Ammonium molybdate tetrahydrate (also referred to as Ammonium heptamolybdate, chemical formula: (NH4)6Mo7O24)), appearing as a colorless solid. It can be manufactured through dissolving the molybdenum trioxide in excess amount of aqueous ammonia and evaporating the solution at the room temperature. It has many applications, e.g. as an analytic reagent for measuring content of phosphates, silicates, arsenates and lead; for the production of molybdenum metal and ceramics; for the production of dehydrogenation and desulphurization catalysts; for the fixing of metals; for electroplating; supplement in the crop fertilizer; as a negative stain in biological electron microscopy; as an analgesic in medical fields. May contain darkened ammonium molybdate crystals that are soluble in water.