Oct., 1956
1465
NOTES
experiments with such a centrifuge it should be possible to measure molecular weights14if the necessary activity data are available, or, for substances of known molecular weight, one may obtain ratios of activity coefficients16 at two different concentrations. Acknowledgments.-It is a pleasure to thank Professors J. W. Williams and L. J. Gosting for their criticism of this manuscript. Financial support to make this investigation possible was supplied by the U. s. Public Health Service (G4196-C). Grateful acknowledgment is hereby recorded. (14) J. W. Beams. H. M. Dixon, 111, A. Robeson and N. Snidow, THIEJOURNAL, 69, 915 (1955). (15) J. S. Johnson, K. T. Kraus and T. F. Young, J . Am. Chsm. Soc., 1 6 , 0 (1954).
THE PHOTOSENSITIZED OXIDATION OF CARBON MONOXIDE ON CUPROUS OXIDE’ BY WILLIAMM. RITCHEY AND JACIC G. CALVERT~ The Mcpherson Chemical Laboratory, The Ohio State Ulziuersity. Columbus, Ohio Received M a y 17, 1066
Photosensitization of the oxidation of CO on Cu20 has been observed in this work. Significant evidence has been obtained for the importance of electron-reactant interaction at the Cu20surface in a rate-determining step of the reaction. The composition, surface area and electrical properties of the catalyst samples used in the study are summarized in Table I. The photochemical rate data for varied reactant pressures and the different catalyst samples are shown in Table 11. Comparison of reaction rates in consecutive runs at a given light intensity (within a pair of horizontal lines in Table 11)is necessary to avoid the complications of arc aging and possible catalyst structural changes which may result from prolonged reactions.
TABLE I1 PHOTOCHEMICAL RATESOF CO OXIDATIONAT 25’ WITH VARIOUS REACTANT PRESSURES AND s- AND Sb-DOPED CuzO SAMPLES Run
1 2 3 4 5
Rcon, mm./ 6 hr.
sample
Cur0
Irrad. time, hr.
Por, mm.
Pco, mm.
d d d d d
6.00 6.00 0.00” 6.00 6.07
162.5 200.3 164.1 160.2 319.3
80.8 42.2 39.5 40.8 83.5
0.504 .546
d e e b c
6.00 6.00 6.00 6.00 6.00
80.6 79.9 80.7 79.7 80.1
20.1 19.4 19.7 21.0 20.2
.542 .400 .424 .432 .332
a
6.00 6 00 5.00 6.07 2.00 6.05 6.00 6.00 6.00 6.00
80.2 80.3 79.9 80.5 78.7 80.2
19 7 19.8 21.0 19.2 20.3 20.0 20.4 20.7 19.0 81.1
.365 ,313 ,339 ,321 ,267 .252 ,294 ,260 ,336 .264
.001 .504
.589 ------------------------
8 9 10 11 12
------------------------16 17 18 19 20 21 22 23 24 25
d d d d e b c d d
80.0 79.6 80.1 80.0
----------------L-------
d 4.00 81.1 20.8 0 .186 3Ib d 4.00 79.8 21.7 .025 10 Dark run; time that the reactants were in contact with the CuzO was the same as in the 6 hr. photochemical runs. b A glass filter was added in this run. It removed 89% of the ultraviolet light X
