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Ammonium heptamolybdate is easily prepared by dissolving molybdenum trioxide in an excess of aqueous ammonia and evaporating the solution at room temperature.
A 2230 (OTTO) Ammonium molybdate tetrahydrate ACS reagent, 81.0-83.0% MoO3 basis Cas no 12054-85-2 - used in the following processes as a precursor in the generation of calcium molybdate (CaMoO4) spherulites.