Cobalt Trimolybdate, CoMo₃O₁₀.10H₂O

Cobalt Trimolybdate, CoMo₃O₁₀.10H₂O, separates in rose- coloured needles on evaporating the solution obtained by boiling cobalt carbonate and molybdenum trioxide with water.

A number of complex salts have been prepared. By interaction of a cobaltous salt with ammonium paramolybdate, a light red crystalline compound, which may be formulated (NH₄)₃H₇[Co(MoO₄)₆]5H₂O, has been isolated. Several sodium compounds, probably of the same type, have been described. A series of green cobaltimolybdates, corresponding to the aluminium and chromium salts, has been obtained by oxidation with hydrogen peroxide or ammonium persulphate of an aqueous solution containing cobaltous acetate and ammonium paramolybdate, or by the action of a permolybdate on a cobaltous salt. The ammonium salt, 3(NH₄)₂O.CO₂O₃.12MoO₃.20H₂O, yields green rhombic crystals. The potassium salt, 3K₂O.CO₂O₃.12MoO₃.15H₂O, is olive green, and only slightly soluble in water. The following salts have also been prepared: 2(NH₄)₂O.CO₂O₃.10MoO₃.12H₂O; 3K₂O.CO₂O₃.10MoO₃.11H₂O; 3BaO.CO₂O₃.9MoO₃.25H₂O.