ISO 9001:2000 certificate (MgSO4 .nH2O n=0-7) from crystalline to powder technical grade, feiilizer grade, food additive grade, pharm grade Appearance White small granular Main content 99.5% min MgSO4 48.59% min MgO 16.27% min Mg 9.81% min PH(5W/V%Sol) 5-8 Ferron(Fe) 0.0015% max Heavy metal (Pb) 0.001 %max Arsenic(As) 0.0002% max