Sodium Metabisulfite is also named Sodium Pyrosulfite, Sodium Metabisulphite is white or slight yellow crystalline powder, with strong smell of SO2, the proportion of 1.4, soluble in water, aqueous solution of Sodium Metabisulfite is acidic, Sodium Metabisulfite contacts with strong acids, released SO2 and generates sodium sulfate, commonly known as Glauber's salt. For a long time in the air, Sodium Metabisulfite can be oxidized into Na2S2O6, so Sodium Metabisulfite can not be stored for a long time. Above 150 degrees Celsius, Sodium Metabisulfite can decompose of SO2. Soluble in water and glycerin, slightly soluble in ethanol. Soluble in water, Sodium Metabisulfite generates into stable sodium bisulfite, pH under 1% aqueous solution ranged from 4.0 to 5.5.