566.    CHUFAROV, G. I., AND AVERBUKH, B. D.  [Reduction of Iron Oxides by Gaseous Reducing Agents.  II.  Rate of Reduction of Magnetic Iron Oxide by Hydrogen.]  Jour. Phys. Chem. (U.S.S.R.), vol. 5, 1934, pp. 1292-1298; Chem. Abs., vol. 29, 1935, p. 5336.

      Samples of magnetic iron oxide of natural origin and prepared from piano wire both show on reduction strongly autocatalytic effects.  The initial speeds of reduction are greater the greater the temperature, 350°-900°, but above 600° the velocity of reduction falls off very quickly with time and the curve for 800° crosses that for 400° and 600° at about 70% reduction.  Above 800° this effect again is less marked.  Piano wire magnetite shows this effect much more pronouncedly than does natural magnetite.  The micropore and ultrapore structures are also different on reduction.  Reduction proceeds in 2 stages, first to FeO then to Fe.  Most rapid, about 60 minutes, 90-100% reduction is obtained at about 600° C.