When procurement managers type “buy sodium bisulfite” into a search engine, they often mean sodium metabisulfite—a distinct chemical with the formula Na2S2O5 and CAS 7681-57-4. This common mix-up can lead to ordering the wrong chemical, causing costly application failures in water treatment, gold mining, and food preservation. At Hailei Chemical, we help industrial buyers clarify this confusion and source high-purity sodium metabisulfite with the exact specifications their process demands.
The similarity in names and overlapping applications make it easy to confuse sodium bisulfite (NaHSO3) with sodium metabisulfite (Na2S2O5). While both are sulfite compounds that release sulfur dioxide (SO2) in acidic conditions, they are chemically distinct and supplied in different forms.
In water, sodium metabisulfite dissolves and hydrolyzes to form sodium bisulfite ions. This chemical behavior explains why the two chemicals are often used interchangeably—and why a search for “buy sodium bisulfite” frequently leads to metabisulfite suppliers.
Ordering the incorrect form can disrupt operations. If your process calls for a dry, easy-to-handle powder with high active SO2 content, sodium metabisulfite is the correct choice. Accidentally receiving a liquid bisulfite solution may compromise dosing accuracy, increase freight costs, or introduce unwanted water into a water-sensitive reaction. For mining, food, and textile applications, the solid sodium metabisulfite (industrial-grade sodium metabisulfite) with a purity of 97–98% is the industry standard.
Many industries depend on sodium metabisulfite’s reducing power. Below are the main sectors where your “buy sodium bisulfite” query should lead you straight to a quality metabisulfite.
Municipal water treatment plants and industrial process water systems use sodium metabisulfite to neutralize residual chlorine and chloramines. The reaction is instantaneous and produces harmless sulfate and chloride ions. Typical dosing: 1.4 mg of sodium metabisulfite per 1 mg of chlorine. The solid powder format makes it easy to prepare stock solutions or feed directly via dry feeders.
In gold extraction, sodium metabisulfite is employed to detoxify cyanide tailings before discharge. The sulfite air (SO2/air) process uses metabisulfite as the SO2 source to oxidize cyanide to cyanate, significantly reducing environmental toxicity. Mining chemical buyers rely on consistent, high-purity metabisulfite to meet strict environmental compliance.
Food-grade sodium metabisulfite is a widely permitted preservative (E223) in the winemaking, dried fruit, and seafood industries. It inhibits microbial growth, prevents enzymatic browning, and acts as an antioxidant. For winemakers, it provides both free and bound SO2 to protect wines during aging. If your recipe calls for “sodium bisulfite,” confirm with your supplier that solid food-grade sodium metabisulfite food grade is the correct input.
After bleaching with chlorine-based agents, textiles are treated with an “anti-chlor” to remove residual chlorine that could weaken fibers. Sodium metabisulfite is the preferred chemical because it decomposes excess hypochlorite without leaving corrosive residues, thereby preserving fabric strength and whiteness.
In the paper industry, sodium metabisulfite serves as a reductive bleaching agent for mechanical pulp. It brightens fibers without degrading cellulose, and it acts as a dechlorination agent after chlorine dioxide bleaching stages. The solid metabisulfite provides a stable, high-purity SO2 source that integrates seamlessly into existing chemical dosing systems.
Understanding the manufacturing process helps buyers assess product quality and impurities. Sodium metabisulfite is produced by passing sulfur dioxide gas through an aqueous slurry of sodium carbonate or sodium hydroxide. The exothermic reaction forms sodium bisulfite, which upon concentration and cooling crystallizes as sodium metabisulfite. The chemical steps are:
The resulting crystals are centrifuged, dried, and sieved to produce the free-flowing white powder that is packed in 25 kg bags, 1000 kg supersacks, or custom packaging. Leading manufacturers control heavy metals, iron, and arsenic to meet food-grade specifications (e.g., FCC, JECFA) or technical-grade requirements.
One of the most researched properties is sodium metabisulfite solubility in water because dosing efficiency depends on it. Sodium metabisulfite is highly soluble:
When dissolved, it releases SO2, so solutions are moderately acidic (pH 4.0–5.5 at 10% w/w). For industrial use, a 5–20% stock solution is typically prepared in stainless steel or HDPE tanks. Ensure adequate ventilation because dissolved SO2 can off-gas, especially in warm environments. For continuous dechlorination, metering pumps must be calibrated to account for solution strength and temperature-dependent solubility.
If you are preparing a laboratory solution for analytical or medical use (such as the sickling test), always use fresh distilled water and an airtight container to prevent premature oxidation of the sulfite to sulfate.
Though sodium metabisulfite is versatile, specific process conditions may call for an alternative reducing agent. Here are common scenarios where exploring a sodium metabisulfite alternative makes sense.
Sodium metabisulfite slightly lowers pH. In applications requiring strictly neutral pH (e.g., sensitive reverse osmosis membranes), ascorbic acid (vitamin C) is a viable alternative. It quenches chlorine without altering pH and is fully biodegradable, but it is more expensive and less stable in solution.
In boiler water treatment, sodium sulfite (Na2SO3) or catalyzed sulfite are often preferred over metabisulfite because they are designed for high-temperature oxygen removal and scale inhibition. Sodium metabisulfite could be used, but its SO2 release profile differs.
Food producers who need to minimize sodium content may switch to potassium metabisulfite (E224), which provides an equivalent amount of SO2 per mole but with potassium instead of sodium. This is particularly relevant in low-sodium preserved foods.
In large-scale industrial operations like sugar refining or certain mining processes, compressed SO2 gas can be more economical than solid metabisulfite. However, gas handling requires significant safety infrastructure.
Despite these alternatives, sodium metabisulfite remains the most cost-effective solid sulfite for the majority of dechlorination, preservation, and anti-chlorine tasks due to its high active SO2 content (typically 65% available SO2) and ease of transport.
While Hailei Chemical primarily serves industrial sectors, laboratory and medical customers also inquire about preparing sodium metabisulfite solutions for the sickling test—a diagnostic assay for sickle cell disease. The standard protocol requires a 2% (w/v) sodium metabisulfite solution.
How to prepare sodium metabisulfite for sickling test:
Our food-grade and analytical-grade sodium metabisulfite maintains low heavy-metal profiles, making it suitable for critical laboratory applications where impurities could interfere with test results.
Whether your initial search is “buy sodium bisulfite” or “sodium metabisulfite supplier,” evaluating the following parameters will ensure you receive the right product.
Weifang Hailei Fine Chemical Co., Ltd. has decades of experience exporting high-purity sodium metabisulfite to buyers in over 50 countries. Our product, CAS 7681-57-4, delivers a consistent 97–98% purity (higher for food grade) and is backed by comprehensive documentation—COA, MSDS, and third-party test reports. Whether you need full container loads for a mining operation or smaller batches for a food processing plant, our logistics team ensures on-time delivery with the correct UN-compliant packaging.
We understand that many of our customers initially search for “buy sodium bisulfite.” Our team is ready to clarify specifications and provide exactly the sulfite chemical your process requires.
Make the right choice for your water treatment, gold mining, food preservation, or textile application. Request a quote today and let our experts support your supply chain with reliable, technical-grade or food-grade sodium metabisulfite.
When sourcing chemical agents for water treatment, gold mining, or food preservation, the properties of sodium bisulfite are frequently the first technical checkpoint. In professional industrial procurement, “sodium bisulfite” almost always refers to sodium metabisulfite (Na₂S₂O₅), the anhydrous and more stable form that instantly generates bisulfite ions upon dissolution. A sound grasp of these properties—from molecular structure to storage behavior—empowers buyers to specify the correct grade, avoid handling pitfalls, and optimize process efficiency. At Hailei Chemical, we supply food-grade and industrial-grade sodium metabisulfite with 97–98% purity, backed by rigorous quality control and global logistics expertise.
Industrial buyers often encounter the term “sodium bisulfite” on tender documents and spec sheets, yet the shipped product is routinely sodium metabisulfite. This is not a discrepancy; it reflects the aqueous chemistry of the two compounds. Sodium metabisulfite (Na₂S₂O₅) is a stable, crystalline powder that, when dissolved in water, undergoes hydrolysis to yield two equivalents of sodium bisulfite (NaHSO₃):
Na₂S₂O₅ + H₂O → 2 NaHSO₃
In practice, the properties of sodium bisulfite as experienced in solution are realized from sodium metabisulfite. For this reason, the chemical industry uses the names interchangeably for many applications, although the dry storage and handling characteristics clearly belong to metabisulfite. Procurement professionals who understand this relationship can write clearer specifications and avoid confusion with true sodium bisulfite solutions, which are less stable and more expensive to transport.
Searching for the sodium metabisulfite molecular formula must return one definitive answer: Na₂S₂O₅. The substance carries CAS number 7681-57-4 and a molecular weight of 190.11 g/mol. Its structure centers on a disulfite ion (S₂O₅²⁻), where two sulfur atoms are linked by a direct S–S bond, each additionally bound to three oxygen atoms. This configuration imparts a high reducing potential and the ability to release sulfur dioxide (SO₂) under acidic conditions or heating.
The crystalline solid is white to yellowish-white and appears as free-flowing granules or powder in commercial grades. When evaluating supplier specifications, confirming the exact CAS and molecular formula is the first step toward verifying material identity—critical in regulated industries such as food processing and potable water treatment.
Procurement managers and plant engineers need a clear profile of the physical properties of sodium bisulfite/metabisulfite to design safe receiving, storage, and feeding systems. Below are the key parameters that influence day-to-day operations:
Redox chemistry is the heart of sodium metabisulfite’s industrial value, and the properties of sodium bisulfite in an aqueous medium define its practical reactivity. Once dissolved, the bisulfite ion acts as a powerful reducing agent, participating in reactions that are central to water treatment, mining, and food preservation.
In water and wastewater plants, bisulfite is employed to neutralize free chlorine and chloramine residuals. The reaction is rapid and stoichiometric:
NaHSO₃ + Cl₂ + H₂O → NaHSO₄ + 2 HCl
About 1.46 kg of pure sodium metabisulfite is required to remove 1 kg of chlorine. Understanding this ratio allows operators to size dosing equipment accurately. The ability to achieve undetectable chlorine residuals without introducing toxic byproducts makes the material indispensable in reverse osmosis pretreatment and effluent dechlorination.
One of the most critical safety applications of sodium metabisulfite is the destruction of free cyanide in gold leach tailings. The bisulfite ion, together with an oxygen source (usually air), oxidizes cyanide to the far less toxic cyanate:
CN⁻ + S₂O₅²⁻ + O₂ + H₂O → CNO⁻ + 2 SO₄²⁻ + 2 H⁺
Mine site laboratories regularly monitor ORP (oxidation-reduction potential) to confirm that enough metabisulfite has been added. The dose depends on the cyanide concentration but typically ranges from 2 to 8 grams of sodium metabisulfite per gram of free cyanide. Buyers in this sector place a premium on high purity and low heavy metal levels to meet stringent environmental compliance.
The food industry relies on the sodium metabisulphite in food as a preservative (E223) with antioxidant and antimicrobial functions. In solution, the bisulfite ion scavenges oxygen and inhibits enzymatic browning in dried fruits, fruit juices, and wine. The active species reacts with carbonyl compounds to form stable sulfonates, preserving color and freshness. The permitted residual SO₂ level in food products varies by regulation—for example, the EU allows up to 200 mg/kg in certain dried fruits—so food processors must select a certified food-grade powder with guaranteed purity and minimal arsenic, lead, and selenium content.
Sodium metabisulfite uses in winemaking deserve special attention. Winemakers prefer potassium metabisulfite for routine sulfite additions, but sodium metabisulfite is occasionally used for cleaning and sanitizing equipment, and in some regions for must sulfiting where potassium buildup is not a concern. The bisulfite ion releases free SO₂, which acts as an antimicrobial agent against wild yeasts and bacteria and as an antioxidant to prevent oxidative spoilage. The amount needed depends on pH—lower pH requires less free SO₂ to achieve the same molecular SO₂ concentration. A winery procurement team sourcing sodium metabisulfite must demand a purity of at least 97% and ensure the product is free from foreign odors that could taint wine.
In pulp mills, sodium metabisulfite serves as a reducing bleach assistant, especially in mechanical pulping where it brightens lignin-rich pulp without degrading fiber strength. The bisulfite ion reduces chromophoric groups, enhancing brightness. Similarly, in textile finishing, a mild bisulfite rinse removes residual chlorine from fabrics after hypochlorite bleaching, preventing yellowing and fiber degradation. The properties of sodium bisulfite as a chlorine scavenger make it a cost-effective alternative to activated carbon in many post-bleach baths.
A thorough understanding of commercial specifications prevents costly non-conformances. At Hailei Chemical, we supply industrial and food grades with the following typical parameters :
| Parameter | Industrial Grade | Food Grade (E223) |
|---|---|---|
| Purity (as Na₂S₂O₅) | 97.0% min | 97.5–98.0% min |
| SO₂ Content | 65.0% min | 65.0% min |
| Iron (Fe) | ≤ 0.005% | ≤ 0.001% |
| Heavy Metals (as Pb) | ≤ 0.002% | ≤ 0.001% |
| Arsenic (As) | ≤ 0.0002% | ≤ 0.0002% |
| Selenium (Se) | — | ≤ 0.003% |
| pH (5% solution) | 4.0–5.0 | 4.0–5.0 |
| Water Insoluble | ≤ 0.05% | ≤ 0.02% |
Buyers serving regulated markets—especially beverage, dairy, or municipal drinking water—should request a Certificate of Analysis (CoA) for each lot and verify compliance with FCC, JECFA, or EU standards as appropriate. Our quality management system ensures batch traceability from production to shipment.
The physical and chemical properties of sodium metabisulfite dictate specific packaging and storage protocols to preserve product integrity. Standard packaging includes 25 kg woven polypropylene bags with an inner polyethylene liner, 1000 kg FIBC bulk bags, and drums for smaller quantities. The liner must provide a robust moisture barrier because even slight humidity ingress triggers decomposition, leading to caking and SO₂ loss.
Warehouse conditions should maintain temperatures below 30 °C and relative humidity below 60%. Stacking should allow air circulation, and opened bags must be re-sealed promptly. Under these conditions, the shelf life ranges from 12 to 24 months depending on initial purity and packaging integrity. In tropical and monsoon climates—such as those in Bangladesh where interest in sodium metabisulfite price in bangladesh is growing—suppliers must offer packaging with enhanced moisture protection and possibly arrange container liners for sea freight to prevent deterioration during transit.
Chemical importers in South Asia closely watch the sodium metabisulfite price in bangladesh due to the country’s expanding textile, leather, and food processing sectors. Prices are influenced by international sulfur and soda ash feedstock costs, shipping freight, and local duties. A reliable long-term supplier like Hailei Chemical can provide stable pricing through direct factory contracts, flexible CIF Chittagong or Mongla terms, and volume flexibility from FCL to break-bulk shipments. When evaluating price quotations, buyers should consider the total delivered cost, including moisture-proof packaging and demurrage risks, not just the EXW price per metric ton.
Responsible buyers integrate EHS (Environment, Health, Safety) criteria into sourcing decisions. Sodium metabisulfite is classified as an irritant, and its solid form can cause eye and respiratory irritation. Proper PPE includes dust masks, goggles, and gloves. Under REACH and GHS, it carries H318 (causes serious eye damage) and H302 (harmful if swallowed) hazard statements. Our Safety Data Sheets (SDS) are always supplied with shipments and available for review before purchase.
On the environmental side, bisulfite ions oxidize to sulfate in wastewater, a benign species at typical discharge concentrations. When used in cyanide destruction, the resulting cyanate further hydrolyzes to ammonia and carbonate, dramatically reducing ecotoxicity. This green chemistry aspect makes sodium metabisulfite a preferred choice over chlorine-based cyanide oxidizers, which can form toxic cyanogen chloride.
A well-written purchase order prevents costly discrepancies. Based on the properties of sodium bisulfite outlined, include these details:
Our team at Hailei Chemical will provide a detailed technical data sheet for each shipment, aligning with these parameters to make your incoming inspection seamless.
With over a decade of experience exporting to more than 40 countries, Weifang Hailei Fine Chemical Co., Ltd. combines manufacturing control with supply chain reliability. Our product consistency is validated by ISO-certified management systems, while our logistics team handles the complexities of hazardous goods documentation (Class 8 for some concentrations) and customs clearance. We offer sample evaluation, contract manufacturing, and monthly production capacity of 3,000 MT to support large-scale industrial demands.
Whether you need sodium metabisulfite uses in winemaking or high-tonnage deliveries for a gold mining operation, our technical service engineers are available to assist with application-specific recommendations. We understand that the sodium metabisulfite molecular formula on paper must translate into consistent real-world performance.
Choosing the right sodium metabisulfite grade begins with a clear understanding of its physical and chemical properties. Let our experts help you match those specifications to your process requirements. Request a competitive quotation for industrial or food-grade sodium metabisulfite, including tailored packaging and delivery to your port. We look forward to powering your success with reliable chemistry and global reach.