Ammonium metavanadate is a white solid, although samples are often yellow owing to impurities of V2O5. It is an important intermediate in the purification of vanadium. Ammonium metavanadate is a white crystalline powder. Slightly soluble in water and denser than water. Decomposes at 410°F. May release toxic fumes. Moderately toxic. An irritant. Used as a dryer for paints and inks, and for dyes. Loses ammonia upon heating.