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.