Sodium metabisulfite is a white or yellow crystalline powder or small crystal with a strong SO2 odor, a specific gravity of 1.4, soluble in water, and the aqueous solution is acidic. When it is in contact with a strong acid, it releases SO2 to form a corresponding salt. When it is left in the air, it oxidizes. It is Na2S2O6, so the product cannot be stored for a long time. Above 150 degrees Celsius, SO2 is decomposed. Other name:Sodium pyrosulfite Quality standard:FCCV/E223/USP CAS NO.:7681-57-4 HS CODE:28321000 M.F.:Na2S2O5 Specification:Industry grade/Food grade Appearance:White crystalline powder em Food Grade Industry Grade Purity ( As Na2S2O5) 98.0% min 96.0% min Sulfur Dioxide( SO2) 65.0% min 65.0% min Arsenic ( As ) 0.0002% max - Heavy metals ( As Pb ) 0.0005% max - Selenium (Se ) 0.0005% max - Iron (Fe) 0.001% max 0.002% max Water insoluble 0.02% max 0.05% max PH value : 4.0-4.8 4.0-4.8 Remark : Conformed with FCCV and E223 Standard