... Purity(Na2S2O5): 96% Min 3.SO2 Content: 65% Min 4.CAS No.:7681-57-4 sodium metabisulfite (1)Molecular formula ... : Na2S2O5 (2)CAS No.: 7681-57-4(3) Physical appearance: white or ... powder(4)Specification:Main Content: 96%min, Water Insoluble: 0.05%max, Iron: 50ppm max, Pb: 10ppm max, ... As: 2ppm max ,pH: 4.0-4.6(5)Bag marks:Sodium metabisulphite, N.W.: ...