... the addition of arsenic and heavy metals in solution purification agents, filtration, evaporation, cooling crystallization, centrifugal separation, drying. Used as food ... %maxFe0.002%maxAs0.0002%maxWater-insoluble0.04%maxHeavy Metal0.005%max Molecular formula(NH4)2SO4Molecular weight132.13Element CompositionIf pure substance, nitrogen ...