Magnesium Sulphate heptahydrate, Purity:98% Fertilizer grade Specification:MgSO4.7H2O:99.5% minMgSO4 48.59% minMgO 16. ... (As) 0.0002% maxInsoluble 0.01%maxUse: --Mainly used in fertilizer, tanning, pringting and dyeing,activator,papermaking,plastic,porcelain,pigment matchmaking ... ,moisture. if you are interested in it,pls contat us. Magnesium Sulphate Heptahydrate