Sodium pyrosulfite is white or yellow crystalline powder or small crystals, with a strong SO2 odor, specific gravity of 1.4, soluble in water, acidic aqueous solution, and strong acid contact with SO2 emitted corresponding salts, long-standing air, then oxidized to Na2S2O6, so the product can not last. Higher than 150 degrees Celsius, that is, decomposition of SO2.

Application
The pharmaceutical industry is used for the production of chloroform, phenylpropanone and benzaldehyde. Rubber industry is used as coagulant. The printing and dyeing industry is used as a dechlorination agent for cotton cloth after bleaching, and a cotton textile finishing agent. The leather industry is used for leather treatment, making the leather soft, plump, tough, waterproof, folding, wear-resistant and other properties. Chemical industry is used to produce hydroxyvanillin, hydroxylamine hydrochloride and so on. Photosensitive industries are used as developing agents.
1. It is used as bleaching agent, mordant, reducing agent, rubber coagulant, organic synthesis, pharmaceutical and perfume.
2. It is used as chromatographic reagent, preservative and reducing agent, and used in dye and pharmaceutical industry.
3. The pharmaceutical industry is used to produce chloroform, phenylpropanesulfone and benzaldehyde. 
4. The rubber industry is used as coagulant. 
5. Dyeing and printing industry is used as dechlorination agent of cotton fabric after bleaching and auxiliary agent of cotton cloth scouring and refining.
6. Leather industry used in leather processing, can make leather soft, plump, tough, waterproof, folding resistance, wear resistance and other properties. 
7. Chemical industry is used to produce hydroxyvanillin and hydroxylamine hydrochloride. 
8. The photographic industry is used as developer, etc.Molecular formulaNa2S2O5