Sodium sulfite (Na2SO3) is a white, crystalline or powdered inorganic salt used mainly as a reducing agent and oxygen scavenger. It dissolves readily in water to form a mildly alkaline solution that is easy to dose in continuous industrial processes. Its main value lies in removing dissolved oxygen and neutralizing residual oxidants such as chlorine quickly and predictably. Because it is effective, economical, and widely available, it is a standard chemical across pulp and paper, boiler water treatment, municipal water treatment, and many reducing-agent applications, offering a cost-effective alternative to more specialized scavengers.
Weifang Hailei Fine Chemical Co., Ltd supplies sodium sulfite as a standard 96% powder, plus dedicated pulp bleaching grade and water treatment grade products. All three are built on a minimum 96% Na2SO3 purity, each processed for the impurity profile and physical properties its end use demands. The pulp bleaching grade targets reliable dechlorination, while the water treatment grade focuses on oxygen scavenging and chlorine removal in water systems. As a source factory in Weifang, Shandong, Hailei offers consistent, batch-controlled material and can align specifications with buyer requirements.
A 96% specification means the product contains at least 96% sodium sulfite (Na2SO3) by weight, the balance being mainly water of crystallization and small amounts of related sodium salts. It matters to procurement managers because it determines how much active reducing agent is delivered per tonne and therefore the effective dosing efficiency. Consistent purity reduces dosing errors and minimizes side reactions or insoluble residues. When comparing quotes, confirm what the stated percentage refers to and request the supporting certificate of analysis.
Sodium sulfite is commonly produced by absorbing sulfur dioxide gas into an aqueous sodium carbonate or sodium hydroxide solution, which neutralizes the SO2 to form a sulfite solution. This is then crystallized, separated, dried, and milled or screened to the required particle size and purity. Some producers also refine sulfite recovered as a by-product of other industrial processes. The finished product is graded by Na2SO3 content and test items such as iron, water-insoluble matter, and solution clarity.
Weifang, Shandong, is one of China's major inorganic-salt chemical production bases, with mature raw-material supply, brine and soda resources, and dense downstream logistics. Sourcing from a source factory there shortens the supply chain, improves cost competitiveness, and gives buyers direct access to technical and quality information. A manufacturer like Weifang Hailei, which also makes calcium chloride, magnesium chloride, and industrial salt, can consolidate multi-product orders and provide consistent export documentation.
In pulp and paper bleaching, chlorine-based chemicals brighten pulp, but a residual oxidant must be removed before the pulp moves to the next stage. Sodium sulfite reacts rapidly with this residual chlorine and related oxidizing species, converting them to harmless compounds and preventing damage to cellulose fibers. This dechlorination step protects pulp strength, brightness, and downstream process equipment. The pulp bleaching grade is controlled for low iron and other impurities that could stain pulp or interfere with bleaching chemistry.
Dissolved oxygen in boiler feedwater is a primary cause of pitting and localized corrosion of boiler metal surfaces. Sodium sulfite reacts with dissolved oxygen to form sodium sulfate, chemically binding the oxygen so it cannot corrode the system. It is widely used in low- and medium-pressure industrial boilers for its fast reaction and low cost. Dosage is calculated from feedwater oxygen content, temperature, and sulfite residual, usually with a small excess maintained for protection.
In water and wastewater treatment, sodium sulfite mainly removes residual chlorine and chloramines after disinfection, before discharge, reuse, or entry into sensitive downstream equipment. Dechlorination protects aquatic life and prevents chlorine from damaging reverse-osmosis membranes, ion-exchange resins, and other treatment components. The water treatment grade is chosen for reliable, fast dechlorination and low contaminant introduction. Dosage is set by measuring chlorine residual and adding a slight excess.
Beyond pulp and water treatment, sodium sulfite serves as a general-purpose reducing agent. In photographic processing it preserves and protects developing agents from premature oxidation. In dyeing, textile, and leather processes it provides a controlled reducing environment for certain steps. Industrial and photographic grades are used wherever a mild, predictable reducing action is needed in chemical manufacturing. Buyers with uses outside the listed grades should discuss the specific requirement with the supplier.
First identify what the sodium sulfite must do in your process and which parameters matter most: Na2SO3 content, impurity limits such as iron, particle size, moisture, or solution clarity. Pulp and paper buyers should choose the pulp bleaching grade, while boiler and water treatment operators should choose the water treatment grade. For general reducing-agent use, the standard 96% powder is the usual starting point. Share your process conditions so the supplier can recommend the best match rather than the closest generic product.
Reputable suppliers provide a certificate of analysis (COA) per batch, and buyers should review typical test items including Na2SO3 content, iron (Fe), water-insoluble matter, chloride content, solution pH, and appearance. Depending on the application, heavy-metal limits or particle-size distribution may also matter. Compare the supplier's specification sheet with your own incoming-inspection limits and verify with third-party testing where useful. Batch-to-batch consistency is often as important as absolute values.
Sodium sulfite powder is commonly packed in 25 kg woven polypropylene bags with an inner polyethylene liner, and larger volumes in 50 kg bags or roughly one-tonne big bags. For export, bags are palletized, stretch-wrapped, and sometimes corner-protected for safe container loading. Because the product is moisture- and air-sensitive, the inner liner and sealing are important to preserve reducing power. Confirm packaging, pallet configuration, and labeling before shipment.
Sodium sulfite is a reducing agent that slowly oxidizes to sodium sulfate on exposure to air, moisture, or heat, so storage affects shelf life. Keep it in a cool, dry, well-ventilated warehouse, away from strong oxidizers, acids, and moisture, and reseal bags after partial use. High humidity causes caking and accelerates oxidation, so first-in-first-out rotation is recommended. Avoid acid contact, which releases sulfur dioxide gas.
For export, the MOQ is usually set by container economics, so buyers commonly order a full 20-foot container of roughly 20–25 tonnes of bagged product. Smaller trial or LCL orders are often possible for evaluation at a higher unit cost. Lead time depends on production schedules, stock, packaging, and destination, and is confirmed at quotation. Plan for production time plus ocean freight when scheduling replenishment. Confirming the exact MOQ and lead time early helps align your inventory planning with the factory's production schedule.
Sodium sulfite pricing is driven mainly by raw-material costs—soda ash or caustic soda and sulfur—plus energy, packaging, and logistics. Purity and grade matter, since tighter impurity control commands a higher unit price. Order volume, packaging, palletization, and destination freight and documentation all affect landed cost. Because markets follow raw-material and energy prices, quotes are time-limited and should be re-confirmed at firm order.
First confirm whether the vendor is a producing source factory or a trading intermediary, since a factory generally offers better traceability, technical support, and price stability. Review production capability, batch consistency, COA documentation, quality-control practices, and shipping experience to your region. Request samples and, where possible, check references or arrange an audit. Evaluate responsiveness and technical competence as well.
Sodium sulfite is generally shipped as general cargo rather than dangerous goods, simplifying ocean and road transport. The main concern is moisture protection, so bags or big bags should stay dry and containers clean and watertight. Documentation including invoice, packing list, bill of lading, and safety data sheet should accompany the shipment. For humid climates or long routes, discuss moisture protection in advance. Clean container checks and careful loading are part of a reliable export process.
Sodium sulfite has relatively low acute toxicity, but dust can irritate eyes and the respiratory tract, so use dust masks, safety glasses, and gloves when handling large quantities in poor ventilation. Avoid acid contact, which releases sulfur dioxide gas, and keep it away from strong oxidizers. Standard first aid includes flushing eyes or skin with water and moving to fresh air after dust inhalation. Keep a current SDS on site.
All three are sulfur-based reducing agents but differ in structure, SO2 content, and solution pH behavior. Sodium sulfite (Na2SO3) is the fully neutralized form, acting mainly as a direct oxygen scavenger and mild reducing agent. Sodium metabisulfite (Na2S2O5) releases sulfur dioxide and behaves as an acidic sulfite source where free SO2 is needed. Sodium bisulfite (NaHSO3) sits between them and is common in liquid dosing systems. The choice depends on pH tolerance, required reducing power, and whether free SO2 is needed.
Yes—most source factories, including Weifang Hailei, can provide small samples so buyers can validate the product against their own process before committing. Running a trial with the actual grade, dosage, and conditions is the most reliable way to confirm suitability and avoid specification mismatches. Technical support is also normally available to match the grade, recommend storage and handling, and advise on dosing. Request the COA with the sample.
As a source factory, Weifang Hailei can typically accommodate packaging and labeling customization such as specific bag sizes, customer-branded or neutral labels, palletization patterns, and documentation requirements. Customization usually involves minimum quantities and longer lead times, agreed at quotation. Buyers with OEM or private-label needs should provide label artwork and packaging specs early. Clear communication up front avoids loading delays. Confirming these requirements at the quote stage also prevents costly rework later.
A complete export shipment typically includes a commercial invoice, packing list, and bill of lading, plus a certificate of analysis and safety data sheet (SDS/MSDS). Depending on destination and buyer requirements, a certificate of origin or other compliance documents may be requested. Confirm the exact documentation set and format before shipment, especially for markets with specific customs requirements. Keeping documents aligned with the shipped batch ensures smooth clearance. A complete, accurate document set is a key part of professional export supply.