Sodium Metabisulfite SYNONYM: Sodium Pyrosulfite FORMULA: Na2S2O5 M. W.: 190.10 CAS NO.: 7681-57-4 GRADE: tech. grade DESCRIPTION: white or light yellow crystalline powder. SPECIFICATIONS: CONTENT (SO2) 65.0% MIN. IRON (Fe) 0.005%MAX. INSOLUBLE IN WATER 0.05%MAX. PH VALUE 4.0-5.6 PACKING: in pvc plastic film with a polypropylene over bag. net weight: 25, 50, 1000kilograms per bag.