3058.     SCHENCK, R., FRANZ, H., AND WILLEKE, H.  [Equilibrium Relations in the Reduction, Oxidation, and Carburization of Iron.  IX.  (10).  Influence of Foreign Oxides Upon the Equilibria.]  Ztschr. anorg. Chem., vol. 184, 1929, pp. 1-38; Chem. Abs., vol. 24, 1930, p. 1788.

        By means of an apparatus and a method previously described, the effect of MnO, ZnO, BeO, CaO, and Al₂O₃ on the equilibrium obtained during the reduction of Fe oxides by CO was studied.  The mixed oxides usually were obtained by the ignition of a mixture of the corresponding nitrates, which had been formed by evaporation of a solution.  In the case of the lime mixtures, mixed hydroxide and carbonates were ignited; the MnO mixtures were obtained by ignition of a mixture of oxalates.  The molecule mixtures used were Fe₂O₃:MnO 1:8, 1:1, 2:1 at 800°; Fe₂O₃:ZnO 1:1, 2:1, 1:10 at 700°, Fe₂O₃:Al₂O₃ 1:10, 1:3, 1.5:1 at 800°, 900°; Fe₂O₃:CaO 1:10, 1:1, 1.5:1, 3:1 at 900°, 1,050° Fe₂O₃:BeO 2:1, 1:1, 1:18 at 800°.  Even when the foreign oxide is not reduced by CO it affects the equilibrium of the Fe₂O₃ reduction if it (1) forms mixed crystals with the oxides of Fe, for example, Al₂O₃ with Fe₂O₃ or MnO with FeO; (2) forms compounds with the oxides of Fe as spinels or ferrites.  This is the case with Al₂O₃, MnO, ZnO, and particularly with CaO.  The mixed crystals become more difficult to reduce than the wüstite phase, the greater the content of foreign oxide.  Oxides that form neither mixed crystals nor compounds do not affect the equilibrium in any way, for example, BeO.  ZnO does not affect the wüstite-metal equilibrium.  The reduction of ZnO by CO is hampered by the presence of any oxide phase of Fe.