3413.     TORPOV, N. A., AND BORISENKO, A. I.  [Solid Solutions in the System NiO-Fe2O3.]  Doklady Akad. Nauk. S.S.S.R., vol. 63, 1948, pp. 705-708; Chem. Abs., vol. 43, 1949, p. 4552.

        (1) Thermograms of Ni₂O₃ show 3 endothermal effects, the 1^st 2, at 180° and 340°, corresponding to loss of hygroscopic and crystal H₂O, respectively, the 3d, at 815°, to Ni₂O₃→2 NiO+1/2 O₂.  On account of this dissociation, it is irrational to use Ni₂O₃ to produce Ni ferrite.  (2) Firing NiO+Fe₂O₃ mixtures prepared by drying the precipitated hydrates and pressing under 3,000 kg. per cm.², at high temperatures is accompanied by deoxidation of the Fe₂O₃; thus, with the molecular ratios NiO:  Fe₂O₃=2:3, 1:3, and 1:5, the amount of FeO after 3.5 hr. firing at 1,100°, 1,200°, 1,300°, 1,500°, was, respectively, 0, 0.70, 1.75, and 3.18; 0, 0.66, 2.67, 5.46; 0.08, 0.86, 4.32, 5.88%.  (3) Products obtained by 40 hr. firing of NiO+Fe₂O₃ mixtures at 1,100°±10° showed, in petrographic examination, 1-phase structure only at the initial molecular ratios 1:1 and 2:3, at the latter ratio, crystallization of the ferrite is somewhat less distinct.  With the molecular ratios 3:2, 2:1, and 3:1, product shows 2 phases, one of which is identified as Ni ferrite, the other NiO.  Products of mixtures 1:2, 2:5, and 1:3 are equally 2-phase.  (4) Debyegrams show disappearance of the Fe₂O₃ lines in the 2:1 product, and also of NiO lines in the 1:1 and 2:3 products.  Combination of the results shows that the 3:1, 2:1, and 3:2 products are mixtures of Ni ferrite and NiO, 1:1 is the pure ferrite, 2:3 is a solid solution of Fe₂O₃ in Ni ferrite, whereas 1:2, 2:5, 1:3, and 1:4 are all mixtures of that solid solution and Fe₂O₃.