D_A DIMARS

NATIONAL BUREAU OF STANDARDS REPORT

PRELIMINARY REPORT

ON THE THERMODYNAMIC PROPERTIES OF

SELECTED LIGHT-ELEMENT AND

SOME RELATED COMPOUNDS

(The previous semiannual reports in this series have the NBS

Report Nos. 6297, 6484, 6645, 6928, 7093, 7 192, 7437, 7587,

7796, 8033, 8186, 8504, 8628, 89 19, 9028, 9389, 9500, 960 1, and 9803.)

9905

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

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

1901. Today, in addition to serving as the Nation’s central measurement laboratory,

the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and

provides central national services in three broad program areas and provides central national services in a fourth. These are: (1) basic measurements and standards,

(2) materials measurements and standards, (3) technological measurements and

standards, and (4) transfer of technology.

The Bureau comprises the Institute for Basic Standards, the Institute for Materials

Research, the Institute for Applied Technology, and the Center for Radiation Research.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the

United States of a complete and consistent system of physical measurement, coor- dinates that system with the 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 an Office of Standard Reference Data and a group of divisions organized by the

following areas of science and engineering

:

Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Cryogenics2—Radio Physics2—Radio Engineering2—Astrophysics2—Time

and Frequency.2 THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to methods, standards of measurement, and data needed by industry, commerce,

educational institutions, and government. The Institute also provides advisory and

research services to other government agencies. The Institute consists of an Office of

Standard Reference Materials and a group of divisions organized by the following areas of materials research:

Analytical Chemistry—Polymers—Metallurgy — Inorganic Materials —Physical

Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides for the creation of appropriate opportunities for the use and application of technology within the Federal Government and within the civilian sector of American industry. The primary functions

of the Institute may be broadly classified as programs relating to technological meas- urements and standards and techniques for the transfer of technology. The Institute

consists of a Clearinghouse for Scientific and Technical Information,3 a Center for

Computer Sciences and Technology, and a group of technical divisions and offices

organized by the following fields of technology:

Building Research—Electronic Instrumentation — Technical Analysis — Product

Evaluation—Invention and Innovation— Weights and Measures —Engineering

Standards—Vehicle Systems Research.

THE CENTER FOR RADIATION RESEARCH engages in research, measurement,

and application of radiation to the solution of Bureau mission problems and the

problems of other agencies and institutions. The Center for Radiation Research consists of the following divisions:

Reactor Radiation—Linac Radiation—Applied Radiation—Nuclear Radiation.

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

2 Located at Boulder, Colorado 80302.

3 Located at 5285 Port Royal Road, Springfield, Virginia 22151.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

221-0404 i July 1968 9905

221-0405

221-

0426

222-

0423

313-0430

316-0426

316-0513

PRELIMINARY REPORT

ON THE THERMODYNAMIC PROPERTIES OF

SELECTED LIGHT-ELEMENT AND

SOME RELATED COMPOUNDS

(The previous semiannual reports in this series have the NBS

Report Nos. 6237, 6484, 6645, 6928, 7093, 7 192, 7437, 7587,

7796, 8033, 8186, 8504, 8628, 8919, 9028, 9389, 9500, 9601,

and 9803.)

Technical Summary Report

on the Thermodynamic Properties

of Light-Element Compounds

Reference: U. S. Air Force, Office of Scientific Research,

Order No. ISSA 67-6

IMPORTANT NOTICE NATIONAL BUREAU OF STA

for use within the Government. B and review. For this reason, the whole or in part, is not authoriz Bureau of Standards, Washington

the Report has been specifically p

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

accounting documents intended

.ibjected to additional evaluation

isting of this Report, either in Office of the Director, National

the Government agency for which

ties for its own use. <NB>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

ABSTRACT

Thermodynainic and related properties of substances

important in current high-temperature research and development activities are being investigated under contract with

the U. S. Air Force Office of Scientific Research (USAF

Order No. ISSA 67-6) and the Advanced Research Projects

Agency (ARPA Order No. 20). This research program is a direct contribution to the Interagency Chemical Rocket

Propulsion Group (Working Group on Thermochemistry) and,

simultaneously, to other organizations oriented toward

acquiring the basic information needed to solve not only

the technical problems in propulsion but also those

associated with ballistics, reentry, and high-strength

high-temperature materials,. For given substances this

needed basic information comprises an ensemble of closely

related properties being determined by an extensive array

of techniques. Some of these techniques, by relating

thermodynamic properties to molecular or crystal structure,

make it possible to tabulate these properties over far

wider ranges of temperature and pressure than those actually

employed in the basic investigations.

This report presents in detail the methods, results,

and interpretation of six recent NBS experimental investigations of thermodynamic and related properties. Maasurements

of the heats of reaction with hydrogen of chlorine trifluoride and its two free elements gave on preliminary calcut

is 10 kcal/mol less exothermic. Precise measurements of the

heat capacity of sintered beryllium oxide gave generally

lower heat capacities (by up to 30$ at 55 K) and an appreciably lower entropy (S^q ^5

a 3*291 ±0.00i± cal/K mol) than

l
previously accepted, A new millisecond apparatus for

measuring simultaneously the heat capacity, electrical

resistivity, arid hemispherical total emittance of electrical conductors is described (respective estimated errors:

1*5%9 0,6%, and 3% at 2^00 K; less at 1800 K). Preliminary

results are given for molybdenum (1800-2800 K)« The reaction between beryllium metal and aluminum oxide was

studied mass-spectrometrically (1511-17U3 K). The resulting

second-law and third-law heats of four reactions involving

the gas species Be, At, 0, A^O* and AtO are compared. From

a continuation of the spectroscopic investigation of the

alkali -hydroxide molecules, the high-tenderature microwave

spectra of RbOH and the matrix-isolation infrared spectra of

RbOH and NaOH (plus the deuteroxides in all cases) were

observed, and are analyzed to give bond lengths, frequency

fundamentals, nuclear quadrupole coupling constants, and

vibration-rotation interaction constants. The essentially

linear shapes and unusual bending potentials of these

molecules are very similar to those found earlier for CsOH,

and suggest a similar behavior of all the alkali hydroxides.

Thomas B. Douglas

Project Leader

Charles ¥. Beckett

Assistant Division Chief for Thermodynamics

Heat Division, Institute for Basic Standards

ii
Chap

TABLE OF CONTENTS

Abstract

Page

i

1. FLUORINE FLAME CALORIMETRY III. THE HEAT

OF FORMATION OF CHLORINE TRIFLUORIDE . . . (by R. C. King and G. T. Armstrong) 1

1. Introduction 1

2. Experimental Apparatus and Procedures ... 2

2.1 The Reaction Vessel and Flow System . . 2

Fig. 1. Assembly of Reaction

Vessel 3

Fig. 2. Combustion Chamber and

Primary Solution Vessel . k

Fig. 3« The Oxidizer Flow Line . 5

2.2 Water Removal from the Reaction Vessel . 6

2.3 Experimental Procedures 6

Table 1. W

Tater Changes in

Reaction Vessel ... 7

2,h The Samples 8

Table 2. Analyses of Oxidizer

Gases 10

3* Calibration of the Calorimeter 11

Table 3* Calibration of the

Calorimeter.

The 02-Hp Reaction . . 12

1;. The Completeness of the Reactions .... 13

Table h» The Completeness of the

C&F^-^-^O Reaction . . li|

5. Reaction Heat Measurements 15

Table 5« The Completeness of the

C “H2

- H2 0 and

C^-I^-HF Reactions . 17

Table 6. The CAF^-I^-f^O Reaction:

Typical Reaction

Quantities ..... 18

Table 7* The Reaction:

Typical Heat Measurements 19

Table 8. The Heat of the

Cj^F^-^-^O Reaction

(303 °K

)

..... 20

iii
Chap. 2

TABLE OF CONTENTS (Continued)

Page

References

Table 9* The Cj^-J^-HgO and

C^2 “H?”HFaqTypical

Reaction Quantities . . 21

Table 10. The C42 -H

?

-H2 0 and

CA2 -H2 -HF

aq

Reactions:

Typical Heat Measurements C\J <\j • Table 11. The Heats of the

C^-Hg-^O and

CX2 -H2

~HFaq

Reactions

(303 ®K) . 23

Table 12. The F2

-II2 -HCX

ac)

Reaction:

Typical Heat Measurements . 2h

Table 13* The Heat of the

F2 -H

2

-fCJ8 aQ Reaction

(303.6 °K) . 25

Table lk» Preliminary Calculation

of the Heat of Formation

of Chlorine Trifluoride 26

. 27

. HEAT CAPACITY AND THERMODYNAMIC PROPERTIES OF

BERYLLIUM OXIDE, BeO, FROM 15 TO 370 K ~

(by George T. Furukawa and Martin L. Re illy

)

28

Abstract 28

I. Introduction * ....28

II. Sample * • ........... 30

III. Apparatus and Method ........ 31

IV

.

Results ••••••o...... 33

Table 1. Spectrochemical Analysis

of the Sintered Beryllium

Oxide (BeO) Pellet . * . 37

Table 2. Thermodynamic Functions

for Beryllium Oxide (BeO),

Solid Phase 38

Table 3* Comparison of Enthalpy

Values of Table 2 with

the Experimental Relative

Enthalpy Data of Victor

and Douglas ..... 39

References . . 4O

Fig. 1. Percentage Deviation of

the Empty Sample Vessel

Heat Capacities . . . . 1;3

iv
TABLE OF CONTENTS (Continued)

Fig, 2. Percentage Deviation of

Page

the Beryllium Oxide

Sample Heat Capacities . . uu

Fig. 3* Percentage Deviation of

Fig. h»

the Beryllium Oxide

Sample Heat Capacities • . Observed Values of

C/T^ vs. T. • • • • • U6

Fig. 5. A Comparison of Results

Published by Other

Investigators with Those

Obtained in this Research • hi

Chap. 3- DYNAMIC MEASUREMENT OF HEAT CAPACITY , ELECTRICAL RESISTIVITY AND HEMISPHERICAL

TOTAL EMITTANCE OF MOLYBDENUM IN THE

RANGE l800 -2 600 K

" ~

(by A. Cezairliyan , M. S. Morse, H. A. Berman.

G. M. Foley, and C. W. Beckett) ....... It-8 Abstract i|8

I. Introduction • . . • h9

II. Description of the Method 51

a. Heating Period . . 52

b. Cooling Period 53

c. Relations for Properties 53

III. Description of the System ....... 5U

a. Specimen and Test Cell 5U

Fig. 1. Functional Diagram of

Millisecond Thermodynamic

Measurements System ... 55

b. Rest of Main Circuit ....... 56

c. High-Speed iPyrometer . 56

d. High-Speed Digital Data Acquisition

System 57

Fig. 2. Functional Diagram of

High-Speed Digital Data

Acquisition System . . .59

IV. Experimental Results 60

Fig. 3* Heat Capacity of

Molybdenum as a Function

of Temperature . • . .61

Fig. 1|. Electrical Resistivity of

Molybdenum as a Function

of Temperature . . . .62

v
TABLE OF CONTENTS (Continued)

Page

Fig • 5« Hemispherical Total

Errdttance of Molybdenum as a Function

of Temperature . . 63

V. Discussion • •••••••••••• 61i

Table 1. Estimated Errors • • . • 6?

Acknowledgment •••••••••••66

References 6 7

Chap, lu MASS SPECTROMETRIC STUDY OF THE BERYLLIUM- ALUMINA REACTION

(by J. Efimenko) ..69

Introduction 69

Experimental • « * . . . « • « . • . . o9

Results 69

Discussion 70

Table !• Dataz Ion Intensities . . 72

Table 2# Auxiliary Data .... 73

Table 3* Reaction Enthalpies ... 714- Table U. Partial Pressures ... 75

Fig. 1. A van’t Hoff plot for

the reaction

Be(g) + ( s )

=• BeO(s) + 2A&(g) + 20(g) . 76

Fig* 2. A van ! t Hoff plot for

the reaction

2A/& (g) + 0(g) = AA2 0(g) . . 77

Fig. 3* A van 1 1 Hoff plot for

the reaction

Be(g) + A£2 0(g)

- BeO(s) + 2A^(g) ... 78

Fig. U* A van ! t Hoff plot for

the reaction

Be(g) + A/9 O0 (s

)

= BeO(s) +~2U0(g) ... 79

Chap. 5. STRUCTURE OF THE ALKALI HYDROXIDES. III . MICROWAVE SPECTRA OF RbOH AND RbQD

(by Chi Matsumura and David R. Lide , Jr • )

. . .80

Abstract 80

Introduction . . . 81

Experimental • ••••• . 8l

Analysis of Spectrum . . 83

vi
TABLE OF CONTENTS (Continued)

Page

Nuclear Quadrupole Coupling » Vibration-Rotation Interactions

Structure .......

Acknowledgments . • . • References

Table I

.

Table II.

Table III.

Table IV.

Table V.

Table VI.

Table VII.

Observed frequenc:

in Rb^OH and Rb°-

es

OD . Observed frequencies

in Rb87 OH and Rb87 OD . Effective rotational

constants and nuclear

coupling constants

for various vibrational states of RbOH and

RbOD ...... 4 -doubling constants

Variation of rotational. constants with

Fit of BOv|0 to

power series • • • Structural parameters

of rubidium hydroxide .

8U

85

86

86

87

88

92

9h

95

96

97

98

Chap. 6. STRUCTURE OF THE ALKALI HYDROXIDES. IV. THE

INFRARED SPECTRA OF MATRIX ISOLATED RbOH, RbOD AND NaOH, NaOD

(by N. Acquista and Stanley Abramowitz) .... 99

Abstract 99

Introduction 100

Experimental 100

Experimental Results 102

Table 1. Observed Bands for

Monomeric Alkali

Metal Hydroxides . . . 105

References 106

Fig. 1. The spectra of matrix

isolated RbOH in argon . 107

vii
TABLE OF CONTENTS (Continued)

Fig* 2* The spectra of matrix

Page

isolated NaOH in argon . . 108

Fig. 3* The spectrum of matrix

isolated NaOH in argon • . 109

Fig* k» The spectrum of matrix

Fig* 5.

isolated NaOH (and that

of NaOD) in argon . no

The spectrum of matrix

isolated NaOD in argon • . m

viii
Chapter 1

FLUORINE FLAME CALORIMETRY III.

THE HEAT OF FORMATION OF CHLORINE TRIFLUORIDE

R. C. King and G. T. Armstrong

1. INTRODUCTION

A study of the heat of formation of chlorine trifluoride lias

been conducted using flame calorimetry. Chlorine trifluoride is

an extremely reactive compound, which reacts spontaneously with many

substances leading to multiple reaction products. For this reason

there are few reactions which are suitable for a well-defined study

of its heat of formation.

For this study the chlorine trifluoride was reacted with

hydrogen, using an experimental approach and procedures similar to

those used in an earlier study on the heat of formation of oxygen

difluoride [1]. The product acids were dissolved in water to form

an aqueous solution inside the calorimeter. The heats of the auxiliary reactions of chlorine and fluorine with hydrogen to form the

aqueous solutions of the mixed acids were also measured. The equations

for the reactions studied are:

C1F3 (g) + 2Hg (g) + 100H2 0(1) - [HC1 • 3HF* lOOF^ 0] (1) (1)

|Cl2 (g) +iMg) + [ 3HF • lOOHg 0 ]( l)-* [HC1« 3HF» lOOHgOlCl) (2)

|Mg) +|H=(g) + [HCl-lOOIfeO]®- [HC1' 3HF* lOOHg 0] (1) (3)

Retaining the product acids inside of the calorimeter in a known

thermodynamic state has several advantages which have already been

discussed [1]. It is believed that the systematic errors in the heats

of reactions (2) and (3) are similar to those in reaction (1), and

that most of the systematic errors will cancel in the calculation of

the heat of formation of chlorine trifluoride, leading to a more

accurate value. The agreement between the heats of reactions (2)

and (3) and the heats of formation of the aqueous solutions of the

respective acids can be used is an indication of the overall validity of

the procedures used in this study.

This report presents a brief description of the experiments and

some preliminary results on the heats of the reactions and the calculated heat of formation of chlorine trifluoride.

1
2 . Experimental Apparatus and Procedures

2.1 The Reaction Vessel and Flow System

The overall design of the reaction vessel is illustrated in figure

1. It is similar to the one used and described earlier [1], The

main modification is the use of a secondary solution vessel of larger

volume (more like the primary solution vessel).

The mixture of hydrogen chloride and hydrogen fluoride formed

in the chlorine trifluoride -hydrogen reaction was observed to be

extremely corrosive. To lessen loss of the acid by corrosion, a removable

platinum liner (0.002 in. thick) was placed in the combustion chamber

(A). (See figure 2) For the chlorine-hydrogen reactions, a platinum

liner was placed on the underside of the lid to the combustion chamber.

Platinum in this position was found to be very unsuitable for the

chlorine-trifluoride experiments. In these experiments the liner on the lid

would vaporize, leading a soot-like deposit on the walls of the combustion chamber. A spec tr ©chemical analysis of this deposit revealed

it to be platinum.

The undersides of the Monel lids (J) to the solution chambers

were coated with Teflon. For an experiment each solution vessel

o contains 100 cm of water. Additional details of the reaction vessel

and the procedures for using it have already been described [1],

The overall design of the flow system is similar to that used

earlier. The major modification was introduced in the oxidizer flow

line. Previously, a Pyrex float-type flowmeter was used to

indicate the rate of flow of the oxidizer. Because of the extreme

reactivity of chlorine trifluoride, a mass flowmeter was inserted in

the oxidizer flow line to be used in addition to the float-type

flowmeter. This modification is shown in figure 3. For the chlorinetrifluoride-hydrogen reactions, the Pyrex flowmeter was replaced with

a stand-in Monel tube. However, the Pyrex flowmeter was used satisfactorily for the Os-Hd, Cl2 -H^, and F2 -Hg reactions and was found

very useful for monitoring the 02 -Hg and Cl2 -Hg flames.

COMBUSTION CHAMBER AND SOLUTION VESSEL

J

Figure 2. Combustion Chamber and Primary

Solution Vessel, Combustion chamber;

B, Hydrogen inlet; G } Oxidizer inlet; D,

Flame position; E, Spark electrode; F_, Platinum tubing; G, Teflon adapter; H, Polyethylene gas disperser; 1^ Primary solution

chamber; Lid for solution vessel; To

secondary solution vessel.

h
(U G 1 o OJ H3 1 5-i 4-J QJ 3 <D U

oj O £ OJ G m 5 G

•H o a. 4 £ r—1 3 4-1 3 •H r-4 O 1“f W 4-1

T““f £

CO o

fo £ 2

54 •\ •H

OJ PQ ^ 'V N Q •H • n <U •

5-i •" > i—)

•H 3 5-4 r-4 <D C 0) G CO •H 4-J P> CO g QJ QJ

0) 4-1 £ •*> >

43 G 3 fa H O C O 1 • ^ o

4-1 5-i *r4 • <U CU •U ro r—1 X u CJ fa QJ 3 G

oj E 5-4 X3 a u G >> CO 54 3 W G C

00 to &0

•H •\ ^ 5-4 G

fa •< U 4J • H 5
2.2 Water Removal from the Reaction Vessel

The water changes in the reaction vessel were checked by weighing the saturators and absorber (magnesium perchlorate) before and

after each experiment. These water changes are compared in Table 1.

It is generally observed that there is consistency in the water

changes in the reaction vessel for a given reaction. The addition

of water by the hydrogen which enters into reaction can account for

the increase in water for the Qg -Eg , C1F3 -Hg-Eg0, and Clg-Hg-HgO

reactions. The reactions for these experiments extended over periods

ranging from 15 to 20 minutes, whereas the reaction periods for

the Clg-I^-H and Fg-Hg-HCI reactions were shorter, ranging from

eight to twelve minutes. Therefore, in the latter experiments less

hydrogen was reacted and as a result, less water was added, yielding

an overall net removal of water from the reaction vessel. It is

assumed that the net change in water in the reaction vessel is

averaged over the entire experiment, which lasts for about 65 minutes.

We assume also that the heat effect associated with the net change in

water in the reaction vessel is a constant part of the drift of the

calorimeter temperature. Therefore, no correction is applied to the

temperature rise of the calorimeter, except for the condensation of

water carried in by the part of the hydrogen that reacts,

2.3 Experimental Procedures

The procedures for conducting an experiment, the ignition system,

and methods for calculations have been described [lj. For each

reaction, the oxidizer was reacted in excess hydrogen - nTT /n = 2 0 7 7 Hg oxidizer

6
12

3

4

5

6

12

3

4

5

6

7

12

3

4

12

3

4

5

6

12

3

4

Table 1

Water Changes in Reaction Vessel

Water Removed Water Carried

in

Increase

g g g

Oxygen- Hydrogen Reaction

0.7634 0.8615 0.0981

0.8477 0.8574 0.0097

1.0371 1.0635 -0.0264

1.0463 0.9446 -0.1017

0.7795 0.8828 0.1033

0.7060 0.7508 +0.0448

Chlorine Trifluoride- Hydrogen-Water Reaction

0.5458 0.5975 +0.0517

0.5959 0.5781 0.0178

0.7055 0.7589 -0.0534

0.5679 0.6636 0.0957

0.6038 0.6484 +0.0446

0.7337 0.7408 0.0071

0.6448 0.7184 0.0186

Chlorine - Hydrogen-Water -React ion

0.3229 0.6809 +0.3580

0.3016 0.5931 0.2915

0.5554 0.8235 0.2681

0.8892 1.4887 0.5995

C h 1 or ine - Hydr ogen- HF -Reaction

0.8163 0.7222 -0.0941

0.9960 0.8689 -0.1271

- 0.8010 - 0.7147 0.7313 +0.0166

0.6777 0.6136 -0.0641

0.8135 0.7377 -0.0758

Fluor ine-Hydrogen- HCl aq

- Reaction

0.7667 0.7328 -0.0429

0.8284 0.7703 -0.0581

0.9450 0.8921 -0.0529

1.0401 0.8510 -0.1891

7
2.4 The Samples

a. Hydrogen

A commercial grade of high-purity hydrogen was used directly

from the cylinder. The analysis of the sample has already been

presented [ 1 ]

b. The Oxidizer Gases

Each sample of the oxidiger gases was obtained commercially.

The high-purity oxygen was obtained in a 200 cu.ft. cylinder and was

transferred to a weighable spherical bulb for the calibration experiments. The pressure in the sample bulb was 17 atm. The analysis

of the sample has already been presented [1],

Chlorine Trifluoride . A large sample (80 g) of the chlorine

3 trifluoride was transferred to a 250 cm weighable bulb for the

reactions. The sampling procedure consisted of evacuating and

conditioning the bulb and then filling with chlorine trifluoride by

condensation with dry ice. The chlorine trifluoride was passed over

activated NaF to remove the HF in the sample.

The chlorine trifluoride sample was contained as a liquid under

its vapor pressure of about 0.4 atm gauge at room temperature. So

that the gas and liquid phases of the sample would have similar

concentrations of the impurities, a smaller container would have

been more desirable. In preliminary experiments, a smaller cylindrical

container was used and found to be less satisfactory because of

3 difficulties in controlling the flame. Therefore, the 250 cm bulbs

were used and were immersed in a beaker of water (30°C) to maintain

the pressure of chlorine trifluoride.

8
After removal of the hydrogen fluoride, the remaining impurities

are more volatile than the chlorine trifluoride. It is possible

that the sample becomes purer in chlorine trifluoride as a series of

experiments is completed. To check this point, duplicate analyses

were performed on the sample at different times. The results showed

the sample to contain 0,47 and 0.45 mole % impurities.

No one method is available which can provide a complete and

accurate analysis of the chlorine trifluoride sample. For this

study, a combination of the mercury absorption, mass spec trome trie

and infrared methods are being used. The limitation of the mercury

absorption method is that other reactive fluorides are absorbed with

the chlorine trifluoride. The Cl-Q-F compounds are possible impurities

in the chlorine trifluoride sample. These gases would be absorbed

by the mercury, causing an error in the overall mole percent of the

C1F3 , and the absorption of these gases may liberate oxygen, causing

an error in the analysis for free oxygen in the sample. Because of

the unavailability of a better method for a complete analysis of the

gas, mercury absorption was used and the residual gas was analyzed

by mass spectrometry. The general procedures for these methods have

been described [1], An improvement in the mercury absorption introduced for these analyses was first to condition the mercury and container and then re-evacuate prior to filling to the final pressure

of one atm. The results of the analyses are given in Table 2.

Additional analyses on the chlorine trifluoride sample using other

methods including infrared analysis are planned.

Chlorine . The chlorine was a commercial research grade sample

and no attempt was made to purify it. The chlorine was determined by

mercury absorption and the impurities were measured by mass spectrometry. In the mercury-absorption, it was necessary to heat the

9
Table 2

Constituent

ClFo

Cl2

F2

Q>

N2

Ar

CCfe CF4 c3 f8 c2 f6 c4 f8

sc^f3

SiF4

Analyses of Oxidizer Gases

Sample

C1F3 Cla

(gas phase)

Weight Percent

99.82 - - 99.93

.15 .02

.01 .05 * *

.01 k

* - k - k - k aa

F2

99.85

.11

.004 *

.012

.02 **

*

**

Not detected

Detected

10
sampling bulb to achieve complete absorption of the chlorine. The

Pyrex bulb was filled to one atm and then agitated and heated

gradually with hot water. The analysis of the chlorine sample is

given in Table 2.

Fluorine . The analysis of the fluorine sample given in

Table 2 was obtained earlier by the mercury absorption and mass

spectrometric methods [2]. The fluorine was transferred to the

sample bulbs using a manifold described earlier [1],

It is noted that the major impurities in the oxidizer gases are

oxygen and nitrogen. It is shown later that a correction is applied

to the heat measurement data for the heat of reaction of the impurity

oxygen with hydrogen.

3. Calibration of the Calorimeter

A preliminary calibration of the calorimeter is obtained from

the known heat of the oxygen- hydrogen reaction. The selected value

for the heat of this reaction is based on the work of Rossini [4],

The procedures and corrections for using this reaction for calibrations are outlined by Rossini.

Table 3 shows the heat measurement data and the corrections

applied for a typical experiment on the oxygen-hydrogen reaction,

ms is the mass of the oxygen sample. The mass of oxygen reacted is

based on the analysis which shows the sample to be 99.987 weight percent oxygen. (corr), Atc and t ave are respectively, the corrected

temperature rise, the correction to the temperature rise and the

average temperature of the calorimeter. t(ave) is the temperature

of the reaction. The heat corrections applied are q(ign), the

ignition energy, q(vap), the heat effect of the condensation of the

water in the reacting hydrogen, and q(temp), the heat of tempering

the reacting gases from the room temperature to tave . These corrections were applied to q(02 ), the heat of the reacting oxygen, to

11
Table 3

Calibration of the Calorimeter.

The -1^ Reaction.

Experiment 6

ms , g 2.7795

At(corr), °C 2.26511

Atc , °C 0.05849

t(ave), °C 30.43

qCQa), J -49,619

q(ign), J -28

q (vap) , J -215

q (temp) , J 38

q (obs) , J -49,824

E, J^C)" 1 21995.8

t&, J(°C)

_1 -6.5

E(calorim), J(°C)“'*' 21989.3

E(calorim) Average for 6 expfcs,, 21983.9

Standard deviation of the mean, J(°C)“^ 4.5

12
obtain the observed heat, q(obs). 4e is a correction to the energyequivalent for one-half of the water formed in the reaction. The

average value for six experiments is given. In an earlier study,

the heat of the reaction based on electrical calibrations was

determined in our apparatus. The close agreement between Rossini's

value and our value suggests that our procedures are valid. The

standard deviation of the mean shown in Table 3 is larger (0.027.) than

expected. Additional calculations of the data may reveal the reason

for this standard deviation of the mean.

4. The Completeness of the Reactions

For the oxygen-hydrogen reaction, the amount of reaction is

based on the weight of oxygen introduced into the reaction vessel.

Earlier comparisons between the amount of oxygen reacted and the

amount of water formed showed that the oxygen was completely reacted.

The completeness of the C1F3 -I^-I^0 reaction was determined by

analyses of the product solutions. Each solution was analyzed for

H*, and for two typical experiments analyses were performed for

Cl and F . These results are given in Table 4. n^(obs)/n^f(calc)

for these experiment resembles the results for the Fs -Hg-HgO reactions

[1], The generally low values can be explained by the extremely

reactive nature of the product acid mixture [HC1*3HF] the lowest

value for experiment 1 suggests that more conditioning of the

combustion chamber took place in that experiment. No explanation

is offered for the erratic but favorable value for experiment 6.

A comparison between the n^- and np“ shows a value of 0.3337,

which agrees fairly closely with the theoretical ratio of 0.3333.

This suggests that very little, if any of the C1F3 sample is other

Cl-F compounds. The presence of these would change the value for

nci"/nF~*

13
Table 4

The Completeness of the C1FS »Hg -Hg 0 Reaction

Experiment IHg n (HF+HCl) 9 obs nm-(obs)

No. nH+(calc)

g moles

1 5.3218 0.22313 0.9710

2 5 . 5074 .23262 .9782

3 5.3577 .22461 .9757

4 5.1142 .21545 .9756

5 4.4999 .19024 .9790

6 5.2142 .22349 .9926

7 4.9769 .21035 .9787

n

Cl"

" np- ~

0.05579 mole

0.16716 mole
All of the analyses for the C1F3 experiments were performed

in the Analytical Chemistry Division at the National Bureau of

Standards. The and Cl~ were determined by the conductometric

method and the F

” was measured by potentiometric titration with

La(N03 ) s

. The data for the Clg-I^-HgO and Clg-I^-HF^ reactions are given

in Table 5. The reactions are generally more complete than the

ClFg-Hg-I^O reactions. The n^^/n^j. is larger than the stoichiometric,

suggesting that the amount of acid not recovered is consumed by

corrosion.

5. Reaction Heat Measurements

ClFg-Hg-HgO. Typical reaction quantities for this system are

given in Table 6. (reacted) is based on n^_(obs), and (corros)

is based on n^(calc-obs) . The other notations have the same meaning

given earlier [1],

The typical heat measurements and the corrections to the heat

data are given in Table 7. With the exception of 4>e, q (corros) and

q' , the symbols have the same meaning as for the oxygen- hydrogen

Ulr 3

experiments. is a correction to the energy equivalent for one-half

the product formed, q(corros) corrects for the corrosion by CIF^

qpll7 is the total heat without q(corros) and q

1 , includes q (corros). Ulr 3 ^-*-^3 In calculating q (corros), it is assumed that the C1F3 reacts with

nickel to give NiCl2 and NiF2 . The heat of the C1F3 -I^-1^0 reaction is given in Table 8. Similar

to the earlier work the heat of reactions were calculated in three

different ways [1], Referring to Table 7, £H(1) is q^_, /n^(calc);

AH(2) is qclF /nH

+(obs), and z^H(3) is q' clF /n^+(obs). We assume

that AH(3) is the most valid treatment of the data because it is based

on the heat effect, corrected for corrosion, which the reaction showed

evidence of, and also because n^p(obs) is the actual amount of acid

present in the solution. The AH(2) and £H(1) values for experiment

six suggest that the good recovery of the acid as shown in Table 4

IS
may be high. This is suggested also because the standard deviation

of the mean for AH(1) where the amount of reaction is based on nyf(calc)

is lower than that for £H(3) based on njj4-(obs). A check on the

analyses for experiment six may explain the discrepancy. In the meantime, the average value for /_\R(3) is used in the calculation of the

heat of formation of chlorine trifluoride.

Calculations similar to those given for the ClFg-Hg-HaO reaction

were made for the Cl2 -1^-I^0 and Cl2 -HFaq

solutions and the results

are given in Tables 9-11. The notations have been explained for the

ClFg-Hg-HgO experiment. Table 10 shows typical calculations for

AH(1), £H(2), and AH(3). q(corros) is based on the heat of the reaction of chlorine with nickel*

Table 11 gives the values of £H(1), Z^H(2) and ZH(3). The

uncertainty figures are the standard deviation of the mean and do not

represent the overall uncertainty in the heats of reaction. We assume

here also that AH(3) is the most accurate treatment of the data. We

observe that the average values for the heat of formation [HCl^HgO]

and [HCl*HF

aq] differ by 0.22 kcal mol ^

} but become identical when

the standard deviation of the mean is applied to each. The preliminary

value for AHf [HC1«501^ 0] of -39.71 kcal mol ^ can be compared with the

"selected" value of -39.521 kcal mol ^[1],

Preliminary data for the Fs -Eg ~HClaq

reaction are given in Tables 12

arri 13. These results are based on the amount of fluorine reacted. The

notations used are the same as described for the earlier reactions.

In Table 14, the preliminary value for the heat of formation of

chlorine trifluoride is calculated. This value can be compared with

-i

the current selected values of -38. [3] and -38.869 ± 1.0 [5] kcal mol

16
Table 5

The Completeness of the

Cl2

- Hg -* H- 0 and Clg-Hg-HF^ Reactions

Experiment

No.

ms

S

nHCl (°^s )

moles

n^jCobs)

nHd(calc )

Cls-Ife-M

1 9.6607 0.26976 0.9907

2 6 .7661 .19053 .9990

*3 6.6417 .18702 .9990

4 7.6865 .21625 .9982

CI2 "^3 "H^aq

1 2.1408 0.06019 0.9975

2 2.5748 .07250 .9989

3 4.4517 .12526 .9982

4 4.5999 .12793 -

5 2.2925 .06416 .9923

*nCi-(°bs) = 0.18715 mole

^H(obs) = 1.0007

nH+

17
Table 6

The C1F3 -Bp -Hg 0 Reaction

Typical Reaction Quantities

Expt. No. 6

n (calc), moles

rrr 0.22516

n (obs)^ moles

rrr .22349

nClF ( reactec^ t moles .055873

An^ip (corros), moles .00042

"ife

0 ' moles 5.55

84

h^O/HrCI 33

18
Table 7

The C1F3 -Hg-Hg0 Reaction

Typical Heat Measurements

Expt, No.

m

At

s' 8

(corr)

9 C

t(ave), °C

btt, J(°C)' 1

E(calorim), J(°C)

q(obs), J

-1

5.2142

2,48202

.05437

30.69

6.5

21990.4

54581

Corrections to the heat measurements

q (ign)

,

J -33

q(Qs), J -131

q (vap)

y

J -144

q(temp), J 36

q(corros), J -421

^C1F3

9 J

<icif3

> J

-54303

-53882

19
Table 8

The Heat of the G1F3 -I^»H^0 Reaction. 303°K

C1F3 (g)+2Ifc (g)+100Ife0(l) - [HC1-3HF.100%0I(1)

Expt, No. -£H(2)

kJ (mol G 1F3

)

1

*ah(3)

2 963.51 985.06 962.64

3 962.74 987.09 961.74

4 962.57 986.70 961.58

5 964.61 985.30 963.81

6 964.70 981.95 964.42

7 963.65 984.54 962.80

Av.

3 • d • m

963.63

.37

985.11

.75

962.83

.45

20
Table 9

The Cls-l^-HgO and C

1

2 - Hg - HFaq

.

Typical Reaction Quantities

CL^-H^O Clg -Hp -HFaq

Experiment No. 4 1

n^^(calc), mole 0.21625 0.06034

nHci(°bs)> mole 0.21636 0.06019

v» mole « .16665

\0' mole 5.55 5.45

n

HCl ( °bs) ' nHCl

(calc) .00028 .00015

Zkid (corros) .00014 .00008

^o/^ci 25.7 90.3

^O

/

n

HF

- 32.7

n

HCl

#n

HF

- 0.36

21
Table 10

The Gig - Eg 0 and Cls -Hg-HFaq Reactions

Typical Heat Measurements

Clg-Ife-HsO Cl2 -Hg -HFaq

Expt„ No. 4 6

V 8 7.6865 1.5869

At(corr), °C 1.63739 .33382

*c>

° C .04724 .02717

t(ave), °C 30.92 30.33

Ze, J(°C)" 1 6.3 -7.1

E(calorim), J(°C)"^' 21998.9 21985.5

9(obs), J 36020 7339

Corrections to the heat measurements

q (ign) y J -28 -15

q(Q=), J -23 -6

q (vap)

,

J -132 -27

q (temp) , J 40 9

q(corros), J -3 -

qcv 3

"1

-35861 -7297

qcl /n(calc )

q

' C1 /n(obs )

,

q'

cl /n(obs ) }

2

kJ(mol

kJ (mol

kJ (mol

soln)

soln)

^

soln)

^

-166.21

-166.51

-165.83

-165.08

-164.60

-163.72

22
vO as CO O o

CM co CO sO c CM CM 1—4 r—4

CM co oCOOCO

COo O

+1 +1

as

uo

+1 +1

co /*v o co O CM i-4 vO 00 CM

m CM p^ 00 00 d CO vO co t-4 P" O CM CO CM O i—4

t—4

<± o w *-) • • • • * •H uo uo vO vO vO Os U0 <± VO U0 co uo as

4J <j vO vO vO vO vO co vO 'O VO vO vO VO vO co u 1 H 1—4 f—1

T-^ r*4 l—l i-4 i-4 i—4T—4i—4 i-H cd

<D Picr

cdi 3?lcv r-4 o o

04 uoO

vO

UO

CO

r-^ T3d +1 +1 +1 +1

cd

<u o as uo as

© oo VO VO uo CO co O uo CM O

i—4 &

CM i—i vO CM vD i—4 as r-4 as O o CTv O U0 00

33 V-/ H-J • • • • • • cd i 3* X vO r- P- p> as p. uo P'- 00 VO <t VO Ov H <J vO vO vo vO VO co v-x vo vO VO vo VO vO VO CO

0}

1-4 CJ

a> rC

„4J 44Ow

•U

cd s

<v siH §O

!Sa

<DB

•Hu

<1) aKw o

3?o

UOT O CO O VO uo i-4 co• U0 VO Pr—4

vO VO VO vo o

3?om+/*s50 p?

-I"

50

V-/W

1-4 *

CM CO <f

ascoO

+1

CO

SOSO

aso

+i

co

p-as

co i i c d i

*-)><

cdo o

3?OuosA+

/—n50

'w' 3** HjW

50

V-'

r-4* &o CO r—4 <± as uo CO 3?O

00 o p- p» 00

m

uo uo vO uo <r <1- uo vO VO VO vO vo vO • i—4 i—4 i—4 T—l ?—4

r—4

CM CO U0 SO

CO

COO

+1

UOVO

COO

+1

vO <f

<j- uoOv

co O6

'w'><

cdo

23
Table 12

The Fjg-Hg-HGlaq Reaction

Typical Heat Measurements.

Expt. No. 3

ms> § 3.3330

(corr ) , °C 2.55912

°C 0.05977

t(ave), °C 30.51

te, J^c)- 1 -3.4

E(calorim), J(°C)"^ 21980.5

q(obs), J 56251

Corrections to the heat measurements

q (ign) 9 J -51

q(o2 ), J -86

q(vap)

,

J -112

q(temp)^ J 28

if3

, J 56030

n^Ccalc), moles 0.17518

AHp^ } kJ (mol HF soln)

^ -319.84

2b
Table 13

The Heat of the F3 ~I%-KClaq

Reaction. 303. 6°K

|F2 (g) + |Hg (g) + 50Hg 0(1) - [HF + 0.31HC1 + 50Hg0](l)

Expt. No. V

mole

"hCI

mole

"nVv -^R

kJ(mol HF soln)

1 0.11626 0.0549 48 320.50

2 0.17518 0*0549 32 319.84

3 0.13190 0.0549 42 318.84

Average 319.72

25
Table 14

Preliminary Calculation of the

Heat of Formation of Chlorine Trifluoride.

AHr

(303 °K)

kJ

(1) ClFg(g) + 2Hg (g) + XOO^O(l) -* [3HF-HC1>100I^0](1) -962.83

(2) |cxa (g) + §Mg) + [3KF.X00^0](X>- [3HF.*X.X00%0] (i> -165.18

(3) |fs (g) +|%(g) + [HCX-XOOI^O](Xr [3HF.HCX*XQ0R,0] (X) -959.19

(4) (g) +

|f8 (g) - cxf3 (g) i

' -161.54

-38.61

26
References

1. R. C. King and G. T e Armstrong, J, Res. NBS 72A . 113 (1968).

2. E. S. Domalski and G. T. Armstrong, J. Res. NBS 71A , 195-202

(1967).

3. D. D. Wagman, W. H. Evans, I. Ha low, V. B. Parker, S. M.

Bailey, and R. H. Schumm, Selected Values of Chemical Thermodynamic Properties, Part 1. Tables for the First TwentyThree Elements in the Standard Order of Arrangement, NBS

Technical Note 270-1 (U. S. Government Printing Office,

Washington, D. C. 20402, 1965).

4. F. D. Rossini, J. Res. NBS 6 , 1 (1931) R. P. 259; see also

Chapter 4 Experimental Thermochemistry, ed. F. D. Rossini (Interscience Publishers, Inc., New York, N. Y., 1956).

5. JANAF Thermochemical Tables, PB 168370, Dow Chemical Co.,

Midland, Michigan (Clearinghouse for Federal Scientific and

Technical information, Springfield, Va., August 1966).

27
The heat capacity of very fine powders is expected to be higher

than that of large crystals, the relative effect of particle size

becoming larger with decrease in temper at'ure . The values of heat

-8 ° capacity of MgO powder of average cube size of 2 x 10 m (200a)

reported by Giauque and Archibald [7] are considerably higher than

those of large fused MgO crystals reported by Barron, Berg, and

Morrison [2] (130$ at 20 K, 17$ at 50 K, 7$ at 100 K, 3.3$ at 150 K,

2.6$ at 200 K, and 1.3$ at 250 K). Kelley [15] reported heat-capacity

measurements on BeO powder of unspecified crystallite size. The

measurements reported by Aslanian and Weil [1] and by Gmelin [8]

were on samples from the same source prepared by hot sintering under

pressure (sintering temperature unspecified). Aslanian and Weil [1]

reported that the three measurements (between 2 and UK) made on the

sample (as received, annealed at 800 C, and annealed at 1200 C)

were the same within the experimental accuracy.

Commercially available beryllium oxide powder is usually prepared by thermal decomposition of the hydroxide, the hydroxide being

obtained by precipitation from the halide, sulfate, or acetate

solution by increasing the pH. The crystallite size of the powder

is dependent largely upon the decomposition temperature. Duval and

Duval [3] interpreted their thermal gravimetric analysis work to

indicate that the decomposition of Be^H)^ to BeO and H^O starts

around 150 C and complete decomposition occurs only on heating to

951 Co Funston, Kirkpatrick, and Turner [U] reported a flat in the

thermogram of the decomposition process at about 850 C. The crystallite size of the BeO powder obtained by decomposing Be(0H)

2

(precipitated from beryllium basic acetate (Be, 0(0C0CHQ )^) at 850 to ^ ^ 0

-8

1000 C was reported by Funston et al [U] to be around 2 to 5 x 10- m

o (200 to 500 A). Calcination at higher temperatures yield larger

crystallites [U]«

29
The sample investigated by Kelley [15] was assumed to be a very

fine powder, considering the probable method of preparation and the

expected particle size discussed above* For the heat -capacity

measurements presented in this report the BeO sample was sintered at

1700 to l800°C for about 2k hours in order to obtain large crystallites.

The results of the measurements obtained on the sample of average

crystallite size of 3 x 10 m were found to be considerably lower

than those reported by Kelley [l5]. The values were so extremely

different that repeat measurements on a sample of even larger crystallite were considered to be desirable. A BeO sample prepared by arc fusion and of fairly uniform crystallite size of about 6 x 10 m

was subsequently obtained. Since the measurements on the second sample

are being delayed because of pressing work on other substances and

since the measurements on the second sample will probably show relatively small differences, if any, the results of the measurements on

the first sample are being given in this report. (The crystallite

sizes of the two samples are not widely different.)

II. Sample

In order to obtain a BeO sample of large crystallite size, commercially available high-purity BeO powder was pelletized by

F. P. Knudsen of the Inorganic Materials Division of the Bureau into

short cylinders of about 3/8" diameter and 1/8" long. The pellets

were then fired in a gas furnace at about 1700 to l800°C for 2b hours.

Some erosion and, consequently, reduction in the size of the pellets

occurred through vaporization of BeO in presence of water vapor at

the furnace temperatures [10, 13 , 25].

Spectrochemical analysis of the sintered sample by B. F. Scribner

of the Spectrochemical Analysis Section of the Bureau showed the impurities given in Table 1.

30
A petrographic (microscopic) examination of the BeO sample was

made by A. Van VaLkehburg of the Crystallography Section of the Bureau.

The crystallites ware found to have an average length of about

-6

3 x 10 ' m with the smallest ones about 1 x 10 m. The crystals were

clear with some voids*

Since the BeO pellets were slightly too large, they were split

into halves along their axes and introduced into the calorimeter

sample vessel through its l/hu opening [5]. The vessel containing

the sample was alternately pumped to a high vacuum and purged several

h 2 times with dry helium gas and finally sealed with 1.316 x 10 N/m

(98*7 mm Hg) pressure of helium gas. The mass of sample investigated

was 77.35U g.

III. Apparatus and Method

The heat-capacity measurements on the BeO sample were carried

out in an adiabatic calorimeter very similar in principle and design

to that described previously [21]. The sample vessel was suspended

within the adiabatic shield system by means of a nylon string instead

of the filling tube shown in the above reference. Details of the

calorimeter design and its operation will be described in a subsequent

publication.

Briefly, the calorimeter sample vessel, constructed principally

of copper, was a short cylinder with spherical sections for its ends.

A re-entrant well, located at the axis with its opening at the bottom

of the vessel, contained a heater-platinum resistance thermometer

assembly. In order to attain rapid temperature equilibrium, copper

vanes were arranged radially from the central well to the outer wall

of the vessel. A thin coating of pure tin applied to the entire inner

surfaces held the vanes in good thermal contact with the vessel and

provided a chemically inert surface. The space between the vanes was

no greater than 8 mm. A specially designed gold-gasket, screw-cap

closure was attached at the top of the vessel.. The outer surface of

31
the vessel was gold plated and polished. A thin gold-plated copper

shell enclosed the sample vessel to provide a more reproducible

surface temperature for adiabatic control. The shell was in good

thermal contact with the sample vessel around a ring located on the

upper cylindrical, portion of uhe vessel.

The adiabatic shield was constructed entirely of copper. It was

a cylindrical shell with conical ends. Heater wires were wound on

the outer surface. The inner surface was gold plated and polished

to minimize the heat transfer by radiation.

Constantan versus Chromel-P differential thermocouples were

attached to the adiabatic shield and to the outer thin shell of the

sample vessel for temperature control. During the heat-capacity

measurements the- shield temperature was maintained as close as possible to that of the thin shell of the sample vessel by means of

the thermocouples and the shield heaters.

The electrical power to the calorimeter heater was measured by

means of a Wenner potentiometer in conjunction with a saturated

standard cell* volt box* and standard resistors. The standard cell

and the standard resistors were calibrated at the National Bureau of

Standards in terms of the United States standards of emf and ohm. A

const ant -current power supply stable to about 2ppm was used to

furnish electrical power to the calorimeter heater. The duration of

each heating interval was determined by means of a high-precision

interval timer operated on the 60-Hz frequency standard provided by

the National Bureau of Standards. The 60-Hz frequency standard is

based on a 100-kHz quartz oscillator which is stable to 1 part in lO1-

1

over a 2U-hour period. The 100-kHz oscillator is maintained in terms

of the 60-kHz broadcast from WWVB. An electronic counter containing

a 1-MHz quartz oscillator was used simultaneously in the measurement

of the heating interval. The estimated uncertainty, including the

assymetry in the on-off switch operation to the calorimeter heater,

in the determination of the heating interval is not greater than

32
±0.01 sec for any heating period, none of which was less than 2 min

in these experiments.

Temperatures were determined by means of a platinum-resistance

thermometer installed in the re-entrant we3.1 of the calorimeter vessel.

At the time of these measurements the resistance of the thermometer

was measured with a high-precision manually operated Mueller bridge

capable of measurements up to 422*11110 ohms to the nearest 0.00001 ohm.

(At present an automatic Mueller bridge is being used.) The thermometer (laboratory designation; L-l8) was calibrated above 90 K in accordance with the 1948 International Practical Temperature Scale [22]. The

temperatures in kelvin were obtained by adding 273*15 to the temperatures

in degrees Celsius (°0) o Below 90 K, the thermometer was calibrated

on the NBS-1955 provisional scale which is numerically 0.01 K lower

than the former NBS-1939 provisional scale [12].

IV. Results

Two series of heat-capacity measurements were carried out, one

on the calorimeter vessel with the sample (gross) and the other on

the empty vessel (tare). The measured energy increments (AQ) and the

corresponding thermometer resistances (R) before and after heating

[Chapter 2, NBS Report No. 9500, issued 1 January 1967] were analyzed

on the high-speed digital computer to obtain dQ/cLR of the sample (net)

as a function of the thermometer resistance [6]. After adjusting for

the heat capacity of the helium exchange gas and for the small difference in the mass of the vessel for the tare and gross measurements,

the values of heat capacity (dQ,/dT) of the sample were then calculated

at equally spaced integral temperatures from the R versus T calibration

and dR/dT for the thermometer using the relation:

dQ/dT = (dQ/dR) (dR/dT) . (l)

Briefly, the procedure was to obtain the polynomial equation

of the form

N

dQ/dR - E a ((AnR)/R) (2)

n«0 n

33
to represent the experimental data on the empty calorimeter vessel

(tare). The polynomial equation for the empty vessel was then

evaluated to obtain values of AQ (tare) corresponding to the thermometer resistance intervals observed for the gross measurements in order

to obtain the energy increments for sample only, i.e.,

AQ(sample) « AQ(gross) - AQ(tare). (3)

The best polynomial equation giving dQ/dR for sample only was next

obtained and dQ/dT calculated according to eq. (l) above. For the

sample an equation of the form

dQ/dR * E a R

n

(it)

was found to fit the data adequately.

Figure 1 shows the percentage deviation of the experimental data

on the empty vessel from the polynomial equation fitted to the data

by the method of least squares. A fifteenth degree polynomial

equation (eq. (2), n * 0 to n * 15) was found to fit the data from

15 to 370 K well within ±0,0k percent. The slight trend shown in the

figure suggests that a better equation could be obtained, but the

maximum deviations are small enough to be negligible for the present

study. The first and second derivatives of the equation were found

also to have the properties expected of a "heat -capacity curve".

Figures 2 and 3 show the deviation of the sample data (net) from

the final smooth values based upon the polynomial equation (eq. (1;),

n ranging from -1 to +8) fitted to the data in the range V? to 370 K

combined with the extrapolation of the data to 0 K as shown in

Figure h* The values of dQ/dT obtained from the polynomial were

adjusted slightly below i|0 K to be consistent with the extrapolated

values to 0 K. Figure h shows the C/T^ versus T plot of the final

values of heat capacity extrapolated to 0 K. The values of heat capacity on MgO reported by Barron, Berg, and Morrison [2] were used as

a guide in the extrapolation. The observed values of heat capacity

on BeO are shown for comparison with the extrapolation. The Debye

characteristic temperature 0 at 0 K corresponds to 1269 K

(0 K intercept * (2 x 12 iAl/5)(l/0^ ) )

•

3h
Considering the precision of the measurements and the possible

systematic errors, the estimated uncertainty in the smoothed values

of heat capacities is 0.1 percent above 100 K. Below 100 K the net

heat capacity becomes a progressively smaller fraction of the gross

heat capacity with decrease in temperature. At the lowest temperature® of the measurements (l5»6 K) the heat capacity of the sample

constituted only 2.3 percent of the gross, hence the uncertainty in

the values at 15 K may be as high as 5 to 10 percent.

The thermodynamic properties were calculated by tabular numerical. integration using the values of heat capacity obtained from 0 to

370 E with the usual thermodynamic relations

T

% - K

” > (5)

and

T

(C/T)dT ,

°T ” ^

K

“ TS

T

’

(6 )

The values are given in Table 2.

The values of heat capacity reported by previous investigators

are compared with the present measurements in Figure 5. The values

reported by Kelley [15] and those by Gmelin [8] are for most of the

temperature range of the measurements unusually higher than the

values found in the present study. The deviations of the values

reported by Kelley [15] were found to increase with decrease in temperature. At 55 K the deviation is +U5 percent and from about 200 to

290 K the deviations do not exceed 1 percent. The values reported by

Gmelin [8] are on the average about 20 percent higher between 15 and

75 K. The extrapolated values (below 15 K) obtained for this report

are higher than the experimental values reported by Gmelin [8]. The

Debye characteristic temperature reported by Gmelin is ll|00 ±10 K as

3?
compared to 1269 K taken for this study. The values reported by

Gunther [11] are about 30 percent lower.

The enthalpy difference between 273*15 and 373*15 K obtained

from the heat-capacity measurements (Table 2) was compared with the

experimental relative enthalpy values reported by Victor and

Douglas [23]* Victor and Douglas reported measurements on two

-5

samples. Sample 1 consisting of crystallites of 2.5 x 10 m on an

edge was similar to the sample used in the present study. Sample 2

-5 -6

was needle-like, 1 x 10 m in length and 1 x 10 m in cross section.

The comparison is summarized in Table 3* The results of the present

study are between the values reported by Victor and Douglas for the

two samples. The agreement is within a few tenths of a percent of

either sample.

The unusually large deviation in the values of heat capacity at

the lower temperatures with fairly close agreement at the higher

temperatures can be ascribed to the particle size effects [2,16,17]*

The increasing positive deviation with decrease in temperature of

the values reported by Kelley [15] suggests that his sample was

probably very finely divided. The heat treatment of the samples

investigated by Gmelin [8] suggests that his samples and the sample

used in the present study were similar. The wide deviations in the

results shown in Figure 5 are probably due to experimental differences.

Finely divided samples are subject to contamination by adsorbed impurities. Unless special precautions are taken to remove the adsorbed

impurities, significant variations in the experimental heat capacities

would be expected from the impurities present, any change in the

surface properties, or compound formation at the surface.

The new values of heat capacity are now being combined with other

high temperature relative enthalpy data up to 2500 K. A combined

table of thermodynamic properties will be presented in the forth-coming

semi-annual report. The measurements on the second sample of BeO are

being considered for the near future.

36
Table 1

Spectrochemical Analysis of the

Sintered Beryllium Oxide (BeO) Pellet

Element

Parts per

Million

PJj ho

Ca 200

Fe 10

Mg <L5

Mn <10

Si 25

The limit of detection for Ti was 20 ppm and for

P was 200 ppm

37
TABLE 2

THERMODYNAMIC FUNCTIONS FOR BERYLLIUM OXIDE (BE 0 ) SOLID PHASE

MOL - 0 .0250116 KG

(t - 273.15 + •c

CAL * 4.1840 J

T “

(

Gj-H^ ) /T /T ,S ?-S

o'

It -CALit ‘MOL _CAL_

lt* MOL

itL

MOL

.00 .000 .000 .000 • 000 .000 • 000

3.00 .000 .000 .000 • 000 .000 • 000

10.00 .000 .000 .000 .001 .000 • 000

IS. 00 • 000 .000 .001 .006 .002 • 00 2 20.00 .000 .001 .001 • 018 .004 • 006

25.00 .001 .002 .002 .045 .007 .015

30.00 .001 .003 • 004 .094 .013 .031

35.00 .002 .005 .007 .176 .020 • 058

AO . 00 .002 .008 .010 .304 .031 • 099

45.00 .004 .011 .015 .495 .046 • 160

50.00 .005 .015 .020 .770 • 065 .247

55.00 .007 .021 .028 1.153 .089 • 366

60.00 .009 .028 .037 1.674 .120 • 526

65.00 .011 • 036 *048 2.367 .158 • 736

70 . CO .014 .047 .061 3.264 .202 1.007

73.00 .018 .0 59 .077 4.402 .254 1*350

80.00 .022 .073 .095 5.820 .314 1.778

85.00 .027 .089 .116 7.560 .383 2.305

90.00 .033 .107 .140 9.661 .488 2.944

95.00 .039 .128 .167 12.155 .540 3.710

100.00 .046 .151 .197 15.077 .630 4.619

105.00 .054 .176 .230 18.463 .726 5.685

110.00 .063 • 203 .266 22.349 .829 6.924

115.00 .073 .233 .305 26.769 .939 8.351

120.00 .083 .265 .348 31.753 1.055 9.983

123.00 .095 .299 .393 37.331 1.177 11*834

130.00 .107 .335 .442 43.532 1.304 13.921

135.00 .120 .373 .494 50.380 1.436 16.259

140.00 .135 .414 . 54-8 57.899 1.572 18.862

145.00 .150 • 456 .606 66.108 1.712 21.747

150.00 • 166 .500 . 666 75.027 1.856 24.926

155.00 .163 .546 .730 84-. 671 2.002 28.415

160.00 .201 .594 .795 95.053 2.151 32.227

165.00 .220 .644 .864 106.19 2.302 36.374

170.00 • 240 .695 .935 118.08 2.455 40.871

175.00 .261 .747 1.008 130.73 2.609 45.728

180.00 .283 .801 1.084 144.16 2.763 50.958

185.00 .306 .856 1.162 158.37 2.918 56.572

190.00 .329 .912 1.242 173.35 3.074 62.580

195.00 .354 .970 1.324 189.10 3.229 68.992

200.00 .379 1.028 1.407 205.63 3.384 75.819

205.00 .405 1.088 1.493 222.94 3.538 83.068

210.00 .432 1.148 1.580 241.01 3.691 90.748

215.00 .460 1.209 1.668 259.84 3.843 98.868

220.00 .488 1.270 1.759 279.44 3.994 107.44

225.00 .518 1.332 1.850 299.78 4.143 116.46

230.00 • 548 1.395 1.943 320.86 4.291 125.94

235.00 .578 1.458 2.036 342*66 4.437 135.88

240.00 .610 1.522 2.131 365.23 4.581 146.30

245.00 • 642 1.586 2.227 338.50 4.724 157.20

250.00 .674 1.650 2.324 412.47 4.865 168.58

255.00 .708 1.714 2.422 437.14 9.003 180*44

260.00 .742 1 . T79 2.520 462.50 5.140 192.80

265.00 .776 1.844 2.620 488.54 5.274 205.65

270.00 .811 1.908 2.719 515.24 5.407 218.99

273.15 .833 1.949 2.783 532.40 5.489 227.66

275.00 .847 1.973 2.820 542.60 5.537 232.84

280.00 .883 2.038 2.921 570.61 5.665 247.19

285.00 .919 2.103 3.022 599.25 3.791 262.05

290.00 .957 2.167 3.124 628.51 5.914 277.42

295.00 .994 2.232 3.226 658.38 6.035 293.29

298.15 1.018 2.272 3.291 677.51 6.110 303.55

300.00 1.032 2.296 3.328 688.86 6.154 309.68

305.00 1.071 2.360 3.431 719.92 6.270 326.57

310.00 1.110 2.424 3.534 751.55 6.384 343.99

315.00 1.149 2.488 3.637 783.75 6.495 361.91

320.00 1.189 2.552 3.740 816.50 6.605 380.36

325.00 1.229 2.615 3.843 849.79 6.711 399.32

330.00 1.269 2.678 3.947 883.61 6.816 418.79

335.00 1.310 2.740 4.050 917.95 6.918 438.78

340.00 1.351 2.802 4.153 952.79 7.018 459.29

345.00 1.392 2.864 4.256 986.13 7.116 480.32

350.00 1.434 2.926 4.359 1024.0 7.213 501.86

355.00 1.476 2.987 4.462 1060.3 7.308 523.91

360.00 1.518 3.047 4.565 1097.0 7.401 546.48

365.00 1.560 3.108 4.668 1134.3 7.494 569.56

370.00 1.603 3.167 4.771 1172.0 7.586 593.16

373.15 1.630 3.205 4.835 1193.9 7.645 608.36

M

C AND SC APPLY TO The REFERENCE STATE OF ThE SOLIS AT ZERO DEK K»

0 0 38
Table 3

Comparison of Enthalpy Values of Table 2 with the

Experimental Relative Enthalpy Data of Victor and Douglas

1 cal * U .18U0 J

Victor and Douglas [23] This Work

Temperature

Intervals Sample 1 Sample 2

K J/mol J/mol J/mol

273-l5"323°l5 1270,3 1278.6

1271.5 1278.2

1270.9

(average)

1278. ii (average

)

1276.1

273.15-373.15 2765.2 278U.5

2776.5 2785-7

2789.1

2770.9

(average)

2786.

(average

)

2775-9

39
References

[1] J. Aslanian and L. Weil, Contribution of Specific Heat Measurements below U°K to the Observation of Helium Diffusion after

Annealing in Irradiated Beryllium Oxide, Cryogenics 3, 36-39

(1963).

[2] T. H. K. Barron, W. T. Berg, and J. A. Morrison, On the heat

capacity of crystalline magnesium oxide, Proc. Roy. Soc . (London)

250A, 70-83 (1959).

[3] T. Duval and C. Duval, Sur la Thermogravimetrie des Precipites

Analytiques. VI. Dosage du Glucinium (Beryllium), Anal. Chim.

Acta. 2, 53-56 (19U8).

[JU] E. S. Funston, W. J. Kirkpatrick, and P. P. Turner, Preparation

of High Purity BeO Powder, J. Nuclear Mat. 11, 310-319 (1961;).

[5] G. T. Furukawa, M. L. Reilly, and J. H. Piccirelli, Calorimetric

Properties of Some Alkali Pentaborate Hydrates from 15 to 370°K,

J. Res. NBS 68a (Phys. and Chem. ) No. k, 381-389 (1961;).

[6] G. T. Furukawa and M. L. Reilly, Application of Precise HeatCapacity Data to the Analysis of the Terrperature Intex-vals of the

NBS (1955) and the International Practical Temperature Scales

in the Region of 90°K, J. Res. NBS (Phys. and Chem.) 69A, 5-12

(1965).

[7] W. F. Giauque and R. C. Archibald, The Entropy of Water from the

Third Law of Thermodynamics. The Dissociation Pressure and

Calorimetric Heat of the Reaction Mg(0H)2 88 MgO + H2O. The Heat

Capacities of Mg(0H)2 and MgO from 20 to 300°K, J. Am. Chem.

Soc. 59, 561-569 (1937).

[8] E. Gmelin, Mesures de la chaleur specifique de 1

! oxyde de

beryllium et de l*oxyde de calcium a basses temperatures,

Compt. rend. 262C

,

1U52-1U55 (1966).

[9] M. A. Greenbaum, J. Weiher, and M. Farber, The Thermodynamic

and Physical Properties of Beryllium Compounds. VIII. Heat of

Fusion and High-Temperature Heat Capacity of Beryllium Oxide,

J. Phys. Chem. 69, 1*035-1*037 (1965).

[10]

L. I. Grossweiner and R. L. Seifert, The Reaction of Beryllium

Oxide with Water Vapor, J. Am. Chem. Soc. 7U, 2701-2701; (1952).

P. Gunther, Uhter suehungen uber die spezifische Warme bei tiefen

Temperaturen, Ann. Physik 5l, 828-846 (1916).

UO

[ 11 ]
[12] H. J. Hoge and F. G. Brickwedde, Establishment of a Temperature

Scale for the Calibration of Thermometers between 15° and 83°K,

J. Res* NBS 22, 351-373 (1939) RP1188.

[13] C. A* Hutchison, Jr. and J. G. Malm, The Volatilization of

Beryllium Oxide in the Presence of Water, J. Am. Chem. Soc. 71,

1333-1339 (191+9 ).

[ill] V. V. Kandyba, P. B. Kantor, R. M. Krasovitskaya, and

E. N. Fomichev, Determination of Enthalpy and Heat Capacity of

Beryllium Oxide in the Temperature Range 12 00-282 0°K, Doklady.

Akad. Nauk. S.S.S.R. 131 , 566-567 (I960).

[15 ] K. K. Kelley, The Specific Heats at Low Temperatures of Beryllium

Oxide and Beryllium Orthosilicate (Phenacite), J. Am. Chem.

Soc. 61, 1217-1218 (1939).

[16] W. H. Lien, Heat-Capacity Studies at Liquid Helium Temperatures

and Below. Part Is The Alkali Metals, Part II: Small Particles

of Magnesium Oxide, U. S. At. Energy Comm. UCRL-9880, 72pp. (1962).

[17] W. H. Lien and N. E. Phillips, Heat Capacity of Small Particles

of MgO between 1.5° and 5°K, J. Chem. Phys. 29, I5l5-l5l6 (1958).

[18] A. Magnus and H. Danz, Die spezifische Wanme von Wolfram, Bor,

Borstickstoff und Berylliumoxyd , Ann. Physik (If.) 8l, 1+07 -U2I4- (1926).

[19] L. F. Nilson and 0. Pettersson, Ueber Molekularwarme und

Molekularvolumina der seltenen Erden und deren Sulfate, Ber.

chem. Gesell. 13, 1559-1565 (1880).

[20] E. N. Rodigina and K. Z. Gomel f skii. Enthalpy of Beryllium and

Lithium Oxides at High Temperatures, Zhur. Fiz. Khim. 35,

I828 -I83I (1961).

[21] R. B. Scott, C. H. Meyers, R. D. Rands, Jr., F. G. Brickwedde,

and N. Bekkedahl, Thermodynamic Properties of 1,3-Butadiene in

the Solid, Liquid, and Vapor States, J. Res. Natl. Bur. Std. 35,

39-85 (19U5).

[22] H. F. Stimson, International Practical Temperature Scale of 1958.

Text Revision of I960. J. Res. NBS (Phys. and Chem.) 65A, No. 3,

139-155 (1961).

[23] A. C. Victor and T. B. Douglas, Thermodynamic Properties of

Magnesium Oxide and Beryllium Oxide from 298 to 1200°K, J. Res.

NBS (Phys. and Chem.) 67A, No. 5, 325-32 9 (1963).

51
[2U] B. E. Walker, Jr., C. T. Ewing, and R. R. Miller, Specific Heat

of Some High Temperature Materials, J. Chem. Eng. Data 7,

595-597 (1962 ).

[25] W. A. Young, The Reactions of Water Vapor with BeryUia-Alumina

Compounds, J. Phys. Chem. ok , 1003-1006 (i960).

k2

025%

of

Gross

Observations

200

300

Temperature,

K

Fig.

2.

Percentage

Deviation

of

the

Beryllium

Oxide

Sample

Heat

Capacities.
Percentage

Deviation

(Obs.-Calc.

Temperature, K

% Fig* 3. Percentage Deviation of the Beryllium Oxide Sample Heat Capacities.

U5
•X.frf

‘

cl/

0

r n

0 10 20 30 40 50

Temperature, K

Fig# 4. Observed Values of C/T^ vs# T# The Curve Shows the Extrapolation

of the Heat Capacity to 0 K.

k6
GUnther,

1916

o

o

<r

o

o<*">

o

o

CM

OO

o

4)3

U

4>&

Cl H

(S0N“P»H®7TRnd) UO-pejA^Q

U7

Fig.

5,

A

Comparison

of

Results

Published

by

Other

Investigators

with

Those

Obtained

In

this

Research.
Chapter 3

DYNAMIC MEASUREMENT OF HEAT CAPACITY, ELECTRICAL RESISTIVITY AND

HEMISPHERICAL TOTAL EMITTANCE OF MOLYBDENUM IN THE RANGE 1800 - 2800 K

A. Cezairliyan, M.S. Morse, H.A. Berman,

G.M. Foley*, and C.W. Beckett

ABSTRACT

A system for the simultaneous dynamic measurement of heat

capacity, electrical resistivity, and hemispherical total

emittance of electrical conductors at high temperatures (above

1800 K) with millisecond resolution is described. The specimen

is heated from room temperature to its melting point by a single

heavy current pulse of subsecond duration. Temperature of the

specimen is measured with a high-speed photoelectric pyrometer

of 0.4 ms time resolution. Dynamic recording of variables:

current, voltage, and temperature, required for the determination

of the above properties, is achieved by a high-speed digital data

acquisition system. Preliminary results on molybdenum in the

temperature range 1800 - 2800 K are presented.

* Leeds and Northrup Company, North Wales, Pennsylvania, also Guest

Worker at NBS.
I. Introduction

In view of the growing interest and urgency in understanding

the behavior of matter at temperatures above the limit of accurate

steady-state experiments, it has become necessary to develop

dynamic methods for the measurement of properties of substances.

They show great promise at high temperatures since the duration of

a dynamic experiment may be so short that the role of various

phenomena, such as heat transfer, chemical reactions, evaporation,

diffusion, etc. which set the upper limit in steady-state experiments,

becomes negligible. In recent years, considerable progress has

been made in high-speed thermodynamic measurement methods and

related instrumentation techniques. A general review of these

methods is in preparation [5].

Over the past fifty years several investigators [3, 4, 6, 9,

11-16, 19-22] have developed dynamic techniques for the measurement

of specific heat of electrical conductors. They differ considerably

from each other depending on the pulse power source and the method

of measurement of specific variables. In general, either heavy

batteries or capacitors were used as the pulse power source. In all

cases, power imparted to the specimen was obtained from pulse current

and voltage measurements. The temperature of the heating specimen

was measured either by thermocouples or was determined from dynamic

electrical resistivity measurements. The first method has several

limitations and cannot be used for very high speed work. The second

h9
one requires a separate steady-state determination of the electrical

resistivity of the specimen as a function of temperature. In almost

all of the recent investigations oscilloscopic techniques were employed

for the dynamic recording of variables.

As a step toward establishing accurate high-speed thermodynamic

measurement methods, investigations have been and continue to be

undertaken in the High-Speed Thermodynamics Laboratory at the National

Bureau of Standards. The first phase of this program is concentrated

on the development of a dynamic technique for the accurate measurement

of heat capacity of solid electrical conductors at high temperatures.

The preliminary version of a high-speed (millisecond resolution)

method for the measurement of heat capacity has been described [6].

The present study is an extension of this earlier work with several

major changes in the physical system, measurement techniques, and

calculation methods. They are summarized in the following paragraph.

Instead of the continuous detection of the radiation from the

specimen by means of a photomultiplier tube, a millisecond resolution

photoelectric pyrometry technique was employed for the dynamic

temperature measurements. This eliminates most of the uncertainties

that result from the instability of the radiation detector. A highspeed, multichannel, digital data acquisition system has replaced the

oscilloscopes, improving the recording accuracy by approximately two

orders of magnitude. Also, several changes were made in the test cell.
specimen, and voltage probes. Another major improvement in the

results is due to a change in the formulation of the calculations.

Instead of assuming a constant value for the emittance, obtained

from the literature, in the present work the hemispherical total

emittance of the specimen was measured under dynamic conditions

and this value was used in the calculations for the thermal radiation

r correction.

In order to check the operation of the system, dynamic

experiments of millisecond resolution were conducted and heat

capacity, electrical resistivity, and hemispherical total emittance

of molybdenum were measured in the temperature range 1800 - 2800 K.

Results reported in this chapter are of preliminary nature in the

sense that they are based on only a small portion of the data taken,

and that simplified relations are used in computing the pertinent

properties

II. Description of the Method

The dynamic method employed in this study for the measurement of

specified properties is based upon rapid joulean heating of the

specimen by a single pulse of direct current and measuring the

pertinent variables with millisecond resolution. Heat capacity and

electrical resistivity are calculated from data obtained during the

heating period. In order to apply a correction for the radiation loss,

hemispherical total emittance is calculated from the data of the

initial cooling period. In the following paragraphs the formulation

51
of the relationships between various variables is presented.

a. Heating Period

The energy balance for the specimen during the heating period

can be expressed as Energy Imparted * Energy Stored + Energy Losses

In high temperature dynamic experiments of millisecond resolution

the major source of power loss is that due to thermal radiation.

Using the proper quantities, the above relation for unit time becomes

ei = c n(dT/dt), + eoA (T 4 -T 4

) (1)

p h s e Where

e = potential difference across the effective specimen (V)

i = current through the specimen (A)

Cp= heat capacity (J gm-at-1 K

_1

)

n = weight of the effective specimen (gm-at)

e = hemispherical total emittance

a = Stephan-Boltzmann constant (5.6697 x

10“ 8 W m

-2 K

4

) A = effective surface area (m2

) s T = temperature (K)

T

£= room temperature (K)

(dT/dt)^= heating rate (K s” 1 ) Solving Eq. (1) for c one obtains

p

ei - goA (T 4-T 4

) s e (2)

c =

P n(dT/dt)

h

52
b. Cooling Period

The energy balance for the specimen during the initial cooling

period can be written as Energy Loss = Energy Radiated

which for unit time can be expressed as

“C n (dT/dt ) = £<jA (T 4-T4

) (3)

p c s e where

(dT/dt) = cooling rate (K s *) c Solving Eq. (3) for c^ one obtains

eaA (T 4-T 4

) _ s e P -n(dT/dt)

c

c. Relations for Properties

Combination of Eqs. (2) and (4) yields

ei = eaA (T 4-T4

) - eaA (T4-T4

) s e s e

Defining,

(dT/dt),

M (6)

(dT/dt)

c and substituting Eq. (6) in Eq. (5) and solving for e one obtains

(dT/dt) h

(dT/dt)

c

ei

(7)

aA (T 4-T 4 )(l + M)

s e

In this study Eq. (7) is used to calculate hemispherical total

emittance of the specimen which, in turn, is substituted in Eq. (2) to

obtain heat capacity.

53
Electrical resistivity is calculated with the aid of the

equation

RA

p = T

-5- (8)

where,

p = electrical resistivity (ft m)

R = resistance of effective specimen (ft)

A = cross-sectional area (m2

) c L = effective length (m)

III. Description of the System

The system used in this study consists of a principal electrical

circuit and auxiliary measuring circuits. The principal circuit

includes the specimen in series with a battery bank, a variable

resistance, a shunt, and a switch. The measuring circuits include

detectors and other related equipment and circuitry necessary for

the dynamic measurement and recording of the pertinent quantities.

A functional diagram of the complete system is presented in Fig. (1)

.

a. Specimen and Test Cell

The molybdenum specimen used in the experiments is a tube of

the following nominal dimensions: length = 4 in. (101.6 mm), outside

diameter = 0.25 in. (6.35 mm), thickness = 0.02 in. (0.51 mm). A

small rectangular hole (1.09 mm long, 0.56 mm wide) was fabricated in

the wall at the middle of the specimen to approximate blackbody conditions. Calculations indicate that the quality of blackbody, based

5U
oE ^

!5m

CD

x

<

SI

55

Fig.

1.

Functional

Diagram

of

Millisecond

Thermodynamic

Measurements

System.
on geometrical considerations, thus achieved is 99.5 percent.

Potential measurements were made using molybdenum knife edges each

at a distance of 12.5 mm from the end clamps. This allows the

"effective" portion of the specimen to be free from sharp temperature gradients. It is calculated that for the longest pulse (highest

temperature) used in the experiments temperature non-uniformity

between the midpoint of the specimen and the plane of the voltage

probe due to transient axial thermal conduction is less than 0.1

percent. The specimen is free to expand in the downward direction.

The specimen clamps and the walls of the test cell are water cooled.

Experiments can be conducted either with the specimen in vacuum or

in inert gas.

b . Rest of Main Circuit

The power supply for the pulse heating of the specimen is a

28 V heavy-duty battery bank. A series connected, water-cooled,

variable resistance enables one to adjust the main current and

thus to control the heating rate. The fast-acting switch is

operated by a series of time-delay units which control the pulse

length in addition to providing timing pulses to other electronic

measuring and recording instruments. A standard resistor (0.001 ft) placed in the main circuit enables one to measure the heavy pulse

current flowing through the specimen.

c. High-Speed Pyrometer

The temperature of the rapidly heating specimen is measured by

means of a high-speed photo,eXectric pyrometer, which peTmits 1200

56
evaluations of the specimen temperature per second. The pyrometer

passes a precisely timed sample of radiation from the specimen

through an interference filter (wavelength 650 nm, bandwidth 10 nm)

to an electron multiplier photocell. The anode current of the

photocell during the exposure of 208 ps is integrated and the

resulting integrator voltage is recorded. Then, the integrator is

reset to permit it to integrate the anode current due to a similar

sample of radiation from a calibrated, gas-filled tungsten filament

lamp, suitably attenuated by an optical attenuator. Thus, the

pyrometer collects the results of an interlaced sequence of exposures

to specimen and reference source. Successive exposures to the

reference lamp are taken through a sequence of three different

optical attenuators mounted on a rotating disc, resulting in a staircase of reference exposures with approximately 50 percent attenuation

for each step. This scheme is used for temperature measurements

up to 2500 K, the limit of reliable operation of gas-filled lamps.

For the measurement of higher temperatures, calibrated optical

attenuators are placed in the path of the radiation from the specimen,

d. High-Speed Digital Data Acquisition System

The signals at the output of detectors corresponding to the

voltage, current, and temperature are in analog form. Normally,

in dynamic experiments such signals are measured by oscilloscopic

techniques. However, the expected recording accuracy of such methods

cannot be better than one percent. In order to improve the overall

accuracy, a high-speed digital data acquisition system has been

57
designed and constructed to meet the special requirements of the

experiments. The system consists of a multiplexer, analog- todigital converter, a core memory together with control and interfacing equipment. Oscilloscopes are used to monitor the general

pattern of the experimental results, and to detect any anomalies.

All signals are brought to the multiplexer through isolation

amplifiers in order to avoid the inaccuracies arising from common

ground points. The multiplexed signals (aperture time 50 ns) go to

the analog-to-digital converter which has a full-scale reading of

±10 V, and a full-scale resolution of one part in 8192. Digital

output from the converter consists of 13 binary bits plus a sign

bit. This output is stored in a core memory having a capacity of

2048 words of sixteen bits each.

All the above takes place during a dynamic experiment of subsecond duration. After the experiment is over, information stored in

the core memory, which is in parallel binary coded form, is converted

to serial binary coded decimal form and retrieved in the form of

numeric printing and punched paper tape. Since the laboratory has

access to a remote-control, time-sharing computer, it is possible

to unload the memory directly to the computer. This allows one to

process the data immediately after an experiment, bypassing the

intermediate stage of punching paper tape. A functional diagram of

the high-speed data acquisition system is presented in Fig. (2).

58
MULTIVERTER

3h I

<=> + , z£L o <Z *”

z o,n

W in

g <£

? £EZ

Q- O “ 22CL

CM

00

•H

Pm

59

Functional

Diagram

of

High-Speed

Digital

Data

Acquisition

System.
IV. Experimental Results

The molybdenum specimen (99.

9

+

percent pure, outer surface

polished) was pulse heated in vacuum and data were taken during

heating, as well as cooling periods. Pulse length varied from 285 ms

to 380 ms depending on the temperature level. The entire temperature range (1800 - 2800 K) was covered in three steps. Hemispherical

total emittance was calculated from Eq» (7), and a linear function

for the entire range was obtained by least mean square approximation

of the individual results which yields a standard deviation of

2 percent. Heat capacity was calculated from Eq. (2) after substituting the function for emittance. A quadratic fit over the entire

temperature range gave a standard deviation of 0.3 percent. Electrical

resistivity was calculated from Eq. (8). A linear fit over the entire

range gave a standard deviation of 0.2 percent. Dimensions, in

electrical resistivity and hemispherical total emittance calculations,

were based on their room temperature values . Preliminary results on

heat capacity, electrical resistivity and hemispherical total emittance

are presented in graphical form in Figs. (3), (4), and (5), respectively. Pertinent preliminary equations for the above properties in

the range 1800 to 2800 K are given below.

c = 34.58 - 1.096 x 10~ 2 T + 5.696 x 10" 6 T

2 (9)

P

p = -9.798 + 3.146 x 10~ 2 T (10)

e = 5.209 x 10- 2 + 1.139 x 10“ 4 T (11)

60
oo

00

C\J oo

CO

OJoo

<d"

OJoo

OJ

OJooo

OJoo

00oo

co

h-

.IV IAI9- D d 0

61 ii! 0) M

4-1O

-l-J •Ha

CtJ a,

cd u

4-1 cd

QJ PC II

00 •H

ptl IIifI
{WiO-jyrl) d

62

Fig.

4.

Electrical

Resistivity

of

Molybdenum

as

a

Function

of

Temperature.
HEMISPHERICAL

TOTAL

EMITTANCE

OF

MOLYBDENUM

o

odd ^

ro c\J

w

(-

63

Fig.

5.

Hemispherical

Total

Emittance

of

Molybdenum

as

a

Function

of

Temperature.
In temperature calculations , the scattered light effect in

the high-speed pyrometer, as well as the departure from blackbody

conditions were taken into account. The scattered light correction

factor was 0.953 and the computed blackbody quality was 0.995.

V. Discussion

The results based on a limited number of experiments do not

indicate any sharp increase of heat capacity at high temperatures

(T<0.96T

m

» where T^ is the melting point). Comparison of the results

of this work with those in the literature shows that present values

are, in general, higher than those obtained by most "drop" methods,

with the exception of Kirillin et al. [8], and lower than those

of the two "pulse" methods of Taylor and Finch [19] and Rasor and

McClelland [17].

Electrical resistivity agrees very closely with Worthing’s [23]

results and it is approximately two percent lower than the values

given by Taylor and Finch [19].

In the literature, there is considerable scatter in the values

of hemispherical total emittance. This can be expected since

emittance is strongly dependent on surface conditions. The results

of this work fall, in general, within the limits of the available

data in the literature.

A preliminary list of estimated errors is given in Table 1.

Studies so far indicate that temperature measurements have an estimated

6k
Table 1

Estimated Errors*

1. In Temperature Measurements

Pyrometer reproducibility

Scattered ligh correction

Light source alignment

Radiation standard lamp

Blackbody quality (geometrical)

Specimen temperature non-uniformity

Magnetic fields

Estimated error in K

at 1800 K

1

1

1

1

1

2

<1

at 2500 K

2

2

2

2.5

2

3

<1

Estimated total error in temperature 3 6

2. In Electrical Measurements

(for single determination with ms resolution)

Estimated error in percent

4.

Skin effect <0.01

Inductive effects <0.01

Thermoelectric effects <0.01

Voltage measurement <0.05

Current measurement <0.05

Power measurement <0.07

Resistance measurement <0.07

In Interpretation of Results Estimated error in percent

Effect of specimen evaporation <0.01 (at 2800 K)

Effect of thermionic <0.02 (at 2800 K)

Time synchronization <0.01

Length measurement 0.02

Weight measurement 0.01

Effective specimen weight 0.1

Heating rate 0.3 (at 1800 K)

0.6 (at 2500 K)

Estimated Total Error in Properties at 1800 K at 2500 K

percent

Heat capacity 1 1.5

Electrical resistivity 0.6 0.6

Hemispherical total emittance 2 3

* Estimates of both random and systematic errors are given as being

equivalent to "one standard deviation".

65
error of 3 K at 1800 K, and 6 K at 2500 K. Errors in the measurement

of electrical quantities give an estimated error of 0.07 percent

in power and resistance. Combination of various errors gives an

approximate value of the total error in each of the properties

measured: heat capacity 1 percent at 1800 K, 1.5 percent at

2500 K, electrical resistivity 0.6 percent at both levels, hemispherical total emittance 2 percent at 1800 K and 3 percent at 2500 K.

It should be emphasized that the results reported in the

chapter are preliminary. The final results will be presented when

the processing of the entire data on molybdenum is completed.

Acknowledgment

The authors would like to extend their appreciation to

Messrs. J. Queiser, A.N. Graef, and M.E. Wilke for their expert

assistance in constructing the test cell, auxiliary mechanical

components, and machining of the specimen.

66
References

1 .

2 .

3.

4.

5.

6 .

7.

8 .

9.

10 .

11 .

12 .

13.

14.

15.

16.

17.

Abbott, G.L., N.J. Alvares, and W.J. Parker, WADD-TR-61-94 , II (1962).

Askwyth, W.H. , R.J. Yahes, R.D. House, and G. Mikk, NASA-CR-56496 (1964).

Avramescu, A., Z. Tech. Physik, 21), p. 213, (1939).

Baxter, H.W. , Nature, 153 , p. 316, (1944).

Beckett, C.W. , and A. Cezairliyan, "High-Speed Thermodynamic

Measurements and Related Techniques," in J.P. McCullough, Ed.,

EXPERIMENTAL THERMODYNAMICS, Vol. I, CALORIMETRY OF NON-REACTING SYSTEMS,

Butterworths , Washington, to be published.

Cezairliyan, A. , "A High-Speed (Millisecond) Method for the Simultaneous

Measurement of Enthalpy, Specific Heat, and Resistivity of Electrical

Conductors at High Temperatures, in ADVANCES IN THERMOPHYSICAL PROPERTIES

AT EXTREME TEMPERATURES AND PRESSURES, ASME, New York, 1965.

Kirillin, V.A., A.E. Sheindlin, and V.Y. Chekhovskoi, Int. J. Heat

Mass Transfer, _5, p. 1, (1962).

Kirillin, V.A. , A.E. Sheindlin, V.Y. Chekhovskoi, and V.A. Petrov.

"Enthalpy and Heat Capacity of Molybdenum at Extremely High Temperatures",

in J.R. Moszynski, ed. , PROC. OF FOURTH SYMPOSIUM ON THERMOPHYSICAL

PROPERTIES, ASME, New York, 1968, p. 54.

Kurrelmeyer, B. , W.H. Mais , and E.H. Green, Rev. Sci. Instr., 1_4, p. 349.

(1943).

Lowenthal, G.C.,

Nathan, A.M. , J.

Pallister, P.R.,

Pasternak, R.A.

Sci. Instr. , 33

Aust. J. Phys., L6, p. 47, (1963).

Appl. Phys., 2_2, p. 234, (1951).

J. Iron Steel Inst., 161 , p. 87, (1949).

E.C. Fraser, B.B. Hansen, and H.U.D. Wiesendanger , Rev.

p. 1320, (1962).

Pasternak, R.A. , H.U.D. Wiesendanger, and B.B. Hansen, J. Appl. Phys.,

J34, p. 3416, (1963).

Pochapsky

Pochapsky

Rasor, N.S

(1960).

T.E., Acta Met., _1, p. 747, (1953).

T.E. , Rev. Sci. Instr., 25_ y p. 238, (1954).

, and J.D. McClelland, J. Phys. Chem. Solids, 15, P- 17,

67
18. Rudkin, R.L., W.J. Parker, and R.J. Jenkins, "Measurement of Thermal

Properties of Metals at Elevated Temperatures", in C.M. Herzfeld, ed.,

TEMPERATURE, ITS MEASUREMENT AND CONTROL IN SCIENCE AND INDUSTRY,

Vol. Ill, Reinhold, New York, 1962, Part 2, p. 523.

19. Taylor, R.E., and R.A. Finch, J. Less-Common Metals, 6_, p. 283, (1964).

20. Wallace, D.C., Phys. Rev., 120 , p. 84, (1960).

21. Wallace, D.C., P.H. Sidles, and G.C. Danielson, J. Appl. Phys., 31 , p. 168, (1960).

22. Worthing, A.G., Phys. Rev., 1^, p. 199, (1918).

23. Worthing, A.G., Phys. Rev., 2J3, p. 190, (1926).

68

Chapter b

MASS SPECTROMETRIC STUDY OF THE BERYLLIUM -ALUMINA REACTION

J. Efimenko

Introduction

The reduction reaction of alumina with beryllium was performed

as an adjunct to the beryllia -alumina system which has been investigated

in a metallic environment. Beryllium was selected as the reducer since

it has a lower vapor pressure than aluminum. It was of interest to

observe the predominant vapor species under such reducing conditions

and to obtain data on the vapor reactions occurring in this system.

Experimental

For this study, beryllium powder, less than 200 mesh, was tried

and metal chips were used. Beryllium powder was mixed with carbon-free

alumina and placed into a tungsten cup inside a tungsten effusion cell.

In the second case, a chip of beryllium metal was placed on the bottom

of the cup and covered with alumina. The mass spectrometer and geometry

were those used for the alumina -beryllia studies. An effusion cell

with one millimeter orifice was employed with the beryllium powderalumina mixture and a 0.5 mm orifice-effusion cell with beryllium

chip-alumina mixture. A silver calibration was carried out with the

0.5 mm orifice effusion cell.

Results

It was possible to observe ion intensities of the reactant,

beryllium, as well as the products, aluminum, its reduced oxides and

oxygen, employing the second cell. Table 1 presents ion intensitytemperature data for the range 1511-1743K.

From the various equations that could describe this reducing

system, the following were selected for computation:

(1) Be(g) + Al2 03 (s) ^ BeO(s) + 2Al(g) + 20(g)

(2) 2Al(g) + 0(g) Al2 0(g)

(3) Be(g) + Als 0(g) 5± BeO(s) + 2Al(g)

(4) Be(g) + Al2 03 (s) Be0(s) + 2A10(g)

69
From the data, Table 1, and auxiliary data in Table 2, apparent

equilibrium constants were computed. Second law plots for these

reactions are shown in Figures 1, 2, 3, and 4. Enthalpies o£ these

reactions were computed and are listed in Table 3.

Discussion

The reduction reaction with beryllium powder produced copious

amounts of A1 and A12 0 species at a rapid rate. It was difficult to

detect gaseous Be and A10 under these conditions. Also, a decrease

in intensities of A1 and A12

0‘ occurred and on examining the effusion

cell at the end of the experiment, the orifice was found to be filled

with a solid.

Only the data from the second experiment, using a chip of

beryllium underneath a layer of alumina, were employed. The data

with index nos. 1 and 13 appear anomalous and were not considered in

the second law treatment. The last points taken at the maximum

temperature, 1420°C (uncorr.), show a loss of ion intensity and this

effect is assumed to be coincident with the filling of this orifice.

The ion intensities, identified by index no. 1, are larger than others

at equivalent temperatures and this is probably due to contamination

from the previous energetic experiment.

The causes for the scatter in the ion intensities are unknown

and should require further investigation. During the experiments, ion

intensities could be duplicated at a fixed temperature, which indicated

that the electronic circuits were dependable. Since the ion intensities

at 1200°C, Table 1, index nosw 2 and 10, could not be duplicated, unknown

changes may have occurred inside the effusion cell. The data shown in

Table 1 were obtained over a period of five days with discontinuous

operation. The effusion cell was maintained at a selected temperature

on the average for thirty minutes and many times for one hour while

the data were recorded.

Reaction enthalpies, Table 3, were obtained by the second law

and third law calculations. For the second law least squares fit,

data corresponding to index nos. 2, 3, and 7 were given weights of

0.5, the remaining points, weights of 1.0. The tabulated enthalpies

are mean values. The second law values in this table are least squares

fit with the standard deviations in the slopes.

The reaction enthalpies show a reasonable inter -consistency

The enthalpy difference between reaction 4 and 1 give the formation

enthalpy of two A10 molecules. Reaction 2 gives the enthalpy of forming two Al-0 bonds in the A12 0 molecule. Although the Al-0 bonds in

70
these two molecules are not the same, they differ by approximately

5 kcal. The difference in enthalpies from reactions 4 and 1 is 147

kcal, and reaction 2 gives 161 kcal. However, this type of calculation

does not indicate the reliability of the enthalpy values themselves.

The partial pressures in Table 4 were obtained with the aid of

a silver calibration using the 0.5 mm orifice effusion cell. These

pressures involve the usual error associated with ionization crosssections of molecules but are of interest for relative comparison of

partial pressure magnitude among the species observed.

71
Data

-

Ion

Intensities

o

CM

, <"-4

rHOJWWTONrorooico r-i h co Hbbbbbbbbbbbbb i—4 r-l r~4 i—4 i—4 i—4 r—4 r—4 i—4 i—4 i—4 r—4 xxxxxxxxxxxxx

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to •H

•d

<u

CO

CO

a)a

x

d

d

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cod

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tod

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d

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72
TABLE 2

Auxiliary Data

Specie Multiplier

Efficiency

Ionization

Cross-section

M

+ Y, (D cr, (2)

Be

+ 280 2.5

o\ 180 1.6

Al + 294 5.0

A10+ 250 6 .

6

AlsO+ 260 11.6

Ag 107 153 10.1

(1) Author ’ s values.

(2) R. F. Pottie, J. Chem. Phys. 44> 916 (1966).

Window-prism transmissivity, A

Ag sample

Silver sensitivity

1.71 X lCT 50^1 5.950 X 1C

T

3 gm (99.9% pure)

1.1683 X 1CT 6 amp/atm at 1361°K

Enthalpy Functions - Free Energy Functions

(Be, 0, Al, A10, BeO) NBS Report 6928, July 1960

(A12 03 ) NBS Report 6484, July 1959

73
TABLE 3

Reaction

1

2

3

4

Reaction Enthalpies

2nd Law 3rd Law

^?sea kcal/mol kcal/mol kcal/mol

265 ± 0.5 264 286.7

- 155 ± 3 - 150 - 161.2

3 ± 8 0.7 - 39

134 ± 3.0 126 140.0

NOTE: Cal. X 4.1840 = joule
Partial

Pressures,

a

tms

o

«

<c

Cu

<Cu

O

Cu

0> PQ

P-i

S-c u

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<u H

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75
Figure 1. A van't Hoff plot for the reaction:

Be(g) +A12 03 (s) ^ BeO(s) + 2Al(g) + 20(g), £Hj B82 = + 265 kcal/mol

at the mean reciprocal temperature, 6.3210 X 1QT4 °KT'L

. 76
Figure 2. A van't Hoff plot for the reaction:

2Al(g) + 0(g) ^AlgOCg), £H?b 8 2 * “ 155 kcal/mol.

77
Figure 3. A van't Hoff plot for the reaction:

Be(g) + Al3 0(g) BeO(s) + 2Al(g), AH? 582 = 3 kcal/mol.

78
Figure 4. A van't Hoff plot for

Be(g) + Alg

0

3 (s) BeO(s) + 2A10(g), £H? 5q2 = 134 kcal/mol.

19

I -IQ9 . ..

8 „
Chapter 5

STRUCTURE OF THE ALKALI HYDROXIDES.

III. MICROWAVE SPECTRA OF RbOH and RbOD*

Chi Matsumura* and David R. Lide, Jr.

National Bureau of Standards, Washington, D. C.

ABSTRACT

The microwave spectra of gaseous RbOH and RbOD have been measured

with a high-temperature spectrometer. The spectra are generally

similar to those observed in CsOH and indicate an essentially linear

structure for rubidium hydroxide. The variation of rotational constant

with excitation of the bending mode shows anomalies similar to those

found in CsOH. The Rb-0 bond length is found to be 2.30 while the

0-H distance is 0.96^_ Analysis of the nuclear quadrupole hyperfine

85

structure gives eqQ values of -67.9 Mc/s in Rb OH and -35 Mc/s in

87

Rb OH.

tThis research was supported by the U.S. Air Force Office of Scientific

Research. Contribution of the National Bureau of Standards, not

subject to copyright.

*Present address: Government Chemical Research Institute, Tokyo,

Japan.

80
INTRODUCTION

As reported in pci per I of this series, the microwave spectrum of

gaseous cesium hydroxide indicates a linear or near- linear structure

for the molecule. However, the dependence of the rotational constant

B on the vibrational quantum number v0 showed several anomalies. B v 2 v was found to decrease with increasing excitation of the bending mode v^,

which is opposite from the normal behavior in linear molecules.

Furthermore, the dependence on v^ was strongly non-linear, and the

deuterium isotope effect was very large. A study has now been carried

out on the spectrum of rubidium hydroxide. Similar anomalies have

been found, which suggests that they are a general feature of the

alkali hydroxide molecules.

EXPERIMENTAL

The microwave spectrometer used in this study was the same as described in I, except for a small modification. The pumping system

was improved and a larger diameter tube was used for the vacuum jacket

in order to allow more efficient removal of the water vapor which was

formed by the rapid decomposition of RbOH at the operating temperature.

In spite of this improvement, the water vapor still caused appreciable

broadening of the lines. The RbOH spectrum was weaker and somewhat

more difficult to obtain than that of CsOH.

85

As the Rb atom has two isotopic species 72% of Rb and 28% of

87

Rb , and both species have large nuclear quadrupole moments, many weak

lines had to be measured. Therefore, most measurements were done by

81
slow sweep recording in order to obtain high sensitivity. However, the

thermionic emission which was discussed in the previous paper^ made the

application of a high Stark modulation voltage extremely difficult.

The thermionic emission caused not only a wandering base line but also

large amplitude random noise, so that the observation of £ states, which

required high modulation, was possible only under optimum conditions.

The conditions were not easily controlled in these experiments, but the

lining of the waveguide with very pure silver (99.99%) was effective

for preventing the thermionic emission, and careful cleaning of the

waveguide and quartz tube also reduced the difficulties.

The measurement of temperature was done with a thermocouple which

was placed at the side of the waveguide. Since both the waveguide and

the thermocouple were heated mainly by radiation from the furnace, and

the temperature was not homogeneous, the thermocouple gave only a rough

indication of the gas temperature. However, 550-600°C was believed to

be the typical operating temperature. Because of the inhomogeneity of

the temperature, the effective cell length was probably shorter than the

oven length (45 cm) . It seemed that the sample at the center portion

of the cell was vaporized first and the working region expanded

gradually. Although this effect reduced the sensitivity of the

spectrometer, the gaseous molecules were produced for an extended

period (1-2 hours).

82
ANALYSIS OF SPECTRUM

Most observations were made on the J - 2 -* 3 transition., since

the sensitivity of the microwave spectrometer was optimized in this

frequency region. Another merit of this transition was the convenient

magnitude of the nuclear quadrupole splitting. The J = 1 -* 2 and the

j = 3 _* 4 transitions of some states were observed for confirmation

of assignments and calculation of nuclear quadrupole coupling constants.

In some cases, the double -resonance procedure was helpful for finding

or confirming £ states. The observed frequencies of the J = 2 — 3

transitions are listed in Tables I and II.

As was the case with cesium hydroxide, the spectrum of rubidium

hydroxide indicates an essentially linear molecule with a large number

of low-lying vibrational states. The assignment of vibrational satellites

was done by Stark identification and from considerations of the reasonable

relative positions of lines in the series. The separation between lines

85 87 of molecules containing Rb and Rb is the same order of magnitude

as vibrational satellite shifts, so that the spectra overlapped each

other. The hyperfine patterns were helpful in discriminating them.

The values were calculated from J = 2 — 3 transitions by using

the equation

v = [2B

v±-f (v

2

+l)](J+l) - 4D(J+1)[CJ+1) -/]. (1)

A value of D = 0.0067 Mc/s was used for this calculation. It was

3 2 2 2 obtained from the equation D = 4BJ

) /uj c

« • It was not possible

e 23 . p

83
to obtain a good experimental D value from the transitions J = 2 — 3

and J ~ 1 -* 2 because of hyperfine complications, so that the calculated

value seems to be more reliable. The B values are listed in Table III,

v

and the values of q r are given in Table IV.

Jit 0 0

The frequencies of the (02 0) and (12 0) states of RbOD could not

be measured because of the exact overlapping with the (01^0) and

(11^0) lines, respectively. On the other hand, the latter two

lines were measured by using small Stark modulation. The overlapping was

confirmed by comparison with the shape of the same lines in the normal

isotopic species.

NUCLEAR QUADRUPOLE COUPLING

Since the line width in this molecule is fairly large while the

hyperfine splitting in the transition J =* 2 -* 3 is small, it was

difficult to determine the eqQ values with high accuracy. The splitting

in the transition J = 1 -» 2 is larger, but the line strength of the

weak components is not sufficient for accurate measurement. Assumed

values of eqQ were used for analysis of weaker satellite lines from

the higher vibrational states and for the RbOD species.

The values of eqQ are included in Table III. They are small in

85 87 spite of the very large Q values of Rb and Rb . This shows that

the Rb-0 bonding is almost completely ionic. The values of eqQ are the

same order as those in Rb^Cl (eqQ = “52.675 Mc/s) and Rb^Cl

(eqQ = -25.485 Mc/s). Though the error in the measurement of eqQ is

fairly large, it may be Concluded that eqQ decreases markedly with

increase of v^. The patterns of hyperfine structure for Ji «= 0, 1, and

8U
2 states fit exactly to the model of a linear molecule within the

experimental error. This is further support for the linearity of the

alkali hydroxide molecules.

VIBRATION-ROTATION INTERACTIONS

The gross features of the rubidium hydroxide spectrum are very

similar to those found in cesium hydroxide. The variation of with

v^ (see Table V) is quite regular, yielding a

^ values of 43.7 Mc/s in

RbOH and 38.2 Mc/s in RbOD. The dependence of on the Rb isotope

is too 6mall to be measured accurately. On the other hand, the

variation of B^ with v^ is strongly non-linear, is in the opposite

direction from that in normal linear molecules, and shows a large

deuterium isotope effect. These anomalies are not so pronounced as in

the cesium compound but are still quite noticeable.

It was found in cesium hydroxide that the B^ values could be fit

2 2

to a power series containing terms in (v^+l) , (v^+l) and i . The same

is true for rubidium hydroxide. A least squares fit resulted in the

following coefficients

:

Rb

85

OH: B = 6321.57-33.38

Rb

85

0D:

V

B = 5730.85-11.16

Rb

87

OH:

V

B = 6297.05-32.31

Rb

87

OD:

V

B =

V

5707.57-10.32

' 2 ^' ' ' 2

' *

r2

+l) + 1.08 (v

2

+l) 2

- 1.15 l

2

r +1) + 1.613 (v +1)

2

- 2.04 l

2

r 2

+l) + 0.88 (v

2

+l)

2

- 1.13 l

2

.

85 85

In Rb OH and Rb OD, where the fit was over- determined, the inclusion

3 of a (v0+l) term leads to no significant improvement. In the other

two species the number of B values was just sufficient to determine

85 the coefficients given above. The precision of the fit for Rb OH and

8?
8 5 and Rb OD is illustrated in Table VI.

The general similarity of the vibration-rotation interactions in

CsOH and RbOH suggests that the anomalous behavior is characteristic of

the alkali hydroxide molecules, and is not the result of some accidental

resonance. Furthermore, the ability to fit the variation of B with v- v 2

in both molecules to a truncated power series lends some confidence

to the identification of the coefficients of the series with the usual

spectroscopic constants Yo? * an<^ Yj?^‘ Some progress has been made

in the explanation of the anomalous values of these constants; the

details will be reported in a subsequent paper.

STRUCTURE

The interatomic distances have been calculated from the rotational

constants of RbOH and RbOD on the assumption of a linear model.

Following the procedure used for CsOH, the calculation was done both

with the ground state constants and with the extrapolated constants

obtained from the power-series fit discussed in the last section. The

results are given in Table VXIc Essentially the same distances were

85 87 obtained from the constants of the Rb and Rb species.

As was found for CsOH, the 0-H distance derived from the

extrapolated B values has a more reasonable magnitude. The' Rb-0 distance

of 2.30- K is not far from the r value of 2.265 S. in RbF.

5 e ACKNOWLEDGMENTS

We wish to acknowledge the preliminary search for the RbOH spectrum

carried out by R. L. Kuczkowski . We also appreciate helpful discussions

with J. T. Hougen.

86
REFERENCES

1. D. R. Lide and

2. H. K. Nielsen,

R* L. Kuczkowski, J. Chem. Phys . 4.6, 4768 (1967).

Rev, Mod. Fhys. 23, 90 (1951).

87
' 85 85

Table I. Observed frequencies in Rb OH and Rb OD in Mc/s

(J = 2 -* 3 transition) .

State

( 00

°

0)

37600.7 •

37594.3 34301.9

37591.3 34299.0

37589.4 34297.3

37584.7 34292.3

(01 0) x+

5/2

3/2

5/2

9/2

7/2

5/2

3/2

9/2

3/2

1/2 J

5/2 1

11/2J

( 7 /2 , 9 /2 )

7/2 I

5/2 J

( 7 /2 , 9 / 2 )

F ~ F ' Rb

85

OH Rb° 5

OD

5/2 5/2 37744.8

7/2 ( 7 /2 , 9 / 2 ) 1> 37741.2 34324.6

9/2 U'2 j1 5/2 7/2 37738.3 34321.6

3/2 5/2

|

37734.9 34317.9

1/2 3 / 2 J

9/2 ( 7 /2 , 9 /2 ) 37728.6 34311.9

(01

X0) X5/2

3/2

5/2

9/2

7/2

5/2

3/2

9/2

3/2

1/2

5/2

11/2 J

( 7 /2 , 9 /2 )

7/2 1

5/2

( 7 / 2 , 9 /2 )

37541.0

37534.9 34242.9

37532.0 34240.1

37530.6 34238.5

37525.5 34233.5

88
Table I Continued

( 02

°0)

\

7/2 (7/2, 9/2 ) i> 37430.5 34242.8

9/2 il/2

5/2 7/2 37417.1 34240.0

3/2 5/2 !> 34236.0

1/2 3/2

1/2 (1/2, 3/2) 37394.0 34228.8

3/2 (i/2,:

r

04 to

•s CM o 37385.2 34220.1

(02^0) 9/2 (7/2, 9/2, 11/2 )j

5/2 (3/2, 5/2, 7/2) 37375.6 34210.4

' 7/2 (5/2, 7/2, 9/2) 37372.2 34207.1

5/2 5/2

> 37362.2 34278.3

9/2 11/2

1 7/2 (7/2, 9/2) 37358.9 34275.4

(03

i

0) x+

5/2 7/2 1? 37357.2 34273.5

3/2 5/2

. 9/2 (7/2, 9/2) 37352.5

5/2 5/2]

> 37238.1 34152.2

9/2 11/2 ^ (03

X 0) 7/2 (7/2 ,9/2) 37235.0 34149.3

5/2 7/2

37233.0 34147.8

3/2 5/2

j

89
Table I Continued

< 04

2

0 )

( 10

°

0)

1/2 (1/2, 3/2)

1

l

37179.4

3/2 (1/2, 3/2, 5/2)

37170.7 34189.2

f

9/2 (7/2,9/2,11/2) J

5/2 <3/5, 5/2,7 /2) 37160.9 34179.2

7/2 (5/2, 7/2, 9/2) 37157.8 34174.8

7/2 (7/2, 9/2) J 37479.1 34095.4

9/2 11/2

3/2 5/2 1 37472.7 34089.0

1/2 3/2 j

9/2 7/2

37466.7 34082.9

9/2 9/2

(H L 0) 1+

5/2 5/2

9/2 11/2 _

r

7/2 (7/2, 9/2)

5/2 7/2

3/2 • 5/2

. 9/2 (7/2, 9/2)

37333.6

37330.8

37329.0

37324.1

34071.0

34068.2

34066.4

(H 1 0) X5/2 5/2

> 37269.2 34010.2

9/2 11/2

7/2 (7/2, 9/2) 37266.4 34007.5

5/2 7/2

> 37264.9 34006.1

3/2 5/2^

9/2 (7/2, 9/2) 37260.0

90
Table I. Continued

\

7/2 ( 7 /2 , 9 / 2 )

> 37164.5 34010.5

9/2 11/2 r ; 5/2 7/2 34007.6

1/2 ( 1 /2 , 3 /2 ) 37140.7 33995.2

3/2 ( 1 /2 , 3 / 2 , 5 / 2 )

2

> 37132.0 33986.8

( 12

^ 0) 9/2 ( 7 / 2 , 9 /2 , 11 / 2 )

5/2 ( 3 /2 , 5 /2 , 7 /2 ) 37122.3 33977.3

7/2 ( 5 / 2 , 7 / 2 , 9 /2 ) 37119.2 33974.1

(200)

7/2 ( 7 /2 , 9 /2 ) 1

? 37216.9 33866.8

9/2 11/2 1

5/2 7/2 37213.9 . 33863.9

"N 3/2 5/2

> 37210.8 33860.7

1/2 3/2

J

9/2 ( 7 /2 , 9 /2 ) 37204.8

91
Table II. Observed frequencies in Rb^OH and Rb

87

OD in Me/

(J - 2 -« 3 transition).

State F ** F'

87

Rb OH

87

Rb OD

7/2 9/2

37597.8 34188.4

0 5/2 7/2

(00

U

0) > 3/2 5/2

37595.6 34186.6

1/2 3/2 _

.

(01

X0) 1+

3/2

7/2

1/2

5/2

3/2

7/2

3/2

9/2

3/2

7/2

5/2

1

.J 7/2

(O^O) i7/2

1/2

5/2

3/2 5/2

( 02

°0)

7/2

5/2

3/2

1/2

37455.1

37450.8

37448.7

37444.0

37391.7

37389.7

37287.5

37285.6

34165.1

34163.4

34106.9

34105.1

34106.9

34105.2

92
Table II. Continued

1/2 3/2 37246.8

o 7/2 (5/2, 7/2, S/2) 37241.1 34082.5

(02 u)

3/2 (3/2, 5/2) 37238.3

5/2 (3/2, 5/2, 7/2) 37232.8 34074.2

7/2 9/2

37337.1 33960.8

(10°0)

5/2 7/2 , > 5/2 7/2

> 33959.0

3/2 5/2^

93
Table III. Effective rotational constants and nuclear

coupling constants (in Mc/s) for various

vibrational states of RbOH and RbOD.

State B (Rb

ba

01-I) V

B (Rb

S5

0D) V

a

eqQ

00°0 2 6290.15 5720.77 -67.9

oi

1 o n . 6260.55 5711.69 -67.6

02°0 2 6238.37 5707.08 (-67.9)

02

2

0 A 6230.13 5702.57 -67.4

03

X0 TT 6216.43 5702.34 (-67.6)

04

2

0 A 6194.38 5697.42 -67

10°0 22 6246.45 5682.50 -65.9

lib TT 6216.70 5673.24 -67

12°0 2 6194.03 ( ‘-6

6

6

6

)

12 2 0 A 6187.95 .3

20°0 2 6202.75 5644.40 -64.2

State Bv

(Rb

87

OH) B (Rb

87

OD)

V

eqQ

00°0 2 6266 .35 5698.13 -35

oi

1 o rr 6236.84 5689.32 -33

02 °0 2 6214.63 5684.53 -31

02

2

0 A 6206.48 5680.02 -32

10°0 2 6222.90 5660.18 (-33)

The numbers in parentheses are assumed values.

9k
Table IV. ^-doubling constants (Mc/s).

State q (Rb

85

OH) q (Rb

85

OD) q (Rb

87

OH) q (Rb

8?

0D)

(O^O) 9.87 9.82 9.85 9.70

m

1

®) 10*33 10.51

(u1 ©) 10.73 10.12

j

95
Table V , Variation of rotational constants with in Mc/s.

ft AJ V

2 0vo 0 iv9 0

B. £ n

- B. l n lv

2

0 2v

2

0

Rb

8

"0H

0° 43.70 43.70

l

1

43.85

2° 44.34

2

2

42.18

Rb

S5

0D

0° 38.27 38.10

l

1

38.45

2° 38.71

2

2

38.82

87 Rb OH

0° 43.45

Rb

87

OD

0° 37.95

%
Table VI. Fit of 2_ 0v

3 ° to power series in Mc/s

.

Rb

85

0H Rb

85

OD

State Calc B j* 0v

2

0

Obs-Calc CalC B

0v*0

Obs-Calc i

00°0 6290.10 0.05 5720.77 0.00

01

X0 6260.33 0.17 5711.70 -0.01

02°0 6238.57 “0.20 5707.09 -0.01

02

2

0 6230.38 -0.25 5702.49 -0.08

03

X0 6216.48 -0.03 5702.34 0.00

04

2

0 6194.10 0.28 5697.45 -0.03

91
Table VII. Structural parameters of rubidium hydroxide in R

in i I r I w ' r i i rr j -j . i ~mm

From B_,0A

oo o From "B "a

e

r (RbO) 2.316 2.305

r (OH) 0.913 0.965

a

The first term in Eq. (1) was used as "B ." This

e set of values is felt to be the more reliable one.

98
Chapter 6

STRUCTURE OF THE ALKALI HYDROXIDES

IV. THE INFRARED SPECTRA OF MATRIX ISOLATED RbOH, RbOD and NaOH, NaOD

N. Acquista and Stanley Abramowitz

ABSTRACT

The infrared spectra of matrix isolated RbOH, RbOD, NaOH and NaOD

have been observed. Both the alkali metal oxygen stretch, v^, and the

bending mode, > has been assigned for each species. The metal oxygen

stretching mode is found at 354.4, 345, 431, and 422 cm ^ for RbOH,

RbOD, NaOH, and NaOD, respectively; the bending mode, v^i is observed

at 309.0, 229, 337, and 250 cm *

, respectively. Combination of the

results of this study with the microwave measurements for RbOH and RbOD

indicates an essentially linear structure for this species. The

isotope shift for observed in NaOH coupled with reasonable bond

lengths indicates an equilibrium configuration of NaOH which probably

does not deviate significantly from linearity. The assumption of a

linear model with a harmonic bending potential yields a force constant

of .046 and O 053 md-jj for RbOH and NaOH, respectively. These results

are consistent with our previously reported results for CsOH.
INTRODUCTION

The second paper of this series described the infrared spectra of

1 matrix Isolated CsOH and CsOB. With the exception of the work by

2 Spinar and Hargrave , this is the only report on the infrared spectrum

3

of an isolated alkali metal hydroxide. Other work on these systems

was confined to solutions or single crystals which give little information on the structure of the monomeric species. Encouraged by the

success encountered with CsOH a similar experiment was attempted for

RbOH and NaOH. The present paper presents the infrared spectra of

matrix isolated RbOH, RbQD, NaOH, and NaOD.

EXPERIMENTAL

The experimental techniques used have been described previously

4

by Mann e_t al c The infrared spectra were obtained with a Perkin- Elmer

301 grating spectrophotometer with a wavenumber range of 4000-50 cm

Refrigeration was provided by an Air Products Cryotip operated in the

range of 20-33° K. ^ An electron bombardment furnace mounted in a

vertical housing was utilized to vaporize the samples from double

boiler silver Knudsen cells. In the course of this work it was found

that the species studied react with tungsten, molybdenum, stainless

steel, nickel, nickel oxide, iron, copper, gold, and platinum at the

high temperatures needed to obtain the spectra.

The RbOH and NaOH which were obtained from commercial sources were

heated gradually to temperatures of about 600°C in order to remove water

and other volatile impurities. Extended periods of outgassing were

required in order to remove impurities which masked the spectrum of the

100
various monomeric species. The deuteroxides were prepared from their

respective hydroxides as previously described. However, it was

difficult to prepare pure deuteroxides in this manner. Impurities

thought to be oxides, peroxides, and/or superoxides tended to broaden the

spectrum in the alkali metal oxygen stretching regions making it

difficult to locate the vibrational frequencies of these modes with the

usual accuracy. The difficulties in estimating temperatures of the

effusing gas and the ratio of the matrix diluent to the sample (M/S)

were similar to those in the case of CsOH.^ M/S ratios of 300:1 to

1000:1 and temperatures of 700°C and 900°C for RbOH and NaOH, respectively

are probably representative of the conditions utilized in these experiments ,Diffusion studies in which the deposited sample was allowed to

warm up to 33° K were performed in an effort to differentiate between

monomeric and polymeric species. This method was partially successful

for NaOH, however as was the case for CsOH, RbOH does not diffuse

readily, even at 33°K, probably because of its high molecular weight.

The use of double boiler techniques in order to differentiate between

monomeric and polymeric absorptions was more useful. It would be

desirable, particularly for NaOH to go above 950°C for this purpose,

however only silver crucibles were found to be relatively inert to NaOH

at these high temperatures. One run was obtained with a platinum

crucible at about 1100°C, in which the corrosion of the crucible took

place near the pinhole of the cell (as opposed to the bottom or side)

allowing some NaOH effusing at this temperature to be trapped in an

argon matrix.

101
The frequencies were determined by using atmospheric water lines

as calibration standards. Spectral slit widths of about 1 cm ^ were

used for frequency measurements which therefore are accurate to about

-I

0.5 cm except where noted.

EXPERIMENTAL RESULTS

These molecules have three normal modes: two of these V- and v 0 1 3

are the M-0 and 0-H stretching mode, while is the bending mode.

Several strong bands appear in the region of 600-200 cm ^ in both

RbOH and NaOH. Figure 1 shows the pertinent portion of the spectra

of RbOH in this region observed from two samples labeled a and b.

Spectrum b was obtained from a sample effusing at a higher temperature

-1

than a. The band observed at 354.4 cm is assigned to the Rb-0

stretching mode, v^, while the band at 309 cm ^ is assigned to the

bending mode, v^« A frequency of 371.3 has been observed for the v

Q

vibration of RbF in the gas phased All other bands in the spectrum

decrease in intensity relative to these two as the temperature of the

double boiler Khudsen cell (from which RbOH is effusing) is raised.

These features also maintain their intensity relative to each other

over a wide temperature range also indicating they belong to the same

species. The bands whose relative intensity decrease are due to polymeric

species of RbOH, however it has not been possible to make definite

assignments. Upon deuteration the Rb-0 frequency shifts to 345±3 cm ^

The rather broad band observed for in RbOD is thought to be due to

oxide, peroxide, and/or superoxide impurities introduced during

102
deuteration. All these species could be expected to have bands in this

region. A band also appears at 229±3 cm ^ which is assigned to v^, the

RbOD bending mode. This isotope shift observed for is in excellent

agreement with that calculated for a linear model to the harmonic

oscillator approximation using the bond distances derived by Matsumura

g and Lide from an analysis of the microwave spectrum of RbOH and RbOD.

Infrared spectra of matrix isolated NaOH in the region of the

and fundamentals are shown in Figure 2. Spectrum b was obtained

from a higher temperature than a and spectrum c results from allowing

diffusion to take place in sample b. It can be seen that the 431 cm

^

is more intense relative to the others in spectrum b than in a, while

diffusion results in a diminution of the relative intensity of this

feature as can be seen in c. This indicates that the 431 cm ^ band is due

to a low molecular weight species, and it is assigned to v^, the Na-0

stretching mode of monomeric NaOH. Confirmation of this hypothesis

as well as an assignment for can be found in Figure 3. This spectrum

was obtained at a higher temperature in excess of 1000°C using a platinum Khudsen cell in which the corrosion took place at the top of the

cell. Three features appear in this spectrum at 431, 400, and 337 cm

The relative intensity of the 431 cm ^ to the 400 cm ^ feature confirms

its assignment as the vibration. The 337 cm ^ is then assigned to

the NaOH bending mode. This assignment is in agreement with

Spinar and Margrave's observation of 437±10 cm ^ in the gas phase

for the Na-0 stretching mode. Unlike CsOH and RbOH, however the NaOH

103
v fundamental is rather far from the 522 cm observed for the v_

1 vibration of NaF in the gas phase. The assignment of the other

features observed In the spectrum between 450 and 250 cm ^ to particular polymers of NaOH is not possible.

The spectrum of NaOD observed in this region is shown in Figure 4.

A comparable spectrum of NaOH is also given for comparison. By analogy

-I with NaOH the V- fundamental is found at 422±3 cm . The breadth of

1 this feature is probably due to oxide , peroxide, and/or superoxide

impurities introduced during the synthesis of NaOD from NaOH. Confirmation of this assignment is found by observing shifted to

250 cm ^ as shown in Figure 5. This shift is consistent with a linear

model for NaOH having bond lengths of 1.93 and 0.97 X for the Na-0 and

0-H bonds, respectively. It is consistent with the explanation of the

breadth of to note that two to three times longer deposition times

are required to develop v in NaOD than is required for NaOHo A

z compilation of the data obtained together with previous results for

CsOH can be found in Table 1.

The 0-H stretching modes, v^, should appear in the neighborhood

-1 -1

of 3600 cm for RbOH and NaOH and 2560 cm for RbOD and NaOD. The

spectra were studied in these regions, but no meaningful assignments

could be made because of water absorption.

10i|
TABLE 1

OBSERVED BANDS FOR MONOMERIC ALKALI METAL HYDROXIDES

Molecule v i v v ,, Microwave

1 r „ r MO OH

CsOH 335.6 309.8

2.40 0.96

CsOD 330.5 226

RbOH 354.4 309.0

2.31 0.97

RbOD 345±3 229±3

NaOH 431 337

NaOD 422±3 250

105
REFERENCES

lo N. Acquista, S. Abramowitz, D* R. Lide, J. Chem. Phys . 49 , (July 15) 1968

2. Lo H. Spinar, L. Margrave, Spectrochim. Acta 12, 244 (1958).

3. K. Nakamoto, Infrared Spectra of Inorganic and Coordination

Compounds (John Wiley & Sons, Inco , New York, 1963) p. 73o

4. Do E. Mann, G. Vo Calder, D. White, K. S. Seshadri, M. J. Linevsky,

J. Chem. Phys. 46, 1138 (1967).

5. Certain commercial instruments are identified in order to specify

the complete experimental procedure. In no case does such

identification imply a recommendation or endorsement by the

National Bureau of Standards

6. D. R. Lide, R. L. Kuczkowski, J. Chem. Phys. 46_, 4768 (1967).

7. S. E. Veazey, W. Gordy, Phys. Rev c 138 , A1303 (1965).

8« Co Matsumura, Do Ro Lide, to be published.

106
RbOH/Ar

107

Figure

1

-

The

spectra

of

matrix

isolated

RbOH

in

argon.

Curve

a

refers

toa

sample

which

effused

from

the

crucible

at

a

higher

temperature

than

the

sample

represented

in

curve

b.
NaOH/Ar

N

co

cooo

cooo

CO

^r u

108

Figure 2-

The

spectra

of

matrix

isolated

NaOH

in

argon.

Curve a

refers

toa

sample

which

effused

from

the

crucible

ata

lower

temperature

than

the

sample

represented

in

curve

b.

Curve c

was

obtained

from

the

sample

represented

in

curve b

by

allowing

diffusion

to
j

v/hOdn

Figure 3-

The

spectrum

of

matrix

isolated

NaOH

in

argon.
NaOD/A

«o

00

CN

110

Figure

4

-

The

spectrum

of

matrix

isolated

NaOH

in

argon.

The

spectrum

of

matrix

isolated

NaOD

in

argon.
I

I

lOMM-NBS-DC

111

o

W)

ctf

Figure

5

-

The

spectrum

of

matrix

isolated

NaOD

in