Process for producing ammonium metatungstate

A process is provided for producing ammonium metatungstate comprising fluid bed roasting ammonium paratungstate at a temperature over the range of about 275 DEG C. to 305 DEG C. for a time at least sufficient to provide a roasted product in the form of a precursor of ammonium metatungstate, forming an aqueous slurry of the precursor and digesting the precursor at a pH of about 3 to 4 for a time at least sufficient to effect substantially complete dissolution of said precursor, filtering the digested slurry to produce a clear filtrate, and further processing the clear filtrate by evaporation to provide crystals of substantially pure ammonium metatungstate.