Sodium pyrosulfite is a white or yellow crystalline powder or small crysta l, with strong SO2 smell and specific gSodium pyrosulfite is a white or yellow crystalline powder or small crystalravity of 1.4. It is soluble in water and the aqueous solution is acidic. When contacting with strong acid, SO2 will be released to generate corresponding salts. If it is kept in the air for a long time, it will be oxidized to na2s2o6, so the product cannot be kept for a long time. Above 150 ℃, SO2 will be decomposed.