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.