Sodium metabisulfite is white or yellow crystalline powder or small crystals, with a strong smell of SO2, the proportion of 1.4, soluble in water, acidic aqueous solution, and acid contact with the release of SO2 and generates the corresponding salts, long home air, the oxidation As Na2SO4, so the product can not go far. Higher than 150 กใ C, the decomposition of SO2