3338.     ---------------.   [TAYLOR, H. S., AND LIANG, S. C.]  Heterogeneity of Catalyst Surfaces for Chemisorption.  II.  Zinc Oxide-Chromic Oxide, Manganous Oxide-Chromic Oxide, Chromic Oxide Gel.  Jour. Am. Soc., vol. 69, 1947, pp. 2989-2991; Chem. Abs., vol. 42, 1948, p. 1793.

        As described in the previous paper in this series, the techniques of measuring chemisorption with increasing and decreasing temperatures at constant pressure were applied to a study of ZnO-Cr₂O₃ catalysts and Cr₂O₃ gel.  These substances reveal heterogeneity of surface.  MnO-Cr₂O₃ catalysts do not show desorption-readsorption phenomena on raising the temperature.  The isobar on decreasing temperature consequently was horizontal over a considerable temperature range.  The surface, nevertheless, exhibits a partial heterogeneity.  The criterion of “pumping-off at temperature” was shown to be doubtful in distinguishing van der Waals’ and chemisorption of H₂ in certain temperature ranges with these catalysts.