2536. NYSTRÖM, E. H. R. [Ferromagnetic Iron Hydroxides and Oxides.] Swedish Patent 134,706, Mar. 4, 1952. Chem. Abs., vol. 47, 1953, p. 236.

Ferromagnetic Fe hydroxides obtained by precipitation of an Fe salt in a known manner is powdered by spraying the precipitate after washing out soluble salts into a drying atmosphere at a temperature not > 350° but high enough to dehydrate the hydroxide. Preferably an oxidizing atmosphere is used to oxidize the Fe to a higher valence.