Anhydrous sodium sulfite

  Anhydrous sodium sulfite

White crystal or powder, odorless, soluble in water, very slightly soluble in ethanol, and almost insoluble in ether. It is white hexagonal prismatic crystal, soluble in water (12.54g/100ml at 0°C; 283g/100ml at 80°C), it has a maximum solubility of about 28% at 33.4°C, and the aqueous solution is alkaline. It is slightly soluble in alcohol, insoluble in liquid chlorine and ammonia. It is easily oxidized into sodium sulfate when exposed in air, and decomposed into sodium sulfide in high temperatures. It is a strong reducing agent, generating sodium bisulfate when reacting with sulfur dioxide and generating the corresponding salts when reacting with strong acids.

English name: Sodium Sulfite Anhydrous

Molecular formula: Na2SO3   Molecular weight:126.04    CAS No.: 7757-83-7

Application: Anhydrous sodium sulfite has a wide range of application. It plays an important role in the pharmaceutical, papermaking, leather, printing and dyeing, plant fiber bleaching and food industries. It is also used as film developer, bleaching agent, deoxidizer in printing and dyeing industry, reducing agent for perfume and dyes, antioxidant additive in tanning leather industrial, lignin removal agent in paper industry, reducing agent for the production of metamizol, Aminophenazone and sodium aminosalicylate in pharmaceutical industry, reducing agent for production of dehydrated vegetables in food industry to prevent the deterioration and yellowing of green pigments in vegetables, as well as photographic coupler for determination of antimony, magnesium, copper, zinc, and phosphorus.

Items National Standard  Usual Values

Sodium sulfite content (Na2SO3) /%

≥96.0 ≥97.0
Iron content (Fe) /% ≤0.01 ≤0.001

Freebase content (Na2CO3) /%

≤0.60 ≤0.4
Heavy metal content (Pb) /% ≤0.001 ≤0.0005
Arsenic content (As) /% ≤0.0002 ≤0.0002
Clarity Passes test Passes test


Quality StandardHG/T 2967-2000

Premium Grade
First Grade
Sodium sulfite content (Na2SO3), % ≥97.0 ≥96.0 ≥93.0
Iron content (Fe), % ≤0.003 ≤0.005 ≤0.02
Insoluble matter content, % ≤0.02 ≤0.03 ≤0.05

Freebase content (Na2CO3), %

≤0.10 ≤0.40 ≤0.80
Sulfate content (Na2SO4), % ≤2.5
Chloride content (NaCl), % ≤0.10

Items Usual Values

Sodium sulfite content (Na2SO3), %

Iron content (Fe), % ≤0.001
Freebase content (Na2CO3), % ≤0.05
Heavy metal content (Pb) /% ≤0.0001
Arsenic content (As) /% ≤0.0001
Clarity   Passes test
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