Sodium Metabisulfite, Sodium Pyrosulfite, Sodium Bisulfite Anhydrous, Natrium Pyrosulfite, SMBS, E223, 7681-57-4

Sodium Metabisulfite, Sodium Pyrosulfite, Sodium Bisulfite Anhydrous, Natrium Pyrosulfite, SMBS, E223, 7681-57-4

General Information

• Chemical Name: Sodium Metabisulfite

• E Number: E223

• CAS Number: 7681-57-4

• Molecular Formula: Na₂S₂O₅

• Molecular Weight: 190.05 g/mol

• Other Names: Sodium Pyrosulfite, Disodium Disulfite, Metabisulfite, SMBS

Physical Properties

• Appearance: White crystalline powder (sometimes slightly yellowish)

• Odor: Faint sulfur smell

• Density: 1.48 g/cm³

• Melting Point: Decomposes at 150 °C (does not truly melt)

• Solubility: Highly soluble in water (540 g/L at 20 °C)

• Stability: Sensitive to air and moisture; must be stored in dry conditions

Chemical Properties

• pH in solution: 3.5 – 5 (acidic)

• Reactivity:

  • Incompatible with strong oxidizers and strong acids

  • Releases toxic sulfur dioxide (SO₂) gas when in contact with acids

• Toxicity: Harmful if inhaled; irritant to skin and mucous membranes

Chemical Behavior

• In aqueous solution: Produces bisulfite ions (HSO₃⁻), which act as strong reducing agents.

• With acids: Produces SO₂ gas, which is toxic and pungent.

• With oxidizing agents: Can react violently, so storage must avoid such chemicals.

Industrial Applications

• Textile Industry: Used as an antichlor (neutralizes chlorine after bleaching) and dye fixative.

• Paper and Adhesives: Processing aid.

• Leather Industry: Depilatory agent (removes hair from hides).

• Organic Chemistry: Raw material for producing sodium hydrosulfite.

• Cosmetics: Preservative and disinfectant.

• Rubber and Electroplating: Processing additive.

Food Industry Applications

Sodium Metabisulfite is widely used as a food additive (E223):

• Antioxidant: Prevents oxidation, extending shelf life.

• Preservative: Inhibits microbial growth.

• Color Stabilizer: Maintains color in dried fruits, juices, and wines.

• Fermentation Control: In winemaking, suppresses unwanted microorganisms and regulates fermentation.

Examples:

• Wine: Controls fermentation and prevents spoilage.

• Dried Fruits (apricots, raisins): Preserves color and prevents browning.

• Canned Foods & Pickles: Acts as a disinfectant and preservative.

• Fruit Juices: Prevents oxidation and stabilizes flavor.

Health and Safety

• Inhalation: Can cause respiratory irritation and trigger asthma-like reactions.

• Skin Contact: Irritant; may cause allergic reactions.

• Food Consumption: Safe within regulated limits, but sensitive individuals (especially asthmatics) may react adversely.

• Storage: Must be kept dry, away from acids and oxidizers.

Summary Table

Industrial Sectors

1. Textile Industry

• Used as an antichlor to neutralize residual chlorine after bleaching.

• Acts as a dye fixative, helping colors bind more permanently to fibers.

2. Paper & Adhesives

• Functions as a processing aid in paper manufacturing.

• Improves adhesive formulations by stabilizing chemical reactions.

3. Leather Industry

• Serves as a depilatory agent, removing hair from hides during leather preparation.

4. Chemical Manufacturing

• Key raw material in producing sodium hydrosulfite, a strong reducing agent.

• Used in synthesis of cellulose esters and other organic compounds.

5. Cosmetics

• Acts as a preservative and disinfectant in certain formulations.

• Helps prevent microbial growth in creams and lotions.

6. Rubber & Electroplating

• Used as a stabilizer and processing additive.

• In electroplating, helps control oxidation reactions.

Food Industry

Preservative & Antioxidant

• Prevents oxidation, extending shelf life of foods.

• Inhibits microbial growth, reducing spoilage.

Color Stabilizer

• Maintains bright color in dried fruits (apricots, raisins, apples).

• Prevents browning in juices and processed foods.

Winemaking

• Controls fermentation by suppressing unwanted microorganisms.

• Preserves flavor and prevents spoilage.

Canned Foods & Pickles

• Acts as a disinfectant and preservative.

Safety Considerations

• Inhalation: Can irritate respiratory system, especially in asthmatic individuals.

• Skin Contact: May cause irritation or allergic reactions.

• Food Use: Safe within regulated limits, but sensitive individuals may react.

• Storage: Must be kept dry, away from acids and oxidizers to prevent toxic SO₂ release.

In short:

• Industrial sectors use it for bleaching, fixing, depilating, stabilizing, and chemical synthesis.

• Food industry uses it as a preservative, antioxidant, and color stabilizer.