2272.     MICHEL, A., AND CHAUDRON, G.  [Stabilized Cubic Ferric Oxide.]  Compt. rend., vol. 201, 1935, pp. 1191-1193; Chem. Abs., vol. 30, 1936, p. 692.

        Solid solutions of varying amounts of NaFeO₂ in Fe₂O₃ were prepared by adding various amounts of aqueous NaOH to precipitated Fe(OH)₃, the product being reduced to Fe₃O₄, oxidized at 300° and then heated to 650°.  The Curie point decreased regularly with increasing content of Na₂O, while the side of the unit cube (a) increased with equal regularity, the figures for an oxide containing about 5% Na₂O being about 400° and 8.52 Å., and (by extrapolation) 675° and 8.32 Å. for pure Fe₂O₃.  The dissociability of Fe₂O₃ (into Fe₃O₄ and O₂) decreases rapidly with increase in Na₂O, and with 5% thereof it is virtually undissociable at 300°.  Though the content of Na₂O is reduced by hydrolysis in hot H₂O or by AcOH, no change in Curie point or a occurs until after reheating to 650°.  Solid solutions of other ferrites behave similarly, the limit solutions of those of Be, Ag, and K having Curie points at 220°, 270°, and 250°, respectively.