Whether you source chemicals for a municipal water treatment plant, a gold mine in India, or a food processing facility, understanding the properties of sodium metabisulfite is critical to making safe, cost-effective, and performance-driven procurement decisions. Sodium metabisulfite (Na2S2O5, CAS 7681-57-4) is a versatile inorganic sulfite used globally for dechlorination, cyanide detoxification, food preservation, pulp bleaching, and textile anti-chlorine treatment. Yet many buyers overlook how the product’s chemical identity, solubility, stability, and purity directly impact dosage, handling, and final application outcomes. This guide breaks down the essential physical and chemical properties, explains how sodium metabisulfite is made, compares it with sodium bisulfite, and provides practical usage directions—all from the perspective of a procurement manager or process engineer sourcing industrial-grade material.
To use the product effectively, you must first know its core properties. Sodium metabisulfite is a white to yellowish crystalline powder with a pungent sulfur dioxide odor. It is freely soluble in water (54 g/100 mL at 20°C) and slightly soluble in alcohol. The aqueous solution is acidic, with a pH around 4.0–5.5 for a 5% solution, due to the release of sulfurous acid. On a molecular level, sodium metabisulfite is the disodium salt of disulfurous acid (H2S2O5), meaning each molecule contains two sulfur atoms bridged through an S–S bond, which distinguishes it from simple sulfites.
Key physical constants: molecular weight 190.11 g/mol; melting point >150°C with decomposition; apparent density approx. 1.1–1.3 g/cm³. When heated above 150°C, it decomposes, releasing sulfur dioxide (SO2) and leaving sodium sulfite (Na2SO3) and sulfate residues. This thermal behavior is important if your process involves drying or exposure to high temperatures.
The properties of sodium metabisulfite that matter most in industrial use are its strong reducing action in aqueous media and its ability to generate SO2 under acidic conditions. In water, it dissociates into sodium (Na⁺) and metabisulfite ions (S2O52−), which further hydrolyze to bisulfite (HSO3−) and sulfite (SO32−) species. This equilibrium gives it excellent reactivity for removing chlorine, oxygen, and heavy metal oxidants. The high assay (97–98% Na2S2O5 for Hailei Chemical’s food and industrial grades) ensures low iron (≤10 ppm), heavy metals (≤5 ppm as Pb), and minimal insoluble matter, meeting EU, FCC, and USP standards for critical applications.
Understanding the production pathway helps buyers evaluate supply chain consistency and impurity profiles. Sodium metabisulfite is manufactured by reacting sulfur dioxide (SO2) with a sodium base—typically sodium carbonate (soda ash) or sodium hydroxide (caustic soda)—under controlled aqueous conditions. The process can be summarized in two main steps:
High-quality producers—like Hailei Chemical—use food-grade sulfur and purified water, ensuring the final product meets both industrial and food-grade specifications. The choice of sodium source influences residual alkalinity: soda ash yields a product with slightly higher sodium carbonate traces, while NaOH route gives a purer bisulfite intermediate but requires tighter process control. Knowing this helps you request the right certificate of analysis (CoA) for your specific purity and particle size needs.
A common point of confusion is the relationship between sodium bisulfite (NaHSO3) and sodium metabisulfite. While both are sulfite-based reducing agents, their chemical structure and practical behavior differ. Sodium bisulfite is a monoprotic salt of sulfurous acid, typically existing only in aqueous solution or as a labile solid. Sodium metabisulfite, on the other hand, is the dehydrated dimer of sodium bisulfite: two bisulfite ions lose one water molecule to form the S–S bonded metabisulfite. When dissolved in water, sodium metabisulfite hydrolyzes to sodium bisulfite and then to sulfite species, so the active chemistry is often similar. However, there are key practical differences:
For most procurement scenarios involving solid sulfite chemicals, sodium metabisulfite offers better shelf life and concentration. Always verify which form your process actually requires; switching from a liquid bisulfite to dry metabisulfite can cut logistics costs significantly but may require dissolving equipment.
Proper usage hinges on matching the properties of sodium metabisulfite to your process chemistry. Below we cover general guidelines for four key sectors.
In municipal and industrial water treatment, sodium metabisulfite is used to neutralize free chlorine and chloramines before discharge or membrane protection. The stoichiometric reaction is: Na2S2O5 + 3 Cl2 + 5 H2O → 2 NaHSO4 + 6 HCl. Typically, 1.34 mg of pure Na2S2O5 removes 1 mg of Cl2. Because commercial product is ~97% pure, a safety factor of 1.1–1.2 is used. A 10% solution is prepared and dosed via metering pump. Stirring and contact time of 5–15 minutes assure complete dechlorination. Online ORP sensors can automate the feed rate.
In gold leaching operations, residual cyanide must be destroyed to meet tailings discharge limits. Sodium metabisulfite provides SO2 gas in the well-known INCO process, oxidizing cyanide to cyanate. A typical usage rate is 5–10 kg metabisulfite per ton of ore depending on cyanide concentration. A 20% solution is injected into tailings slurry along with copper sulfate catalyst, at pH 8–9, with vigorous air sparging. The technical-grade sodium metabisulfite with high purity and low iron is essential to avoid precipitates that clog nozzles.
As an E223 additive, sodium metabisulfite inhibits enzymatic browning in dried fruits, wines, and vegetable preserves. Dosage varies: 200–500 ppm SO2 equivalent in wine must, or dipping solutions of 1–2% w/v for sliced apples and potatoes. Always use food-grade material that meets FCC/USP standards, free from arsenic and heavy metals. Important: sodium metabisulfite is an allergen; final products must declare sulfite content if above 10 ppm.
In pulp and paper mills, metabisulfite solutions (5–10%) remove residual chlorine-based bleach from pulp before papermaking, preventing yellowing and fiber damage. In textile finishing, it serves as an anti-chlor agent after hypochlorite bleaching to neutralize excess chlorine before dyeing. For both, a gentle reducing environment (pH 4–6, ambient temperature) works best.
India is one of the largest import markets for sodium metabisulfite due to its booming water treatment, mining, and food sectors. If you are searching for a sodium metabisulfite supplier in India, you need a partner who combines consistent product quality with logistics expertise. Hailei Chemical exports bulk sodium metabisulfite to major Indian ports (Nhava Sheva, Chennai, Mundra) in 25 kg woven bags, 1000 kg supersacks, or custom packaging. Our 97–98% purity with low heavy metals and iron aligns with BIS and food additive standards, while our logistical support—including full customs documentation, REACH compliance data, and pre-shipment samples—simplifies your import process.
When qualifying any international supplier, request a detailed CoA showing not just Na2S2O5 assay but also iron, arsenic, selenium, and chloride content. Scrutinize the product’s physical properties like bulk density and particle size distribution (typically 40–120 mesh) if your process uses dry feeders. Hailei Chemical’s technical team can provide specification sheets tailored to your application, ensuring the properties of sodium metabisulfite you receive precisely match your needs.
It is an acidic salt. A 5% aqueous solution has a pH of about 4.0–5.5 due to the formation of sulfurous acid. This mild acidity makes it ideal for reducing environments without drastically altering process pH.
Yes, in many applications. Sodium metabisulfite releases sulfite ions upon dissolution. The main advantage is higher SO2 equivalent per kilogram and better dry stability. However, for some food or pharmaceutical processes requiring precise sodium sulfite, direct substitution should be validated.
Store in a cool, dry, well-ventilated area away from acids and oxidizers. Sealed bags prevent moisture absorption, which would trigger decomposition and caking. Under proper conditions, shelf life exceeds 12 months without significant loss of SO2 content.
A simple iodometric titration determines available SO2 content. If the assay has dropped below your required threshold (e.g., 97%), the product may have degraded due to moisture ingress. Hailei Chemical uses quality-controlled packaging to maintain assay throughout transit.
When sourcing a bulk supply of sodium metabisulfite, having a deep grasp of its properties—from solubility and pH to redox behavior and impurity limits—empowers you to optimize processes and avoid costly misapplications. Whether you need food-grade powder for fruit preservation or industrial-grade crystals for cyanide destruction, our sodium metabisulfite product page provides full specifications and order options. To discuss your volume, packaging, or documentation requirements with our technical sales team, request a competitive quote today.
For procurement managers and chemical engineers sourcing bulk reducing agents, a thorough understanding of the properties of sodium metabisulfite is the foundation of successful formulation, safe handling, and cost-effective supply chain management. From water dechlorination at municipal treatment plants to cyanide detoxification in gold mines and sulfite preservation in food processing, this versatile inorganic compound delivers reliable performance only when its chemical and physical characteristics align with end-use requirements.
At Weifang Hailei Fine Chemical Co., Ltd., we supply sodium metabisulfite (Na₂S₂O₅, CAS 7681-57-4) in both food-grade (FCC compliant) and industrial-grade (97–98% purity) to buyers across India, Southeast Asia, Africa, and the Middle East. This guide decodes every property you need to evaluate before issuing a purchase order, helping you avoid caking in storage, insufficient SO₂ release, or regulatory non-compliance.
Understanding what is sodium metabisulfite made from clarifies its inherent properties. Industrially, sodium metabisulfite is produced by saturating a sodium carbonate or sodium hydroxide solution with sulfur dioxide (SO₂). The exothermic reaction first forms sodium bisulfite (NaHSO₃) in solution, which is then carefully dehydrated through cooling and controlled crystallization to yield solid sodium metabisulfite:
2 NaHSO₃(aq) → Na₂S₂O₅(s) + H₂O
The product is a white to yellowish crystalline powder or granular material with a pungent SO₂ odor. Because its synthesis relies on high-purity SO₂ gas and a low-iron process environment, the quality of inputs directly determines the final product’s heavy metal profile and clarity in solution. For food-grade material, additional purification steps ensure compliance with FCC or E223 monographs, making it safe for use as a preservative in dried fruits, wines, and starch syrups.
A technical evaluation begins with the core properties of sodium metabisulfite. These data points influence dissolution rates, dosing precision, and compatibility with other process chemicals.
These parameters are not just laboratory curiosities—they directly affect real-world outcomes. For instance, the acidic pH of a metabisulfite solution makes it ideal for acidifying and preserving high-sugar food systems, while the decomposition temperature dictates safe storage away from heat sources.
Sodium metabisulfite is traded primarily in two purity specifications: industrial grade (typically 97–98% Na₂S₂O₅) and food grade (≥98% plus strict limits on iron, arsenic, and heavy metals). The property differences may seem subtle, but they have outsized impacts in sensitive applications.
Industrial grade (97–98%): Optimized for water treatment, gold mining (cyanide destruction), and pulp & paper bleaching. A lower assay of 97% still supplies more than 65% equivalent SO₂ content, but the 1–2% inert salts or sulfate residues can affect clarity in closed-loop water systems. Buyers should monitor iron content (<0.003% typical), since dissolved iron can catalyze unwanted oxidation or stain pulp.
Food grade (FCC/E223): Must meet purity thresholds for arsenic (≤3 mg/kg), lead (≤2 mg/kg), and selenium. The absence of chloride by-products ensures no off-flavors in wine or dried fruit. At Hailei Chemical, our food-grade sodium metabisulfite is manufactured under rigorous HACCP-guided protocols to guarantee compliance with international food safety standards.
When specifying your purchase, always request a Certificate of Analysis (COA) detailing assay, SO₂ content, pH of 10% solution, iron, heavy metals, and water-insoluble matter. The sodium metabisulfite product page provides typical Hailei COA ranges to simplify your comparison.
Many industrial buyers wonder about the interchangeability of sodium bisulfite and sodium metabisulfite. While both provide SO₂ in solution, their chemical properties lead to different dosing behaviors and storage considerations.
| Property | Sodium Metabisulfite (Na₂S₂O₅) | Sodium Bisulfite (NaHSO₃) |
|---|---|---|
| Physical form | Dry crystalline powder/granules | Often supplied as solution (approx. 40%) or crystalline solid (less stable) |
| SO₂ equivalent | Approx. 65–67% by weight | Approx. 22–24% in commercial solutions; solid bisulfite contains 60–65% but is hygroscopic |
| pH of solution | 4.0–5.5 (10% solution) | 2.5–4.0 (solution), more acidic |
| Stability in storage | Excellent when kept dry; >12 months shelf life | Solution prone to oxidation by air; solid form absorbs moisture rapidly |
| Shipping | Dry bulk; cost-effective long-distance shipping | Solution requires tankers or IBCs; higher freight per active SO₂ |
| Typical applications | Water dechlorination, gold mining, food preservative, pulp bleaching, textile | On-site chlorine neutralization, reducing agent in chemical synthesis, leather tanning |
The choice often boils down to logistics and pH buffering. For intercontinental shipments where freight cost and product stability matter, dry sodium metabisulfite is the preferred form. Upon dissolution in water, it forms sodium bisulfite ions, delivering the same reducing action. However, if your process demands immediate solution without handling dry powder, a pre-made bisulfite solution might be convenient—though it costs more per kilogram of SO₂ delivered. Hailei supplies both dry sodium metabisulfite and can direct you to logistics partners for sodium bisulfite solutions where needed.
Knowing how to use sodium metabisulphite safely and efficiently starts with respecting its reactivity profile. The compound’s core property is its ability to release sulfur dioxide in acidic conditions or when heated, making it a potent oxygen scavenger and antimicrobial agent.
In municipal and industrial water treatment, sodium metabisulfite instantly neutralizes free chlorine and chloramines. The stoichiometric reaction requires 1.34 parts of pure Na₂S₂O₅ per part of chlorine. A typical dosing rate is 2–3 mg/L of a 10% metabisulfite solution per mg/L residual chlorine, adjusted for mixing efficiency. Because the reaction drops pH slightly, systems with low alkalinity may need buffering.
The SO₂/air process (INCO method) uses metabisulfite as the SO₂ source to oxidize cyanides (CN⁻) to cyanate (OCN⁻), catalyzed by copper. The reducing property here must be carefully controlled: a solution pH between 8.5 and 9.5 optimizes cyanide destruction while minimizing off-gassing of HCN. Miners often dose metabisulfite at 2–4 grams per gram of WAD cyanide.
As an E223 additive, sodium metabisulfite inhibits enzymatic and non-enzymatic browning in dried fruits, frozen seafood, and wine. The effective SO₂ concentration for antimicrobial action is 50–400 ppm, depending on the product. Its ability to lower pH helps stabilize ascorbic acid and color. Importantly, residual sulfite must meet local labeling laws—typically <10 ppm SO₂ in final product.
In mechanical pulping, metabisulfite acts as a reducing bleach to brighten lignin-rich pulps without degrading cellulose. The property of preserving fiber strength while increasing brightness by 5–8 ISO points makes it valuable for newsprint and tissue grades. Typical application: 1–3% on oven-dry pulp at pH 5–6.
After chlorine bleaching, fabrics carry residual chlorine that can yellow or weaken fibers. A 0.5–2 g/L sodium metabisulfite bath, based on its rapid dechlorination property, eliminates this risk. The slightly acidic pH helps close fiber cuticles, improving dye uptake in subsequent steps.
For detailed application recipes and custom formulation support, refer to our comprehensive sodium metabisulfite application guide.
Procuring sodium metabisulfite without verifying properties against recognized standards can lead to inconsistent batch performance, rejected shipments, or even plant shutdowns. A rigorous supplier evaluation framework should include the following analytical benchmarks.
Request a batch-specific COA with every shipment. Third-party testing by SGS, Bureau Veritas, or Intertek adds an extra layer of trust. Hailei Chemical routinely arranges pre-shipment inspections against these parameters to ensure that the properties of sodium metabisulfite you order are exactly what you receive.
The shelf life and performance of sodium metabisulfite depend critically on storage conditions. Exposure to moisture and heat degrades its reducing power and turns the powder into a hard, unworkable mass.
Key recommendations:
Understanding these environmental sensitivities allows you to plan inventory turnover and avoid waste, directly protecting your investment in each purchased ton.
India is one of the world’s largest importers of sodium metabisulfite, driven by expansive water treatment programs, a massive gold import sector, and a growing food processing industry. If you are seeking a sodium metabisulfite supplier in India, working directly with a chemical exporter in China can often offer cost advantages of 12–18% compared to local distributors, provided you manage shipping and quality inspection efficiently.
Hailei Chemical serves Indian buyers through Nhava Sheva, Mundra, Chennai, and Kolkata ports. Our typical packaging in 25 kg HDPE bags with inner liner is palletized and shrink-wrapped for tropical climates. We also offer 1000–1250 kg big bags and custom private labeling. For oil & gas or mining tenders, we provide full documentation: COA, MSDS, Certificate of Origin, and fumigation certificates as required by Indian customs (HS Code 28321010).
The same logistics expertise applies to buyers in the Middle East (Jebel Ali, Dammam), Southeast Asia, and Africa. Our in-house team coordinates FCL and LCL shipments, transit times, and demurrage avoidance. By consolidating volumes, we help you optimize landed costs without compromising the high purity and consistent properties of sodium metabisulfite you require.
Since 2005, Weifang Hailei Fine Chemical Co., Ltd. has been manufacturing and exporting sulfur-based chemicals under strict ISO 9001 and industry-specific certifications. Our sodium metabisulfite is produced in a dedicated facility with advanced crystallization controls, ensuring every batch meets the precise physical and chemical properties detailed in this guide. We maintain ready stock in our warehouse, enabling 7–15 day lead times for standard FCL orders.
When you partner with Hailei, you gain:
Don’t leave your procurement to chance. If you need a reliable supply of sodium metabisulfite that matches the property specifications critical to your operation, request a quote today. Visit our sodium metabisulfite product page to download the latest COA, MSDS, and application brochures, and let us customize a shipment that meets your exact volume and grading needs.
For procurement managers and chemical engineers sourcing bulk reducing agents, a thorough understanding of the properties of sodium metabisulfite is the foundation of successful formulation, safe handling, and cost-effective supply chain management. From water dechlorination at municipal treatment plants to cyanide detoxification in gold mines and sulfite preservation in food processing, this versatile inorganic compound delivers reliable performance only when its chemical and physical characteristics align with end-use requirements.
At Weifang Hailei Fine Chemical Co., Ltd., we supply sodium metabisulfite (Na₂S₂O₅, CAS 7681-57-4) in both food-grade (FCC compliant) and industrial-grade (97–98% purity) to buyers across India, Southeast Asia, Africa, and the Middle East. This guide decodes every property you need to evaluate before issuing a purchase order, helping you avoid caking in storage, insufficient SO₂ release, or regulatory non-compliance.
Understanding what is sodium metabisulfite made from clarifies its inherent properties. Industrially, sodium metabisulfite is produced by saturating a sodium carbonate or sodium hydroxide solution with sulfur dioxide (SO₂). The exothermic reaction first forms sodium bisulfite (NaHSO₃) in solution, which is then carefully dehydrated through cooling and controlled crystallization to yield solid sodium metabisulfite:
2 NaHSO₃(aq) → Na₂S₂O₅(s) + H₂O
The product is a white to yellowish crystalline powder or granular material with a pungent SO₂ odor. Because its synthesis relies on high-purity SO₂ gas and a low-iron process environment, the quality of inputs directly determines the final product’s heavy metal profile and clarity in solution. For food-grade material, additional purification steps ensure compliance with FCC or E223 monographs, making it safe for use as a preservative in dried fruits, wines, and starch syrups.
A technical evaluation begins with the core properties of sodium metabisulfite. These data points influence dissolution rates, dosing precision, and compatibility with other process chemicals.
These parameters are not just laboratory curiosities—they directly affect real-world outcomes. For instance, the acidic pH of a metabisulfite solution makes it ideal for acidifying and preserving high-sugar food systems, while the decomposition temperature dictates safe storage away from heat sources.
Sodium metabisulfite is traded primarily in two purity specifications: industrial grade (typically 97–98% Na₂S₂O₅) and food grade (≥98% plus strict limits on iron, arsenic, and heavy metals). The property differences may seem subtle, but they have outsized impacts in sensitive applications.
Industrial grade (97–98%): Optimized for water treatment, gold mining (cyanide destruction), and pulp & paper bleaching. A lower assay of 97% still supplies more than 65% equivalent SO₂ content, but the 1–2% inert salts or sulfate residues can affect clarity in closed-loop water systems. Buyers should monitor iron content (<0.003% typical), since dissolved iron can catalyze unwanted oxidation or stain pulp.
Food grade (FCC/E223): Must meet purity thresholds for arsenic (≤3 mg/kg), lead (≤2 mg/kg), and selenium. The absence of chloride by-products ensures no off-flavors in wine or dried fruit. At Hailei Chemical, our food-grade sodium metabisulfite is manufactured under rigorous HACCP-guided protocols to guarantee compliance with international food safety standards.
When specifying your purchase, always request a Certificate of Analysis (COA) detailing assay, SO₂ content, pH of 10% solution, iron, heavy metals, and water-insoluble matter. The sodium metabisulfite product page provides typical Hailei COA ranges to simplify your comparison.
Many industrial buyers wonder about the interchangeability of sodium bisulfite and sodium metabisulfite. While both provide SO₂ in solution, their chemical properties lead to different dosing behaviors and storage considerations.
| Property | Sodium Metabisulfite (Na₂S₂O₅) | Sodium Bisulfite (NaHSO₃) |
|---|---|---|
| Physical form | Dry crystalline powder/granules | Often supplied as solution (approx. 40%) or crystalline solid (less stable) |
| SO₂ equivalent | Approx. 65–67% by weight | Approx. 22–24% in commercial solutions; solid bisulfite contains 60–65% but is hygroscopic |
| pH of solution | 4.0–5.5 (10% solution) | 2.5–4.0 (solution), more acidic |
| Stability in storage | Excellent when kept dry; >12 months shelf life | Solution prone to oxidation by air; solid form absorbs moisture rapidly |
| Shipping | Dry bulk; cost-effective long-distance shipping | Solution requires tankers or IBCs; higher freight per active SO₂ |
| Typical applications | Water dechlorination, gold mining, food preservative, pulp bleaching, textile | On-site chlorine neutralization, reducing agent in chemical synthesis, leather tanning |
The choice often boils down to logistics and pH buffering. For intercontinental shipments where freight cost and product stability matter, dry sodium metabisulfite is the preferred form. Upon dissolution in water, it forms sodium bisulfite ions, delivering the same reducing action. However, if your process demands immediate solution without handling dry powder, a pre-made bisulfite solution might be convenient—though it costs more per kilogram of SO₂ delivered. Hailei supplies both dry sodium metabisulfite and can direct you to logistics partners for sodium bisulfite solutions where needed.
Knowing how to use sodium metabisulphite safely and efficiently starts with respecting its reactivity profile. The compound’s core property is its ability to release sulfur dioxide in acidic conditions or when heated, making it a potent oxygen scavenger and antimicrobial agent.
In municipal and industrial water treatment, sodium metabisulfite instantly neutralizes free chlorine and chloramines. The stoichiometric reaction requires 1.34 parts of pure Na₂S₂O₅ per part of chlorine. A typical dosing rate is 2–3 mg/L of a 10% metabisulfite solution per mg/L residual chlorine, adjusted for mixing efficiency. Because the reaction drops pH slightly, systems with low alkalinity may need buffering.
The SO₂/air process (INCO method) uses metabisulfite as the SO₂ source to oxidize cyanides (CN⁻) to cyanate (OCN⁻), catalyzed by copper. The reducing property here must be carefully controlled: a solution pH between 8.5 and 9.5 optimizes cyanide destruction while minimizing off-gassing of HCN. Miners often dose metabisulfite at 2–4 grams per gram of WAD cyanide.
As an E223 additive, sodium metabisulfite inhibits enzymatic and non-enzymatic browning in dried fruits, frozen seafood, and wine. The effective SO₂ concentration for antimicrobial action is 50–400 ppm, depending on the product. Its ability to lower pH helps stabilize ascorbic acid and color. Importantly, residual sulfite must meet local labeling laws—typically <10 ppm SO₂ in final product.
In mechanical pulping, metabisulfite acts as a reducing bleach to brighten lignin-rich pulps without degrading cellulose. The property of preserving fiber strength while increasing brightness by 5–8 ISO points makes it valuable for newsprint and tissue grades. Typical application: 1–3% on oven-dry pulp at pH 5–6.
After chlorine bleaching, fabrics carry residual chlorine that can yellow or weaken fibers. A 0.5–2 g/L sodium metabisulfite bath, based on its rapid dechlorination property, eliminates this risk. The slightly acidic pH helps close fiber cuticles, improving dye uptake in subsequent steps.
For detailed application recipes and custom formulation support, refer to our comprehensive sodium metabisulfite application guide.
Procuring sodium metabisulfite without verifying properties against recognized standards can lead to inconsistent batch performance, rejected shipments, or even plant shutdowns. A rigorous supplier evaluation framework should include the following analytical benchmarks.
Request a batch-specific COA with every shipment. Third-party testing by SGS, Bureau Veritas, or Intertek adds an extra layer of trust. Hailei Chemical routinely arranges pre-shipment inspections against these parameters to ensure that the properties of sodium metabisulfite you order are exactly what you receive.
The shelf life and performance of sodium metabisulfite depend critically on storage conditions. Exposure to moisture and heat degrades its reducing power and turns the powder into a hard, unworkable mass.
Key recommendations:
Understanding these environmental sensitivities allows you to plan inventory turnover and avoid waste, directly protecting your investment in each purchased ton.
India is one of the world’s largest importers of sodium metabisulfite, driven by expansive water treatment programs, a massive gold import sector, and a growing food processing industry. If you are seeking a sodium metabisulfite supplier in India, working directly with a chemical exporter in China can often offer cost advantages of 12–18% compared to local distributors, provided you manage shipping and quality inspection efficiently.
Hailei Chemical serves Indian buyers through Nhava Sheva, Mundra, Chennai, and Kolkata ports. Our typical packaging in 25 kg HDPE bags with inner liner is palletized and shrink-wrapped for tropical climates. We also offer 1000–1250 kg big bags and custom private labeling. For oil & gas or mining tenders, we provide full documentation: COA, MSDS, Certificate of Origin, and fumigation certificates as required by Indian customs (HS Code 28321010).
The same logistics expertise applies to buyers in the Middle East (Jebel Ali, Dammam), Southeast Asia, and Africa. Our in-house team coordinates FCL and LCL shipments, transit times, and demurrage avoidance. By consolidating volumes, we help you optimize landed costs without compromising the high purity and consistent properties of sodium metabisulfite you require.
Since 2005, Weifang Hailei Fine Chemical Co., Ltd. has been manufacturing and exporting sulfur-based chemicals under strict ISO 9001 and industry-specific certifications. Our sodium metabisulfite is produced in a dedicated facility with advanced crystallization controls, ensuring every batch meets the precise physical and chemical properties detailed in this guide. We maintain ready stock in our warehouse, enabling 7–15 day lead times for standard FCL orders.
When you partner with Hailei, you gain:
Don’t leave your procurement to chance. If you need a reliable supply of sodium metabisulfite that matches the property specifications critical to your operation, request a quote today. Visit our sodium metabisulfite product page to download the latest COA, MSDS, and application brochures, and let us customize a shipment that meets your exact volume and grading needs.
For procurement managers and chemical engineers sourcing bulk reducing agents, a thorough understanding of the properties of sodium metabisulfite is the foundation of successful formulation, safe handling, and cost-effective supply chain management. From water dechlorination at municipal treatment plants to cyanide detoxification in gold mines and sulfite preservation in food processing, this versatile inorganic compound delivers reliable performance only when its chemical and physical characteristics align with end-use requirements.
At Weifang Hailei Fine Chemical Co., Ltd., we supply sodium metabisulfite (Na₂S₂O₅, CAS 7681-57-4) in both food-grade (FCC compliant) and industrial-grade (97–98% purity) to buyers across India, Southeast Asia, Africa, and the Middle East. This guide decodes every property you need to evaluate before issuing a purchase order, helping you avoid caking in storage, insufficient SO₂ release, or regulatory non-compliance.
Understanding what is sodium metabisulfite made from clarifies its inherent properties. Industrially, sodium metabisulfite is produced by saturating a sodium carbonate or sodium hydroxide solution with sulfur dioxide (SO₂). The exothermic reaction first forms sodium bisulfite (NaHSO₃) in solution, which is then carefully dehydrated through cooling and controlled crystallization to yield solid sodium metabisulfite:
2 NaHSO₃(aq) → Na₂S₂O₅(s) + H₂O
The product is a white to yellowish crystalline powder or granular material with a pungent SO₂ odor. Because its synthesis relies on high-purity SO₂ gas and a low-iron process environment, the quality of inputs directly determines the final product’s heavy metal profile and clarity in solution. For food-grade material, additional purification steps ensure compliance with FCC or E223 monographs, making it safe for use as a preservative in dried fruits, wines, and starch syrups.
A technical evaluation begins with the core properties of sodium metabisulfite. These data points influence dissolution rates, dosing precision, and compatibility with other process chemicals.
These parameters are not just laboratory curiosities—they directly affect real-world outcomes. For instance, the acidic pH of a metabisulfite solution makes it ideal for acidifying and preserving high-sugar food systems, while the decomposition temperature dictates safe storage away from heat sources.
Sodium metabisulfite is traded primarily in two purity specifications: industrial grade (typically 97–98% Na₂S₂O₅) and food grade (≥98% plus strict limits on iron, arsenic, and heavy metals). The property differences may seem subtle, but they have outsized impacts in sensitive applications.
Industrial grade (97–98%): Optimized for water treatment, gold mining (cyanide destruction), and pulp & paper bleaching. A lower assay of 97% still supplies more than 65% equivalent SO₂ content, but the 1–2% inert salts or sulfate residues can affect clarity in closed-loop water systems. Buyers should monitor iron content (<0.003% typical), since dissolved iron can catalyze unwanted oxidation or stain pulp.
Food grade (FCC/E223): Must meet purity thresholds for arsenic (≤3 mg/kg), lead (≤2 mg/kg), and selenium. The absence of chloride by-products ensures no off-flavors in wine or dried fruit. At Hailei Chemical, our food-grade sodium metabisulfite is manufactured under rigorous HACCP-guided protocols to guarantee compliance with international food safety standards.
When specifying your purchase, always request a Certificate of Analysis (COA) detailing assay, SO₂ content, pH of 10% solution, iron, heavy metals, and water-insoluble matter. The sodium metabisulfite product page provides typical Hailei COA ranges to simplify your comparison.
Many industrial buyers wonder about the interchangeability of sodium bisulfite and sodium metabisulfite. While both provide SO₂ in solution, their chemical properties lead to different dosing behaviors and storage considerations.
| Property | Sodium Metabisulfite (Na₂S₂O₅) | Sodium Bisulfite (NaHSO₃) |
|---|---|---|
| Physical form | Dry crystalline powder/granules | Often supplied as solution (approx. 40%) or crystalline solid (less stable) |
| SO₂ equivalent | Approx. 65–67% by weight | Approx. 22–24% in commercial solutions; solid bisulfite contains 60–65% but is hygroscopic |
| pH of solution | 4.0–5.5 (10% solution) | 2.5–4.0 (solution), more acidic |
| Stability in storage | Excellent when kept dry; >12 months shelf life | Solution prone to oxidation by air; solid form absorbs moisture rapidly |
| Shipping | Dry bulk; cost-effective long-distance shipping | Solution requires tankers or IBCs; higher freight per active SO₂ |
| Typical applications | Water dechlorination, gold mining, food preservative, pulp bleaching, textile | On-site chlorine neutralization, reducing agent in chemical synthesis, leather tanning |
The choice often boils down to logistics and pH buffering. For intercontinental shipments where freight cost and product stability matter, dry sodium metabisulfite is the preferred form. Upon dissolution in water, it forms sodium bisulfite ions, delivering the same reducing action. However, if your process demands immediate solution without handling dry powder, a pre-made bisulfite solution might be convenient—though it costs more per kilogram of SO₂ delivered. Hailei supplies both dry sodium metabisulfite and can direct you to logistics partners for sodium bisulfite solutions where needed.
Knowing how to use sodium metabisulphite safely and efficiently starts with respecting its reactivity profile. The compound’s core property is its ability to release sulfur dioxide in acidic conditions or when heated, making it a potent oxygen scavenger and antimicrobial agent.
In municipal and industrial water treatment, sodium metabisulfite instantly neutralizes free chlorine and chloramines. The stoichiometric reaction requires 1.34 parts of pure Na₂S₂O₅ per part of chlorine. A typical dosing rate is 2–3 mg/L of a 10% metabisulfite solution per mg/L residual chlorine, adjusted for mixing efficiency. Because the reaction drops pH slightly, systems with low alkalinity may need buffering.
The SO₂/air process (INCO method) uses metabisulfite as the SO₂ source to oxidize cyanides (CN⁻) to cyanate (OCN⁻), catalyzed by copper. The reducing property here must be carefully controlled: a solution pH between 8.5 and 9.5 optimizes cyanide destruction while minimizing off-gassing of HCN. Miners often dose metabisulfite at 2–4 grams per gram of WAD cyanide.
As an E223 additive, sodium metabisulfite inhibits enzymatic and non-enzymatic browning in dried fruits, frozen seafood, and wine. The effective SO₂ concentration for antimicrobial action is 50–400 ppm, depending on the product. Its ability to lower pH helps stabilize ascorbic acid and color. Importantly, residual sulfite must meet local labeling laws—typically <10 ppm SO₂ in final product.
In mechanical pulping, metabisulfite acts as a reducing bleach to brighten lignin-rich pulps without degrading cellulose. The property of preserving fiber strength while increasing brightness by 5–8 ISO points makes it valuable for newsprint and tissue grades. Typical application: 1–3% on oven-dry pulp at pH 5–6.
After chlorine bleaching, fabrics carry residual chlorine that can yellow or weaken fibers. A 0.5–2 g/L sodium metabisulfite bath, based on its rapid dechlorination property, eliminates this risk. The slightly acidic pH helps close fiber cuticles, improving dye uptake in subsequent steps.
For detailed application recipes and custom formulation support, refer to our comprehensive sodium metabisulfite application guide.
Procuring sodium metabisulfite without verifying properties against recognized standards can lead to inconsistent batch performance, rejected shipments, or even plant shutdowns. A rigorous supplier evaluation framework should include the following analytical benchmarks.
Request a batch-specific COA with every shipment. Third-party testing by SGS, Bureau Veritas, or Intertek adds an extra layer of trust. Hailei Chemical routinely arranges pre-shipment inspections against these parameters to ensure that the properties of sodium metabisulfite you order are exactly what you receive.
The shelf life and performance of sodium metabisulfite depend critically on storage conditions. Exposure to moisture and heat degrades its reducing power and turns the powder into a hard, unworkable mass.
Key recommendations:
Understanding these environmental sensitivities allows you to plan inventory turnover and avoid waste, directly protecting your investment in each purchased ton.
India is one of the world’s largest importers of sodium metabisulfite, driven by expansive water treatment programs, a massive gold import sector, and a growing food processing industry. If you are seeking a sodium metabisulfite supplier in India, working directly with a chemical exporter in China can often offer cost advantages of 12–18% compared to local distributors, provided you manage shipping and quality inspection efficiently.
Hailei Chemical serves Indian buyers through Nhava Sheva, Mundra, Chennai, and Kolkata ports. Our typical packaging in 25 kg HDPE bags with inner liner is palletized and shrink-wrapped for tropical climates. We also offer 1000–1250 kg big bags and custom private labeling. For oil & gas or mining tenders, we provide full documentation: COA, MSDS, Certificate of Origin, and fumigation certificates as required by Indian customs (HS Code 28321010).
The same logistics expertise applies to buyers in the Middle East (Jebel Ali, Dammam), Southeast Asia, and Africa. Our in-house team coordinates FCL and LCL shipments, transit times, and demurrage avoidance. By consolidating volumes, we help you optimize landed costs without compromising the high purity and consistent properties of sodium metabisulfite you require.
Since 2005, Weifang Hailei Fine Chemical Co., Ltd. has been manufacturing and exporting sulfur-based chemicals under strict ISO 9001 and industry-specific certifications. Our sodium metabisulfite is produced in a dedicated facility with advanced crystallization controls, ensuring every batch meets the precise physical and chemical properties detailed in this guide. We maintain ready stock in our warehouse, enabling 7–15 day lead times for standard FCL orders.
When you partner with Hailei, you gain:
Don’t leave your procurement to chance. If you need a reliable supply of sodium metabisulfite that matches the property specifications critical to your operation, request a quote today. Visit our sodium metabisulfite product page to download the latest COA, MSDS, and application brochures, and let us customize a shipment that meets your exact volume and grading needs.
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.
When sourcing chemicals for large-scale industrial applications, understanding the properties of sodium metabisulfite is not just a technical formality—it’s the foundation for safe handling, efficient use, and consistent product quality. Sodium metabisulfite (Na₂S₂O₅), often referred to as SMBS, is a versatile inorganic compound with roles spanning water treatment, gold mining, food preservation, and even niche cosmetic uses. For procurement managers and chemical engineers, grasping its physical, chemical, and safety properties ensures you select the right grade, store it correctly, and minimize operational risks. In this guide, Hailei Chemical, a trusted exporter of high-purity sodium metabisulfite, breaks down everything you need to know about this essential chemical’s properties, from its reactivity and solubility to its health implications and regulatory documentation.
The properties of sodium metabisulfite begin with its molecular identity. With the chemical formula Na₂S₂O₅ and CAS number 7681-57-4, it appears as a white to yellowish crystalline powder or granular solid. It is highly soluble in water (about 54 g/100 mL at 20°C), releasing sulfur dioxide (SO₂) upon dissolution—a reaction that underlies most of its industrial utility. The compound is actually a dimer of sodium bisulfite (NaHSO₃), existing in equilibrium when dissolved. When dry, it is relatively stable, but in the presence of moisture or acids, it decomposes, making proper packaging (typically 25 kg HDPE bags with inner liners) critical for supply chain integrity.
For buyers, the purity of SMBS is a defining property. Industrial grades typically range from 97% to 98%, while food-grade material must meet stricter specifications, often exceeding 98% purity with low heavy metal and arsenic content. Hailei Chemical consistently supplies both grades, ensuring that the SO₂ release curve—a property directly tied to the product’s reducing power—meets the demands of each application. For instance, in water dechlorination, a fast and complete release of SO₂ is essential to neutralize residual chlorine; in food preservation, controlled release and high purity prevent off-flavors and regulatory violations.
Beyond the chemical, the physical properties of sodium metabisulfite impact everything from material handling to dosing accuracy. The typical bulk density ranges from 0.9 to 1.2 g/cm³, and the product is hygroscopic—meaning it absorbs moisture from the air. This necessitates airtight storage in cool, dry conditions to prevent caking and premature decomposition. Particle size distribution can be customized: powder forms dissolve quickly for solution preparation, while granular or compacted forms reduce dust formation and are preferred in automatic dosing systems. Understanding these physical nuances allows buyers to align the product with their specific facility requirements, minimizing waste and downtime.
Any industrial chemical requires a clear-eyed assessment of its hazards, and the sodium metabisulfite health risks are well-documented. The primary route of exposure is inhalation of dust or the sulfur dioxide gas released when the product contacts moisture or acids. Acute symptoms include respiratory irritation, coughing, and shortness of breath. Prolonged or repeated exposure can exacerbate asthma and other lung conditions. Skin and eye contact can lead to irritation, and ingestion—unlikely in industrial settings but a concern in food environments—can cause gastrointestinal distress. However, when handled with appropriate personal protective equipment (PPE)—including dust masks or respirators, safety goggles, and chemical-resistant gloves—the risks are effectively managed. Hailei Chemical provides detailed safety guidelines with every shipment, aligning with GHS hazard classifications (H302, H318, EUH031).
For procurement teams, mitigating health risks starts with selecting a supplier who offers not only high-purity product but also robust safety data. The greater danger often lies in impurities or inconsistent composition, which can alter the toxicological profile. A reliable partner like Hailei Chemical ensures that every batch is manufactured under tight quality control, reducing the presence of free sulfur trioxide or insoluble matter that could compound health concerns. Proper ventilation and engineering controls in storage and mixing areas are standard practice, but buyers should also verify that their supplier’s packaging minimizes dust emission during unloading—a small design feature with big safety implications.
The sodium metabisulfite MSDS PDF (now more commonly called a Safety Data Sheet, SDS) is the single most important document in a chemical buyer’s compliance toolkit. An SDS contains 16 sections covering identification, hazard information, composition, first-aid measures, fire-fighting guidance, accidental release measures, handling and storage, exposure controls, physical and chemical properties, stability and reactivity, toxicological data, ecological information, disposal considerations, transport information, regulatory status, and other relevant details. When evaluating a supplier, requesting and reviewing the SDS PDF before purchase is non-negotiable. Look for completeness: vague or missing sections, especially in toxicological or ecological fields, are a red flag. The document should clearly state the product’s purity, CAS number, GHS hazard pictograms (corrosive and irritant), and emergency telephone numbers.
Hailei Chemical’s sodium metabisulfite SDS is meticulously prepared and updated to comply with REACH (EU), OSHA HCS (US), and other global standards. It specifies that the product decomposes above 150°C, releasing toxic sulfur dioxide gas, which is critical for fire-fighting teams and warehouse designers. It also provides exposure limits: the Threshold Limit Value-Time-Weighted Average (TLV-TWA) for sodium metabisulfite is typically 5 mg/m³. International buyers should compare the SDS against their local regulatory requirements—customs clearance can be delayed if the SDS doesn’t match the destination country’s format. As part of our commitment to transparency, Hailei Chemical provides the latest SDS PDF upon request and encourages clients to integrate its data into their own site safety protocols.
While industrial uses dominate the market, sodium metabisulfite in skin care is a niche but growing application. Its role here is not as a direct active but as a preservative and antioxidant in formulations like creams, lotions, and hair products. As a reducing agent, it helps prevent oxidation of sensitive ingredients, extending shelf life. It also functions as a hair-waving agent in some permanent wave solutions by cleaving disulfide bonds in keratin. However, this use brings unique challenges: skin contact with sodium metabisulfite can cause allergic reactions in sulfite-sensitive individuals, so cosmetic formulators must adhere to strict concentration limits (typically below 1%) and label accordingly to comply with regulations like the EU Cosmetics Regulation (EC) No 1223/2009.
For buyers supplying the personal care sector, the grade and purity of sodium metabisulfite become paramount. Industrial or technical grades may contain trace metals that catalyze unwanted side reactions or cause skin irritation. Food-grade material is often the minimum standard, but some cosmetic manufacturers demand even higher purity—essentially analytical-grade material. The particle size must be ultra-fine to ensure uniform dispersion in emulsion systems, and heavy metal content must be certified below 10 ppm for lead and 1 ppm for mercury. Hailei Chemical works with clients to provide sodium metabisulfite that meets these stringent specifications, backed by third-party laboratory analysis. While not every buyer will explore this avenue, understanding the cosmetic potential can open new market segments and higher-margin opportunities.
In food preservation, the term sodium bisulfite food preservative is often used interchangeably with sodium metabisulfite, but they are distinct chemicals governed by the same active species. Sodium metabisulfite (E223) is actually a more concentrated form of sulfite: when dissolved in water, one mole of Na₂S₂O₅ yields two moles of sodium bisulfite (NaHSO₃). This means SMBS offers a higher sulfite payload per kilogram, making it more economical for food processors. It is widely used as a preservative in dried fruits, wine, fruit juices, and processed potatoes to inhibit enzymatic and non-enzymatic browning, control microbial growth, and preserve color and flavor. The US FDA permits sulfite usage but mandates labeling above 10 ppm residual SO₂, due to the risk of asthmatic reactions in sensitive consumers. The EU similarly requires declaration when sulfite concentrations exceed 10 mg/kg or mg/L.
For bulk food preservative buyers, the choice between sodium metabisulfite and sodium bisulfite solutions is often driven by handling convenience and cost. SMBS is a dry, stable powder; sodium bisulfite is typically supplied as a liquid solution, which introduces storage and transportation complexities. The solid form of sodium metabisulfite thus reduces freight weight and simplifies inventory management. Purity and impurity profiles are critical: food-grade SMBS must meet specifications for heavy metals, selenium, and arsenic content as per JECFA or FCC monographs. When sourcing from Hailei Chemical, you can request full certificates of analysis that demonstrate compliance with these food safety standards. We supply both standard food-grade powder and non-dusting granules for automated food processing lines, ensuring that the preservative properties translate into reliable product performance.
To make an informed purchasing decision, buyers must connect the properties of sodium metabisulfite to their specific industrial context. In gold mining, for example, the reducing power of SMBS is used to detoxify cyanide tailings. Here, the reaction rate—determined by solubility and particle size—is critical. A fine powder dissolves rapidly, ensuring faster cyanide destruction, while granular forms may be preferred for controlled, continuous dosing. The exothermic nature of the dissolution also means that large-scale mixing requires temperature monitoring to avoid hot spots. Mining companies often demand technical grades with purity above 97% and strict limits on iron and chloride, as these impurities can interfere with the cyanide destruction process or the subsequent recovery of precious metals. Hailei Chemical’s sodium metabisulfite for mining is produced to meet these exacting standards, with customized packaging that allows for direct addition to treatment tanks.
In pulp and paper bleaching, SMBS serves as an antichlor—a reducing agent that neutralizes residual chlorine after bleaching stages. The property that matters most here is the precise stoichiometry of the reaction: Na₂S₂O₅ + Cl₂ + 3H₂O → 2NaHSO₄ + 4HCl. Incomplete dechlorination can lead to corrosion of papermaking equipment and yellowing of the final product. Therefore, the product must have a reliable SO₂ release capacity and low inert content. Water treatment plants using SMBS for dechlorination of drinking water or wastewater face similar precision requirements. They also prioritize low heavy metal content to avoid introducing contaminants into the water supply. By mapping the property set to the application, buyers can move beyond generic specifications and collaborate with their supplier to define the optimal grade, form, and packaging configuration—a strategic process that Hailei Chemical facilitates through technical consultation.
Beyond the intrinsic properties of sodium metabisulfite, extrinsic quality parameters set different suppliers apart. Reputable manufacturers adhere to internationally recognized specifications. A typical industrial-grade analysis includes: purity (Na₂S₂O₅) ≥ 97.0%, iron (Fe) ≤ 0.003%, water-insoluble matter ≤ 0.05%, heavy metals (as Pb) ≤ 0.001%, and arsenic (As) ≤ 0.0001%. Food-grade specifications are tighter, with purity often exceeding 98.0% and even lower heavy metal limits. The absence of anti-caking agents or other additives is also a mark of quality, especially for food and pharmaceutical applications. Hailei Chemical’s production facility in Weifang, China, utilizes advanced controlled-reaction technology to consistently meet these benchmarks. Batch-level testing is standard, and we provide full documentation for every shipment, including COA, SDS, and where required, kosher or halal certifications for food-grade material.
For overseas buyers, transparency extends to logistics. The hygroscopic nature of sodium metabisulfite means that ocean freight conditions—temperature fluctuations, humidity—can degrade the material if packaging is suboptimal. Our bag construction includes moisture-barrier liners and palletization with shrink wrap to protect the product during transit. We also recommend storage in climate-controlled warehouses upon arrival. These practical dimensions of the supply chain are as vital as the molecular properties themselves. By partnering with Hailei Chemical, you gain more than a chemical supplier; you gain a partner attuned to the full lifecycle of the product, from production line to your plant floor.
Industrial buyers often default to price comparison, but a property-centric evaluation yields better long-term value. Consider these factors:
Hailei Chemical invites you to apply this framework. Request a sample, compare the COA against your internal specs, and discuss any customization needs with our technical team. We offer direct support for product trials, including guidance on dissolution protocols and safety integration.
Understanding the properties of sodium metabisulfite is the key to optimizing your industrial process, ensuring worker safety, and maintaining product quality. Whether your need is for high-purity food-grade preservative, mining-grade cyanide detox reagent, or water treatment antichlor, Hailei Chemical delivers consistent, documented, and precisely specified sodium metabisulfite to ports worldwide. Visit our Sodium Metabisulfite product page to download detailed technical data, safety documentation, and request a competitive quotation. For tailored solutions and bulk pricing, contact our sales team today—we are ready to support your next procurement cycle with the quality and reliability your business demands.