Copper Molybdates

The salt 4CuO.3MoO₃.5H₂O is a heavy green amorphous substance which is obtained by precipitating a boiling solution of a copper salt with ammonium molybdate. By boiling copper carbonate with excess of molybdic acid and water, fine blue needles of the compound CuO.3MoO₃.9H₂O are stated to crystallise on cooling. Copper ammonium molybdates, CuO.(NH₄)₂O.5MoO₃.9H₂O and CuMoO₄.2NH₃.H₂O, and the compound (NH₄)₂Cu(MoO₄)₂.2NH₃, have been described.