853.    EUCKEN, A., AND HUNSMANN, W.  [Calorimetric Study of Physical and Activated Adsorption of Hydrogen on Nickel.]  Ztschr. Physik. Chem., vol. B 44, 1939, pp. 163-184; Chem. Abs., vol. 34, 1940, p. 666.

     Heat of adsorption of H₂ on Ni was studied calorimetrically, 20°-273° K.  Desorption was also measured in the same temperature range with a hot-wire manometer.  2 heats of activation for desorption were detected:  1 corresponds to 14% of the adsorbing centers and amounts to 9-10 keal. per mol; the other accounts for the remaining 86% and is 18-22 kcal. per mol.  The heat of adsorption increases linearly from 4-21 kg.-cal. per mol.  The van der Waals heat of adsorption is about 800 cal. per mol. and depends strongly on the density of coverage of the surface.  Low-temperature tunnel effects could not be detected.

      EVANS, G. M.  See abs. 3657.