Sodium Sulfite

The sodium salt of sulfurous acid, providing the same sulfite preservative chemistry as Sodium Metabisulfite but with a different SO2 release profile and lower acidity. Selected in applications where the pH-shift of Sodium Metabisulfite would be problematic.

White crystalline powder, hygroscopic. Highly water-soluble (approximately 250 g/L at 20 °C). One gram releases approximately 0.5 grams of sulfur dioxide on acidification.

We supply food-grade, pharmaceutical-grade, and industrial-grade Sodium Sulfite from manufacturers in China holding ISO, Halal, Kosher and other certifications relevant to the product and production.

Common market grades include Standard Food Grade (FCC compliant), Pharmaceutical Grade meeting BP/USP specifications for use as an antioxidant in injectable and oral formulations, Photographic Grade for film and print developer preservation, and Industrial Grade for pulp bleaching, water treatment, and dye manufacturing.

Bulk and reduced-MOQ shipments. Batch-level COA covering assay, iron, heavy metals, and microbiology.

Sodium Sulfite (Na2SO3) is the simple disodium salt of sulfurous acid and the most basic member of the sulfite preservative family. The compound is functionally equivalent to other sulfites as a preservative but differs in pH effect: a 1 percent solution of Sodium Sulfite has pH approximately 9 to 10, whereas a 1 percent solution of Sodium Metabisulfite has pH approximately 4 to 5.

Industrial production proceeds by reaction of sodium hydroxide or sodium carbonate with sulfur dioxide gas in stoichiometric excess of alkali, followed by crystallization. Careful control of the alkali-to-acid ratio determines whether the product is Sodium Sulfite, Sodium Bisulfite, or Sodium Metabisulfite.

Regulated as E221 in the EU within the sulfite family (E220 through E228), classified as Generally Recognized as Safe by the U.S. FDA with the same restrictions on raw fruit and vegetable use, and approved by JECFA with the group Acceptable Daily Intake of 0.7 mg per kg body weight expressed as sulfur dioxide. Residual sulfite labeling requirements apply identically across all sulfite ingredients.

The molecule's antimicrobial, antioxidant, and enzymatic-browning-inhibition functions are identical to other sulfite forms; the practical difference is the alkaline solution pH which makes Sodium Sulfite the preferred sulfite form in pharmaceutical injectable formulations (where acidic pH would degrade active ingredients) and in boiler feedwater (where alkaline pH protects against corrosion).

Strategic positioning is concentrated in pharmaceutical and industrial applications. Food use is smaller than Sodium Metabisulfite because most food preservation applications require low pH to activate the sulfite preservative function, and Sodium Metabisulfite delivers both sulfite and acidity in a single ingredient.

• Dried fruit and vegetable preservation: lower-acidity alternative to Sodium Metabisulfite
• Sugar refining: clarification of sugar syrups and decolorization
• Wine and beer preservation in markets where Sodium Sulfite is the preferred sulfite form
• Pharmaceutical antioxidant in injectable and oral formulations
• Photographic developer and fixer preservation
• Pulp bleaching in paper manufacturing
• Water treatment: oxygen scavenging in boiler feedwater systems
• Textile and dye manufacturing: reducing agent in vat dyeing
• Leather processing: dehairing and tanning
• Chemical synthesis intermediate