565.    CHUFAROV, G. I., AND LOKHVITZKAYA, A. P.  [Reduction of Iron Oxides by Gaseous Reducing Agents.  I.  Velocity of Reduction of Ferric Oxide by Hydrogen.]  Jour. Phys. Chem. (U.S.S.R.), vol. 5, 1934, pp. 1103-1113; Chem. Abs., vol. 29, 1935, p. 3901.

      Apparatus is described.  Artificial and natural Fe₂O₃ containing 98.6% Fe₂O₃, 0.35% Al₂O₃ and 1.1% SiO₂ were used.  For both, an autocatalytic character of the speed of reduction by H₂ was revealed sharply.  The 1^st stage, reduction to magnetite, is not autocatalytic.  The remaining stages, belonging to the type of intersurface reactions, proceed autocatalytically.  The anomalous course of the reduction curve above 600° is due to changes in the microporosity and ultramicroporosity of the solid product.  The rates of reduction at temperatures 300°-900° are shown by a series of 11 graphs for various conditions of particle size, degree of previous reduction, etc.  The porosity of the product is greater the lower the reduction temperature.