... metabisulfite 2.White or light yellow powder 3.purity:97%, 98% Sodium metabisulfiteCAS No 7681-57-4Molecular Formula Na2S2O5Molecular Weight 190 ... Fe): 30ppm maxAppearance: White or yellowish Crystal PowderFood grade:Purity: 98.0% min Sulfur Dioxide: 66.0% min Water Insolubles: 0 ... , photographic chemical, leather, rubber, food, and brewing industry. Sodium Metabisulfite97%, 98%