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Send EmailSodium Sulfite, Natrium Sulfid, Sodium Sulphite, Disodium Sulfite, E221, 7757-83-7
SODIUM SULFITE
CAS Number: 7757-83-7
E Number: E221
1. IDENTIFICATION
| Property | Information |
|---|---|
| Chemical Name | Sodium sulfite (Disodium sulfite) |
| Chemical Formula | Na₂SO₃ |
| Molecular Weight | 126.05 g/mol |
| Appearance | White crystalline powder or granules |
| CAS Number | 7757-83-7 |
| EINECS Number | 231-821-4 |
| UN Number | Not classified as dangerous goods |
2. PHYSICAL AND CHEMICAL PROPERTIES
| Property | Value |
|---|---|
| Melting Point | >500 °C (decomposes) |
| Boiling Point | Not applicable (decomposes) |
| Density (20°C) | Approx. 2.63 g/cm³ (anhydrous) |
| Solubility in water (20°C) | 270 g/L (freely soluble) |
| pH (5% solution, 20°C) | 9.0 – 10.5 (alkaline) |
| Bulk Density | 0.8 – 1.2 kg/L (depending on form) |
| Oxidation Sensitivity | Slowly oxidizes to sodium sulfate (Na₂SO₄) in air |
| Odor | Slight sulfur dioxide smell when wet |
Solution Density (20°C, approximate values):
| Concentration (wt%) | Density (g/cm³) |
|---|---|
| 1 | 1.008 |
| 5 | 1.045 |
| 10 | 1.095 |
| 15 | 1.147 |
| 20 | 1.202 |
Note: Exact values vary with temperature and purity.
3. CHARACTERISTICS & REACTIVITY
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Reducing Agent: Strong reducing agent; reacts with oxygen, chlorine and other oxidizers.
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Alkaline Nature: Aqueous solutions are basic.
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Air Oxidation: Slowly converts to sodium sulfate (Na₂SO₄) when exposed to air. Must be stored in airtight packaging.
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Reaction with Acids: Contact with strong acids releases toxic and suffocating sulfur dioxide (SO₂) gas.
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Sulfonation / Sulfomethylation: Can add sulfite groups to organic molecules.
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Thiosulfate Formation: Reacts with elemental sulfur to form sodium thiosulfate (Na₂S₂O₃).
4. APPLICATIONS (CORRECTED)
| Industry | Application |
|---|---|
| Pulp & Paper | Sulfite pulping process to remove lignin from wood (NOT Kraft process) |
| Food (E221) | Preservative, antioxidant (dried fruits, wines, potato products); colour & freshness stabilizer |
| Water Treatment | Oxygen scavenger (boiler feed water, pipelines); dechlorination |
| Textile | Chlorine removal after bleaching; reduction processes before dyeing |
| Photography | Preservative in developer solutions (prevents oxidation) |
| Chemical Industry | Production of sodium thiosulfate, sodium bisulfite, sulfonated compounds |
| Leather | Sulfitation of tanning extracts |
| Pharmaceuticals | Antioxidant in some injectable solutions |
| Mining | Flotation processes (certain ores) |
5. SAFETY AND HEALTH INFORMATION (MSDS SUMMARY)
NFPA 704
| Health (Blue) | Fire (Red) | Reactivity (Yellow) | Special |
|---|---|---|---|
| 1 (Mild irritation) | 0 (Does not burn) | 0 (Stable) | None |
Hazard Statements (CLP/GHS)
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H315: Causes skin irritation.
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H319: Causes serious eye irritation.
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H334: May cause allergy or asthma symptoms if inhaled.
Safety Precautions (P-statements)
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P261: Avoid breathing dust.
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P280: Wear protective gloves/eye protection.
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P302+P352: If on skin, wash with plenty of soap and water.
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P304+P340: If inhaled, remove person to fresh air.
Occupational Exposure Limits (example)
| Region | Type | Value |
|---|---|---|
| USA (ACGIH) | TWA | 5 mg/m³ (as sulfite salts) |
| EU | TWA | 5 mg/m³ |
6. TRANSPORT & STORAGE
| Property | Information |
|---|---|
| Packaging | 25 kg multi‑layer paper or PP bags, palletized |
| Storage Conditions | Cool, dry, well‑ventilated area; keep tightly closed to avoid moisture and air (prevents oxidation) |
| Incompatible Materials | Strong acids (release SO₂ gas), strong oxidizers (peroxides, permanganates) |
| Transport Classification | Not classified as hazardous (but avoid SO₂ release to environment) |
7. OTHER NAMES & SYNONYMS
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Sulfurous acid, sodium salt (1:2)
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Disodium sulfite
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Anhydrous sodium sulfite
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Sodium sulfite (Na₂SO₃)
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E 221
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S‑WAT
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Natriumsulfit (German)
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Sulfito de sodio (Spanish)
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Sulfite de sodium (French)
8. REGULATORY INFORMATION (Summary)
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European Union: Registered under REACH (EC) 1907/2006. As food additive E221 compliant with Regulation (EC) 1333/2008.
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Turkey: Compliant with Turkish Food Codex (TGK) Additives Regulation.
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USA (FDA): GRAS (Generally Recognized as Safe) status, but labeling required for sulfite‑sensitive individuals.
Important: This TDS is exclusively for Sodium Sulfite (Na₂SO₃, CAS 7757‑83‑7). Do not confuse with Sodium Sulfate (Na₂SO₄). For emergencies or a detailed Material Safety Data Sheet (MSDS), contact the manufacturer / supplier.
