Ammonium metavanadate is the inorganic compound with the formula NH4VO3. It is a white solid, although samples are often yellow owing to impurities of V2O5. It is an important intermediate in the purification of vanadium.The compound is prepared by the addition of ammonium salts to solutions of vanadate ions, generated by dissolution of V2O5 in basic aqueous solutions, such as hot sodium carbonate. The compound precipitates as a colourless solidThis precipitation step can be slow.The compound adopts a polymeric structure consisting of chains of [VO3]-, formed as corner-sharing VO4 tetrahedra. These chains are interconnected via hydrogen bonds with ammonium ions.