Standard:
Quality standard 
Item standard
Industry grade: food grade 
Identification in: accordance with standard 
Assay: ≥98.0%, 98.0 - 102.0%
Loss on dry: ≤0.50%; ≤0.30%
Reduzate: ≤0.70%; ≤0.50%
pH: 6.2 - 7.8; 6.2 -7.8
Sulfate: ≤0.05%; ≤0.05%
Chloride: ≤0.07; ≤0.07
Pb: ≤2μg/g; ≤1μg/g 
Arsenic salt: ≤2μg/g; ≤2μg/g 
Heavy metals: ≤10μg/g; ≤10μg/g
Appearance of solution (1.0g, 10ml water): colorless, almost clear