G. J. MACUR,R. K. EDWARDS, AND P. G. WAHLBECK
2956
Multiple Knudsen Cell Effusion. Enthalpies of Vaporization of Indium and Gallium1
by G. J. Macur, R. K. Edwards, and P. G. Wahlbeck Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois
60616
(Received March 88,1966)
I n order to determine several vapor pressures at one well-defined temperature, several Knudsen cells were heated simultaneously in a massive molybdenum block which served to provide a uniform temperature environment. With this multiple-cell technique, it was hoped that the precision in a set of vapor pressure measurements determined in a single isothermal experiment would be better than that achieved in individual pressure measurements. The vapor pressures of liquid indium and gallium were determined. The precision of pressure measurements was better than what is usually achieved with the Knudsen method. The standard enthalpies of vaporization of indium and gallium a t 298°K were found to be 56.58 f 0.10 and 64.62 f 0.22 kcal/g-atom, respectively; these values agree well with the literature values.
I. Introduction The Knudsen effusion method has been used extensively for the determination of vapor pressures of materials a t high temperatures. I n many experiments it would be desirable to determine a set of vapor pressures at one fixed temperature. Examples are (1) the evaluation of activities, through vapor pressure measurements a t a given temperature, of components of an alloy as a function of composition, e.g., activities for the Cu-Au system by Edwards and Brodsky;2 (2) the evaluation of nonideality effects of effusion orifices, e.g., the study by Freeman;3 and (3) the evaluation of effects due to variation of orifice areas, e g . , the nonunit vaporization coefficient. At elevated temperatures there is a considerable error in temperature measurement, and it is very difficult to reproduce temperatures. Therefore, it is most difficult to achieve highly precise agreement in a set of isothermal vapor pressure values which are taken from individual measurements. A higher precision should be achieved when several cells are used simultaneously in an isothermal enclosure. In order to have many Knudsen cell measurements a t a well-defined temperature, 14 Knudsen cells were placed in a large molybdenum block. Thus, it was possible to obtain 14 vapor pressure measurements simultaneously at one temperature. The measurements of vapor pressures of pure liquid The Journal of Physical Chemistry
gallium and indium reported here were performed in preparation for measurements of the activities of gallium and indium in Ga-In liquid solutions. l Standard enthalpies of vaporization of liquid gallium and indium have been calculated from these vapor pressures.
11. Experimental Section Apparatus. The apparatus as used in this experiment is shown in Figure 1. It consisted of a highspeed vacuum pumping system, an inert gas inlet system, pressure gauges, an electrical furnace with a temperature controller, a temperature-measuring device, and a set of Knudsen cells in a thermostating molybdenum block. The vacuum pumping system consisted of an oil diffusion pump with forevacuum produced by a mechanical pump. Argon could be admitted through the stopcock at the top of the apparatus. The Philips gauge was used to measure pressures below 1 torr, and (1) Based on a thesis by G . J. Macur, submitted to the Illinois Institute of Technology in partial fulfillment of the requirements for the Ph.D. degree, June 1965. (2) R. K. Edwards and M. B . Brodsky, J . Am. Chem. SOC.,78, 2983 (1956). (3) R. D . Freeman, Technical Document No. ASD-TDR-63-754, 1963. He has attempted t o establish isothermal conditions for effusion by heating eight Knudsen cells simultaneously in a thermostated block.
ENTHALPIES OF VAPORIZATION OF INDIUM AND GALLIUM
O B S E R V A T 10 N POR T 1 k MEASURING THERMOCOUPLE
/ CONTROLLING THERMOCOUPLE
Figure 1. Multiple Knudseii cell effusion apparatus.
the Helicoid gauge was used to measure higher pressures. The electric furnace was a Hevi-Duty HDT-812 furnace capable of achieving 1260". Its power was controlled by a West JSB-2, 5 KVA saturable-core reactor controller regulated by a sensing thermocouple; the temperature was controlled to within =!=lo.The temperature of the experiment was determined from the emf of a platinum-platinum-10% rhodium thermocouple Calibrated at the freezing points of antimony, silver, and copper. Calibration before and after the experiments showed no appreciable change. The effusion cells were fabricated of alumina, AP35 (99% A1203), by the XcDanel Refractory Porcelain Co. A cap and cylinder design was used; the caps were cemented and fired to the cylinders. The effusion cells were 60 mni long and 14 mm in 0.d. with a wall thickness of ca. 1 mm. The nominal orifice diameters ranged from 0.5 to 1.8 mni in 0.1-mm intervals. Effective orifice areas were determined by measuring the rate of effusion of pure mercury from the cells; a separate vacuum apparatus was used for these effective orifice area measurements. The vapor pressure of mercury was calculated from the equation suggested by Carlson, et ai.,4 based on the data of Busey and G i a ~ q u e . Two ~ calibration runs were made for each orifice; agreement of the results to ca. 1% was obtained.
2957
For the high-temperature runs, the coefficient of thermal expansion of 7.8 X deg-I for alumina6 was utilized to correct for the expansion of the orifice. The effusion cells were inserted into larger alumina cups which effectively lined the wells in the molybdenum block and also aided insertion and removal of the cells. The thermostating cylindrical block was 5 in. long and 5.75 in. in diameter; 14 wells for the effusion cells and a central well for the thermocouple were drilled in the block. A molybdenum handle was attached to the block. Procedure. Samples were placed in the alumina effusion cells through the orifices with special care not to damage the orifices (which had been calibrated previously). The cells were placed in alumina cups which were then positioned in the molybdenum block in a systematic order. The molybdenum block was lowered into the large alumina tube shown in Figure 1. The calibrated thermocouple was then positioned in its well in the molybdenum block. The large alumina tube with the Knudsen cell assembly was then brought near the water-cooled flange, the mechanical vacuum pump was started, and the alumina tube was pressed against a rubber gasket on the water-cooled flange until the vacuum was sufficient so that atmospheric pressure would hold the alumina tube in place. All electrical connections were then made. With the diffusion pump, a pressure as low as torr was achieved. The temperature of the furnace was brought up to 200' and left overnight for outgassing purposes. The temperature was raised then to 600" over a period of 4 hr. Isolation of the manifold from the pumps was achieved, and argon was added to the system so that the pressure was brought to 0.7 atm. The inert gas at this pressure was used to block effusion until the starting time of the run. The temperature was adjusted then to the desired value; a constant temperature was achieved in about 2 hr. The run was started by evacuation of the manifold, and a timer was started when the pressure reached torr. This pumpdown required ca. 2 min. During the course of the run, temperature and pressure were monitored. After an appropriate period of time, the run was stopped by adding argon to 0.7 atm after isolating the manifold from the vacuum pumps. The temperature
(4) K. D. Carlson, P. W. Gilles, and R. J. Thorn, J . Chem. Phys., 38, 2725 (1963). (5) R. H. Busey and W. F. Giauque, J . Am. Chem. SOC.,7 5 , 806
(1953). (6) Bulletin No. D 763, "Physical Properties," McDanel Refractory Porcelain Go., Beaver Falls, Pa.
Volume 70, Number 9 September 1968
G. J. MACUR, R. K. EDWARDS, AND P. G. WAHLBECK
~~
Table I: Data for the Vaporization of Indium Av Mass loss,
Temp, OK
Time, min
P!
AH'nes,
atm X 10-6
kcal/gatom
10 -6
% av dev
kcal/gatom
Av P, atm X
AH'zes,
Cella
mg
B. B' C D E F G
9.41 8.80 13 22 17.21 18.51 35.50 44.94
720.2
1.488 1.528 1.507 1.469 1.538 1.493 1.505
57.10 57.04 57.07 57.14 57.02 57.09 57.07
1.504
1.2
57.08
1273.6
B. B* C D E F G
48.54 41.95 69.72 97.48 95.48 178.23 235.93
760.4
7.486 7.107 7.751 8.115 7.738 7.313 7.708
56.51 56.64 56.42 56.30 56.42 56.57 56.43
7.602
3.4
56.47
1373.4b
B. B* C
182.68 209.19 273.24 199.28 360.13 203.54 329.05
600.4
37.00 46,54 39.89 21.78 38.32 10.97 14.12
56.44 55.81 56.23 57.88 56.34 59.75 59.06
...
...
...
561.66 487.53 798.72 1063.28 1100.96 2156,59 2846.25
474.3
148.89 141 97 152.63 152.15 153.36 152.10 159.83
56.30 56.44 56.23 56.24 56.21 56.24 56.09
151.5
2.3
56.25
11.36
720.4
56.58
1.767
2.3
56.62
1198.0
D E F G 1472.7
1196.5
B. B* C D E F G
B* B*c C D E F G
1220,3
B* C D E F G
1273.8
B. C D E F Gd
1320.7
B.
c
D
E F Gd ~~
The Journal of Physical Chemietry
I
I
1.795
...
...
16.14 19.60 28.32 32.95 57.38
1.838 1.670 1.792 1,751 1.755
56.53 56.76 56.59 56.64 56.64
...
14.02 19.38 26.90 35.06 42.50 43.70
640.4
2,515 2.506 2.605 2.520 2.566 2.561
56.86 56.87 56.77 56.85 56.81 56.81
2.545
1.2
56.83
25.28 37.10 49.02 66.34 77.53 185.57
466 .Q
6,585 6,966 6.893 6.826 6.802 9.343
56.84 56.70 56.72 56.75 56.76 55.95
6,814
1.5
56.75
37.32 39.22 51.85 69.71 83.62 181.57
192.2
56.39 56.30 56.32 55.87 56.30 55.72
18.00
5.8
56.24
16.96 17.55 17.38 20.63 17.50 21.87
ENTHALPIES OF VAPORIZATION OF INDIUM AND GALLIUM
2959
Table I (Continued) Av A v P, atm X 10 -5
70
AH’298,
a 1‘ dev
kcal/gatom
Cella
Mass loss, mg
1289.2
B. C D E F Gd
21.58 31.03 40.89 54.25 64.71 138.93
273.6
9.306 9.645 9.517 9,384 9,400 11.615
56.62 56.53 56.56 56.60 56.59 56.05
9.450
1.0
56.58
1248.9
B. C D E F Gd
24.85 34.52 43.99 58.02 69.91 106.10
510.2
5.658 5.666 5.407 5.296 5.359 4.681
56.24 56.14 56.25 56.30 56.27 56.62
5.477
2.7
56.24
Temp, OK
Time,
P, atm X
min
10-6
AHOzss,
kcal/gatom
The orifice areas in square centimeters for the cells at 50” were: B., 0.0009568; B*, 0.001051; C, 0.001458; D, 0.001947; E, 0.002000; F, 0.003950; G, 0.004962. Expansion-of-orifice corrections were made using the coefficient of thermal expansion of 7.8 X 10-6 deg-1.6 These data are not reliable because an air leak developed during the run and are shown for comparison only. These data are not included in the over-all averages. Data for cell B* are not shown for this and later runs because it contained an alloy. Data for cell G are not considered reliable because a crack developed in the cell wall. Data are shown only for completeness and are not included in the averages.
’
of the furnace was lowered in a systematic manner to prevent cracking of alumina. After the furnace cooled, the apparatus was dismantled, the mass loss of the effusion cells was determined, and vapor pressures were calculated. Materials. Iridium wire was purchased from A. D. Rlackay, Inc., with a stated purity of 99.999%. The wire was washed with pure benzene prior to insertion into the effusion cells. The indium wire was easily inserted into the cells. Gallium metal was purchased from A. D. AIackay, Inc., with a stated purity of 99.999%. Since gallium reacts slowly with moist air, the amount of exposure to the laboratory atmosphere of the gallium was minimized. Gallium was introduced into the effusion cell by hypodermic syringe. Argon used as the inert atmosphere was purchased from the Matheson Co., with a stated minimum purity of 99.998%.
111. Results and Discussion Vaporization of Indium. I n Table I are found the experimental data, Le., temperature, cell designation, effective orifice area, mass loss, duration of run, and the calculated vapor pressure. The indium vapor has been assumed to be monatomic. I n a mass spectrometric study of indium-rich indium-antimony solutions vaporizing from molybdenum Knudsen cells, DeMaria, et al.,? found the ratio of diatomic to mon-
atomic indium to be of the order of (1-3) X 10-j. The “third law’’ standard enthalpies of vaporization were calculated by using free energy functions, (Go Hozss)/T, for gaseous and liquid indium tabulated by Hultgren, et aZ.* Also tabulated in Table I are the average pressure observed for the set of cells in each run, the average per cent absolute deviation from the mean pressure, and the average third-law standard enthalpy of vaporization a t 298°K. One usually expects an irreproducibility of about in vapor pressure measurements with single Knudsen cells, although this may be reduced to about 5%”” under favorable conditions. The uncertainty in pressure measurements at a given temperature is less than 2% in the work being reported. There was no correlation between location of the cell in the molybdenum block and the value of the observed pressure. Thus, the large molybdenum block distributed the heat uniformly and reduced the temperature variation which appears to have decreased the irreproducibility. (7) G. DeMaria, J. Drowart, and M. G. Inghram, J. Chem. Phys., 31,
1076 (1959).
(8) R. Hultgren, R. L. Orr, P. D. Anderson, and K. K. Kelley,
“Selected Values of Thermodynamic Properties of Metal Alloys,” John Wiley and Sons, Inc., New York, N. Y., 1963. (9) J. L. Margrave, “Physicochemical Measurements a t High Temperatures,” J. 0’11.Bockris, J. L. White, and J. D. MacKenzie, Ed., Butterworth and Co. (Publishers) Ltd., London, 1959, Chapter 10.
(10) R. J. Ackermann and R. J. Thorn, Progr. Ceram. Sci., (1961).
1,
39
Volume 70,Number 9 September 1966
G. J. MACUR,R. K. EDWARDS, AND P. G. WAHLBECK
2960
Table 11: Third-Law Evaluation of Selected Indium Data"
Investigator
No. of observations
koal/g-atom
Method
53
56.58 ir O . l O b
Multiple effusion Effusion Transportation Effusion Torsioneffusion Boiling point (1 atm) Boiling point (1 atm) Effusion
This work Alcock, et ~ 2 Alcock, et aL1I
.
~
~
AH'zos,
57.24 57.08
7 3
Anderson12 Herrick's
8 88
58.23 58.09 & 0.15
Kohlmeyer and Spandau16
1
56.33
RIcGonigal, et
1
56.54 ir 0.83
9
56.79
aL17
Priselkov, et ~ 1 . 1 4 (recalcd) Lyubimov and Lyubitov'e (recalcd)
10
Calculated with the use of (Go - H O m ) / Tfunctions by Hultgren, et a1.8
;
-
5 7.2
I
=
0 l-
57.0 '
5
56.9
a
;
0.10
0.20
0.30
0.40
0.50
t
0.6 8 7 . 2
i
57. I 57.0 56.9 56.8 56.7
a 56.7 J
56.6
-
ai 5 6 . 5
-
2
Y
-
a
a
*
I 56.4
a
56.3 56.2
I
I
56.6
- 56.5 - 56.4 - 56.3
0,
O N
I
I
I
56.2
The variation of AH0298 is seen in Figure 2 to be small and independent of orifice area, and, thus, there is no indication of a nonunit evaporation coefficient. The vapor pressure data are compared in Figure 3 with data by Alcock, et al.,11 Anderson,12 Herrick,13 and Priselkov, et a l l 4 Third-law standard enthalpies of vaporization at 298°K are tabulated in Table I1 with values by Alcock, et aZ.,ll Anderson,12 Herrick,13 Kohlmeyer and Spandau,15 Lyubimov and Lyubitov,16 McGonigal, et aZ.,l7and Priselkov, et aL1* The vapor pressure data obtained in this work agree well with the results of Rlcock and Cornish11 and PriselThe Journal of Physical Chemistry
Mass spectrometer
57.95 f 0 . 4
Container material
Alumina Beryllia Beryllia Quartz Graphite
(?I Graphite Porcelain Quartz
* Average deviation.
kov, et al.14 Agreement is less good with Herrick13 and the early work of Anderson.12 The AHOW value of this study is in agreement with those of Alcock and Cornish, l1 Kohlmeyer and Spandau, l5 McGonigal, et aZ.,17and Priselkov, et aZ.,l4and in less good agreement with those of Anderson,12Herrick,ls and Lyubimov and Ly~bit0v.l~ Evaluation of the several studies leading to AHom values does not lead to an objective basis for discriminating in favor of the results of any particular investigation. Therefore, it is probably best to choose 57.51 kcal/mole, the average weighted according to the number of observations, and to allow the uncertainty of 1.25 kcal/mole so as to include all data. Vaporization of Gallium. In Table I11 are found the experimental data, the calculated vapor pressures, and the calculated third-law enthalpies of vaporization. The gallium vapor has been assumed to be monatomic. I n a mass spectrometric study by Martynovich, l8 (11) C. B. Alcock, J. B. Cornish, and P. Grievsen, IAEA Symposium on Thermodynamics with Emphasis on Nuclear Materials and Atomic Transport in Solids, Vienna, 1965,No. SM-66/34. (12) J. S. Anderson, J. Chem. SOC.,141 (1943). (13) C. C. Herrick, Trans. A I M E , 230, 1439 (1964). 1141 Y.A. Priselkov, Y. A. SaDozhnikov,A. Y. Tsepleyeva, and V. V. karelin, Izv. Vysshykh Uchebn. Zavedenii, Khim.-i Khim. Tekhnol., 3, 447 (1960).
(15) E. J. Kohlmeyer and H. Spandau, Z . Anorg. Chem., 253, 37 (1945). (16) A. P. Lyubimov and Y . N. Lyubitov, Obrabotlca Stali i Splavou, Moskov, Inst. Stali im I . V. Stalina, Sbornik, 36, 191 (1957). (17) P. J. McGonigal, J. A. Cahill, and A. D. Kirshenbaum, J . Inorg. Nucl. Chem., 24, 1012 (1962).
2961
ENTHALPIES OF VAPORIZATION OF INDIUM AND GALLIUM
- 25
1
-24-23
1
A 0
-22
1
I
1
I
I
I
I
I
I
I
T H I S WORK Alcock at. at. EFFUSION Alcock et. at. T R A N S P O R T A T I O N Anderson Priselkov et. al. Herrick
A
-
I
-
I
I
I
I
I
1 0 o'
o n
Y
-
0
O
o o
6
0
- B o o
A
0
6 k
;;-20 -19
a cn
g
%
-18
0
rp
t-
0
a
-16
- 12- 1 1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
1
Figure 3. Comparison of vapor pressure data for indium.
the ratio of diatomic to monatomic gallium was found to be of the order of (2-4) X Also Drowart and HonigIg studied the vaporization of gallium from graphite using a mass spectrometer; they concluded that monatomic gallium was the major species. The irreproducibility found in these multiple-effusion measurements for gallium vapor pressures was 4.6%. This is somewhat larger than that for the indium measurements but does not seem to be attributable to temperature variation within the molybdenum block; it is to be noted that sets of results for both elements were obtained simultaneously a t each block temperature. Sources of error which appear peculiar to the results for gallium were observed. A partial plugging of the orifice (by a gray material) of the cells containing gallium was detected occasionally in postexperimental observations. It seems plausible to suspect that molybdenum oxide particles (originating in a previous apparatus failure), subjected to vibration, fell from upper portions of the apparatus and into the effusion orifices (larger for the case of gallium than
for indium) ; then, some reduction reaction within the cell led to volatilization and reaction-deposition of the observed dark gray material. Another possible source of error was cracking of some cells due to expansion on freezing of gallium; thus, some cracks in some cells were observed, and hence the inference seems reasonable that some cracks may have escaped detection. Also "bumping" of gallium during initial pumpdown seems a possibility (in some cases small droplets were found on the top of the effusion cell after an experiment). The variation in third-law AH0298 of vaporization of gallium is seen in Figure 4 to be small and independent of orifice area. Thus, there is no indication of nonunit evaporation coefficient. The vapor pressure data are compared in Figure 5 with data by Alcock, et al.," Munir and Searcy,20 ~
(18) G. M. Martynovich, Vestn. Mosk. Univ., Ser. Mat., Mekhan., Astron., F i t . i Khim., No.2, 151 (1958);No.5, 67 (1958). (19) J. Drowart and R. E. Honig, Bull. SOC.Chim. Beiges, 66, 411 (1957).
Volume 70, Number 0 September 1066
G. J. MACUR,R. K. EDWARDS, AND P. G. WAHLBECK
2962
Table I11 : Data for the Vaporization of Gallium Av Temp, OK
1198.0
1273.6
Cell"
koal/gatom
720.2
1.551
64.27
1.405
5.2
64.51
...
...
6.43 6.87 7.86 8.60
1.282 1.442 1.381 1.370
64.72 64.44 64.54 64.56
H I
17.73 17.13 25.13 36.77 34.11 41.54 46.98
760.4
7.390 6.158 6.173 7.152 6.983 7.119 6.953
64.25 65.85 64.70 64.33 64.39 64.34 64.40
6.847
5.7
64.75
87.34 51.70 12.59 7.80 73.85 179.43 272.67
600.4
64.02 65.85
...
...
...
472.3
168.0
8.9
64.74
K L M* N
243.90 288.69 177.00 403.45 508.49 568.28 729.27
Hf
...
720.4
1.380
7.9
64.54
I
4.08 3.31 4.28 6.65 7.66 9.08
H I
N
H
I JB,k
J*' K*h,b
L
M :i N
H
I J*f"c
K* L M: N
H
I J* K* L M: N 1320.7
dev
Jb K L M N
M*d
1273.8
% av
atm X
3.63
J K L
1220.3
Time, min
AH'nos,
...
N
1196.5
Av P, atm X 10-0
I*
?rl
1472.7
io-
AH'z~E, keal/gatom
P,
H
J K L
1373.4'
Mass loss, mg
H I
J*
The Journal of Physical Chemistry
...
47.80 2.44 4.06 1.99 19.85 37.65 52.99 174.7 178.4
... 134.9 178.9 156.4 185.5
...
... ...
...
... ... 64.67 63.74 64.09 64.63
... 65.45 64.72 65.01 64.52
...
1.502 1.069 0.964 1.394 1.408 1.376
64.28 65.07 65.32 64.44 64.42 64.47
4.99 5.28 3.52 7.22 9.12 10.20 11.73
640.4
2,419 2,207 1.291 1.848 2.172 2.130 2.028
64.35 64.58 65.87 65.00 64.61 64.66 64.77
2.13
6.1
64.66
9.20 10.84 11.81 15.37 18.16 21.46 24.58
466.9
6.477 6.582 6.295 5.717 6.279 6.511 6.144
64.59 64.55 64.66 64.90 64.67 64.57 64.72
6.29
3.3
64.66
10.46 12.50 13.54
192.2
64.27 64.22 64.32
17.70
1.5
64.24
17.54 18.09 17.21
ENTHALPIES OF VAPORIZATION OF INDIUM AND GALLIUM
2963
Table I11 (Continued) Av Temp, OK
Cella
1320.7
K* L M
::
N 1289.2
H
I J* K* L jq$i.k
?j
H I
1248.9
J*4,k
K*E,.k Le,'" M2.k p , k
Mass loss, mg
Time, min
P* atm X 10-8
AH'298, kcal/gatom
Av P, atm X 10-0
AH029s,
% av dev
kcal/gatom
20.01 21.69 24.92 29.37
192.2
17.75 17.87 18.03 17.50
64.16 64.22 64.20 64.28
17.70
1.5
64.24
8.40 10.27 11.42 14.30 16.30 8.22 22.33
273.6
9.789 10.32 10.08 8.807 9.330 4.129 9,240
64.29 64.16 64.22 64.56 64.42
9.60
4.7
64.35
7.25 8.60 4.25 8.10 8.41 7.25 13.03
510.2
4.460 4.564 2,940 2.633 2,542 1.922 2.847
64.29 64.23 65.33 65.60
4.51
1.1
64.26
... 64.44
... ... 65.40
a The orifice areas in square centimeters for t,he cells a t 50' were: H, 0.004955; I, 0.005750; J, 0.008434; K, 0.010604; L, 0.010310; M, 0.012156; N, 0.014022. Expansion-of-orifice corrections were made using the coefficient of thermal expansion of 7.8 x 10-8 deg-l.a
Some gallium was lost in handling before weighing. Data from this run are shown only for completeness because an air leak developed during the run. These data are not included in the over-all averages. Cell M was broken and was replaced by a similar new Error made in weighing before run so cell designated as M*. Low mass loss due to partial plugging of orifice by foreign material. Cell J was broken and was replaced by a similar new cell designated as J*. Cell K was broken mass loss could not. be calculated. and was replaced by a similar new cell designated as K*. Cell &I* was broken and was replaced by a similar new cell designated as M:. There is no apparent reason for this low result, but it was rejected because it was considered to be statistically improbable. These data are not included in the averages.
'
'
Table IV : Third-Law Evaluation of Selected Gallium Dataa
Investigator
This work
No. of observations
AH029s, koal/g-atom
56
Method
64.62 4I 0.22b
Alcock, et a/."
9 3
64.83 65.04
Cochran and Fosterz*
6
68.964I0.19
Harteckzs Blunir and Searcyzo
20 53
66.30i.l.10 6 5 . 4 4 f 0.23
Speiser and Johnston?'
19
6 4 . 8 6 2 ~1.10
Calculated with the use of (Go - H0298)/Tfunctions by Hultgren, et aZ.8
'peiser and Johnston;21 the agreement is good' Third-
law AH029s values for vaporization are tabulated in Table IV with values by Alcock, et al.," Cochran and Foster,22H a r t e ~ k ,Rfunir ~ ~ and and Speiser and Johnston.20 The value obtained from this study
Multiple effusion Effusion Transport ation Recording effusion Effusion Torsioneffusion Effusion
Container material
Alumina Beryllia Beryllia Alumina Quartz Graphite Quartz
' Average deviation.
(20) Z.A. Munir and A. W. Searcy, J. Electrochem. SOC.,111, 1170 (1964). (21) R. Speiser and H. L. Johnston, J. Am. Chem. SOC., 75, 1469 (1953). (22) C. N. Cochran and L. M. Foster, J. Electrochem. Sac., 109, 144 (1962).
Volume 70,Number 9 September 1066
G. J. MACUR,R. K. EDWARDS, AND P. G. WAHLBECK
2964
65.0 64.9
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1.10 O R I F I C E A R E A C m 2 X lo2 Figuie 4. Variation of AH0298 of vaporization for gallium with orifice area.
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___o_ THIS
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The Journal of Phyeical Chenttktry
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96 1000/To K
Figure 5. Comparison of vapor pressure data for gallium.
1
ENTHALPIES OF VAPORIZATION OF INDIUM AND GALLIUM
2965
kcal/g-atom, respectively. Evaluation of this work agrees with the cfher values cited with the exception 1.25 other literature values leads to 57.51 of the values by Cochran and Foster22and H a r t e ~ k . ~ with ~ and 65.00 sfi 0.5 kcal/mole, respectively. Munir and Sercy20have discussed the discrepancy with the value of Cochran and Foster,22and Speiser and Acknowledgments. The authors gratefully acknowlJohnston2l have discussed the discrepancy with the edge the support of this research by the Air Force value of HarteckZ3 A value of 65.00 0.5 kcal/mole Office of Scientific Research through Contract No. has been chosen based on the average of all values A F 49(638)-346 and the Atomic Energy Commission weighted according t o the number of observations exthrough Contract KO. AT(l1-1)-1029. G. J. AI. clusive of those by Cochran and Fosterzzand those by wishes to thank the Illinois Institute of Technology Harteck.23 for a fellowship for the 193-1959 academic year. Conclusions. A multiple-effusion cell apparatus has G. J. AI. and R. I
