during

normal use and while observing reasonable precautions regarding

exposure to moist air will be insignificant. Consequently,

until the effect of phosphorous pentoxide and the products

resulting from the use of drying agents is known, tubes and

other devices will be prepared using dried nitrogen dioxide.

Nitrogen dioxide reacts with water as follows

:

4N0

2 + H

2

2HN0

3 + N

2

N 2°3 N0

2 + NO

The compound, N

? 0^, is green, and "wet" nitrogen dioxide

initially exhibits a color best described as greenish brown

which after standing becomes the brown typical of nitrogen

dioxide. An attempt will be made to measure the apparent

water content of freshly prepared devices by measurement of

the color assuming that the spectral characteristic of a mixture of N0„ and N„CU differs from that of NO, '2~3 '2*

(E. E. Hughes)

31
6. CARBON MONOXIDE STANDARDS

Investigation of the analysis and storage of carbon monoxide

in air mixtures have defined the conditions necessary to produce

an SRM in the 10-1000 ppm range. This SRM could be certified to

about ± 2-3 percent of the stated concentrations. As previously

noted [16], there is no evidence of loss of carbon monoxide from

mixtures when stored in stainless steel cylinders at 60 °C for

two weeks. Further aging tests of six weeks duration at 60 °C

of two stainless steel cylinders containing 6.5 ppm carbon monoxide in air indicated no loss of carbon monoxide. In contrast,

the carbon monoxide concentration of an 8.5 ppm carbon monoxidein-air mixture stored in a mild steel cylinder at 60 °C for about

one week decreased to 4.5 ppm. The carbon monoxide was determined by catalytic conversion to methane [1] and by subsequent

comparison with methane in air standards.

The instrumental parameters which give optimum separation

of carbon monoxide and methane on the molecular seive column

and optimum conversion of carbon monoxide to methane on the

nickel catalyst are as follows

:

Catalyst temperature - 450 °C

Hydrogen flow to nickel catalyst - 25 cc/min

Column temperature - 85 °C

Hydrogen flow through column - 90 cc/min

Good peak separation is assured if the molecular seive column

is pre-conditioned by passing helium through it at the rate of

100 cc/min for 12 hours, at 300 °C. This permits the use of

the flow rates for helium and hydrogen given above, which are

higher than the previously recommended values.

The apparatus described earlier [1] was modified so that

hydrogen could be introduced into the helium carrier gas stream

just ahead of the nickel catalyst, instead of being mixed with

the helium carrier before its entrance into the molecular seive

column.

32
A series of carbon monoxide in air mixtures was prepared

in stainless steel cylinders in order to study the stability

of such mixtures at room temperature. The results are given

in Table 7.

Table 7. Stability of carbon monoxide mixtures.

Carbon monoxide concentration, ppm by volume

Cylinder Calculated from From From From

number pressure data analysis analysis analysis

1-71 1-71 2-71 4-71

2X 92.3 89.9 89.9 88.9

33S 101 90.7 92.5 93.1

2Z 17.4 16.7 16.7 16.7

40S 16.5 15.9 15.9 15.6

1 941 896 886

100 941 890 889 879

These results indicate that there was no loss of carbon

monoxide within the limits of experimental error (± 2-3 percent)

However, the concentrations based on analysis average about

5 percent below the concentration calculated from the pressure

measurements during mixing. This is due to the incomplete reduction of carbon monoxide to methane over the nickel catalyst.

This reaction appears to be about 95 percent efficient at best.

A nickel catalyst (catalyst I) prepared according to the

method of Stevens [17] } but without using a fluidizer for evaporation of the water gave the same results as a catalyst (catalyst

II) prepared as above but using a fluidizer. These results are

shown in Table 8. No change in conversion efficiency was

observed when the catalyst temperature was varied over the range

of 320 to 510 °C.

Analysis of mixtures of carbon monoxide in air for use as

SRM's will be based on comparison of the SRM material with

laboratory standards prepared by gravimetric measurements of

the carbon monoxide and air. Uncertainties in the analysis due

to catalyst inefficiency will be eliminated by this method.

33
Table 8. Comparison of catalyst performance.

Carbon monoxide concentration, ppm by volume

Sample Calculated from From analysis From analysis

number pressure data catalyst I catalyst II

1 941 879 887

2 1080 1028 1022

Similarly, the use of SRM's as calibration standards would

eliminate such an uncertainty when using the same analytical

method for air pollution measurements . Both the laboratory

standards and the SRM's will be prepared and stored in

stainless steel cylinders.

(E. E. Hughes, J. M. Ives)

34
7. PARTICULATE STANDARDSA. General Considerations

The chemical composition of the particulate constituents

of the atmosphere is becoming of increasing interest. While

present ambient air standards consider only the mass concentration of total particulates 5 emission standards for stationary

and mobile sources are being developed for hazardous metals and

asbestos, and standards for other constituents will no doubt be

established.

While analytical data are being collected and reported

on various constituents of atmospheric particulates, there

is presently no way to evaluate their reliability. Likewise

there is no supply of material available for use in checking

new methodology, to permit interlaboratory evaluations of

referee methods, and to provide analytical control of measurement systems or networks.

To improve the situation described above, to advance the

state of the art of particulate analysis, and to provide a medium for the exchange of analytical techniques and methodology,

the National Bureau of Standards proposes to issue a particulate

matter reference material. This material will be a large sample

or samples of urban atmospheric particulate matter which will be

carefully mixed to provide maximum uniformity of composition.

It will be exhaustively analyzed and issued with a certificate

of analysis, indicating the limits of analytical uncertainty.

The objective is to achieve a "complete" analysis of the

material. In this framework, the "not-determined" category will

be kept to a minimum and its constituents will be determined in

the future, as possible. Users of the material will be encouraged to report their findings about its composition. Such information will be used to supplement and up-date the compositional

characterization of the material.

A major problem, up to the present time, has been to obtain

a satistactory material. A satisfactory material should be a

35
cal urban particulate material, collected in such a manner

as not to distort its composition. It should be collected over

a reasonably short period of time so that large seasonal changes

in composition would not occur during sampling. At least 10

pounds and preferably 100 pounds of material are required.

Several candidate materials have been examined and rejected

for such reasons as: excessive content of filter fragments;

large proportions of insect parts; non-representative composition,

e.g. fly ash. The most desirable sample presently appears to be

one collected by a bag-house filter. After several cycles of

operation, the material removed after each cycle should be representative of that collected during the cycling period. In other

words, little filter hold-up would be expected. Such a method

of collection appears to require the construction of an expensive,

special sampling apparatus. There are probably other ways in

which a sample of required characteristics could be collected and

suggestions in this respect would be welcomed.

B. Feasibility Studies

A small sample, amounting to 100 g of material, was

furnished to us by Dr. Richard Thompson, of EPA, for

feasibility studies. This material originally came from

the filter of a large building in New York City. A number

of competences in the Analytical Chemistry Division have examined and analyzed this material. While it is not deemed to be

entirely satisfactory as a reference material, even if available in large quantities, it appears that the concept is valid

and that many valuable analytical properties could be certified

on a suitable particulate material.

The results of the various investigations will be reported

in several Progress Reports of the Sections in which the work

was done. The studies made in the Microchemical Analysis

Section are reported in the following.

36
C . Microchemical Investigations

1. General Appearance

The sample is a dark gray dust, fairly uniform in appearance. The dust looks sticky or oily and some portions are

matted together. There are a number of larger pieces of material which can be identified by eye but on the whole the percentage of these is rather small. Some of the things which can be

seen are pieces of paper, fragments of leaves, pieces of string

or thread, plant fragments, and flat chips of paint. No insects or insect parts are seen.

The material which R. Brady (Section 310.07) had extracted with water and benzene was also examined. This 'was no longer "sticky". There was a practical separation of the particles

and fibers in that the fibers had matted together and many of

the particles had been shaken from the fibers.

2

.

Microscopic Examination

Under reflected light, the sample is grayish brown and

appears to be a mass of fibers and particles. Almost all the

fibers are less than 1 ym in length. The particles range in

size from 200 ym down to less than 1 ym. Most of them appear

to be 10 ym or less. There are some conglomerates but they seem

to break up easily when the sample is dispersed in immersion oil

or other media. Very conspicuous components of the dust are

black spheres up to about 200 ym in diameter. These are oil-soot

spheres and will be discussed later, under transmitted light.

A large portion of the particles are opaque.

a. Fibers . As mentioned before, most of the fibers

are short —1 ym or less. A large portion of these, about twothirds, appear to be wood fibers which have probably come from

paper. These fibers are mostly long flat tapering cells with

some nodes. These show first order gray and white colors for the

most part, and show parallel extinction. There are also the flat

baggy cells typical of nonconiferous wood pulp. The appearance

of these fibers is similar to those in several of the larger

37
pieces of paper found in this sample and which look like a filter

paper. This might indicate that the bulk of the fibers in the

dust actually came from the filter and not from the atmosphere.

However, we do not know what kind of filter or filtration was

used. It could be a bag filter or an electrostatic precipitator.

It is doubtful that it is fiber glass, as glass fibers are rather

scarce in the sample. Other fibers present are cotton, wool,

rayon and nylon. Most of these are dyed.

A few fine animal hairs are seen and a few glass fibers

are also seen. These are approximately 5 ym in diameter and

100 to 200 ym long. Asbestos fibers were not seen although they

were looked for especially.

b. Combustion Products . These make up a large part of

the particulate matter in the sample and range in size from

several hundred ym down to submicron size. The most conspicuous

materials are the oil-soot spheres, which range in size from

less than 50 ym to about 200 ym. They are black with a rough

surface. Some are fairly solid, some are just shells, and some

are hardly more than a net of carbon. This Is a characteristic

of oil-soot spheres and depends on the length of time they are

in the hot zone of the furnace and on the amount of air present.

All are fairly easy to crush by pushing on the cover slip.

Oil-soot Is also present as opaque, black irregularly shaped

pieces . Fly ash particles are also present. These are also spheres

and vary in size from a few ym to about a hundred ym and in

color from colorless to black. Some of the larger black fly ash

spheres look somewhat like the oil-soot spheres, but they are

smoother and more regular In shape and are hard. Often they are

magnetic

.

Some incinerator products can also been seen. The most

noticable are partially burned pieces of wood or paper. They

are usually a reddish brown color and semi-transparent. Some

of the wood cell markings can been seen.

38
c. Minerals . Under crossed polars a large number of

small anisotropic materials of a crystalline nature can be seen.

However, they probably do not comprise more than 5 percent of

the sample. Larger pieces are also visible. Of these quartz

is the most prevalent and pieces up to 15-0 ym are seen. Other

materials seen and identified were iron rust (hematite), glass,

and mica or limestone. There were also other crystals, some

quite regular in shape, which could not be quickly identified.

d. Biological Constituents . A few pollen grains are

seen. They look old and can not be identified without staining.

Some spores are also seen but the only one identified is the

rather common Altevnavia . Some plant hairs (Trichomes) are seen

as well as fragments from plants. No recognizable insect parts

appear to be present.

e. Other . There is an appreciable number of flat,

gray, opaque particles which look like paint chips. These are

similar to the larger ones picked from the material. Ignition

and solubility tests indicate that this material is probably a lacquer.

3 . Chemical Analysis

Chemical analysis for various metallic elements were undertaken by several of the competences of this Division as was a preliminary characterization of the organic constituents. DeterTable 9. Analysis of particulate material.

Determined Concentration, percent

carbon 23 .6

hydrogen 2 . 2 nitrogen 1.1

ash 60.0

moisture 3 . sulfate 6.0a

chlorine 1.4 a ammonia 0.7

nitrate 0.4

not determined 9.0

^Included in ash.

39
mination of several anions and several miscellaneous determinations were made in this Section. The methods employed were

essentially conventional procedures and will not be detailed

here, because of the preliminary nature of the determinations.

However, the results are tabulated for illustrative purposes

in Table 9. Much of the "not determined" is believed to be

oxygen combined in the organic material present.

Analytical work is continuing on this material with the

objective of developing methodology for analysis of the proposed

reference standard. This and other work on the sample will be

reported in more detail elsewhere.

(R. A. Paulson, J. K. Taylor)

40
8. MICROCHEMICAL ANALYSIS

Analytical support has been provided to a number of projects

within the NBS , during the past year. This has consisted of

utilizing classical micro- or semimicro-chemical techniques on

such diverse materials as f lame-retardant fabrics, freeze-dried

samples of biological sera, and a wide variety of standard

reference materials . Some of the more Interesting analytical

problems are summarized in the following sections of this report.

A. Residual and Distillate Fuel Oil SRM's

off fuels accounts for more than three-fourths

of the sulfur oxides emitted into the atmosphere. Accordingly, the limitation of the sulfur content of various fuels

Is one of the most Important techniques for air pollution control. M'ost of the analytical techniques presently used require

a materiall off known, sulfur content for their standardization.

Because of the large tonnage of fuels consumed, even a small

analytical error could result in large uncertanties in sulfur

emissions or undue costs in sulfur removal operations.

As part of the NBS program in the air quality area, two

fuel oils, certified for their sulfur content were issued in

1970. These are identified as SRM 1621 Residual Fuel Oil,

S = 1.05 percent, and SRM 1622 Residual Fuel Oil, S = 2.14

percent. The analytical work leading to their certification was

reported in NBS Technical Note 455 [18]. Because the permissible

levels of sulfur are being lowered in many regions, a Residual

Fuel Oil, SRM 1623, S = 0.268 percent, and a Distillate Fuel Oil,

SRM 1624, S = 0.211 percent, have been added to this series.

The oils for these SRMs were obtained from commercial

sources, hence are representative of fuels in common use.

Three samples from each of two five-gallon cans were taken

for analysis of each SRM. Each of the six bottles so taken were

analyzed for sulfur in duplicate in random order. The analytical method used was essentially that described previously [18],

which is a slight modification of ASTM Method D129 . One-gram

41
samples of the oil were combusted in the Parr Oxygen Bomb . Any

iron present was precipitated with ammonium hydroxide and filtered before precipitation of the sulfate with barium. Because

the sulfur contents were low and the capacity of the bomb was

limited to a 1 g sample, the washings from two combustions were

combined for each determination. No inhomogeneity was detected

between bottles, and the results of the twelve determinations for

each SRM were combined. The analytical determinations are

summarized in Table 10.

Table 10. Analysis of fuel oils.

Sample SRM No. 1623 residual fuel oil

Sulfur 0.2681

s = 0.0057

n = 12

95% Confidence limit = ±0.0035

Carbon 87.4%

Hydrogen 12.0%

Water Not detected (<0.1%)

Sediment 0.00%

Ash Not detected (<0.005%)

Sample SRM No. 1624 distillate fuel oil

Sulfur 0.211%

s = 0.0071

n = .12

95% Confidence limit = ±0.0044

Carbon 86.6%

Hydrogen 12.5%

Water Not detected (<0.1%)

Sediment 0.00%

Ash Not detected (<0.005%)

42
Tests were made to determine the loss of volatile constituents. Approximately 10 grams of oil were placed in weighing

bottles and allowed to stand open at room temperature. The results are shown in Table 11. The volatility found was not unexpected and does not constitute a serious analytical problem under

normal conditions of use. However, significant changes in composition could result from the improper practice of storage of an

unstoppered bottle. Accordingly, the user is cautioned to observe the good practice of keeping the bottle stoppered at all

times except when actually withdrawing a sample.

Table 11. Volatility of fuel oil SRM's.

Percent loss

Period of exposure SRM 1623 SRM 1624

1 day 0.67 0.7 3

2 days 0.95 1.19

4 days 1.61 2.10

8 days 2.36 3.40

B. Proposed Bovine Liver SRM

A project has been initiated to issue a sample of dried

bovine liver as a trace element standard. A large quantity of

such material has been prepared and its homogeneity tested.

Certification analysis will be undertaken during the current

year

.

Determinations were made of the nitrogen content of selected

samples of this material as one means of homogeneity evaluation.

A semimicro Kjeldahl method was used on 300 mg samples. The

material had been received from the processor in 25 bottles

which were said to be all from the same batch. Five of these

bottles were randomly selected for analysis. The nitrogen contents, consisting £>f the averages of duplicate determinations

are summarized in Table 12. A high degree of homogeneity is

indicated.

43
Table 12., Nitrogen content of bovine liver.

Bottle number Percent nitrogen

23 iQi. §2

3 10..62

3133 1Q.6

12 10.63

5 10.63

C. Metallo-Organic Chromium Compound SIM 1078b

A commercial lot of the met alio—chromium compound,

tris (1-pheny 1-1, 3-butanediono) chromium (III), intended as a

renewal of SRM 1078a, was analyzed for its chromium content.

The purpose of this SRM is for use in the preparation of call—

brants for engine wear monitoring.

The material was received from the manufacturer in four

bottles, each containing 2.5 kg of the compound. Bottle No. 1

differed somewhat in appearance and had a distinctly different

residual odor and preliminary analysis confirmed that the contents had a different composition from that of the other three.

Accordingly, it was excluded from the scheme for certification

analysis . Four samples were randomly selected from the remaining

three bottles and these were analyzed in sets of 6. Unfortunately,

Sample 2B was ruined in the course of the analysis

.

The SRM was analyzed by digesting 0.8 g samples in a

mixture of sulfuric and nitric acids and fuming off the nitric

acid. One milliliter of 60 percent perchloric acid was added

and heated to dense fumes to insure complete digestion. The

sample was diluted with water and oxidized with ammonium persulfate in the presence of silver ion. The excess persulfate

was boiled off and dilute hydrochloric acid was added to reduce

any manganese present and take the silver out of solution. The

excess chlorine was boiled off and the resulting Cr solution

+2

was titrated potentiometrically with Fe to a potential break

44
which occurred around +0.75 mV. The ferrous ammonium sulfate

solution was standardized at the beginning of each set of titrations against weighed samples of NBS SRM 136b potassium dichromate. The agreement of duplicate standardizations was better

than 3 parts in 10 each day.

As a check of the method, three samples of SRM 10 78a

(chromium-organic standard) were analyzed using the above

procedure. Values obtained for chromium were 9-75 percent,

9.7^ percent, and 9-75 percent, which compare favorably with

the reported value of 9-7 percent. In preliminary work,

samples ©r lf07'Sb were analyzed by the above method but omitting

tine perchloric acid step in the digestion. It was found to be

impossible to totally destroy the organic material and therelore 3 complete oxidation of the chromium was not obtained.

This Incomplete oxidation was Indicated by -an Inability to

maintain a peirmanganlc color In the solutions after the

oxidation step.

The value of the standard deviation,, s, is consistent

with the expected 'uncertainty of the analysis 3 so that a

high degree of homogeneitry is Indicated. The overall

average value "based on 11 degrees of freedom Is 9- 518 ± 0.00 7

where the unce"rtalnty represents the half width of the

95 percent confidence interval. The results of the analysis

are summarized in Table 13-

D. Q-Bromobenzoic Acid SRM 2142

A sample of o-bromobenzoic acid which had been prepared

and purified by Mr. C. W. Stanley of the Office of Standard

Reference Materials was analyzed and certified as SRM 2142

for use as a microchemical standard in the determination of

bromine in organic compounds as well as a standard for carbon

and hydrogen microanalyses. The material was subdivided

into 12 bottles. Six of these were randomly selected for

certification analysis

.

45
Table 13. Chromium content of SRM 1078b.

Bottle Sample

Order a of

Analysis

Percent

Chromium

2 A 2 9.514

C 9 9.539

D 5 9.510

3 A 11 9.513

B 4,7 9.522, 9.525 b

C 1 9.520

D 12 9.529

4 A 8 9.519

B 6 9.498

C 10 9.512

D 3 9.524

Average 9.518 ± 0.007

s 0.011

s of mean 0.003

a Samples were run in sets of six

^Duplicate samples run on different days

Bromine was determined both by the micro-Carius method

and by the macro-sodium peroxide bomb fusion method. At

least one determination was made by each method on each of

the six test samples.

Using the Carius method, accurately weighed 10 mg samples

were digested in 0.5 ml of fuming nitric acid and 15 mg of

silver nitrate for 12 h at 250 °C. After cooling, the tubes

were opened and the contents diluted with water. Following

a digestion period, the silver bromide was filtered on a

weighed micro-filter tube.

46
Using the sodium peroxide bomb method/ 275 mg samples

were mixed with 15 g of sodium peroxide-sugar mixture (14:1)

in a Parr peroxide bomb and ignited. The resulting melt

was washed from the bomb and the solution boiled to destroy

peroxides . Hydrazine sulfate was added to reduce any

bromate present. The solution was made acid with nitric

acid and sufficient 0.1 N silver nitrate solution was added to

precipitate all of the bromide. The precipitate was filtered

off and redissolved in concentrated ammonium hydroxide solution

and reprecipitated by the addition of silver nitrate and nitric

acid.. This precipitate of silver bromide was collected on a weighed fritted-glass filter. Blanks were run with each set.

In addition, two samples of Chlorobenzoic Acid SRM 144 were

taken through the same procedure. Values of 22.63 and 22.61

percent chlorine were obtained to be compared with the theoretical value of 22.65 percent chlorine.

The analytical results are given in Table 14. There is

no significant difference between the bromine content found by

the two methods. The average value, based on all determinations

is 39.80 ± 0.05 percent, where the uncertainty is given at the

95 percent confidence level. The theoretical value for bromine

is 39-75 percent.

Table 14. Bromine content of o -bromobenzoic acid, SRM 2142.

Carius method Bomb method

Bottle No. Percent bromine Bottle No. Percent bromine

7 39.80 11 39.89

10 39.85 7 39.70

2 39.98 2 39.81

7 39.68 4 39.92

10 39.88 7 39.74

11 39.91 2 39.74

12 39.72 4 39.78

4 39.78

2 39.67

mean 39.81 mean 39.80

s 0.11 s .08

s of mean .04 s of mean .03

^7
E. Fluorine Content of Orchard Leaves SRM 1571

Fluorine has been determined in Orchard Leaves SRM 1571.

The method used was the "Tentative Method of Analysis for

Fluorine Content of the Atmosphere and Plant Tissues (Manual

Methods) 12204-01-68T" adopted by the Intersociety Committee

[19]. This is the method that will probably find wide usage

in air pollution analyses of fluoride damage of plants and for

which the present SRM may be useful as a standard. Briefly the

method is as follows: A dry sample of leaves (10 to 15 g) is

weighed in a platinum dish and then made alkaline with a calcium

oxide slurry. The treated leaves are heated on a hot plate

until charring and partial ashing takes place. The ashing is

completed in a muffle furnace at 600 °C. The entire residue or

a weighed portion of it is fused with sodium hydroxide to convert all the fluoride to a soluble form. The melt is disintegrated in hot water and transferred to a Huckabay still [20].

The tentative method given above calls for a Willard-Winter

distillation.

The Huckabay still has a jacket containing boiling tetrachlorethane to maintain a distillation temperature of 145 °C

Sulfuric acid was used instead of perchloric acid in the still.

250 ml of distillate was collected for the spectrophotometric

analysis. An additional 35 ml was usually collected to be certain that all the fluorine had distilled. The fluoride was

determined in an aliquot (usually 35 ml) of the distillate using

the lanthanum-alizarin complexone spectrophotometric method.

When 10-g samples were weighed, the entire residue was used

for distillation. With 50-g samples, a weighed portion (approximately 1/5) of the melt residue was distilled. In this case,

more than one distillation could be made from the same sample.

Usually two were made. In addition, more than one spectrophotometric determination was made on each distillate.

Fluorine blanks were run on the reagents used and amounted to

to about 4 jig for a 10-g sample or its residue equivalent. Each

time a spectrophotometric determination was made, a standard

48
series was also run. This standard series contained from to

50 yg in 50 ml. It was prepared from a stock sodium fluoride

solution. The curve would vary from day to day and also with

new batches of lanthanum-alizarin complexone reagent.

A number of runs were made to determine the efficiency of

the distillation process. Three solutions, each containing

100 yg of F, were distilled under conditions identical to those

of the analysis. Spectrophotometric determination of the fluoride

gave the results listed below, where the multiple numbers indicate

results for aliquots.

Run Number Fluorine Recovered, yg

1 112, 103

2 97, 96

3 108

The results of determination of the fluorine, using six

samples of the SRM are given in Table 15. The multiple results

given for several of the samples are those found for aliquots

of the distillates. The overall average, giving each sample

equal weight, is 3.9 ppm.

Six determinations were made in which the melt was acidified

with perchloric acid, prior to distillation. The results gave

an average value of 5-5 ppm which is slightly higher than the

average found using sulfuric acid.

Several laboratories have analyzed this SRM using a variety of methods and have kindly sent us their results.

The methods used and the results reported are given in Table 16

.

It is a pleasure to recognize the following in this respect.

L. L. Porter, Anaconda Aluminum Company, Columbia Palls,

Montana

A. J. Ellis, Department of Scientific and Industrial Research,

New Zealand

Walter Oyung, Bay Area Air Pollution Control District, San

Francisco, California

D. T. Taves, University of Rochester School of Medicine and

Dentistry, Rochester, New York

49
Table 15. Fluorine content of orchard leaves, SRM 1571.

Sample

number

Weight

of

sample

Weight of

residue

used

f]

Net

.uori

yg

de F

ppm

1 10.42 g All 34

38

36

3.3

3.7

3.5

3.5

2 10.29 g All 34

38

36

3.3

3.7

3.5

3.5

3 40.00 g Total resi due = 4. 502 g a 1.157 g 167

177

4.1

4.4 4.2

b 1.187 154 3.

41.16 Total residue = 4.28 g a 43.37

a

1.077 163 4.0

Total resi due = 5. 56 g

1.237 175 4.0

209 4.8

1.320 193 4.4

193 4.4

4.4

4.4

Table 16. Fluoride content of SRM 1571 report by several

laboratories

.

Laboratory Method Fluoride , ppm

A Technicon AutoAnalyzer (HC104) 8

Technicon AutoAnalyzer (H2SO4) 3

B Micro-diffusion 2.5

Pyrohydrolysis 4.4

C Oxygen flask - fluoride electrode 5.6

D Micro-diffusion 5.9

(W. P. Schmidt, R. A. Paulson)

50
9. FIRE RESEARCH PROGRAM

A study to determine the nature and extent of toxic gases

present in fire-fighting situations was undertaken under the

sponsorship of the Office of Fire Research and Safety at NBS

.

This study is part of a larger program being conducted by the

sponsor to develop better breathing support systems for firemen

An extensive survey was made of pertinent literature and the

information obtained was summarized and Interpreted. This will

be published as a National Bureau of Standards Report "Toxic

Atmospheres Associated with Real Fire Situations". It is concluded that fires can produce extremely hazardous atmospheres

and that good respiratory protection is essential for anyone

involved in a fire situation. An outline of the report 3 essentially the table of contents, is given in Table 17. A brief

summary of each section is given in the following discussion.

Table 17. Toxic atmospheres associated with real fire

situations

.

I. Introduction

II. Statistics on Casualties

III. Review of Some Experimental Results

IV. Specific Toxic Materials Produced in Fires

A. Carbon Monoxide

B. Oxygen Deficiency

C. Carbon Dioxide

D. Hydrogen Chloride

E. Hydrogen Cyanide

F. Nitrogen Dioxide

G. Phosgene

H. Sulfur Dioxide

I. Ammonia

J. Hydrogen Sulfide

K. Miscellaneous Halides and Halogens

L. Other Irritants

M. Miscellaneous Simple Asphyxiants and Gases

with Anesthetic Effects

N. Smoke

0. Combinations of Toxic Gases

V. Recommendations and Conclusion

VI. References

51
The Introduction emphasizes that the atmosphere we breathe

must be within certain limits for normal psychological and

physiological processes to be maintained. While there is a great lack of knowledge concerning combustion and the atmosphere created by fires, there is no doubt that dangerous

combustion products result.

Section II, concerning statistics on fire casualties,

gives the results of several U. S. and British surveys. The

British surveys appear to be thorough, however several of the

U. S. surveys, in order to provide more useful information,

should be better founded statistically. Most surveys show

toxic gases or smoke to be a significant cause of fire

casualties

.

Section III reviews some experimental results on measurement of toxic gases prevalent in fire situations. Various

types of fire tests have been performed in which fire gases

have been analyzed. These range from burning materials in

small flasks to the burning of full sized structures. Most

fire tests on common materials and structures indicate that

such atmospheres are deficient in oxygen and contain CO and

excess C0„ . Increasing ventilation usually favors production

of C0

2

rather than CO.

In a few studies on burning materials, gases such as

HCN, HC1, HF, SO , N0

2

, NH and Clp have been determined.

Except for HC1, which may be formed in relatively large

quantities from polyvinyl chloride, the above mentioned gases

are usually not found in fire atmospheres in concentrations

as high as CO or C0

?

. Several full scale fire tests are

described in which CO, C0 p and p were monitored in certain

locations as a function of time. These show that oxygen can

be depleted to the 3-4 percent level, C0„ can reach 14 percent

or higher, and CO can reach 4 percent or higher.

Specific toxic gases produced in fires are discussed in

Section IV, where feasible, from the standpoint of physiological

52
and psychological effects, formation in fires, and characterization of a situation in which the gas might be produced. In

fire atmospheres, high concentrations of C0

?

and CO are

usually found simultaneously with low

? concentrations.

Carbon monoxide is produced from the incomplete oxidation

of carbonaceous materials in virtually all fire situations.

Carbon monoxide, when respired by humans acts as a chemical

asphyxiant, that is, it prevents the hemoglobin of the blood

from absorbing oxygen. One percent CO in respired air would

be lethal for exposure of less than one minute. Experimental

data indicate CO could easily be present at the 3-4 percent

level in a real fire. Poor ventilation in a fire situation

favors CO formation.

Combustion of materials decreases the oxygen concentration

in the immediate surroundings. Deficient oxygen in a respired

atmosphere causes symptoms such as loss of muscular coordination

and psychological disturbances. An oxygen concentration of

about 6 percent or lower is rapidly fatal. This level can be

reached in fires as various studies have shown.

Carbon dioxide is formed in combustion of carbonaceous

materials . Respiration of 10-12 percent C0 ? in air for more

than a few minutes is fatal due to paralysis of the respiratory

center of the brain. Carbon dioxide may be present at the

above level in fires

.

Hydrogen chloride must be considered in a fire situation

because plastics containing chlorine, when heated to sufficient

temperature in a fire, evolve hydrogen chloride. The large and

increasing use of polyvinyl chloride plastics makes HC1 a more

common constituent of fire gases today than in the past.

Hydrogen chloride is a respiratory irritant which is easily

detected by Its odor before lethal concentrations are reached.

Hydrogen cyanide is formed, usually in small amounts, in

fires involving nitrogen containing materials such as wool,

nylon, and urethanes. It acts as a chemical asphyxiant when

respired and is rapidly fatal at concentrations of about 3000 ppm,

53
Nitrogen dioxide and phosgene are respiratory irritants

and on inhalation of sufficient quantities may cause injury

or death due to pulmonary edema. Nitrogen dioxide is formed

when nitrogen containing materials such as polyamides and

wool are burned. Phosgene may be evolved from burning

chlorine-containing plastics. Sulfur dioxide, ammonia,

hydrogen sulfide, halides , halogens and other irritants may

be formed, generally in rather small amounts, on combustion

of appropriate materials . These gases are classified as

irritants and usually are easily perceived by their irritating

effects or odors.

Simple asphyxiants and gases with anesthetic effects are

discussed but are not of great importance in the usual fire

atmosphere

.

Smoke, namely particulate matter and any absorbed

materials, when inhaled usually causes a mild irritation of

the respiratory tract. Smoke particles when swallowed after

lodging in the pharynx may cause nausea and vomiting. Smoke

is evolved from nearly all materials during the combustion

process, especially under conditions of poor ventilation.

Combinations of high concentrations of toxic gases and

an oxygen deficient atmosphere usually occur simultaneously

in most fire situations. This is well illustrated by several

figures and tables shown in the report. The physiological

and psychological effects of a combination of toxic gases may

be additive, synergistic, or antagonistic. If additive, the

overall effect of the combination represents the sum of the

individual effects, if synergistic, the overall effect is much

greater than the sum, and if antagonistic, the overall effect

is less than the sum. Several studies on animals show that

different combinations of CO, C0

p

, and

?

, varying from normal,

generally produce additive effects. The addition of small

amounts (less than 100 ppm) of HC1, N0

p

, S0

?

, or HCN to atmospheres containing various combinations of CO, C0„, and Op is

found to cause effects which are synergistic.

54
Section V concludes the report and makes recommendations

on how the problem of toxic gases in fires might be better

elucidated. More valid statistical methods and standardized

report forms would help to more clearly define many aspects

of the toxic gas problem as it exists in the U. S.

It is concluded that a combination of toxic gases and

oxygen deficiency, and not CO alone, is the real hazard of a

fire atmosphere. The respiratory function, then, must be

protected against not only CO, but many other gases as well.

There are many variables involved in each individual fire

situation, and this makes difficult the accurate prediction of

the content of a fire atmosphere. Since new materials and

changes in quantities of traditional materials are used in

furnishings and construction of buildings, the usual fire

atmosphere of today may vary considerably from that in the

past or future. Measurement of toxic gas concentrations at

actual fires using Indicator tubes or other measurement devices

would help to better characterize fire atmospheres.

The concentrations at which a toxic gas or combination of

toxic gases exerts deleterious psychological or physiological

effects depends greatly upon such individual characteristics

as age and health. More work is necessary to determine the

effects of various combinations of toxic gases and the

mechanism of any synergistic action which may be involved.

Firemen should know what toxic gases to expect in a fire

situation and what effects these gases might exert. They

should learn to assess a fire atmosphere from visual observation of the surroundings and from odors or irritating effects

produced by gases present in the atmosphere.

(J. M. Ives, E. E. Hughes, J. K. Taylor)

55
10. INTERNATIONAL GRANTS PROGRAM

Two programs, funded under the International Research

Grants Program, are being carried out as an extension of

the research interests of the Section, and for which the

Section Chief is NBS monitor. One at the Technion has been

in existence for six years. A new one at the University

of Zagreb has just been approved.

A. Program at the Israel Institute of Technology

The National Bureau of Standards awarded a grant to the

Technion Research and Development Foundation - Israel Institute

of Technology in 1965 to investigate electroanalytical

techniques for trace analysis. This work, now in its sixth

year, is under the supervision of Professor Magda Ariel.

The initial studies , dealing with development of improved

electroanalytical techniques, have been summarized in earlier

Progress Reports [16,18]. The recent investigations, including

those currently in progress, are reviewed in the following

sections

.

1. Trace Analysis by Anodic Stripping Volt amine try

In the course of this work, undertaken to further the

exploitation of the analytical potential of anodic stripping

voltammetry (ASV) , two new tools have been developed:

a. The Rotated, Nickel Based, Mercury Film Electrode

(MFE) and

b. The Flow Cell

The MFE has been investigated and its behavior compared

to the prevalent Hanging Mercury Drop Electrode (HMDE)

from both theoretical and practical points of view, including

discussion of those points where the MFE diverges in practice

from theoretical behavior. Among the numerous experimental

parameters examined, the most Important were: (a) the

deposition of the mercury film, its thickness, uniformity,

stability, criteria of malfunction, etc. Stated succinctly:

56
the MPE shows improved sensitivity, better resolution of

adjacent current peaks and, due to its ruggedness, is preferable whenever the analytical procedure requires vigorous

solution stirring or electrode transfer (Medium Exchange

without Flow Cell): on the other hand, it has relatively

higher residual current than the HMDE , a narrower useful

potential range and a limited lifetime, often shortened further

by the presence of seemingly innocuous solutes. Best results

are obtained with the mercury film deposited on a nickel

substrate; complete details of construction, coating, operation

and applications to the analysis of complex samples were

reported.

Intermetallic compounds formed in the mercury (amalgam)

phase, either between the mercury and other metals or between

the metals dissolved In it, have been discussed. This

phenomenon, first encountered in stripping voltammetry with

mercury drop electrodes suspended from metal (Pt, Au, eto.)

wires, and usually regarded as an interference, may be

exploited for trace analysis; the depression of the zinc

stripping current by platinum has been shown to provide a

+4 sensitive means for the estimation of traces of Pt in

_7 solution (10 M and less - e.g. the zinc stripping current

obtained, under certain, defined conditions with a 8 ppb

+2

Zn solution, is decreased by 10 percent by the presence

of 4 ppb Pt ) . A linear correlation between this depression

+4 effect and Pt concentration provides the basis for the

latter' s quantitative estimation.

The choice of supporting electrolyte from which preelectrolysis is carried out is often dictated by the composition

of the sample and is unsuited to the subsequent stripping step

for one or more of the following reasons: unsatisfactory

resolution, interferences present in relatively high concentrations, highly sloped base current, etc. The situation may be

improved by effecting a Medium Exchange, i.e. transferring the

electrode into a more suitable electrolyte before the stripping

57
step. The Flow Cell developed in the present work permits

this transfer to be effected without either breaking the

electrical circuit or exposing the electrode to the atmosphere,

thus, preventing losses hitherto connected with this step;

metals such as zinc, which could not be determined by Medium

Exchange are now easily determinable.

The usefulness of the Flow Cell has been demonstrated

through a series of determinations of trace amounts of lead

and copper carried out in a number of standard steel samples

.

These analyses are characterized by the ease and speed of

the procedure involved: due to the Flow Cell, analysis is

carried out directly on the sample solution, without recourse

to preliminary separation steps. Contamination risks are

reduced considerably.

The Flow Cell has also been combined with an ion-exchange

chromatographic column to provide an anodic stripping analogue

of "chromatopolarography " . This combination constitutes

a convenient and sensitive means for obtaining elution

parameters

.

The Flow Cell may also serve as the monitoring part of

a continuous analytical system, with the appropriate electrode choice, according to the analyte involved; due to its

construction, the cell lends itself to convenient intermittent

standardization, by simply diverting the flow from the analyte

to the standardizing solution.

The complex samples analyzed by anodic stripping voltammetry included: (a) zinc in silicates and rocks; (b) trace

metals (Zn, Pb , In, Cd, Cu) in standard glasses; (c) copper

and lead in standard steels. The procedure developed for zinc

in silicates, described and discussed in detail, served to

illustrate the careful and considered technique required for

successful trace analysis.

The controlled purity of the reagents and especially of

the water employed was essential to the success of the project;
an effective purification system for distilled water was

described in detail [18].

Sensitive and selective trace determinations in complex

samples can be effected by stripping voltammetry combined

with the judicious use of these tools.

Six publications have resulted from the above described

activities [21-26].

2 . Spectrophotometric Studies at Optically Transparent

Electrodes

This new project, directed at evaluating the potentialities of combined voltammetry and attenuated total reflectance

spectrometry (ATR) at optically transparent electrodes as a source of data concerning organic electrode reactions, has

gotten off to a good start. Results to date include:

a. Design of a suitable electro-optical cell.

b. Methodology for preparing the semi-transparent

electrodes

.

c. Investigation of potential distribution on the

electrode as related to cell geometry

d. Investigation of absorbance changes in metal

film due to potential modulation

e. Investigation of parameters affecting film

"life-time" and stability.

The internal reflection technique applied in this work

permits spectrophotometric observation of a region extremely

close to the surface of a transparent electrode during an

electrochemical process.

The electrochemical-optical cell was designed according

to the one proposed by W. N. Hansen [27] with some modifications

that help in fixing its exact position in the spectrophotometer

sample holder in a very reproducible way.

The main part of the cell used is the transparent electrode

Three types of electrodes were used: Gold film electrodes

produced by vacuum evaporation technique (with Bi„0~ as inter59
mediate layer) , platinum film electrodes evaporated directly

on glass from a W wire, and a gold film commercial electrode.

Two types of phenomena specific for the thin film

electrodes were investigated in order to understand the

special behavior of this experimental system: (I) iR drop in

the film; (II) absorbance changes in the absence of any

absorbing - species and/or any faradaic process.

The "reversible" system [Pe(II) — Fe(III) dimethylorthophenanthroline complexes] was used as a model for measuring

the extent of potential inhomogeneity on the electrode

surface

.

It could be shown experimentally, by measuring the

potential changes at maximum distance on the film from the

controlled point, that for millimolar solutions the current

densities resulting at 20-50 mV/sec scans do not cause severe

distortion of equipotential conditions. For 10 mJVI solutions

it was proved advisable to use only narrow strips of the

film to avoid considerable iR drops even at low rates of

potential scanning.

The deterioration rate of the film proved to be very

sensitive to high current densities. It was shown that the

deterioration is gradual and is severest near the electrical

connections to the film. This gradual corrosion of the film

causes a gradual increase in the extent of the iR drop in

the film during its "life-time". In the subsequent development

of any analytical method, this will have to be taken into

account and checked by frequent "standard" runs with well

defined systems.

Absorbance changes of the internal reflected beam due to

modulated potential of the film electrode were monitored at

both types of the gold electrodes used. In both cases the

amplitudes and signs of the changes could be related to the

spectrum of the metallic film (which was different for each

type). It could be proved that the effect of the applied

potential is the modulation of the energy level of the free

60
electrons in the film, causing a shift in the optical parameters of the film, and resulting in a shift of several nm in

the spectrum obtained. (These results were in accordance with

the theory proposed for the a.m. phenomenom [28].

The following manuscripts have been submitted for

publication

:

"Processes in Solution and on the Electrode Surface Monitored

by IRS with Metal Film Electrodes", Part I, General Considerations, Part II, The Oxidation of dimethylferrin—the case of a simple faradaic reaction, Gottesfeld, S. and Ariel, M. , submitted to the J. Eleotroanal . Chem

.

"Processes in Solution and on the Electrode Surface Monitored

by IRS with Metal Film Electrodes", Part III, The Oxidation of

Tetramethylbenzidine —an electrochemical reaction with stepwise

electron removal, Gottesfeld, S. and Ariel, M. , submitted to

the J. Eleotroanal . Chem.

"Processes in Solution and on the Electrode Surface Monitored

by IRS with Metal Film Electrodes", Part IV, The Oxidation of

Malachite Green—a case where reflection adsorbance is dominated by the contribution of the adsorbed layer, Gottesfeld, S.

and Ariel, M. , submitted to the J. Eleotroanal . Chem.

"Electro-Optical Study of the Oxidative Adsorption of 1-Naphthol

on Platinum or Gold Electrodes", Laser, D. and Ariel, M. , submitted to the J. Eleotroanal . Chem.

The electrochemistry of bilirubin in dimethylsulfoxide is

being studied by a variety of methods (polarography , controlled

potential coulometry, potential scanning at a rotating platinum

electrode) . This preliminary work is intended as preparation

for a thorough electro-optical study of bilirubin.

3. Anodic Stripping Voltammetry in Propylene Carbonate

Propylene carbonate (PDC) dissolves a wide spectrum of

organic substances; its usefulness in polarography has been

mentioned (e.g.,, Gutman et al. in Monatsh. Chem. 99., 699 (1968).

ASV in such a medium, if feasible, should allow in certain cases

the direct determination of metal traces In organics (without

61
preliminary ashing). With this objective in mind, problems

involving the methodology of working in this medium have been

investigated, and the following conclusions arrived at

:

a. The risk of sample contamination through the

reference electrode may be minimized by employing a silver wire

dipped into a saturated solution of tetraethyl-ammoniumiodide

in PDC, with a "thirsty glass" junction.

-4

b. Vacuum distilled PDC retains approximately 10 M

water; this, while negligible for polarographic purposes, where

-4 relatively high (10 M or higher — see Gutmann et al . 3 loo. ait.)

metal ion concentrations are involved, prevents its use for the

ASV determination of alkali and alkaline earth metals (as a result of the high residual current, ASV in PDC is restricted to

a rather narrow potential range).

c. Available, suitable supporting electrolytes are

not sufficiently pure to satisfy ASV criteria; however, the

linear correlation between i (peak current in ASV) and metal

P _5 _7 ion concentration has been shown to hold for 10 M - 10 M

+ 2 + 2 Zn or Cd solutions (both in water and in PDC) deposited and

redissolved in the absence of added supporting electrolyte.

Due to the considerable ohmic drops involved (of the order of

several hundred mV) , the shape of the stripping peaks is,

naturally, severely distorted; their width causes considerable

overlapping, so that the method will probably be inapplicable

to the analysis of mixtures.

(M. Ariel)

B . Program at University of Zagreb

A project "Electrochemical Study of Metal Ion-Ligand

Interactions in Nonaqueous Solutions by Investigation of

Electrochemical Properties of the Ligand" to be conducted

at the University of Zagreb, Yugoslavia, was approved under

the International Research Grants Program. Professor Ivan

Piljac of the Institute of Inorganic Chemistry, Faculty of

62
Technology, University of Zagreb, is the principal investigator and John K. Taylor is the Project Monitor for NBS . The project will begin about September 1, 1971.

The investigation seeks to find correlations between

the strength of metal ion-ligand interactions and changes

of electrochemical properties of the ligands . Studies will

be made on hydroxyquinones and their conjugate bases in

nonaqueous media by polarography and other electrochemical

methods. Electrochemical measurements will be combined

with spectroscopic ones, using a thin layer optically

transparent electrochemical cell.

(John K. Taylor)

63
11. PERSONNEL AND ACTIVITIES

A. Personnel Listing

John K. Taylor, Section Chief

Alberta L. Nichols, Secretary

Staff

Ernest E. Hughes

Julian M. Ives

Richard H. Johns (Research Associate)

William D. Kinard

Rolf A. Paulson

William P. Schmidt

B. Publications

1. J. K. Taylor, Editor, "Microchemical Analysis Section

Summary of Activities", NBS Technical Note 545, October 1970.

2. C. E. Champion, G. Marinenko, J. K. Taylor, and

W. E. Schmidt, "Determination of Sub Microgram Quantities of

Chromium by Coulometric Titrimetry", Anal. Chem. 4_2_, 1210

(1970) .

3. J. K. Taylor, "Electrochemical Methods of

Microchemical Analysis", Proceedings, VI International

Sumposium on Microchemistry , Vol. D, p. 173, Verlay,

Wiener Medizinischen Akademie (1970).

4. E. E. Hughes and W. P. Schmidt, "Sulfur Dioxide

Permeation Tube, SRM 1625", Certificate of Analysis,

NBS Office of Standard Reference Materials, December 1, 1970.

5. R. A. Paulson and W. P. Schmidt, "Urea, SRM 2l4l",

Certificate of Analysis, NBS Office of Standard Reference

Materials, August 28, 1970.

6. R. A. Paulson and W. P. Schmidt, "O-Bromobenzoic

Acid, SRM 2142", Certificate of Analysis, NBS Office of

Standard Reference Materials, September 1, 1970.

64
7. W. P. Schmidt and R. A. Paulson, "Sulfur in

Residual Fuel Oil, SRM 1623", Certificate of Analysis,

NBS Office of Standard Reference Materials, April 7, 1971

8. W. P. Schmidt and R. A. Paulson, "Sulfur in

Distillate Fuel Oil, SRM 1624", Certificate of Analysis,

NBS Office of Standard Reference Materials, April 7, 1971

|c. Talks

1. J. K. Taylor, "Electrochemical Methods of

Microchemical Analysis". VI International Symposium on

Microchemistry , Graz , Austria, September 1970.

2. J. K. Taylor, "Trace Analysis by Electrochemical

Methods", American Chemical Society National Meeting, Los

Angeles, California, April 1971.

3. E. E. Hughes, "Fundamentals of Gas Analysis",

Instrument Society of America, 17th National Aerospace

Symposium, Las Vegas, Nevada, May 1971-

D. Committee Activities

J. K. Taylor

Service Analysis Coordinator, Analytical Chemistry

Division Member, Review Board, Science Book List,

American Association for the Advancement of Science

Elected member, Council of the American Chemical

Society (ACS)

Member, Panel on Chemistry, Civil Service Board of

Examiners

Member, Board of Managers, Chemical Society of

Washington

Member, Advisory Committee, Laboratory Guide,

American Chemical Society

Chairman, Chemical Education Topical Group, Chemical

Society of Washington

Member, ISO/TC 48 Laboratory Glassware and Related

Apparatus

65
Member, Advisory Panel, NBS Measurements for Air

Quality Program

Member, Advisory Panel, Chemical Technology Journal

Member, Visiting Committee, GSA National Laboratory

Associate Member, IUPAC Commission V.5, Electroanalytical Chemistry.

R. A. Paulson

Member, Service Analysis Committee, Analytical

Chemistry Division, NBS

Collaborator, Committee for Study of Microchemical

Methods, Association of Official Agricultural

Chemists

W. P. Schmidt

Collaborator, Committee for Study of Microchemical

Methods, Association of Official Agricultural

Chemists

Collaborator, Carbon, Hydrogen and Nitrogen Methods.;

Commission on Microchemical Techniques, IUPAC

66
12. REFERENCES

[1] Taylor, J. K., Editor, Mlcrochemical Analysis Section:

Summary of Activities, July 1969 to June 1970,

U. S. National Bureau of Standards Technical Note

545, 1-114, U. S. Government Printing Office,

Washington, D.C. 20402 (December 1970).

Scaringelli, F. P., Frey, S. A., and Saltzman, B. E.,

AIHA Journal No. 28, 260 (1967)

.

[3] Health Laboratory Science 7, No. 1, 4 (1970).

[4] Scaringelli, F. P., O'Keefe, A. E., Rosenberg, E., and

Bell, J. P., Anal. Chem. 42_ 871 (1970).

[5] Hodgeson, J. A., Stevens, R. K., and Martin, B. G.,

Analytical Instrumentation Symposium, Instrument

Society of America, Houston, Texas, April 1971.

[6] Bergshoeff, G. , Pub. No. 342, Research Institute for

Public Health Engineering, Delft, The Netherlands.

[7] Hodgeson, J. A., Baumgardner, R. E., Martin, B. E. and

Rehme, K. A., Anal. Chem. 4j3_ 112 3 (19 71).

Kopezynski, G. L. and Buf alini , J. J., Anal. Chem. 4_3

1126 (1971).

[9] Federal Register, Vol. 30, No. 84, Part II, p. 8196

April 30, 1971.

Tentative Method for the Manual Analysis of Oxidizing

Substances in the Atmosphere, Health Laboratory

Science 7 152 (1970)

.

Saltzman, B. E. and Gilbert, N., Anal. Chem. 31, 1914

(1959).

Tentative Method for Continuous Monitoring of Atmospheric

Oxidant with Amperometric Instruments, Health Laboratory

Science 7, 13 (1970)

.

Stoddart, E. M., J. Chem. Soc. 1938 , 1459-

Stoddart, E. M. , J. Chem. Soc. 1945 , 448.

O'Keeffe, A. E. and Ortmann, G. C, Anal. Chem. 38,

760 (1966).

67
[16] Taylor, J. K., Editor, Micro chemical Analysis Section:

Summary of Activities, July 196 8 to June 1969,

U. S. National Bureau of Standards Technical Note

505, 1-126 , U. S. Government Printing Office,

Washington, D. C. 20402 (October 1969).

[17] Stevens, R. K. and O'Keeffe, A. E., Anal. Chem. 42_,

143A (1970)

.

[18] Taylor, J. K. , Editor, Micro chemical Analysis Section:

Summary of Activities, July 1967 to June 1968,

U. S. National Bureau of Standards Technical Note

455, 1-132, U. S. Government Printing Office,

Washington, D. C. 20402 (October 1968)

.

[19] Health Laboratory Science 6, 64 (1969).

[20] Huckabay, W. B., Anal. Chem. 19, 154 (1947).

[21] Koster, G. , Golko , A. and Ariel, M. , Israel J. Chem.

6, (1968).

[22] Koster, G. and Ariel, M. , Israel J. Chem. 7, (1969).

[23] Ariel, M. , Eisner, V. and Gottesfeld, S., J. Electroanal

Chem. 7, 307 (1964).

[24] Koster, G. and Ariel, M. (to be published).

[25] Koster, G. , Eisner, V and Ariel, M. Anal. Chem. 39

269 (1967).

[26] Gottesfeld, S and Ariel, M. , Israel J. Chem. 7,

(1969) • [27] Hansen, W. N. , Kuwana, T. and Ostergoung, R. A.,

Anal. Chem. 38, 1810 (1966).

[28] Prostak, A. and Hansen, W. N., Phys. Rev. 160 , 600 (1967).

68
form NBS-114A d-71)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS-TN-585

2. Gov't Accession No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE 5. Publication Date MICROCHEMICAL ANALYSIS SECTION: SUMMARY OF ACTIVITIES _ January 1972

July 1970 to June 1971

6. Performing Organization Code

7. AUTHOR(S)

John K. Taylor

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Task/ Work Unit Nc NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

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12. Sponsoring Organization Name and Address

Same

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14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.)

This report describes the scientific program of the Microchemical

Analysis Section of the Analytical Chemistry Division of the National

Bureau of Standards, Insitute for Materials Research during July 1970

to June 1971. General activities are reported in the areas of air

pollution measurement standards including both gases and particulates,

in the field of microchemical analysis, in fire research and in

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grant program. A sulfur dioxide standard reference material for use

in monitoring ambient atmosphere, and the initial work on a similar

standard for stationery sources are described. Research activities

on potential standard reference materials for ozone, nitrogen dioxide,

and carbon monoxide are also described.

17. KEY WORDS (Alphabetical order, separated by semicolons) Air pollution analysis ; Sulfur

dioxide; carbon monoxide; ozone; nitrogen dioxide; fire research;

microchemical analysis; particulate analysis.

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