749.    DURROVSKAYA, A., AND KOBOZEV, N. I.  [Adsorption Properties of Promoted Iron Oxide in Relation to the Distribution of the Promoter in the Oxide Form of Ammonia Catalysts.]  Ata Physicochim., U.R.S.S. (in German), vol. 4, 1936, pp. 841-858; Chem. Abs., vol. 30, 1936, p. 7987.

     Adsorption isotherms of O₂ on pure Fe₂O₃ and on Fe₂O₃ that contained 10% Al₂O₃ were determined at –190° and +400°.  X-ray photographs of Fe₂O₃ samples heated to various temperatures showed that the adsorbing power of Fe₂O₃ decreased as the crystals became larger.  The kinetics of O₂ desorption from promoted and nonpromoted Fe₂O₃ studied at various temperatures, showed that the activation energy of desorption is independent of the presence of a promoter and averages 10,860 cal.  Thus, even in the case of the promoted Fe₂O₃, the adsorption centers are the Fe₂O₃ mols.  It was found that the addition of 10% Al₂O₃ to Fe₂O₃ lowers the specific adsorption of O₂.  This proves that the dissolved Al₂O₃ is strongly adsorbed on the surface of the Fe₂O₃ crystals.  From the data found, the equilibrium constant between the dissolved and adsorbed Al₂O₃ was calculated and an equation derived.  Using this equation, it was shown that with relatively large Fe₂O₃ crystals, 1% Al₂O₃ shielded 50% of the surface of the Fe₂O₃.