... .Monthly output: about 3000MT 4.CAS No.:7681-57-4 sodium metabisulfite (1)Molecular formula: Na2S2O5 (2)CAS No.: 7681-57-4(3) Physical appearance ... : white or slightly yellowish crystalline powder(4)Specification:Main Content: 96 ... 50ppm max, Pb: 10ppm max, As: 2ppm max ,pH: 4.0-4.6(5)Bag marks:Sodium metabisulphite, N.W.: 25kgs, G ...