Ferric ortho-antimonate, FeSbO₄

Ferric ortho-antimonate, Fe₂O₃.Sb₂O₅ or FeSbO₄, is obtained in the heptahydrated condition, 2FeSbO₄.7H₂O, by addition of excess of a concentrated solution of a ferric salt to a boiling solution of sodium antimonate. The di-antimonate, Fe₂O₃.2Sb₂O₅.11H₂O, prepared by precipitating iron ammonium alum with potassium antimonate, is a yellow salt which becomes anhydrous at 100° C.