177a.    --------------. [BEECK, O.] Catalysis and the Adsorption of Hydrogen on Metal Catalysts.  Advances in Catalysis, Academic Press, Inc., New York, vol. 2, 1950, pp. 151-195.

                   Review includes a discussion on adsorption, surface of metal catalysts, H₂ adsorption isobars and the effect of sintering, heat of adsorption of H₂ on Ni, Fe, W, metal films partially covered with other adsorbed gases, sintered films and the criterion for mobility as well as Frankenburg’s experiments and the experiments of Roberts.  The following conclusions are reached:  The adsorption (chemisorption) of H₂ on clean metal surfaces is almost always accompanied by absorption of H₂ into the interior of the structure.  This absorption is a slow activated process and has in the past been mistaken for activated adsorption of H₂ on the surface.  The heat of absorption of H₂ is considerably lower than the heat of chemisorption.  The heats of chemisorption of H₂ on Ni and Fe are nearly identical and decrease from about 30,000 cal. for the sparsely covered surface to about 18,000 cal. for the completely covered surface.  The heat of chemisorption on W decreases from 45,000 cal. to about 13,000 cal. as a function of surface coverage.  The lower values of Frankenburg for higher surface coverage can be satisfactorily explained on the basis of surface impurities on Frankenburg’s W powders.  The heat of adsorption of H₂ on metals has been found to be constant over wide temperature ranges (for Ni by Beeck and coworkers from –183° to 23° C., by Frankenburg on W for temperatures up to over 500°).  The activation energy for the chemisorption of H₂ on all metals studied is extremely low.  Chemisorbed H₂ atoms on Ni are mobile.  They are able to migrate from one crystallographic site to another site even at –183° C.  On Fe, H₂ atoms are mobile at room temperature but are not mobile at –183° C.  The decrease of heat of adsorption as a function of surface coverage can be explained satisfactorily by interaction of the adsorbed atoms with each other.  While the surface of clean metal films appears to be homogeneous with regard to heat of adsorption and surface coverage (the latter within the limits of size of different crystallographic sites), the rate of hydrogenation of ethylene is markedly dependent on the crystal parameter.  On Ni, chemisorption of H₂ is still taking place at 20° K.  The true extent of metal surfaces cannot be measured by the B. E. T. method using N, since N is chemisorbed at –196° C.  The H₂ adsorption at this temperature measures the surface more accurately and is in close agreement with the chemisorption of CO at both liquid N and room temperature and with the van der Waal’s adsorption of krypton.  18 references are given.

                    -------------.  See abs. 3712.