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Sodium Metabisulphite


Sodium Metabisulphite 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 Metabisulphite is acidic, Sodium Metabisulphite contacts with strong acids, released SO2 and generates sodium sulfate, commonly known as Glauber’s salt. For a long time in the air, Sodium Metabisulphite can be oxidized into Na2S2O6, so Sodium Metabisulphite cannot be stored for a long time. Above 150 degrees Celsius, Sodium Metabisulphite can decompose of SO2. Soluble in water, glycerine and ethanol. Sodium Metabisulphite generates into stable sodium bisulphite, pH under 1% aqueous solution ranged from 4.0 to 5.5.

  • Molecular Formula: Na2S2O5
  • CAS No.: 7681-57-4
  • Other name: sodium metabisulfite, sodium pyrosulfite
  • Physical appearance: white or slightly yellowish crystalline powder

Sodium Metabisulphite is mainly used in chemical, pharmaceutical, rubber, leather, printing and dyeing, and other industries. Food grade Sodium Metabisulphite is used in food industry. In food industry, in order to improve the food colour, smell, taste and quality, as well as the demand to preserve, fresh and processing technology, food additives are often added. Sodium Metabisulphite is a kind of food additive, which is used as a preservative, antioxidant in food processing.

In pharmaceutical industry Sodium Metabisulphite is used for purification in chloroform, benzene propyl sulfonic and Benz aldehyde production; Sodium Metabisulphite is used for coagulant in rubber industry; Sodium Metabisulphite is used for antichlor in cotton bleaching, Cotton mill auxiliary and mordant in printing and dyeing industry; Sodium Metabisulphite is used for leather processing in tanning industry, Sodium Metabisulphite can make leather soft, plump and tough, and make leather own waterproof, anti folding, wear resistance properties; Sodium Metabisulphite can be used for the production of Hydroxyvanilline and Hydroxylamine Hydrochloride in chemical industry; Sodium Metabisulphite can be used as developer in photographic industry.


Se.No parameter Unit Standard Value Test Result Analytical Method Remark
1 Appearance White To Yellowish Crystalline Powder / Conform Visual /
2 Odor An Odor Of Sulfur Dioxide / Conform Smell /
3 Purity(Na2S205) % 97.0 min 97.91 Titrimetric /
4 SO2 % 65.3 min 65.86 Titrimetric /
5 Na2SO4 % 3.0 max Turbidimetric /
6 Iron(Fe) ppm 50.0 max 9.1 Colorimetric /
7 Lead(Pb) ppm 20.2 max 2.3 Polarographic/AAS /
8 Arsenic(As) ppm 1.0 max < 1.0 Polarographic/AAS /
9 Insolubility % 0.05 max 0.01 Gravimetric /
10 pH 4.0-4.8 4.5 pH Meter /

Sodium Metabisulphite Function

  • Preservatives
  • Antioxidants
  • Bulking Agent
  • Nutrient Retention Agent
  • Flour dough improver
  • Bleaching agent
  • Reducing agent
  • Coagulant
  • Antichlor
  • Mordant
  • Developer