3414.     TORPOV, N. A., PORAL-KOSHITS, E. A., AND BORISENKO, A. I.  [Solid Solutions in the System CoO-Fe2O3.]  Doklady Akad. Nauk. S.S.S.R., vol. 66, 1949, pp. 905-908; Chem. Abs., vol. 43, 1949, p. 7314.

        In an equimolecular mixture of the precipitated hydroxides, ferritization is complete on 40 hr. heating at 1,100° of pellets dried at 120° and pressed under 3,000 kg. per cm.²  The thermal dissociation 6 Fe₂O₃→ 4 Fe₃O₄+O₂, in mixtures with CoO, is less intense than in mixtures with NiO.  In the presence of excess CoO, the product obtained is porous, and contains, on microscopic examination, 2 phases, 1 dark gray, the other dark yellow.  The amount of the former decreases with decreasing CoO.  With increasing Fe₂O₃ content, the color of the crystals seen in specimens etched with HNO₃ changes from dark yellow in the equimolecular composition to yellow for 2 CoO+5 Fe₂O₃. With further increasing excess of Fe₂O₃, a new, light phase appears along with the yellow crystals, attaining 45-50% in CoO+6Fe₂O₃.  By X-ray examinations, free Fe₂O₃ is present in samples of the composition CoO+3Fe₂O₃ and higher Fe₂O₃ contents. The pure spinel structure of CoO+Fe₂O₃ persists up to Fe₂O₃, contents corresponding to 2 CoO+5 Fe₂O₃.  With excess CoO, from 3 CoO+2 Fe₂O₃ upward, CoO lines appear along with those of the spinel CoO Fe₂O₃.  The latter is consequently, the only compound occurring in this system.  Fe₂O₃ is soluble in this ferrite to the extent of 1.5 mol. per mol. ferrite at 1,100°.  CoO is not soluble in the ferrite.