About this product
Sodium sulphite, also spelled sodium sulfite, is Na2SO3 (CAS 7757-83-7), a white crystalline reducing agent used to remove residual chlorine and dissolved oxygen in water treatment. Supreme Petro Chemicals, a Chennai importer and bulk distributor, supplies the anhydrous technical grade at 97.0% mass min assay as Na2SO3. A batch Certificate of Analysis is supplied with every delivery, and we quote within 4 working hours.
Sodium Sulphite at a glance
- Also known as
- sodium sulfite · disodium sulphite · sodium sulphite anhydrous · Na2SO3
- CAS number
- 7757-83-7
- HSN code
- 2832.10.00
CAS number and formula checked against PubChem on 21 October 2026. Full grade and property values are in the specifications below. More lookups: chemical abbreviations list · CAS number reference.
Applications & Uses
Safety & Technical Documents
MSDS / SDS
Technical data sheet (TDS) & Certificate of Analysis
Batch Certificate of Analysis (CoA) · supplied with every delivery
Need another sheet? Browse the full SDS & TDS library — safety and technical data sheets for every product we supply.
Product DataGrades & Technical Specifications
Grades & Technical Specifications
Physical Properties
- Appearance
- White crystalline powder or granules
- Purity
- ≥ 97% Na₂SO₃
- Solubility
- Freely soluble in water; practically insoluble in ethanol
Supply & Packaging
- Packaging
- 25 kg HDPE bag50 kg woven sack
- Grades Available
- TechnicalFood gradeIndustrial
- Origin
- Imported
Compliance & Storage
- HS Code
- 2832.10.00
- UN Number
- Not regulated
- Hazard Class
- Not classified as dangerous goods
- Storage
- Cool, dry, well-ventilated area. Keep tightly closed — oxidises in air. Avoid heat and moisture.
- Shelf Life
- 24 months from manufacture (sealed)
These specs are indicative. Request a Certificate of Analysis (COA) for batch-specific values.
What is sodium sulphite? Formula, CAS and identity
Sodium sulphite (US spelling sodium sulfite, also disodium sulphite) is the inorganic salt Na2SO3, CAS 7757-83-7, EC 231-821-4. Supreme Petro Chemicals is a Chennai importer and bulk distributor, not a manufacturer, and supplies it as anhydrous Technical Grade with an assay of 97.0% mass min as Na2SO3.
Sodium sulphite is not the same product as sodium metabisulphite (SMBS, CAS 7681-57-4) or sodium bisulphite (CAS 7631-90-5). Those are separate listings with their own grades. Technical grade is not food or pharma grade.
| Item | Detail |
|---|---|
| Other names | Sodium sulfite, disodium sulphite |
| Molecular formula | Na2SO3 (anhydrous) |
| CAS number | 7757-83-7 |
| EC number | 231-821-4 |
| Appearance | White crystalline powder or granules |
| Grade supplied | Technical Grade, anhydrous, assay 97.0% mass min as Na2SO3 |
| Form | Solid, supplied in bags |
| Transport classification | Not regulated for road, sea or air for normal commercial grades (no UN number, no dangerous-goods class). Verify current carrier requirements before each shipment |
| Documents | SDS and TDS (SPC-TDS-PWD-024) on the product page |
Sodium sulphite specification: assay, sulphate, iron, chloride and pH
The technical grade is supplied against the manufacturer's published specification: Na2SO3 assay 97.0% mass min, sodium sulphate 2.0% mass max, iron 15 ppm max and pH of a 10% solution 8.5 to 10.5.
Solubility: freely soluble in water and practically insoluble in ethanol. The SDS gives roughly 27 g per 100 mL of water at 20 C.
| Parameter | Unit | Limit |
|---|---|---|
| Appearance | - | White crystalline powder |
| Assay (as Na2SO3) | % mass | 97.0 min |
| Sodium sulphate (as Na2SO4) | % mass | 2.0 max |
| Iron (as Fe) | ppm | 15 max |
| Chloride (as NaCl) | % mass | 0.2 max |
| Matter insoluble in water | % mass | 0.05 max |
| pH (10% solution) | - | 8.5 to 10.5 |
| Loss on drying | % mass | 1.0 max |
What is sodium sulphite used for? Dechlorination and oxygen scavenging
Sodium sulphite is a reducing agent. It removes residual chlorine and dissolved oxygen, so its main use in water and effluent treatment is dechlorination ahead of RO membranes and oxygen scavenging. SPC lists it alongside SMBS and sodium bisulphite for these duties. Sulphites are also used as reducing and bleach-stopping agents in textile and paper processing.
- Water treatment: dechlorination ahead of RO membranes and dissolved-oxygen scavenging. SPC lists it with SMBS and sodium bisulphite for this duty on its Water Treatment industry page.
- General knowledge: sulphites are also used as reducing and bleach-stopping agents in textile and paper processing, and in photographic and laboratory chemistry. Confirm suitability of the technical grade for your process.
- Dose rates are not published by SPC. The correct dose follows your measured residual chlorine or dissolved oxygen, which is plant-specific.
- Not a food or pharma grade: the grade supplied is Technical. Food or pharma use needs a grade confirmed in writing against the relevant standard.
Sodium sulphite vs sodium metabisulphite (SMBS) vs sodium bisulphite
Sodium sulphite is a neutral-to-alkaline salt (Na2SO3), SMBS is Na2S2O5 and sodium bisulphite is NaHSO3. They are different substances with different CAS numbers and grade specifications, so none can be quoted as a drop-in for another without checking your process. See the SMBS page at /products/sodium-meta-bi-sulphite-smbs and the bisulphite page at /products/sodium-bi-sulphite.
| Product | CAS | What it is and grade per SPC data |
|---|---|---|
| Sodium sulphite | 7757-83-7 | Na2SO3, white solid, mildly alkaline in solution (pH 8.5 to 10.5 at 10%). Technical Grade, 97.0% mass min as Na2SO3. Used for dechlorination and oxygen scavenging. |
| Sodium metabisulphite (SMBS) | 7681-57-4 | Na2S2O5, powder. Industrial Grade (Superior), 96.0% mass min as Na2S2O5. Gives more sulphur dioxide per unit mass than the sulphite (general chemistry). |
| Sodium bisulphite | 7631-90-5 | NaHSO3, powder or solution. Technical Grade, available SO2 35.0% min (mass). |
Sodium sulphite shelf life and supply from Chennai
Sodium sulphite is a solid supplied in bags, not in drums or tankers. We supply from Chennai (head office Periyamet, warehouse Redhills) across Tamil Nadu and South India.
- Form: solid, supplied in bags. Confirm the bag type for your order when you ask for a quote.
- Shelf life: 24 months from manufacture in sealed packaging.
- Source manufacturers on the product page: Aditya Birla Group and GACL.
Sodium sulphite SDS, TDS and Certificate of Analysis
A TDS, an SDS and a batch Certificate of Analysis are available for sodium sulphite.
- TDS: SPC-TDS-PWD-024, Technical Grade, listing the specification above.
- SDS: 16-section safety data sheet. Download both documents from the product page.
- Batch Certificate of Analysis supplied with every delivery. Compare it with the specification above on receipt.
Is sodium sulphite hazardous? Storage, handling and acid incompatibility
Sodium sulphite is not dangerous goods for transport, but the SDS classifies it as Eye Irrit. 2 (H319, causes serious eye irritation), signal word Warning. It is hygroscopic and oxidises slowly in moist air to sodium sulphate, and contact with acids liberates sulphur dioxide gas.
- Store in a cool, dry, well-ventilated area, in original tightly closed containers, away from moisture.
- Keep away from acids and strong oxidisers (for example nitric acid, chlorine, permanganates, peroxides). Acids liberate sulphur dioxide, which the SDS describes as an irritating and toxic fume.
- Avoid generating dust. Wear chemical-resistant gloves and splash goggles; use a particulate respirator if dust is generated and ventilation is poor.
- Not combustible. In a fire, decomposition can give sulphur dioxide fumes.
- Verify current carrier requirements before each shipment. This is a summary, not the safety data sheet; read the SDS before handling.
How to get a sodium sulphite quote from Supreme Petro Chemicals
Call or WhatsApp +91 86087 80096, or use the enquiry form. We quote within 4 working hours.
- Tell us the quantity and delivery location.
- Tell us the process and the grade you need, so we can confirm the technical grade is suitable.
- Review the TDS and SDS, then the quote. A batch Certificate of Analysis is supplied with every delivery.
Figures on this page are drawn from the manufacturer documents and safety data sheets we hold for this product. Content last checked 16 October 2026. Always confirm against the batch Certificate of Analysis supplied with every delivery.
Source Manufacturers
Sourced directly from verified manufacturers for consistent quality and traceability.
Supplied across South IndiaCoimbatoreMaduraiHosurBangaloreHyderabadVisakhapatnamKochi
Frequently Asked Questions
What is sodium sulphite and what is its CAS number and formula?
Sodium sulphite is the inorganic salt Na2SO3, CAS 7757-83-7, EC 231-821-4. It is the same product as sodium sulfite (US spelling) and disodium sulphite. It is a white crystalline powder or granules that acts as a reducing agent, and SPC supplies the anhydrous technical grade with a 97.0% mass min assay.
What is sodium sulphite used for?
It is a reducing agent that removes residual chlorine and dissolved oxygen. SPC lists it with SMBS and sodium bisulphite for dechlorination and oxygen scavenging in water and effluent treatment, for example ahead of RO membranes. Doses depend on your measured chlorine or oxygen level, so confirm grade suitability for your process.
What is the difference between sodium sulphite, sodium bisulphite and sodium metabisulphite?
They are three different substances: sodium sulphite (CAS 7757-83-7, Na2SO3), sodium bisulphite (CAS 7631-90-5, NaHSO3) and sodium metabisulphite or SMBS (CAS 7681-57-4, Na2S2O5). SPC lists each with its own grade and specification, so check the TDS rather than assuming one can replace another.
What is the difference between anhydrous sodium sulphite and the heptahydrate?
Anhydrous sodium sulphite is Na2SO3 with no water of crystallisation. The heptahydrate, Na2SO3.7H2O, carries roughly half its weight as water, so the same weight delivers much less sulphite. The grade SPC supplies is the anhydrous technical grade.
Is sodium sulphite hazardous, and how should it be stored?
It is not regulated as dangerous goods for transport, but the SDS classifies it as an eye irritant (Eye Irrit. 2, H319, Warning). Store it cool, dry and tightly closed, away from moisture, acids and oxidisers, because acids release sulphur dioxide. Shelf life is 24 months from manufacture in sealed packaging.
Is the sodium sulphite food grade or pharma grade?
No. The grade SPC lists is Technical Grade, supplied against the manufacturer's technical specification. For any food or pharma use, ask us in writing and confirm the grade against the relevant standard before ordering.
Who supplies sodium sulphite in Chennai?
Supreme Petro Chemicals, an importer and bulk distributor trading industrial chemicals from Chennai since 1997 (head office Periyamet, warehouse Redhills), supplies it across Tamil Nadu and South India. We are a trader, not a manufacturer. Call or WhatsApp +91 86087 80096 and we quote within 4 working hours.
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