Ferric Molybdate, Fe₂(MoO₄)₃.42H₂O

Ferric Molybdate, Fe₂(MoO₄)₃.42H₂O, is obtained as a yellowish- brown precipitate when an aqueous solution of normal sodium molybdate is treated with ferric chloride. If the di- or para-molybdate is so treated, a yellow precipitate, of composition Fe₂O₃.5MoO₃.aq., separates; with the tetramolybdate a pale yellow precipitate, of composition Fe₂O₃.10MoO₃.110H₂O, is obtained on evaporation. Complex salts, of the type 3R^•₂O.Fe₂O₃.12MoO₃.20H₂O (R^• = NH₄, K), similar to those of aluminium, chromium, and cobalt, have been described.