Description CAS#: 7681-57-4 | Formula: Na2S2O5 | Specifications: Assay 97.0 % - Min, Chloride 0.05 % Max, Heavy metals (as Pb) 0.001 % Max, Insoluble 0.005 % Max, Iron 0.002 % Max, Thiosulfate (%) 0.05 % Max