1145.    -------------.  [GARNER, W. E., AND KINGMAN, F. E. T.] Heat of Adsorption of Hydrogen and Carbon Monoxide on Zinc and Chromium Oxide Catalysts.  Trans. Faraday Soc. vol. 27, 1931, pp. 322-333; Chem. Abs., vol. 25, 1931, p. 4758.

       Heats of adsorption and adsorptive capacity of H2 and CO on ZnO, Cr2O3, and ZnO-Cr2O3 catalysts were measured by means of a vacuum calorimeter previously described.  The heats of adsorption ranged from 25-10 cal. per gm. mol., the maximum value being obtained for the first small quantities adsorbed.  The heat of adsorption of CO on ZnO is the same as that of ZnO-Cr2O3, although the adsorptive capacity is much greater in the latter case.  This indicates that the greater efficiency of the mixed catalyst is due to an enlargement of the internal area of the catalyst.  Cr2O3 and ZnO did not adsorb H2 strongly as the mixed catalyst, but the Cr2O3 adsorbed CO very readily.  At low temperatures H2 and CO are mainly adsorbed without disruption of the molecules, but at 100° and over the adsorption was irreversible, and the gas could only be removed as water and CO2, respectively, by heating to high temperatures.  In the case of the mixed catalyst, the rate of evolution from 1 type of adsorbed film was greater than the rate of condensation to a second type of film, so that on heating to about 100° of a catalyst that had adsorbed H2 at 20°, there occurred an evolution of H2 which was followed by slow readsorption.