NATL INST. OF STAND & TECH

ft UNITED STA SSJ-3 3 bD3 M3

PUBLICATION

U.S.

(EPARTMENT

OF

COMMERCE

National

Bureau

of

Standards

NBS SPECIAL PUBLICATION 260-40

Standard Reference Materials:

SELECTION OF

DIFFERENTIAL THERMAL ANALYSIS

TEMPERATURE STANDARDS

THROUGH A COOPERATIVE STUDY

(SRM 758, 759, 760
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3,

1 901 . 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 Radiation 2—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, DC. 20234.

2 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.
jional Bureau of Standards

1 9 0tC 1974

Ibo ^Selection of Differential Thermal

ps- Analysis Temperature Standards

Through a Cooperative Study

(SRM 758, 759, 760]

Ontario Research Foundation

Toronto, Ontario, Canada

The University of Akron

Akron, Ohio 44384

and

Oscar Menis

Analytical, Chemistry Division

Institute for Materials Research

Li»5 .National Bureau of Standards

' • » Washington, D.C. 20234

H. G. McAdie

Paul D. Garn

z

U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secretary

NATIONAL BUREAU OF STANDARDS, Lawrence M. Kushner, Acting Director,

Issued August 1972
Library of Congress Catalog Card Number: 72-600191

National Bureau of Standards Special Publication 260-40

Nat. Bur. Stand. (U.S.), Spec, Publ. 260-40, 71 pages (Aug. 1972)

CODEN: XNBSAV

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.10:260-40). Price 65 cents.
PREFACE

Standard Reference Materials (SRM's) as defined by the

National Bureau of Standards are "well -characterized materials, produced in quantity, that calibrate a measurement

system to assure compatibility of measurement in the nation."

SRM's are widely used as primary standards in many diverse

fields in science, industry, and technology, both within the

United States and throughout the world. In many industries

traceability of their quality control process to the national

measurement system is carried out through the mechanism and

use of SRM's. For many of the nation's scientists and technologists it is therefore of more than passing interest to

know the details of the measurements made at NBS in arriving

at the certified values of the SRM's produced. An NBS series

of papers, of which this publication is a member, called the

NBS Special Publication - 260 Series is reserved for this

purpose

This 260 Series is dedicated to the dissemination of

information on all phases of the preparation, measurement,

and certification of NBS-SRM's. In general, much more detail will be found in these papers than is generally allowed,

or desirable, in scientific journal articles. This enables

the user to assess the validity and accuracy of the measurement processes employed, to judge the statistical analysis,

and to learn details of techniques and methods utilized for

work entailing the greatest care and accuracy. It is also

hoped that these papers will provide sufficient additional

information not found on the certificate so that new applications in diverse fields not foreseen at the time the SRM

was originally issued will be sought and found.

Inquiries concerning the technical content of this

paper should be directed to the author (s). Other questions

concerned with the availability, delivery, price, and so

forth will receive prompt attention from:

Office of Standard Reference Materials

National Bureau of Standards

Washington, D.C. 20234

J. Paul Cali, Chief

Office of Standard Reference Materials

i ii

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vi
CONTENTS

PAGE

I. INTRODUCTION 2

II. THE SECOND INTERNATIONAL TEST PROGRAM 3

III. MATERIALS

A. Systems Criteria 3

B. Transition Criteria 4

C. Selected Materials .... 5

IV. INVESTIGATORS AND EQUIPMENT 6

V. DATA HANDLING 7

A. Data Preparation 7

B. Data Processing 8

VI. RESULTS - TEMPERATURE DATA 10

A. Tests for Systematic Bias 10

B. Mean Temperature Results 12

C. Influence of Experimental Parameters ... 15

1. Effect of Thermocouple Calibration . . 15

2. T-Thermocouple Placement 17

3. Sample Holder Configuration 22

VII. CONCLUSIONS 31

VIII. ACKNOWLEDGEMENTS 35

IX. REFERENCES 35

APPENDIX A 37

APPENDIX B 41

APPENDIX C 47

vii
LIST OF TABLES

Table No. PAGE

1. Investigators participating in second international test programs and instrument

make 6

2. Mean temperature results (°C) 14

3. Effect of T- thermocouple calibration heating

mode only 16

4. Effect of T- thermocouple calibration cooling

mode only 17

5. Mean temperature results (°C) for thermocouple

place in the sample axially (Code 00) .... 19

6. Mean temperature results (°C) for thermocouple

place in contact with the sample holder

axially (Code 03) 19

7. Mean temperature results (°C) for thermocouple

placed in the reference axially (Code 10) . . 20

8. Mean temperature results (°C) for thermocouple

placed geometrically equivalent to the sample

and reference non-axially (Code 21) 20

9. Mean temperature results (°C) for thermocouple

placed geometrically midway between sample

and reference axially (Code 30) 21

10. Major sample holder configurations reported. . 23

11. Mean temperature results (°C) for sample

holder: cylindrical block, uncovered

cylindrical wells (Code 002) 24

12. Mean temperature results (°C) for sample

holder: cylindrical block, loosely covered

cylindrical wells (Code 012) 24

13. Mean temperature results (°C) for sample

holder: shallow cup, uncovered (Code 402) . 25

14. Mean temperature results (°C) for sample

holder: equal cup, uncovered (Code 502) . . 25

viii
15. Mean temperature results (°C) for sample

holder: deep cup, uncovered, bottom

uniformly = wall (Code 602) 26

16. Mean temperature results (°C) for sample

holder: deep cup, uncovered, bottom nonuniformly = wall (Code 603) 26

17. Mean temperature results (°C) for sample

holder: deep cup, uncovered, bottom

uniformly > wall (Code 604) 27

18. Mean temperature results (°C) for sample

holder: capillary, loosely covered

(Code 701) 27

19. Peak resolution in 4:1 mixtures (by weight

of Si0

2

and K

2 S0

4

31

LIST OF FIGURES

Figure No.

1. Deviations from the mean value as reported

by the 34 investigators (submitted to the

Standards Committee of ICTA) 9

2. Peak resolution from base-line measurements

(see also Table 19) 30

3. Data from 34 cooperating investigators for

each of the 10 substances (submitted to

the Standards Committee of the ICTA) 34

ix

STANDARD REFERENCE MATERIALS:

SELECTION OF DIFFERENTIAL THERMAL ANALYSIS TEMPERATURE

STANDARDS THROUGH A COOPERATIVE STUDY, (SRM 758, 759 , 76 O)

H. G. McAdie

Ontario Research Foundation

Toronto, Ontario, Canada

Paul D. Garn

The University of Akron

Akron, Ohio 44325

and

Oscar Menis

Analytical Chemistry Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

The testing and evaluation program leading to the certification of 10 materials as Standard Reference Materials NBS

758, 759, and 760, for calibrating the temperature scale for

thermal analysis is described. The international cooperative

testing program was set up on the basis of a preliminary program initiated in 1966. Thirty-four laboratories reported to

the Standards Committee of the International Confederation on

Thermal Analysis. The results were obtained on a variety of

apparatus under their conditions of experimentation, except

that the heating rate was prescribed in the range of 4 to

1.0 °C per minute. The data were processed to obtain means

and measures of scatter, not only in total, but separated in

terms of a number of sample number of sample holder parameters

The sample holder geometry was the only parameter having a clear effect on the extrapolated onset and peak temperatures.

The effects of thermocouple position and calibration were

tested, but no significant effect was found. The heating

rate has only a small effect, tending to increase the spread

of onset and peak temperature values from the DTA are somewhat higher than the thermodynamic equilibrium values reported in the literature. Based on the mean values from all the

laboratories the standard deviation was 5 to 8 °C, which includes the bias between laboratories as well as measurement

errors

Key words: DTA; International Confederation on Thermal

Analysis; international cooperative testing; Standard

Reference Materials NBS 758, 759, 760; temperature

scale; thermal analysis.

1
I . INTRODUCTION i

The need for dynamic temperature standards for differential thermal analysis (DTA) has been recognized by a number

of agencies, but no substantial effort to provide these

standards was made prior to the formation of the Committee on

Standardization of the International Confederation for

Thermal Analysis (ICTA) . That Committee began an intensive

study of the problems in 1966. The National Bureau of

Standards participated in the planning and implementation of

a test program designed to screen proposed standards. The

Committee members provided liaison with related organizations

in other countries.

By 1967, priorities had been established and a number of

materials were tested within the scope of the highest

priority, viz. inorganic specimens within the ambient to

1000 °C temperature range. Choice of material was restricted

to those having first order solid state phase changes in the

appropriate temperature ranges . Melting points were excluded

because several types of specimen holders could not retain

liquids, and decomposition processes were considered to be

unsuitable because the atmosphere could not be controlled in

many apparatus. It was clearly defined that these standards

are intended for calibration of the temperature scale under

the conditions of the experiment ; any modification of the

experimental conditions to facilitate the testing of the

reference materials would defeat the purpose.

Samples of twelve materials were distributed to twentyfour laboratories for testing. In 1968 the data were

evaluated and eight of the twelve were selected for large

batch testing and certification. Sufficient quantities of

each material were obtained to make a large number of sets of

Standard Reference Materials. Because of increased interest

in melting points as temperature standards, two high-purity

metals, tin and indium, were added to the test program.

2
Sets of samples were distributed to 34 laboratories in

twelve countries. Data were sent to the Chairman to prepare

for computations. Testing of these samples and evaluation

of the data comprised the ICTA's Second International Test

Program (SITP)

II. THE SECOND INTERNATIONAL TEST PROGRAM

The purposes of the SITP may be summarized:

1. To evaluate further the initial 8 materials as potential

DTA temperature standards, and to evaluate 2 metal melting

points for the same purpose.

V. To provide the experimental basis for certifying each bulk

sample from which test samples were taken.

On the basis of data obtained from the Second International Test Programme, and the recommendation by its Committee

on Standardization, ICTA joins with the National Bureau of

Standards in certifying Standards Reference Materials 758, 759

and 760. The Appendices contain the copies of the certificates

(Appendix C) and a proposed draft of procedures (Appendix A)

submitted to the American Society for Testing Materials.

III. MATERIALS

Examination of a number of specimens of each potential

DTA temperature standard was carried out by various Committee

members, with recommendations being reported by correspondence.

A. Systems Criteria

It is appropriate to review the criteria on which potential systems for DTA temperature standards were selected:

1. Chemical stability - the material should not change on

storage

2. Chemical inertness - the material should not attack materials normally employed in instrument construction.

3. Transitions should be characterized adequately by equilibrium thermodynamic methods.

3
4. Other thermal effects should occur at temperatures removed

from the transition of interest.

5. Materials should not require pre- treatment

6. Materials can be heated in normal atmospheres without

secondary effects.

7. Materials should be available commercially in high purity.

8. Naturally occurring materials are not favored because of

inhomogeneity

9. Expensive and relatively rare materials would be unsuitable for eventual large-scale distribution.

B . Transition Criteria

While melting or freezing points have traditionally been

used as temperature standards, it was decided that Solid

I Solid II first-order phase transitions would be preferable

for use in dynamic DTA. The reasons for this decision were

as follows

1. Not all instrumentation can be used with samples which

melt. A number of common sample holders will not contain

liquids

2. A number of recognized melting point standards (e.g. Pb

,

Zn) may contaminate thermocouples and sample holders

through alloy formation.

3. Use of metal melting points requires the ability to impose a truly inert atmosphere, particularly when the melting point is above a few hundred degrees. Not all DTA

systems have this capability.

4. Use of standard reference organic compounds also requires

good atmosphere control. Such materials may also present

problems of decomposition and/or high vapor pressure which

would eliminate use as standards

5. On melting changes in other physical properties such as heat capacity, thermal conductivity, specific volume, are

often much larger than those accompanying Solid I Solid

II transitions. In the case of metals, high surface ten-
sion may prevent a uniform film or liquid from conforming

to the sample holder shape. Together with the presence

of any oxide layer, this could cause considerable change

in thermal contact and distortion of the record.

6. The effect of impurities on melting points is more pronounced than on Solid I ? Solid II transitions.

Subsequent to selection of eight provisional temperature

standards for DTA, representations to the Committee were

received in favor of including two low- temperature metal

melting points, indium and tin. It was agreed by the Committee that these should form part of the SITP, while

emphasizing the above reservations.

C. Selected Materials

The following materials were selected:

KNOg - Supplied by U. S. National Bureau of Standards.

KC10

4

- Hooker Chemical Ltd., Lot No. 11211.

Ag

2

SO^ - J. T. Baker Analyzed Reagent Powder, Catalog

No. 3436, Lot No. 39230.

Si02 - Supplied by U. S. National Bureau of Standards.

K^SO^ - J. T. Baker Analyzed Reagent Powder, Catalog No.

3282, Lot No. 33157.

B^CrO^ - British Drug Houses Chemicals Ltd. "Analar" Grade,

Catalog No. 10199, Batch No. 821708/690922, to

pass 100-mesh sieve; supplied courtesy of Stanton/

Redcroft Ltd., London, England.

BaCO^ - E. Merck, AG, Darmstadt, Zur Analyse reagent

Catalog No. 1714, Lot No. 7383188; supplied courtesy

of Aktiebolaget Atomenergi, Nylcoping, Sweden.

SrC0

3

- J. T. Baker Analyzed Reagent Powder, Catalog No. 4026,

Lot No. 25187.

In - Alpha Metals, Inc., UHP Spheres 40-80 mesh 99.9991

pure

Sn - Alpha Metals, Inc., UPH Spheres 40-80 mesh 99.9991

pure

5
IV. INVESTIGATORS AND EQUIPMENT

Table 1 lists the investigator and a general description

of the equipment used.

A copy of the revised procedures and data report for the

SITP appear in Appendix A. As part of the statistical

design of the SITP, each investigator was supplied with a random sequence of the numbers 1 to 10 and requested to

examine the samples in this sequence.

Table 1. Investigators participating in second international

test programs and instrument make.

Investigator Instrument Investigator Instrument

AUSTRALIA

Baum

CANADA

Bourgon

McAdie

FRANCE

Cizeron

Harmelin

Jegoudez

GERMANY

Heide

Wiegmann

HUNGARY

Foldvari

Paulik

JAPAN

Kambe

Kato

Oinuma

Otsuka

SOUTH AFRICA

Rigaku Denki 80015

B.D.L. M-2

Stone KA-W

ADAMEL ATD-6 7 B.D.L. M-4

B.D.L. M-2

Hartmann § Braun

Derivatograph

Derivatograph

Derivatograph

Rigaku Denki CN8001

Shimadzu DTA-20B-H

Mitamura 2-100 DTA

Chyo TRDA^-L

SWITZERLAND

Krien

Ostwald

Peters

Wiedemann

U.S.S.R.

Berg

Khripin

Koehler

Piloyan

Rassonkaya

Shklover

U. K. Charsley

Mackenzie

Smith

U.S.A.

Gallagher

Garn

Menis

Oulton

Ware

Linseis L61/1M

Mettler Thermoanaly zer Netzch

Mettler Thermoanalyzer I

Kurnakov Pyrometer PK-59

CKB UP, NTR-64

Own design

Derivatograph

CKB UP, NTR-62

CKB UP, NTR-6 2

Stanton 6-25

Own design

DuPont 900

DuPont 900

Own design

DuPont 900

Stone, LA-FS-2

Stone DTA-12B

Stone DS-2

Kriiger Own design

SWEDEN

Forsyth Netzch

6
V. DATA HANDLING

A. Data Preparation

From descriptions submitted by each investigator,

appropriate code designations for pertinent instrumental

parameters were selected jointly by P. D. Garn and H. G.

McAdie. Corrections to these designations were received at

the following meeting of the Committee and incorporated in

subsequent calculations. In cases where an investigator employed different instrumental parameters for different materials care was taken to separate data from these experiments.

Temperature and area data from each experiment were

coded from the values supplied by each investigator. An

"experiment" was defined as including the heating and cooling

modes if both were carried out. No attempt was made to

measure, review, check or correct these data, however, each

chart record was examined in relation to the data being coded

to reduce transcription errors and avoid misinterpretation.

In cases where obvious discrepancies appeared, or where

further information regarding instrumentation was required,

details were obtained by correspondence.

A number of conventions were adopted:

1. Extrapolated onset temperature was defined as the intersection of the forward-extrapolated baseline with the

backward- extrapolated initial side of the peak, as shown

in Figure 1. The term "onset temperature" throughout this

report refers to that point.

2. Where samples were cycled, only the first cycle data were

coded EXCEPT when only the second cycle data were reported.

It was assumed that data for KNO^ were those for the second

cycle, in view of instructions given. In certain cases

there was some doubt that this material had been cycled.

In other cases data from the second cycle were not reported and it was necessary to use the first cycle results.

3. Replicate experiments from some investigators were made

with identical sample weights. Where information to the

7
contrary was lacking, these were treated as individual

loadings of the sample holder, although it is possible

that only one loading was made and the sample merely

cycled.

4. Sample weights >_ 1000 mg were coded as 999.99 mg.

5. In cases where information recorded on the experimental

charts differed from that in tables, or other typed

summaries, the chart information was used.

B . Data Processing

Coded information was forwarded to P. D. Garn for processing in the computer at the University of Akron. IBM

cards, each containing the data from a single experiment,

were punched and verified in the usual way. Appropriate

corrections were made at the following meeting of the committee and duplicate sets of cards forwarded to 0. Menis and

H. G. McAdie. Certain corrections to data, received by

correspondence too late for inclusion in earlier calculations

were also made.

The basic computer program was revised in format, rather

than in content. Information produced included:

mean

computed standard deviation(s)

maximum observation

minimum observation

number of observations (N)

code numbers of investigators whose data were

included in each of the above calculations,

for each of the following measurements

heating: peak area

onset temperature

peak temperature

Cooling: peak area

onset temperature

peak temperature

8
CM lO OJ

in «r • • CM • >o •

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The sequence of steps in the data processing following

the 1970 committee meeting was as follows:

1. Computations were made on all data as submitted.

2. In a separate program at the U. S. National Bureau of

Standards, 0. Menis and colleagues prepared a ranking

order for all compounds based on the onset temperature

[1] . Replicate values from each investigator were averaged prior to preparation of this ranking, so that only

the one temperature was used for each compound from each

investigator. A number of tests were made for systematic

deviations

3. At the University of Akron, SITP data were used: to compute overall means for all data; to examine the effect of

sample holder configuration; to examine the effect of

thermocouple placement; and to examine the effect of

thermocouple calibration.

VI. RESULTS - TEMPERATURE DATA

A. Tests for Systematic Bias

Before proceeding with re-calculation of the data, a detailed review of the submitted temperatures was made by

0. Menis and the members of the staff of the Engineering

Statistics Division at the U. S. National Bureau of Standards

to investigate the possibility of systematic bias in an investigator's data. Tests were also made to determine trends

in deviations from the overall mean which might result from

a number of sources within the test data.

Calculations and computer plots are summarized in

Tables 2-19. The following conclusions are drawn:

1. Ranking order of onset temperature data indicated the

scatter of results is due to differences between laboratories . 2. Youden plots showed no justification for removing an investigator from the test results on the basis of unaccept10
able systematic bias, as determined by the mean deviation

being greater than ± 3a calculated over all compounds and

all investigators.

3. Some investigators showed better correlation than others,

although generally good precision was observed in each

laboratory

4. Deviations from the overall respective mean temperatures

increased in the following order of measurement positions:

onset (heating) ; peak (heating) ; onset (cooling) ; peak

(cooling). Thus, the average onset temperature obtained

by a given investigator showed the smallest deviation

from the mean of all data for that point.

5. No trend could be established in deviations from the mean

for particular compounds, i.e. no compound gave unusually

precise or imprecise results.

6. No trend could be established in deviations from the overall mean in relation to sample weight, sample holder configuration, well description, sample holder material, heat

sink material, gas flow rate, gas flow pattern, AT couple

characteristics, AT couple location. In each case the

test was based only on the deviation of each investigator's average onset temperature from the mean of all onset

temperatures for the same compound.

7. A trend to increasing difference between onset and peak

temperatures on heating was noted with increasing heating

rate. Wider data scatter was also observed with increasing heating rate.

On the above bases it was appropriate to include all

data, as received from the various investigators, in the

eventual analysis of SITP results. In a very few isolated

cases individual values were excluded on the basis of an

error in test conditions employed or a gross discrepancy

(significantly greater than ± 3a) for a single datum point.

11
B . Mean Temperature Results

Following the tests for bias and deviation trends described in Section 6A, incorporating corrections outlined in

Section SB, a complete re - computation of the data was made.

On the basis of results obtained, the following observations

may be made

1. The average standard deviation on heating for all compounds was ± 6 °C for the onset temperature, and ± 7 °C

for the peak temperature.

2. The average standard deviation on cooling for all compounds was ± 8 °C for the onset temperature and ± 10 °C

for the peak temperature.

3. The spread of temperatures reported for a given transition

on heating varied from 22 to 51 °C for the onset temperature and from 23 to 51 °C for the peak temperatures. In

both cases there was a tendency toward larger spread at

higher transition temperatures.

4. The spread of temperatures reported for a given transition

on cooling varied from 16 to 76 °C for the onset temperature and from 16 to 83 °C for the peak temperature. The

freezing point of Sn and the Sjj -> S^ transitions in

Ag2S0^, BaCO^, and SrCO^ exhibited particularly wide

spreads in both onset and peak temperatures on cooling.

5. With the exception of Ag2SO^, the mean onset temperatures

on heating averaged -1 °C of the accepted equilibrium

transition temperature [2] . For Ag2S0^ an equilibrium

temperature of 430 ± 3 degrees [3] appears to be more

reliable than the 412 degree value cited [2]

6. With the exception of Ag2SO^, the mean deviation of the

onset temperature on heating from the accepted equilibrium

transition temperature [2] was -1 °C. Accepting that an

equilibrium transition temperature for Ag2SO^ of 430 ± 3 °C

[3] is more reliable than the 412 °C cited by NBS [2], the

mean deviation of the onset temperature from the equilibrium

transition temperature was -1.5 °C with a spread of -6 to

12
+3 °C. The mean deviation of peak temperatures on heating

was +6 °C with a spread of +1 to +9 °C from the equilibrium

transition temperature.

7. On cooling , mean onset temperatures for KNO^, In, SiC>

2

, K

2

S0

4

and K

2 Cr0

4

were within -6 to + 2 °C of the equilibrium

transition temperature. For these same compounds mean peak

temperatures ranged from -4 to -8 °C of the equilibrium

value. For Sn , KC10

4

. Ag

2

SO., BaC0

3

and SrCO^. mean onset

and peak temperatures were at least 13 °C below accepted

equilibrium values

8. Mean temperatures for Si0

2 and K2 S04

in a 4:1 mixture by

weight were not statistically different from those for the

individual constituent, so that no effect of dilution was

evident. No difference in precision was noted.

The values for Standard Reference Materials 758, 759,

and 760 are the mean values from Table 2. The standard

deviations in Table 2 reflect principally the variation

between types of instrumentation and other experimental

parameters. Within a laboratory or a single type of instrument the standard deviation will ordinarily be much smaller.

The quoted standard deviations are not uncertainties in the

temperatures of the transitions. The materials from a given

batch will behave the same way in one laboratory as in

another. More extensive tests (for homogeneity) of potassium

nitrate and quartz using a single instrument, yielded values

with ranges of 1 °C for each compound [4] . The deviation

measured by an individual apparatus is a measure only of that

apparatus difference from a norm which is close to the

equilibrium value.

Note that agreement or disagreement with the equilibrium

value is not essential to the use of these Standard Reference

Materials in comparison of other data. It is only necessary

that a single value be accepted. This could be the known

13
thermodynamics value. Deviations of different laboratories

from the same accepted points are used to calibrate differences in the individual instruments and hence to relate

interlaboratory data.

Table 2. Mean temperature results (°C)

Compound

KN0

3

In

Sn

KC10

4

Ag

2 S04

Si0„

K

2 S04

K

2 Cr0

4

eq

Heating

Onset Peak

Cooling

Onset Peak

BaCO.

SrCO.

SiO, in

4:1 mixture

K

2 S0

4 in

4;1 mixture

127.7 63 128 ± 5 135 ± 6 31 12 2 ± 4 119 ± 4 (112- 149) (126- 160) (112- 128) (110- 126)

157 59/60 154 ± 6 159 + 6 29/27 154 ± 4 150 ± 4 (140- 1621 (140- 171) (146- 163) (139- 155)

231.9 57/59 230 ± 5 237 ± 6 22/18 203 ± 16 203 ± 17

(217- 240) (226- 256) (168- 222) (176- 231)

299.5 67/66 299 ± 6 309 ± 8 31 287 i 4 283 ± 5 (280- 310) (296- 330) (278- 296) (274- 295)

430 C A 64 A O A 424 ± 7 kit 433 ± 7 30/27 399 ± 14 399 ± 15

(400- 439) (405- 452) (337- 413) (336- 419)

573 66 571 ± 5 574 ± 5 34/36 572 ± 3 569 ± 4 (552- 581) (560- 588) (565- 577) (559- 575)

583 67 582 ± 7 588 ± 6 30/31 582 ± 4 577 ± 8 (560- 598) (575- 608) (572- 587) (551- 587)

665 63 665 ± 7 673 ± 6 31 667 ± 5 661 ± 8 (640- 678) (656- 692) (652- 675) (630- 671)

810 71 808 ± 8 819 ± 8 29 767 ± 13 7S2 ± 16

(783- 834) (800- 841) (742- 790) (714- 779)

925 67/66 928 ± 7 938 ± 9 31/30 904 ± 15 897 ± 13

(905- 948) (910- 961) (875- 944) (868- 920)

42/40 572 ± 6 575 ± 5 22/23 574 ± 3 570 ± 4 (560- 583) (565- 590) (570- 583) (563- 582)

32/39 582 ± 5 586 ± 6 22/23 584 ± 4 582 ± 4 (572- 595) (574- 600) (570- 595) (570- 594)

See reference [2]

5 See reference [3]

14
C. Influence of Experimental Parameters

The data coding procedures allow for the evaluation of

the influence of 9 instrumental parameters upon any reported

temperature for a given compound:

1. sample weight

2. dilution

3. sample holder configuration and construction

4. gas flow characteristics

5. characteristics of the AT thermocouple

6. characteristics and location of the T- thermocouple

7. effect of thermocouple calibrated.

8. method of temperature measurement

9. heating rate

The effect of heating rate was not statistically significant in the First International Test Program (FITP)

While a heating rate in the range 4 to 10 °C min -1

was requested in the SITP (Appendix B) , actual values reported ranged

from 2 to 11 °C min 1 and the influence of this parameter

was not examined at this time.

1 . Effect of Thermocouple Calibration

An approximately equal number of investigators used

calibrated and uncalibrated T- thermocouples . Of the 18

investigators who stated they employed "calibrated" T-thermocouples, 11 reported calibration at more than one temperature over the range of interest to the SITP. From the data

presented in Table 3 the following observations may be made

for the HEATING mode:

1. There is no statistically significant effect of T-thermocouple calibration with respect to the heating mode.

2. For 9 of the 10 materials, the mean extrapolated onset

temperature for a given compound obtained using a calibrated T- thermocouple is 1 to 8 °C below that obtained

using the uncalibrated T- thermocouple . The same comparison holds for peak temperatures. While the trend in both

15
cases is evident, the differences do not exceed the precision of the data.

3. The mean standard deviation of the onset temperature on

heating is virtually the same for calibrated and uncalibrated T- thermocouples , however, with respect to peak

temperature the mean standard deviation is higher for uncalibrated T- thermocouples

4. For both calibrated and uncalibrated T-thermocouples there

is no appreciable variation of the standard deviation of

either the onset or peak temperatures with temperature.

Table 3. Effect of T- thermocouple calibration heating mode only.

Calibrated Uncalibrated

Compound N_ Onset Peak N Onset Peak

KN0

3

30 127 + 6 134 + 5 33 129 + 5 136 ± 8

In 31/32 153 + 6 158 + 6 28 155 + 5 160 ± 5

Sn 29/31 229 + 5 236 + 5 26 232 + 5 238 ± 6

KC10

4 32/31 298 + 7 308 + 5 35 301 + 4 309 ± 9

Ag

2 S04 31 425 + 6 434 + 5 33 424 + 8 432 ± 9

Si0

2 34 569 + 5 573 + 4 31 573 + 5 576 ± 5

K

2 S04 35 580 + 7 587 + 5 32 584 + 7 590 ± 7

K

2 Cr0

4 31 664 + 5 671 + 4 32 667 + 8 675 ± 8 BaC0

3 38 805 + 7 817 + 7 33 811 + 9 821 ± 9

SrC0

3 38/37 925 + 6 935 ± 8 29 933 + 7 943 ± 8

While fewer data were available on the effect of thermocouple calibration in the COOLING mode (Table 4) the following

observations may be made:

1. There is no statistically significant effect of T-thermocouple calibration with respect to the cooling mode.

2. The mean onset temperature for a given compound obtained

using a calibrated thermocouple ranged from 0 to 18 °C

below that obtained using an uncalibrated thermocouple.

16
3. The mean standard deviation of both onset and peak temperatures is virtually the same for calibrated and uncalibrated T- thermocouples

4. For both calibrated and uncalibrated T -thermocouples there

is no apparent variation of the standard deviation of

either the onset or peak temperatures with temperature.

Table 4. Effect of T- thermocouple calibration cooling mode only.

Calibrated Uncalibrated

Compound N Onset Peak N Onset Peak

KN0

3 17 123 + 4 119 + 4 14 121 + 4 119 + 4

In 17/16 154 + 4 149 + 2 12/11 155 + 4 151 + 6

Sn 16/12 199 + 16 195 + 13 6 217 + 4 220 + 9 KC10

4 17 287 + 5 283 + 6 14 287 + 3 284 + 4 Ag

2 S04 16/13 399 + 8 400 + 10 14 399 + 19 398 + 20

sio

2 20/22 572 + 3 569 + 4 13 571 + 3 569 + 4

K

2 Cr0

4 18/19 582 + 5 574 + 8 12 584 + 2 581 + 3

K

2 Cr0

4 19 666 + 5 658 + 9 12 668 + 4 665 + 5 BaC0

3 18 765 + 13 747 + 17 11 771 + 13 759 + 12

SrC0

3 22 900 + 9 892 + 10 9/8 913 + 21 909 + 13

2 . T-Thermocouple Placement

The following locations for the T- thermocouple existed

in the various instruments used in the SITP.

Code 00 In the sample, axially

01 In the sample, non- axially

02 In the sample, edge

03 In contact with the sample holder, axially

04 In contact with the sample holder, edge

06 In contact with the sample holder support or heat

sink, axially

17
10 In the reference, axially

13 In contact with the reference holder, axially

18 In contact with the reference holder support or

heat sink, edge

20 Location geometrically equivalent to sample and

reference, axially

21 Location geometrically equivalent to sample and

reference, non-axially

30 Location geometrically midway between sample and

reference, axially

40 Shield surrounding sample and reference in a thermally equivalent way

Of these, Code Nos . 01, 02, 05, 06, 13, 20 and 40 were confined to 1 to 2 investigators reporting 1 to 4 data points.

While means were computed in all possible cases, the data

have not been included in Tables 5 to 9 since the influence

of these T- thermocouple locations cannot be evaluated from

such limited results. This is a reflection of the variety

of instrumental designs involved in contributions to the SITP,

rather than a criticism of any particular investigator.

If we restrict data evaluation first to the HEATING mode,

the following general comments may be made:

1. For the extrapolated onset temperature, position 30 generally produced low mean values. Position 21 generally produced high mean values except in the case of melting metals.

Other positions showed less evident order. The differences

did not exceed the sum of respective standard deviations.

2. For the peak temperature, position 30 generally produced

low mean values while position 10 generally produced high

mean values. Other positions showed less evident order.

Again, the differences did not exceed the sum of standard

deviations

3. For the onset temperature, positions 00, 03, 10 and 21

produced mean values ranging within ± 3 °C of the accepted

18
Table 5. Mean temperature results (°C) for thermocouple place

in the sample axially (Code 00)

Heating Cooling

Compound XTN Onset Peak XTN Onset Peak

KN0

3 10 128 + 6 133 + 5 8 125 + 4 123 + 3

In 8 154 + 3 157 +

A4 0/4 158 + 5 154 + I

Sn 6/8 230 + 2 233 + 2 4/3 203 + 10 219 + 19

KCIO^ 10 301 + 3 305 +

•73 8 291 + 5 290 + 4

Ag

2 S04 10 423 + 7 429 + 8 8/6 403 + 6 412 + 4 sio

2 10 572 + 2 574 + 2

08 573 + 4 571 +

A4

K

2 S04

y 582 + 3 586 + L 1 584 + 2 582 + L

K

2 Cr0

4

8 666 + 2 670 + 3 6 668 + 1 665 + 1 BaC0

3

8 809 + 5 817 + 3 6/4 772 + 16 758 + 23

SrC0

3

8 926 + 4 930 + 4 6/4 895 + 5 908 + 7

Table 6. Mean temperature results (°C) for thermocouple place

in contact with the sample holder axially (Code 03)

Heating Cooling

Compound N Onset Peak N Onset Peak

KNO3 16 127 + 7 135 + 6 1 116 116

In 16 154 + 7 158 + 5 1 146 145

Sn 16 229 + 7 236 + 6 2 169 176

KC10

4 16 299 + 7 308 + 7 2 278 278

Ag

2 S0

4 16 425 + 7 434 + 7 2 405 411

sio

2 16 570 + 7 574 + 6 2 571 560

K

2 S0

4 16 582 + 7 588 + 5 2 573 553

K

2 Cr0

4 16 664 + 6 672 + 4 2 658 635

BaC0

3

16 806 + 8 815 + 8 2 744 717

SrC0

3

16 927 + 10 936 + 10 2 883 869

19
Table 7. Mean temperature results (°C) for thermocouple

placed in the reference axially (Code 10)

Heating Cooling

Compound N Onset Peak N Onset Peak

KN0

3

6

1i zy i

j. ± o y 1 4 123 + 2 119 ± 4

In 4 158 + X lob + 2 4 1 150 ± 3

Sn 4 + 1

7 A 1 2 4

+ 3 200 ± 3

KC10

4

7

t n n 71 C J1D 9 4

+ 0 282 ± 2

Ag

2 S04

7 420 + i n ATI 12 4 tut + 5 399 ± 4

sio

2 9

^ 7 n + /I ^7^ + 3 6 575 + 1 571 ± 1

K

2 S04

9 580 + 10 591 + 7 4 585 + 1 578 ± 1

K

2 Cr04

7 659 + 11 675 + 10 4 669 + 1 662 ± 1

BaC0

3 9 806 + 8 818 + 7 4 771 + 1 761 ± 6

SrC0

3

9 928 + 1 944 + 4 5 907 + 7 898 ± 3

Table 8. Mean temperature results (°C) for thermocouple placed

geometrically equivalent to the sample and reference

non-axially (Code 21)

Heating Cooling

Compound N Onset Peak N Onset Peak

KN0

3 16 127 + 4 132 + 4 12 120 + 3 117 + 3

In 17 153 + 6 158 + 5 12 152 + 2 148 + 4

Sn 17 229 + 5 236 + 5 12/9 210 + 14 206 + 14

KC10

4 16/15 299 + 5 306 + 4 11 285 + 2 280 + 4 Ag

2 S0

4 16 427 + 4 433 + 3 10/8 389 + 20 384 + 21

sio

2 16 572 + 5 575 + 4 12 570 + 3 567 + 2

K

2 S04 16 584 + 5 588 + 4 11 581 + 4 576 + 4

K

2 Cr0

4 16 667 + 5 673 + 4 11 667 + 5 661 + 6 BaC0

3 16 808 + 8 819 + 6 11 768 + 13 750 + 15

SrC0

3 15/14 930 + 6 941 + 8 12 902 + 10 893 + 10

20
Table 9. Mean temperature results (°C) for thermocouple placed

geometrically midway between sample and reference

axially (Code 30)

Heating Cooling

Compound N Onset Peak N Onset Peak

KN0

3

4 129 + 4 136 + 3 2 124 120

In 2 148 152 -

Sn 2 224 229 -

KC10

4

4 297 + 5 305 + 6 2 291 284

Ag

2 S04

4 423 + 4 431 + 3 2 407 405

Si0

2 4 568 + 1 570 + 1 2 569 567

K

2 S04

4 579 + 2 584 + 2 2 581 577

K

2 Cr0

4

4 660 + 1 666 + 1 2 663 659

BaC0

3

6 803 + 4 815 + 8

SrC0

3 4 925 + 2 935 + 7

equilibrium transition temperatures for 8 to 9 of the

materials for which reliable equilibrium data exist.

Position 30 gave onset temperatures ranging from +1 to

-9 °C of equilibrium values.

4. For the peak temperature, positions 00, 03, 21 and 30 produced mean values averaging +4 °C of equilibrium transition

temperatures for all materials. Position 10 produced mean

values averaging +9 °C of these equilibrium values.

5. For no material is the effect of T- thermocouple placement

such that the maximum and minimum extrapolated onset or

peak temperatures differ by more than the sum of their

respective standard deviations.

21
Considering only data for the COOLING mode, evaluation

is limited to positions 00, 10 and 21 since only 2 data

points were available for any material examined using

positions 03 and 30. With this further restriction, the

following general comments may be made:

1. For the extrapolated onset temperature, position 21 generally produced the lowest mean values.

2. Cooling peak temperatures occurred at increasing values in

the order of positions 21, 10, 00, for 8 of the 10

materials in the SITP.

3. Because of marked supercooling noted in five (Sn, KCIO^,

Ag2S0^, BaCO^ and SnCO^) of the ten materials studied, it

was not considered of value to examine the influence of

T- thermocouple position upon the difference between measured and equilibrium thermodynamic temperatures in the

cooling mode.

3 . Sample Holder Configuration

Assessment of the effect of sample holder configuration

has been complicated by the fact that certain investigators

used different configurations for different materials. Sometimes this was necessitated by the design of the instrument

or by the materials of construction; sometimes by a desire

to optimize the configuration to the sample. This change in

configuration is particularly true for the two melting point

systems included in the SITP, illustrating the special problems to instrumentation imposed by such systems. Results

from 7 of the 15 sample holder configurations have not been

included in this report since they represent the work of

only one investigator or because they have been employed by

2 investigators only in the case of one or two samples.

The major configurations employed are listed in Table

10 and further detailed in Tables 11-18, while those omitted

from further consideration in this Section are: 011, 304,

305, 422, 505, 615, and 625.

22
In Table 10 the lower

associated with results in

number of data points

the cooling mode.

is always

Table 10. Major sample holder configurations reported.

Code Number of Number of

number investigators data points

002 2 2-6 Cylindrical block, uncovered

cylindrical wells, one R and

one S, well diameter < depth.

012 2 2-3 Cylindrical block, loosely covered

cylindrical wells, one R and one S, well diameter < depth.

402 4-7 3-14 Shallow cup, uncovered, bottom

uniformly = wall.

502 3-4 2-6 Equal cup, uncovered, bottom

uniformly = wall.

602 5-8 6-13 Deep cup, uncovered, bottom

uniformly thinner than < wall.

603 2 2-4 Deep cup, uncovered, bottom

uniformly = wall.

604 1-4 2-10 Deep cup, uncovered, bottom

uniformly = wall.

701 2 0-4 Capillary, loosely covered.

Initially restricting the data evaluation to the

HEATING mode, and with the understanding that due to limited

data, other influences (sample size, thermocouple placement,

eta.) may have shifted some of the average values quite

drastically, some general comments may be made:

1. For the onset temperature, configuration 012 and 602 produced lower mean values while configurations 002 and 603

produced higher mean values. Other configurations produced generally intermediate mean values.

2. For the peak temperature, configuration 60 2 produced lower mean values and configuration 002 produced higher mean

values. Other configurations produced generally intermediate mean values.
Table 11. Mean temperature results (°C) for sample holder:

cylindrical block, uncovered cylindrical wells

(Code 002)

Heating | Cooling

Compound N Onset Peak N Onset Peak

KN0

3

6 135 + 7 147 + 8 2 128 125

In 2 161 170 - -- --

Sn 2 239 253 - -- --

KC10

4

6 306 + 3 322 + 10 2 294 289

Ag

2 S04 4 432 + 5 443 + 10 2 401 410

sio

2 4 577 + 4 582 + 7 2 576 574

K

2 S0

4

5 589 + 5 600 + 10 2 586 582

K

2 Cr04

6 672 + 5 683 + 9 2 669 666

BaC0

3 6 809 + 9 828 + 12 2 761 738

SrC0

3 4 930 + 4 946 + 15 2 900 903

Table 12. Mean temperature results (°C) for sample holder:

cylindrical block, loosely covered cylindrical wells

(Code 012)

Heating Cooling

Compound N Onset Peak N Onset Peak

KNO3 2 130 139 2 125 123

In

Sn

KC10

4

3 299 + 4 310 + 7 2 289 284

Ag

2 S0

4

3 418 + 15 428 + 20 2 401 398

Si0

2 3 570 + 5 574 + 4 2 575 572

K

2 S0

4

3 577 + 14 586 + 9 2 585 578

K

2 Cr04

3 659 + 16 669 + 11 2 670 662

BaC0

3

3 800 + 12 816 + 7 2 770 756

SrC0

3

3 928 + 1 941 + 2 2 900 899

24
Table 13. Mean temperature results (°C) for sample holder:

shallow cup, uncovered (Code 402).

Heating Cooling

Compound N Onset Peak N Onset Peak

KN0

3

13 129 + 2 136 + 4 6 122 + 1 119 + 2

In 8 157 + 2 161 + 3 4/3 154 + 1 149 + 4

Sn 8 233 + 2 238 + 4 2 219 214

KC10

4 14 300 + 3 308 + 4 5 286 + 2 282 + 3

Ag

2 S0

4 14 426 + 2 434 + 4 6 397 + 12 395 + 11

sio

2 14 571 + 2 575 + 3 6 572 + 4 570 + 4

K

2 S0

4 14 581 + 3 586 + 2 6 582 + 6 579 + 7

K

2 Cr04 14 665 + 4 671 + 3 6 667 + 5 663 + 6 BaC0

3 14 807 + 8 817 + 4 6 759 + 8 743 + 9

SrC0

3 14 927 + 6 935 + 4 4/3 902 + 11 893 + 11

Table 14. Mean temperature results (°C) for sample holder:

equal cup, uncovered (Code 502).

Heating Cooling

Compound N Onset Peak N Onset Peak

KN0

3 6 129 + 3 135 + 4 2 120 118

In 6 155 + 4 159 + 5 2 152 150

Sn 6 230 + 6 237 + 6 1 206

KC10

4 6/5 299 + 5 306 + 6 2 285 281

Ag

2 S0

4

6 424 + 5 432 + 5 2/1 403 400

Si0

2 6 573 + 1 576 + 1 2 569 567

K

2 S0

4

6 584 + 2 589 + 3 2 581 576

K

2 Cr0

4

6 668 + 2 673 + 3 2 666 661

BaC0

3 6 811 + 3 819 + 2 2 753 741

SrC0

3 9/8 936 + 8 945 + 7 5 920 ± 22 906 ± 12

25
Table 15. Mean temperature results (°C) for sample holder:

deep cup, uncovered, bottom uniformly = wall (Code 602).

Heating Cooling

Compound XTN Onset Peak N Onset Peak

KN0

3 1U 124 + 8 132 + 5 6 124 + 4 122 + 3

in 14/ 1 0 154 + 6 157 + 1 0/ 5 155 + 2 153 + 2 on 114A 230 + 5 236 + 0 CIA 0/ 4 202 + 8 215 + 18

1 L 294 + 9 305 + pJ 0 290 + 5 288 + 5 Ag

2 b0

4 419 + 8 429 + 1 0/ 5 402 + 4 405 + 4 biu

2 1

J

566 + 6 570 + rb 0/ O 569 + 2 569 + 4

K

2 S0

4 14 576 + 8 584 + 3 6/7 582 + 2 579 + 3

K

2 Cr0

4 12 660 + 6 668 + 3 8 667 + 5 662 + 4 BaC0

3 12 803 + 7 815 + 8 4 778 + 11 768 + 12

SrC0

3 13 924 + 5 932 + 4 6 898 + 9 901 + 13

Table 16. Mean temperature results (°C) for sample holder:

deep cup, uncovered, bottom non-uniformly = wall (Code 603).

Heating Cooling

Compound N Onset Peak N Onset Peak

KN0

3

4 133 + 4 141 + 4 2 121 115

In 4 159 + 3 165 + 1 2 154 148

Sn 4 235 + 3 243 + 2 2 202 200

KC10,

4

4 304 + 4 313 + 1 2 289 280

Ag

2 S0

4 4 426 + 1 437 + 1 2 404 401

sio

2 4 576 + 3 578 + 5 2 574 571

K

2 S0

4

4 590 + 6 595 + 5 2 585 579

K

2 Cr04 4 669 + 2 678 + 3 2 669 662

BaC0

3 4 813 + 7 824 + 6 2 772 767

SrC0

3

4 934 + 5 944 + 5 2 912 900

26
Table 17. Mean temperature results (°C) for sample holder:

deep cup, uncovered, bottom uniformly > wall (Code 604).

Heating Cooling

Compound N Onset Peak N Onset Peak

KN0

3

8 126 + 4 131 + 2 6 118 + 4 116 + 4

In 10 154 + 7 160 + 5 7 154 + 5 149 + 7 Sn 10 231 + 5 237 + 4 6/4 219 + 3 215 + 6 KC10

4

8 299 + 5 305 + 4 6 286 + 1 282 + 4 Ag

2 S04

9 426 + 4 433 + 3 5/4 383 + 26 378 + 28

sio

2

7 573 + 4 575 + 4 5 571 + 2 568 + 2

K

2 S04

8 584 + 3 588 + 3 5 584 + 1 579 + 1 K

2 Cr0

4

8 667 + 4 672 + 3 5 670 + 3 665 + 5 BaCOj 10 815 + 11 823 + 11 7 776 + 10 763 + 9 SrC0

3

8 933 + 6 942 + 7 5 902 + 15 895 + 14

Table 18. Mean temperature results (°C) for sample holder:

capillary, loosely covered (Code 701)

Heating Cooling

Compound N Onset Peak N Onset Peak

KNO3 4 129 + 1 130 + 1 2 124 124

In 2 157 158

Sn

KC10

4

4 302 + 1 303 + 3 2 290 292

Ag

2 S0

4

4 430 + 3 434 + 2 2 412 416

Si0

2 3 577 + 2 578 + 3 1 576 575

K

2 S0

4

3 589 + 3 591 + 3 1 587 587

K

2 Cr04

2 677 680

BaC0

3

2 811 815

SrC0

3

27
3. For the onset temperature, configurations 402, 503 and 604

produced mean values within ± 3 °C of the accepted equilibrium transition temperatures for at least eight of the

nine materials for which reliable equilibrium data exist.

Configurations 012 and 602 produced mean values generally

i lower than accepted equilibrium data, while configurations!

002, 603 and 701 produced generally higher mean values.

4. For the peak temperature, all configurations except 002

and 603 produced mean values within +7 °C of the accepted

equilibrium transition temperature for at least seven of

, the nine materials for which reliable equilibrium data

exist. Configurations 002 and 603 produced mean peak tern- j peratures averaging 12 to 17 °C above the equilibrium

transition temperature.

5. Neglecting the possible effect of heating rate, the average difference between mean extrapolated onset and peak

temperatures was 2 degrees for configuration 701, and 11

to 12 degrees for configurations 002 and 012. For all

other configurations the difference was 7 to 8 °C.

6. For most materials the effect of sample holder configuration is such that the maximum and minimum extrapolated onset or peak temperatures differ by an amount approximately

equal to the sum of their respective standard deviations.

Considering only data for the COOLING mode, evaluation

must be limited to configurations 402, 602 and 604 for which

more than 2 data points were available. With this further

restriction, the following general comments may be made:

1. For the onset temperature, configuration 402 tends to

produce the higher mean values

2. For the peak temperature no ranking could be made with

respect to these three configurations.

3. For the extrapolated onset temperature all three configurations produced mean values averaging 14 °C below

accepted equilibrium transition temperatures.

28
4. For the peak temperatures all three configurations

produced mean values averaging 14-20 °C below accepted

equilibrium transition temperatures.

D. Resolution in the 4:1: SiO ^ : K^ SO^ Mixture

The ability to obtain a measurable peak is occasionally

more important than the ability to resolve close- lying

thermal effects. More often, however, the ability to resolve

two or more separate events is critical. To evaluate the

resolution of the various types of apparatus, the investigators were asked to prepare a 4:1 mixture of silica and

potassium sulfate. This composition gives two approximately

equal peaks separated by about 11 °C. Table 2 indicates

that not all investigators were able to submit experimental

data on the 4:1 mixture (by weight) of Si0

2 and E^SC^. From

the data obtained, there is no statistical difference in mean

temperatures for either transition when compared with the

corresponding temperature obtained when the compound was

heated or cooled by itself. Thus, there was no influence

of "dilution" by the other constituent.

To provide measures of the resolution of the two peaks,

the concept of "base-line separation" (Figures 2a and 2b) was

adopted arbitrarily. If x = the height of the Si0

2 peak,

y = the minimum deviation of the experimental curve from the

base-line in region between the peaks, then percent resolution = [100 -£l-|r)] . As indicated by Table 19 approximately two thirds of

the investigators reporting curves for the mixture achieved

a resolution >_ 90 percent. The effect of construction b is

to raise the "percent resolution" above 100 percent in some

cases due to accompanying base-line shifts. By construction

b, a greater number, approximately three quarters of the

investigators achieved a resolution > 90 percent.

29
T T

a b

Figure 2. Peak resolution from base-line measurements

(see also Table 19)

The purpose of any expression of peak resolution is to

point out gross differences associated with sample holder

configuration, heating rate, sample size and other parameters.

In most cases, resolution ^_ 80 percent by construction a was

associated with sample sizes >_ 200 mg and/or heating rates of

10 to 12 °C min

-1

. It is felt that the data are not sufficient

to reject any particular sample holder configuration in terms

of ability to resolve adjacent thermal affects. However,

data in Table 19 do indicate that the SiC^K^SO^ mixture is

a suitable means for evaluating the ability of a particular

combination of instrumental and experimental parameter to

resolve two thermal effects occurring within 10 °C of each

other.

30
Table 19. Peak resolution in 4:1 mixtures (by weight)

of Si0

2 and K

2 S0

4

-

Sample holder

configuration

Sample

weight

(mg)

Heating

rate

C min -1

Percent resolution

(average)

Fig. 2a Fig. 2b

a a o 002 *7 r\ r\ 300 1 A 10 93 104

All Oil *7 r\ r\ 300 1 A A 10 .

83 87

a i a 012 o i~ h 255 7 . 5 96 109

T A A 304 *y a a 300 12 76 78

A A ^ 402 A T 2 . 3it o 4 .

8

100 100

18 8 91 101

20 5 .

100 100

27 10 94 98

250 5 . 8 92 96

502 — — 100 100

48 . 2 10 76 87

99. 9 5 .

6

93 92

602 80 6.6 98 115

150 2 90 101

235 10 79 79

300 5 97 114

300 8 91 128

300 11 33 41

300 12 56 95

603 40.6 8 88 115

259.9 4.7 97 114

300 5 67 64

615 248.6 4.8 77 91

701 88.9 10 98 108

Distribution

Investigators showing >^ 95% Resolution 25 67

> 90% " 63 75

> 80% 11 71 83

VII. CONCLUSIONS

Because approximately twice as many data were obtained

in the heating mode as in the cooling mode, conclusions will

be confined to the heating mode only. The present standards

are not recommended for use in the cooling mode.

1. Over a group of 34 laboratories involving expert

thermal analysts, no investigator showed an unacceptable

31
systematic bias, as determined by the mean deviation

being greater than ± 3a calculated over all compounds and

all investigators. See also Figure 1.

2. None of these materials gave unusually precise or imprecise results. See Figure 3.

3. On heating, the onset and peak temperatures can be

used with virtually equal reliability (± 6 °C) . The mean

extrapolated onset temperature is closest to the reported

equilibrium thermodynamic transition temperature Cg en ~ erally -1 °C of this value).

4. No statistically significant deviation of individual

results from the mean of all observations could be attributed to individual instrument parameters. This does

not preclude the possibility of compensating effects

within a given combination of parameters affecting one

instrument. A trend to increasing differences between

extrapolated onset and peak temperatures on heating was

noted with increasing heating rate.

5. There is no statistically significant effect of

T- thermocouple calibration in the heating mode. The mean

values for extrapolated onset and peak temperatures are

consistently lower with calibrated thermocouples, but the

difference is generally less than the smaller standard

deviation

6. Of the five T- thermocouple locations for which data

exist from more than one investigator, position 30 generally corresponded with lowest mean onset and peak temperatures on heating. Other positions exerted a less

consistent influence upon these mean values. For no

material was the effect of T- thermocouple location such

that the maximum and minimum onset or peak temperatures

differed by more than the sum of their respective

standard deviations

7. Mean extrapolated onset temperatures for positions 00,

03, 10 and 21, on heating, were within ± 3 °C of the
accepted equilibrium transition temperatures for at least

eight of the nine materials for which reliable equilibrium

data exist.

8. Of the eight sample holder configurations for which

essentially complete sets of data were available on heating from more than one investigator, configuration 602

produced generally low mean extrapolated onset and peak

temperatures while configuration 002 produced generally

high values. Other configurations exerted a less consistent influence upon these mean values. For most materials and configurations the difference between maximum

and minimum extrapolated onset or peak temperatures was

approximately equal to the sum of their respective standard

deviations

9. Mean extrapolated onset temperatures for configurations

402, 502 and 604 were within ± 3 °C of accepted equilibrium

transition temperatures for at least eight of the nine

materials for which reliable equilibrium data exist.

10. While both T- thermocouple locations and sample holder

configurations showed tendencies to influence the mean

onset and peak temperatures on heating, the effect of

these variables is not greater than the overall reproducibility (+5 to 9 °C) of the experimental data. The interaction of a number of instrumental parameters is suspected,

however, the SITP data are not sufficient to permit a more detailed analysis.

11. The 4:1 mixture (by weight) of Si0

2

and K

2 S0

4

is a reasonable system for evaluating the ability of a given

combination of instrumental parameters to resolve two

thermal effects occurring about 10 °C apart. It will be

desirable to have similar pairs of compounds which can be

used to evaluate this resolution in other temperature

ranges

33
t co ro c\j r— CM V OJ CM CJ

CM ro IA« ^ N) cm m

• • to

• I— CO <T>

• • t • co em tn t cvi cm

ro m eocn cm « cm

CM #» CO CO » K> CM* •

c

CO

C_3 CO

O

esi co

CO 3E

CVJ

CVJ CO

CO

CO

CVJ

ro cvi CVJ

I ro

I 0*S33M930

CDO

C

Rj

+->

V)

cd

4->

<4-| O

U

cU

CDU 4-> O

m m

o

i/> 5h CD o cd

+-> +->

CVj +J

•h e M S

V) O

CD u

>

•H

Sh W) c\j h c

+-> aJ

4-> ?H co

CDd. CD O 42 o +-> u

o

rog CD O +-> 5h m

+-> •H

to

CDJh3

bO

•H

34
VIII. ACKNOWLEDGEMENTS

The material contained in this report represents the

labors of 34 different laboratories, all of whom voluntarilycontributed time and effort to participate in the SITP. The

authors are grateful to them and their supporting organizations .For the special support of one of us (H.G.M.) and his

administration of the test program, the authors are grateful

to the Ontario Research Foundation, and to Mrs. Jean Jervis

who reviewed and encoded the data.

For the special support of one of us (P.D.G.) in his

participation in the planning and the computation of data,

the authors are grateful to the University of Akron and to

R. Seaman who prepared the programs.

The authors further acknowledge the assistance of B.L.

Joiner and H.H. Ku of the Applied Mathematics Division and

J.T. Sterling and D.S. Bright of the Analytical Chemistry

Division at NBS

IX. REFERENCES

[1] Youden, W. J. , "Statistical Techniques for Collaborative

Tests," Assocation of Official Analytical Chemists,

Washington, D. C. (1967).

[2] NBS Circular 500, "Selective Values of Chemical Thermodynamic Properties" (1952)

[3] Hedvall, J. A., Lindner, R and Hartler, N. , Acta Chem.

Scand. 4, 1099 (1950).

[4] NBS Technical Note 504. Superintendent of Documents,

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

20402

[5] Lander, J. J., J. Amer. Chem. Soc . 73, 5794 (1951).

35

APPENDIX A

Revised Oct. 1-2, 1969

PROCEDURES

Second International Test Programme

DTA Temperature Standards

International Confederation for Thermal Analysis

Committee on Standardization

1. The operating conditions of each instrument should be

those normally employed.

2. The accuracy of the temperature -measuring thermocouple

should be known. If calibration is required the committee prefers use of recognized melting point standards.

3. All temperature data should be reported to the nearest

1 °C.

4. A time- temperature curve from the temperature-measuring

thermocouple should be included. If temperature is

measured in the sample cell, this record should be obtained using aluminum oxide.

5. Each sample should be examined at one heating rate in

the range of 4 to 10 °C min -1

.

6. Both programmed heating and cooling should be employed

if the apparatus permits. If cooling runs are made the

rate of cooling should approximate the rate of heating.

7. The reference alumina supplied should be calcined to at

least 1000 °C before use.

8. One curve of the reference material against the reference material should be supplied, using the maximum AT

sensitivity employed with the test materials.

37
Samples should be used as received and not pre-treated

in any way, except for potassium nitrate which should be

cycled once to a temperature of 150 to 160 °C prior to

making the reported runs

Samples should not be diluted.

Maximum sample size should be approximately 300 mg

At least two curves should be run on each material. If

more than two curves are run and any rejected the rejected data should be forwarded with the other data

together with the reason for rejection.

Conditions of packing of the sample within the sample

holder should be specified.

The sample atmosphere should be oxygen-free nitrogen at

1 atm pressure dried over MgClO^ or its equivalent.

Where possible the same sample holder or container

should be used for the entire series of tests.

The Committee would appreciate receiving a measurement

of peak area as defined in the accompanying figure, expressed in the units °C per mg of sample. In this way

instrument parameters such as AT thermocouple material

and response, amplifier sensitivity, chart speed, etc.

can be reduced to a denominator common to all instruments . Results should be reported according to the recommendations for good practice defined by the Committee.

The Committee would appreciate samples being examined

in the randomized order provided to eliminate systematic

bias . Duplicate runs are also requested on a 4:1 SiC^K^SO^

mixture (by weight) using the silica and potassium

sulphate provided.

38
Revised Oct . 1-2 , 1969

INSTRUMENT DESCRIPTION

Second International Test Programme

DTA Temperature Standards

International Confederation for Thermal Analysis

Committee on Standardization

Investigator

Instrument Manufacturer

Instrument Model No.

AT Thermocouple Material

AT Thermocouple Wire Diameter (mm)

T-Thermocouple Material

T-Thermocouple Reference Temp (°C)

Was T-Thermocouple Calibrated? Yes . .No. . If yes, how?. .

Location of T-Thermocouple . Method of T Measurement

Sample Holder Material

Description of sample holder size . and shape

Sample atmosphere flow pattern

Sample atmosphere flow rate (cc min )

Please supply a small drawing or photograph of the sample

holder.

39
CTii

4-> UO

CD

c/> •H>

(D

<Di

—

Sh i < Ml

CD

U

Ph o o 0) p*

CO • +-> •H • +-> CD

C/5 E-i

X c/5 I>s W C

i—l

O

03£

CD < ClO iH 6 C « e t—

•H CD

C

o3

C +-> 4-> -H s o 03 OS e

W> c/) •H CD Ctf o (D +-> 03 o a, as H M

•H i—l

4->

C f-< n3 i co o3 O ?H

CD +-> 4-1 03 fH CD -H

H E-h co "d 03 CD e

PiO r-l CD

O o3u co 6

(X 03

H •H +j o m C 3 4-> CO

pi

O 4-> 03 •H 03 5h < +-> 5-i 0 O

E—1 as cd h3 4-> I < c & CD CD •H £ O 4-1 CD > U

0) CD +-> •H o +-> +->

u c •H •H o

l-H < e CO E- i—l e fi

H

03 o CD

(=! PS

u CO r±4

O

O oj o •H E-h cd

<d 4-> <3 Ph

CO 03

ShCD P CD C i—l S 6

03 CO <

5hCD 3 6

Pi 3

CD

Cme

03 CO

40
APPENDIX B

STANDARD METHOD OF CALIBRATION OF TEMPERATURE

SCALE FOR DIFFERENTIAL THERMAL ANALYSIS

1 . Scope

This test is for general use in differential thermal

analysis. It provides means of relating temperatures of

events observed in different laboratories and different

instruments

The test is applicable to all commercial and custombuilt apparatus. It can also be used for instruments classed

as differential scanning calorimeters.

The purpose of this test is to determine the agreement

in temperature under the specific conditions of the principal experiment, and not to determine the transition temperature of the Standard Reference Material. It is necessary to

use the same sample holder assembly and heating rate in

obtaining the peak(s) whose temperature (s) are to be related

to other determinations.

2 . Summary of Method

The method consists of obtaining the differential thermal analysis peak of one or more of the Standard Reference

Materials under the normal operating conditions of the instrument, determining the extrapolated onset and peak

temperatures, and comparing these temperatures with those established for the material. The difference provides a correction which is applied in relating data on test substances to data obtained on other instruments.

In correlating measurements, it will be necessary only

to use NBS Standard Reference Materials whose peak temperatures are in the range of those of the test substance.

However, use of Standard Reference Materials over the useful

range of the instrument and at two or more heating rates

will be an aid in determining the characteristics of the

operator instrument.

41
3 . Significance

The differential thermal analysis peak results from

many influences, some of which are characteristic of the

sample holder assembly rather than the sample. The variations from instrument to instrument in the point of measurement of temperature and differential temperature, in sample

size, in the kinds and composition of sample containers

available with particular instruments and in accuracy of

temperature scales all contribute to differences in measured

temperatures which may exceed twenty degrees. In addition,

some sample holder assemblies will show variations of

measured temperature with sample size and/or heating rate.

It is neither practical nor advisable to standardize sample

holders. The alternative is the use of agreed-upon reference points and measurement of the deviation of the observed

temperature from the reference temperature.

Small or large deviations should not be taken as a measure of the quality of an instrument. The temperatures

assigned to the Standard Reference Materials are the means

calculated from many experimental values obtained on a variety of instruments. Further information on variations

may be obtained from the Committee on Standardization of the

International Confederation for Thermal Analysis.

For sets of experiments performed on the same instrument in the same sample holder at the same heating rate, this

test is generally unnecessary, but in relating data among

instruments of the same type this calibration is desirable.

The use of this method at several heating rates will

also be helpful in separating instrumental effects from

effects arising within the sample.

4 . Definitions of Terms and Abbreviations

This list includes definitions which agree with those

adopted by the International Confederation for Thermal

Analys is

42
Peak - that part of a DTA curve which is attributable to

the occurrence of some single process. It normally is

characterized by a deviation from the established base line,

a maximum deflection, and re-establishment of a base line

not necessarily identical to that before the peak.

Extrapolated Onset - empirically, the temperature found

by extrapolating the base line (prior to the peak) and the

leading side of the peak to their intersection. The section

showing the closest approach to a straight line is taken.

See Figure 2.

Peak temperature - the temperature indicated at the time

of the maximum value of the differential temperature during

that peak.

Differential Thermal Analysis (DTA) - a technique of

recording the difference in temperature (differential temperature) between a substance and a reference material

against either time or temperature as the two specimens are

subjected to identical temperature regimes in an environment

heated or cooled at a controlled rate.

The record is the differential thermal or DTA curve;

the temperature difference (AT) should be plotted on the

ordinate with endothermic reactions downward and t or T on

the abscissa increasing from left to right.

Test Substance - the material whose DTA curve is to be

compared to the DTA curve obtained on another instrument.

5 . Apparatus

The test is designed for all types of apparatus. Most

of the Standard Reference Materials were selected for their

solid $ solid transitions. These may be used in sample

holder assemblies in which liquids cannot be used satisfactorily. For those sample holders which hold liquids

satisfactorily, all of the Standard Reference Materials may

be used.

43
6 . Standard Reference Materials

The temperature standards used in this method are the

materials selected and tested during the second international

test program by the International Confederation for Thermal

Analysis. Except for indium and tin, each exhibits a solid

solid transition which is well-defined and highly reproducible and has been characterized also by isothermal techniques. The materials are chemically stable and substantially

inert

The standards are being issued jointly by the International Confederation for Thermal Analysis and the National

Bureau of Standards. The certified values are the means of

values obtained by 34 laboratories. They are available in

sets from the National Bureau of Standards, SRM 758, 759 and

760. Each set comprises five materials:

SRM 758 - KN0

3

, In (metal) Sn (metal), KC10

4 , Ag

2 S0

4

temperature range: 128 - 430 °C.

SRM 759 - KC10

4 , Ag

2 S04 , Si02

, K

2 S0

4 , K

2 Cr0

4

temperature range: 299 - 665 °C.

SRM 760 - Si0

2

, K

2

SC> 4 , K

2 Cr0

4 , BaC03 , SrC03

temperature range: 573 - 925 °C.

7 . Interferences

Potassium nitrate shows a dependence on previous

history. The material should be heated to 150-160 degrees

prior to standardizing.

The measurements should be made in an inert, dry atmosphere. This simulates conditions under which the values were

established.

8 . Procedure A

Place an amount of the selected Standard Reference

Material, equivalent in weight to the test substance, in the

same or similar type of sample holder as the test substance,

and subject it to the same procedure as the test substance.

44
9 . Procedure B

This procedure is used to acquaint the operator with

the characteristics of the instrument. It requires no formal

report, only entry in the laboratory notebook; posting of

correction near the instrument is also helpful.

A portion of the selected Standard Reference Material

corresponding to typical samples is placed in the selected

sample holder and subjected to the maximum heating rate.

The specimen is cooled and subjected to the minimum heating

rate. The extrapolated onset and peak temperatures are

measured. If either of these values differs greatly with

heating rate, sufficient intermediate heating rates are

used to determine the behavior of the system. The differences

between the measured values and the given values are calculated and tabulated.

A second Standard Reference Material is subjected to

the same testing program. Sufficient Standard Reference

Materials are run to tabulate corrections at each heating

rate over the useful temperature range of the instrument

and sample holder.

The procedure is repeated for other sample holder

assemblies

10 . Report

The report should include the following information:

(a) Appropriate information concerning the test

substance and conditions of the measurement.

(b) The corrected extrapolated onset and peak temperature for each peak.

(c) Notation that the temperatures have been corrected

using Standard Reference Materials.

45

APPENDIX C

Certificates

NBS - ICTA Standard Reference Material 759

DTA Temperature Standards (295-675 °C)

NBS - ICTA Standard Reference Material 758

DTA Temperature Standards (125-435 °C)

NBS - ICTA Standard Reference Material 760

DTA Temperature Standards (570-940 °C)

47

J. S. DeiMauri

of Commerce

Stans

National I L. H. Bi

kal Standards pK Director (fltttxixtatt

NBS-ICTA Standard Reference Material 758

DTA Temperature Standards (125 - 435 °C)

These standards include: high-purity potassium nitrate, indium, tin, commercial grade potassium

perchlorate, and analyzed reagent silver sulfate. They are for use in calibrating the temperature scale on differential thermal analysis and related thermoanalytical equipment under the operating conditions. They are to be used only in the heating mode.

Transition Temperature Data (°C)

DTA Mean Values

Equilibrium Extrapolated

Material Value f 11 Onset Peak

KN03 127.7 128 135

In (metal) 157 154 159

Sn (metal) 231.9 230 237

KC104 299.5 299 309

Ag2 S04 -(a) 424 433

( a ^The value for the transition temperature reported for this material [1] is currently under review. A more recent value of 430 °C

has been reported f2|.

For potassium nitrate only, the first heating of the material is not a reliable measure of the

transition temperature. This sample must be cycled through the transition temperature in situ before recording data.

The extrapolated onset temperature is defined (Point A, Figure 1) as that temperature found by

extrapolating the base line, prior to the peak, and the leading side of the peak to their intersection. The peak temperature (Point B, Figure 1) is defined as the temperature corresponding to the point

of maximum deflection of the differential temperature curve.

Based on the mean value from 34 cooperating laboratories, the standard deviation was 5-8 °C,

which includes the bias among laboratories as well as measurement errors. In the heating mode, onset and peak temperatures have about equal precision. However, the mean extrapolated onset temperatures are closer to the equilibrium transition temperatures.

The materials for these standards were furnished by the Committee on Standardization of the ICTA.

The International Test Program leading to the data on which certification is based was coordinated by H. G. McAdie, Chairman, ICTA Committee on Standardization.

Coordination of efforts leading to certification by NBS was under the chairmanship of O. Menis.

The technical and support aspects involved in the preparation, certification, and issuance of

these Standard Reference Materials were coordinated through the Office of Standard Reference

Materials by T. W. Mears.

Washington, D. C. 20234 J. Paul Cali, Chief June 11, 1971 Office of Standard Reference Materials

(over)

49
The transition temperatures given are the means of values obtained on 28 different types of commercial or custom-made instruments, and do not necessarily agree with the equilibrium

values [1, 2]. Generally, values from DTA are somewhat higher than the equilibrium values and

vary in a complex manner for different instruments and heating rates. Details of the instruments

used, the test conditions and complete data will be given in an NBS Special Publication in the 260

series (in publication).

EXTRAPOLATED ONSET

TEMPERATURE

AT

PEAK TEMPERATURE

T

[1] Nat. Bur. Stand. (U.S.), Circ. 500 (1952).

[2] Hedvall, J. A., Lindner, R., and Hartler, N., Acta. Chem. Scand. 4, 1099 (1950).

50
Cooperating Laboratories

Dr. David E. Baum, Monsanto Australia Limited, West Footscray, Victoria, Australia

Prof. Marcel Bourgon, Universite de Montreal, Montreal, Quebec, Canada

Dr. H. G. McAdie, Ontario Research Foundation, Sheridan Park, Ontario, Canada

Dr. Klaus Heide, Friedrich-Schiller-Universitat, Jena, Germany

Dr. J. Wiegmann, Berlin, Germany

Dr. G. R. Cizeron, Universite" de Paris, Paris, France

Dr. M. Harmelin, C.N.R.S., Paris, France

Mme. J. Jegoudez, Universite de Paris, Paris, France

Dr. M. Foldvari, Hungarian Geological Institute, Budapest, Hungary

Mr. J. Paulik, Technical University of Budapest, Budapest, Hungary

Prof. H. Kambe, University of Tokyo, Tokyo, Japan

Prof. C. Kato, Waseda University, Tokyo, Japan

Prof. K. Oinuma, Tokyo University, Tokyo, Japan

Prof. R. Otsuka, Waseda University, Tokyo, Japan

Mr. J. E. Kruger, National Building Research Institute, Pretoria, South Africa

Dr. R. S. Forsyth, Aktiebolaget Atomenergi, Studsvik-Nykoping, Sweden

I Dr. G. Krien, Institut fur Chemisch-Techn. Untersuchungen, Leverkusen, Germany

Prof. H. R. Oswald, Universitat Zurich, Zurich, Switzerland

Dr. T. Peters, Universitat Berne, Berne, Switzerland

Dr. H. G. Wiedemann, Mettler Instrumentc A. G., Greifensee, Switzerland

Prof. L. G. Berg, Gosuniversitet, Kazan, U.S.S.R.

Prof. E. K. Koehler, Academy of Sciences of the USSR, Novosibirsk, USSR

Dr. I. S. Rassonskaya, Institut Obshchci i Neorganicheskoi Khimii, Moscow, USSR

Dr. G. 0. Piloyan, Academy of Sciences of the USSR, Moscow, USSR

Mr. E. L. Charsley, Stanton Redcroft Limited, London, England

Dr. R. C. Mackenzie, The Macaulay Institute for Soil Research, Aberdeen, Scotland

51
Prof. D. A. Smith and Mr. J. Youren, Queen Mary College, University of London, London, England

Dr. P. K. Gallagher, Bell Telephone Laboratories, Murray Hill, N.J..U.S.A.

Prof. P. D. Garn, University of Akron, Akron, Ohio,U.S.A.

Dr. 0. Menis, D. S. Bright, and J. T. Sterling, National Bureau of Standards, Washington, D.C., USA.

Mr. T. D. Oulton, Englehard Minerals & Chemicals Corp., Edison, N.J..U.S.A.

Dr. R. K. Ware, Owens-Illinois, Toledo, Ohio,U.S.A.

International Confederation for Thermal Analysis Committee on Standardization:

Chairman

Vice-Chairman

Secretary

National Delegates

Representative

Delegates

Ex-Officio

Delegates

(Canada) H. G. McAdie

(U.S.A.) P. D. Garn

(U.K.) R. C. Mackenzie

(France) C. Mazieres

(German D.R.) K. Heide

(Hungary) F. Paulik (Japan) H. Kambe

(Sweden) R. S. Forsyth

(Switzerland) H. G. Wiedemann

(U.S.S.R.) I. S. Rassonskaya

(U.K.) D. A. Smith

(U.S.A.) R. W. Pfeil ASTM (U.S.A.) Vacant ISO Vacant NBS (U.S.A.) 0. Menis

Soc.Anal.Chem. (U.K.) C. J. Keattch

SAMA (U.S.A.) Vacant

ICTA (U.S.S.R.) L. G. Berg

(U.S.A.) C. B. Murphy

(U.K.) R. C. Mackenzie

(U.K.) J. P. Redfern

52
U. S. DeiMauri

(Eertiftcate

NBS-ICTA Standard Reference Material 759

DTA Temperature Standards (295 - 675 °C)

These standards include: analyzed reagent silver sulfate, potassium sulfate, potassium chromate;

commercial grade potassium perchlorate; and natural quartz. They are for use in calibrating the temperature scale on differential thermal analysis and related therm oanalytical equipment under

operating conditions. They are to be used only in the heating mode.

Transition Temperature Data (°C)

DTA Mean Values

Equilibrium Extrapolated

Material Value [1] Onset Peak

KC104 299.5 299 309

Ag2 S04 .(a) 424 433

SiO 2 573 571 574

K2 S04 583 582 588

K2 Cr04 665 665 673

value for the transition temperature reported for this material [1] is currently under review. A more recent value of 430 °C

has been reported [2].

The extrapolated onset temperature is defined (Point A, Figure 1) as that temperature found by

extrapolating the base line, prior to the peak, and the leading side of the peak to their intersection. The peak temperature (Point B, Figure 1) is defined as the temperature corresponding to the point

of maximum deflection of the differential temperature curve.

Based on the mean value from 34 cooperating laboratories, the standard deviation was 5-8 °C,

which includes the bias among laboratories as well as measurement errors. In the heating mode,

onset and peak temperatures have about equal precision. However, the mean extrapolated onset temperatures are closer to the equilibrium transition temperatures.

The materials for these standards were furnished by the Committee on Standardization of the ICTA.

The International Test Program leading to the data on which certification is based was coordi- nated by H. G. McAdie, Chairman, ICTA Committee on Standardization.

Coordination of efforts leading to certification by NBS was under the chairmanship of 0. Menis.

The technical and support aspects involved in the preparation, certification, and issuance of

these Standard Reference Materials were coordinated through the Office of Standard Reference

Materials by T. W. Mears.

Washington, D. C. 20234 J. Paul Cali, Chief June 11, 1971 Office of Standard Reference Materials

(over)

53
The transition temperatures given are the means of values obtained on 28 different types of commercial or custom-made instruments, and do not necessarily agree with the equilibrium

values [1, 2]. Generally, values from DTA are somewhat higher than the equilibrium values and

vary in a complex manner for different instruments and heating rates. Details of the instruments

used, the test conditions and complete data will be given in an NBS Special Publication in the 260

series (in publication).

EXTRAPOLATED ONSET

TEMPERATURE

AT

\ PEAK TEMPERATURE

T

[l] Nat. Bur. Stand. (U.S.), Circ. 500 (1952).

[2] Hedvall, J. A., Lindner, R., and Hartler, N., Acta. Chem. Scand. 4, 1099 (1950).

54
Cooperating Laboratories

Dr. David E. Baum, Monsanto Australia Limited, West Footscray, Victoria, Australia

Prof. Marcel Bourgon, Universite de Montreal, Montreal, Quebec, Canada

Dr. H. G. McAdie, Ontario Research Foundation, Sheridan Park, Ontario, Canada

Dr. Klaus Heide, Friedrich-Schiller-Universitat, Jena, Germany

Dr. J. Wiegmann, Berlin, Germany

Dr. G. R. Cizeron, Universite de Paris, Paris, France

Dr. M. Harmelin, C.N.R.S., Paris, France

Mme. J. Jegoudez, Universite de Paris, Paris, France

Dr. M. Foldvari, Hungarian Geological Institute, Budapest, Hungary

Mr. J. Paulik, Technical University of Budapest, Budapest, Hungary

Prof. H. Kambe, University of Tokyo, Tokyo, Japan

Prof. C. Kato, Waseda University, Tokyo, Japan

Prof. K. Oinuma, Tokyo University, Tokyo, Japan

Prof. R. Otsuka, Waseda University, Tokyo, Japan

Mr. J. E. Kruger, National Building Research Institute, Pretoria, South Africa

Dr. R. S. Forsyth, Aktiebojaget Atomenergi, Studsvik-Nykoping, Sweden

Dr. G. Krien, Institut fur Chemisch-Techn. Untersuchungen, Leverkusen, Germany

Prof. H. R. Oswald, Universitat Zurich, Zurich, Switzerland

Dr. T. Peters, Universitat Berne, Berne, Switzerland

Dr. H. G. Wiedemann, Mettler Instrumente A. G., Greifensee, Switzerland

Prof. L. G. Berg, Gosuniversitet, Kazan, U.S.S.R.

Prof. E. K. Koehler, Academy of Sciences of the USSR, Novosibirsk, USSR

Dr. I. S. Rassonskaya, Institut Obshchei i Neorganicheskoi Khimii, Moscow, USSR

Dr. G. 0. Piloyan, Academy of Sciences of the USSR, Moscow, USSR

Mr. E. L. Charsley, Stanton Redcroft Limited, London, England

Dr. R. C. Mackenzie, The Macaulay Institute for Soil Research, Aberdeen, Scotland

55
Prof. D. A. Smith and Mr. J. Youren, Queen Mary College, University of London, London, England

Dr. P. K. Gallagher, Bell Telephone Laboratories, Murray Hill, N.J..U.S.A.

Prof. P. D. Gam, University of Akron, Akron, Ohio,U.S.A.

Dr. 0. Menis, D. S. Bright, and J. T. Sterling, National Bureau of Standards, Washington, D.C., i U.S.A.

Mr. T. D. Oulton, Englehard Minerals & Chemicals Corp., Edison, N.J..U.S.A.

Dr. R. K. Ware, Owens-Illinois, Toledo, Ohio,U.S.A.

International Confederation for Thermal Analysis Committee on Standardization:

Chairman

Vice-Chairman

Secretary

National Delegates

Representative

Delegates

Ex-Officio

Delegates

(Canada) H. Lr. McAdie

(U.S.A.) P. D.Garn

(U.K.) R. C. Mackenzie

(France) C. Mazieres

(German D.R.) K. Hcide

(Hungary) F. Paulik

(Japan) H. Kambe

(Sweden) R. S. Forsyth

(Switzerland) H. G. Wiedemann

(U.S.S.R.) I. S. Rassonskaya

(U.K.) D. A. Smith

(U.S.A.) R. W. Pfeil ASTM (U.S.A.) Vacant ISO Vacant NBS (U.S.A.) 0. Menis

Soc.Anal.Chem. (U.K.) C. J. Keattch

SAMA (U.S.A.) Vacant

ICTA (U.S.S.R.) L. G. Berg

(U.S.A.) C. B. Murphy

(U.K.) R. C. Mackenzie

(U.K.) J. P. Redfern

56
U. S. Depardfanjf of Commerce

Mauric&H. Stana

(&ttt\Vxtntt

NBS-ICTA Standard Reference Material 760

DTA Temperature Standards (570 - 940 °C)

These standards include: natural quartz; analyzed reagent potassium sulfate, potassium chro- mate, barium carbonate, and strontium carbonate. They are for use in calibrating the temperature

scale on differential thermal analysis and related thermoanalytical equipment under operating conditions. They are to be used only in the heating mode.

Transition Temperature Data (°C)

DTA Mean Values

Equilibrium Extrapolated

Material Value [1] Onset Peak

Si02 573 571 574

K2 S04 583 582 588

K2 Cr04 665 665 673

BaC03 810 808 819

SrC03 925 928 938

The extrapolated onset temperature is defined (Point A, Figure 1) as that temperature found by

extrapolating the base line, prior to the peak, and the leading side of the peak to their intersection. The peak temperature (Point B, Figure 1) is defined as the temperature corresponding to the point

of maximum deflection of the differential temperature curve.

Based on the mean value from 34 cooperating laboratories, the standard deviation was 5-8 °C,

which includes the bias among laboratories as well as measurement errors. In the heating mode,

onset and peak temperatures have about equal precision. However, the mean extrapolated onset temperatures are closer to the equilibrium transition temperatures.

The materials for these standards were furnished by the Committee on Standardization of the ICTA.

The International Test Program leading to the data on which certification is based was coordi- nated by H. G. McAdie, Chairman, ICTA Committee on Standardization.

Coordination of efforts leading to certification by NBS was under the chairmanship of O. Menis.

The technical and support aspects involved in the preparation, certification, and issuance of

these Standard Reference Materials were coordinated through the Office of Standard Reference

Materials by T. W. Mears.

Washington. D. C. 20234

June 11, 1971

J. Paul Cali, Chief

Office of Standard Reference Materials

(over)

57
The transition temperatures given are the means of values obtained on 28 different types of commercial or custom-made instruments, and do not necessarily agree with the equilibrium

values [1]. Generally, values from DTA are somewhat higher than the equilibrium values and vary

in a complex manner for different instruments and heating rates. Details of the instruments used, the test conditions and complete data will be given in an NBS Special Publication in the 260 series (in publication).

EXTRAPOLATED ONSET

TEMPERATURE

AT

PEAK TEMPERATURE

[1] Nat. Bur. Stand. (U.S.), Circ. 500 (1952).

58
Cooperating Laboratories

Dr. David E. Baum, Monsanto Australia Limited, West Footscray, Victoria, Australia

Prof. Marcel Bourgon, Universite de Montreal, Montreal, Quebec, Canada

Dr. H. G. McAdie, Ontario Research Foundation, Sheridan Park, Ontario, Canada

Dr. Klaus Heide, Friedrich-Schiller-Universitat, Jena, Germany

Dr. J. Wiegmann, Berlin, Germany

Dr. G. R. Cizeron, Universite de Paris, Paris, France

Dr. M. Harmelin, C.N.R.S., Paris, France

Mme. J. Jegoudez, Universite de Paris, Paris, France

Dr. M. Foldvari, Hungarian Geological Institute, Budapest, Hungary

Mr. J. Paulik, Technical University of Budapest, Budapest, Hungary

Prof. H. Kambe, University of Tokyo, Tokyo, Japan

Prof. C. Kato, Waseda University, Tokyo, Japan

Prof. K. Oinuma, Tokyo University, Tokyo, Japan

Prof. R. Otsuka, Waseda University, Tokyo, Japan

Mr. J. E. Kruger, National Building Research Institute, Pretoria, South Africa

Dr. R. S. Forsyth, Aktiebolaget Atomenergi, Studsvik-Nykoping, Sweden

Dr. G. Krien, Institut fur Chemisch-Techn. Untersuchungen, Leverkusen, Germany

Prof. H. R. Oswald, Universitat Zurich, Zurich, Switzerland

Dr. T. Peters, Universitat Berne, Berne, Switzerland

Dr. H. G. Wiedemann, Mettler Instrumente A. G., Greifensee, Switzerland

Prof. L. G. Berg, Gosuniversitet, Kazan, U.S.S.R.

Prof. E. K. Koehler, Academy of Sciences of the USSR, Novosibirsk, USSR

Dr. I. S. Rassonskaya, Institut Obshchei i Neorganicheskoi Khimii, Moscow, USSR

Dr. G. 0. Piloyan, Academy of Sciences of the USSR, Moscow, USSR

Mr. E. L. Charsley, Stanton Redcroft Limited, London, England

Dr. R. C. Mackenzie, The Macaulay Institute for Soil Research, Aberdeen, Scotland

59
Prof. D. A. Smith and Mr. J. Youren, Queen Mary College, University of London, London, England

Dr. P. K. Gallagher, Bell Telephone Laboratories, Murray Hill, N.J..U.S.A.

Prof. P. D. Gam, University of Akron, Akron, Ohio, U.S.A.

Dr. 0. Menis, D. S. Bright, and J. T. Sterling, National Bureau of Standards, Washington, D.C., U.S.A.

Mr. T. D. Oulton, Englehard Minerals & Chemicals Corp., Edison, N.J..U.S.A.

Dr. R. K. Ware, Owens-Illinois, Toledo, Ohio.U.S.A.

International Confederation for Thermal Analysis Committee on Standardization:

Chairman (Canada) H. G. McAdie

Vice-Chairman (U.S.A.) P. D. Gam

Secretary (U.K.) R. C. Mackenzie

National Delegates (France) C. Mazieres

(German D.R.) K. Hcide

(Hungary) F. Paulik (Japan) H. Kambe

(Sweden) R. S. Forsyth

(Switzerland) H. G. Wiedemann

(U.S.S.R.) I. S. Rassonskaya

(U.K.) D. A. Smith

(U.S.A.) R. W. Pfeil

Representative ASTM (U.S.A.) Vacant

Delegates ISO Vacant NBS (U.S.A.) 0. Menis

Soc.Anal.Chem. (U.K.) C.J. Keattch

SAMA (U.S.A.) Vacant

Ex-Officio ICTA (U.S.S.R.) L. G. Berg

Delegates (U.S.A.) C. B. Murphy

(U.K.) R. C. Mackenzie

(U.K.) J. P. Redfern

60
FORM NBS-114A (1-71) U.S. dept. OF comm. 1. PUBLICATION OR REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA ^ No.

3. Recipient's Accession No.

4. title and subtitle standard Reference Materials:

SELECTION OF DIFFERENTIAL THERMAL ANALYSIS TEMPERATTTDTJ CTHMFlADnt: TUDnilTU A rnHDFDATTVC CTTTTW CCDM AlUKr; blAINUAKUo IriKUUbri A LuUrLKAl 1 V L blUUi, (^oKM

758, 759, 760)

5. Publication Date August 1972

6. Performing Organization Code

7. author(s) Hi Gj McAdie} P< D< earn, 0. Menis 8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Address Same as No. 9„

13. Type of Report & Period Covered Final

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.)The testing and evaluation program leading

to the certification of 10 materials as Standard Reference Materials NBS

758, 759 and 760, for calibrating the temperature scale for thermal analysis is described. The international cooperative testing program was set

up on the basis of a preliminary program initiated in 1966. Thirty-four

laboratories reported to the Standards Committee of the International

Confederation on Thermal Analysis. The results were obtained on a variety of apparatus under their conditions of experimentation, except

that the heating rate was prescribed in the range of 4 to 10 °C per

minute. The data were processed to obtain means and measures of scatter,

not only in total, but separated in terms of a number of sample number

of sample holder parameters. The sample holder geometry was the only

parameter having a clear effect on the extrapolated onset and peak

temperatures. The effects of thermocouple position and calibration were

tested, but no significant effect was found. The heating rate has only

a small effect, tending to increase the spread of onset and peak temperature values from the DTA are somewhat higher than the thermodynamic

equilibrium values reported in the literature. Based on the mean values

from all the laboratories the standard deviation was 5 to 8 °C, which includes the bias between laboratories as well as measurement errors.

17. key words (Alphabetical order, separated by semicolons) DTA; International Confederation on Thermal Analysis; international cooperative testing; Standard Reference

Materials NBS 758, 759, 760; temperature scale; thermal analysis.

18. AVAILABILITY STATEMENT

f^l UNLIMITED.

1 1 FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

71

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

65 cents

USCOMM-DC 66244-P71

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