3066.     SCHENCK, R., AND WESSELKOCK, H.  [Activation of Metals by Addition of Foreign Substances.  I.]  Ztschr. anorg. Chem., vol. 184, 1929, pp. 39-57; Chem. Abs., vol. 24, 1930, p. 2035.

        Effect of CaO, MgO, MnO, and Al₂O₃ separately and Al₂O₃ and MgO jointly on the oxidation of Ni and Co at 900° in an atmosphere of CO₂ was studied.  The mixtures M:MO (1:10); M:Al₂O₃ (1:3); M:Al₂O₃:MgO (1:10:2) were usually prepared by reduction in H₂ of mixtures of nitrates or oxalates that had been precipitated together.  (See abs. 3055, 3057, and 3058).  The equilibria appearing after the addition of CO₂ at 900° were determined as previously described.  The activities of both Ni and Co were increased by the presence of the oxides in order CaO, MgO, MnO.  These oxides have the same crystal lattice as NiO and CoO.  The activity does not seem to be closely related to the similarity of crystal lattice constants of these oxides with those of Ni and Co.  The irregularities in the progress of the oxidation are attributed to the heterogeneous distribution of the reduced metal in the oxide.  This heterogeneity, which is most evident in the Co-MnO mixtures, is due to the fact that the mixed oxalates are not homogeneous.  Determination of the gaseous equilibrium by fractional oxidation (successive addition of small quantities of CO₂) offers a method for measuring the uniformity of distribution of the metal in the oxide as well as determining the areas containing metal of similar degree of dispersion.  This lack of uniformity may explain the centers of activity often met in mixed catalysts.  The mixtures Co-3 Al₂O₃ and Ni-3 Al₂O₃ exceed finely reduced Fe in activity.  The addition of MgO to these mixtures enhanced their activity.  The activation seems to be specific for O.  The general problem of the activity of metals toward specific elements is indicated by the observations reported.  When the O is transferred from the CO₂ to the metal, which is dispersed in the isomorphous oxide, it takes a position in the lattice occupied before reduction by O₂.  If it is desired to activate a metal toward N₂ the nitride of the metal should be dispersed throughout a stable isomorphous nitride and then reduced to metal.  The reasoning is carried over to activation toward S.