Zinc Molybdates

The anhydrous normal salt, ZnMoO₄, is obtained as microcrystalline needles by fusing together sodium molybdate (2 parts), zinc chloride (3 parts), and sodium chloride (6 parts), and extracting with hot water. On addition of a zinc salt to a solution of an alkali molybdate, an amorphous precipitate of zinc molybdate is formed, which on prolonged treatment with hot water assumes the crystalline form and yields fine white transparent needles of the mono-hydrate ZnMoO₄.H₂O. The crystals are slightly soluble in water, readily soluble in acids. On heating, the compound loses water, but is not completely dehydrated at 100° C. An ammoniated compound, Zn(NH₃)₂MoO₄.H₂O, has been described.

Zinc paramolybdate has not been prepared. A solution of ammonium paramolybdate, when treated with a zinc salt, yields a white, insoluble double salt, of composition 2(NH₄)₂O.ZnO.7MoO₃.15H₂O.