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 ., and (by extrapolation) 675 and 8.32 . 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.