Quality standardItem Standard Food gradeIdentification in accordance with standardAssay% 98.0 - 102.0 Loss on dry % 0.30 max Reduzate % 0.50 max PH 6.2 -7.8 Sulfate % 0.05 max Chloride % 0.07 max Pb u g/g 1 maxArsenic salt u g/g 2 max Heavy metals u g/g 10 max Appearance of solution (1.0g, 10ml water) colorless, almost clear