MICHAEL HOCHAND HERRICK L. JOHNSTON
1184
TABLE I Mass
evapd. mg.
Atom % Ni
Metal deposited on top
Activity a t 0' (arbitrary units) ka
Surface Specific area, activity a t cm.2 O', k~ = k / A
11.77 100 Ni 4521 5-19 9.3 15.7 87.4 Cu 5815 418 13.9 15.7 74.2 Cu 4563 550 8.3 12.55 67.0 Cu 4452 509 8.8 11.3 63.0 Ni 6582 680 9.7 15.15 18.3 Cu 4563 695 6.6 15.8 0 CU 8.314 5300 7 ,028 a The k as h':re specified - lo6 k' where k' is defined by -dP/di = k' .PH*= k' (2P, 7 P0)/2. P is the total pressure a t tJimet, and POis the initial pressure. t is in seconds.
Summary The above experiments show a simple means of obtaining homogeneous alloy films for catalytic work. The results are in approximate agreement
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with those of Hall and Emmett both as regards the variation of activity with alloy composition and the near constancy of the activation energy. They suggest that the presence of unreduced oxide in the bulk catalyst does not appear to be essential to the rather high activities (compared to that of pure Ni) of some of the Cu-Ni alloy catalysts observed for the ethylene hydrogenation reaction. Acknowledgments.-Thanks are due to Dr. Colin T . H. Stoddart for many helpful djscussions. The appointment of &I,I
I
.27 1S I
0
THIS
RESEARCH
Q GRONOW
a
@ SCHOMATE 8
SCHWIETE NAYLOR
185.1G
The heat content of the sample plus container was 3 tinies as large as that of the A1203 sample itself and 3.5 times as large as that of the T h o 2 sample. The error in a single determination of the amount of Hg will be the same as previously, 0.085Y0.4 Combining two determinations, and remembering that the value being calculated is 1/3.5 as large as the measured value, the maximum error in the Hg determination will be 2 X 0.08 X 3.5 = 0.56%. The precision, using the same errors for the u-einht of the samDle and temperature as in the crevious paper14'will be ________ 4 0 . 5 6 ' $- 0.29' 0.052 = 0.63%. Using the liinits for any systematic errors as determined b e f ~ r e 0.3570, ,~ and the maximum uncertainty in the temperature scale14 0.3%, an accuracy for Not of within 1.3Y0 of the true values is obtained. The error? involved are the same as described p r e v i ~ u s l pwii , ~ h the exception of the error in the determination of the amount of Hg, because in this case the enthalpy is the difference of two large numbers. Comparison with Earlier Data.-Figures 1 and 2 show the plot of the mean specific heat, cp = Hot/t, from the different sources. The authors' data on & 0 3 agree well (within 1%) with those of Gronon. and Schn-iete5 and of Shomate and Kaylor.6 The agreement between the authors'
Temp., "C. Fig. 1.-Specific heat of L41JJJ.
+
1200
0
THIS
8
JAEGER
@
SOUTHARO
RESEARCH
8
VEENSTRA
1400
1600 1800 2uw 2200 Temp., "C. Fig. 2.--Specific heat of Tho,.
2430
data 011 Tho, and the data of Jaeger and Veenstra' and of Southards is also good (within 1%). Acknowledgment.-We wish to thank J. B. Zink, A. J. Lamantia and R. TV. Mattox, who helped us with the experimental work. ( 5 ) 11. E. Gronow and H. E. Schwiete, 2. anorg. Chem., 216, 183 (1933). (6) C . €I. Shomate and B. F. Naylor, J . A m . Chem. Soc., 67, 7 2 (1945).
(7) r'. M. ,Jaeger and W. A . Veenstra, Proc. Acad. Sci. Amsterdam. 37, 327 (1939). (8) T. C. Southard, J . A m . Chem. Soc., 6 3 , 3142 (1941).
