The molecular formula MgSO4 .7H2O, zmolecular weight 246.47,appearance colorless needle acicular or slanting column crystal, the relative density 1.68. Qualitative indexHG/T 2680-95 name of index index main content (MgSO4 .7H2O,) 99% Fe 0.01% Insoluble water 0.1% Cl 0.3% Usages: Used in the printing and dying thin cotton fabric, the silk, as the filler for heavy loader of cotton and silk cotton kapok product. And used for the purgative on the medicine, the magnesium fertilizer in the agriculture, used in producing the fresh yeast, the monosodium glutamate and serves as stabilizer of the calcium hydrogen phosphate in producing dentifrice .