... used as fertilizer for rubber, palm trees ;2. In industries: used in tanning, porcelain, pigment, match, fireproof materials, Mg-salt, dyeing, medicine ... ,%,≤0.002Cl ,%,≤0.20As ,%,≥0.5Pb ,%,≤1Water insoluble,%,≤0.05 Magnesium Sulphate Heptahydrate fertilizer grade