When procurement managers and chemical engineers evaluate a commodity chemical like sodium metabisulfite, they rarely start with the molecular diagram. Yet the sodium metabisulfite chemical structure is precisely what makes this inorganic salt indispensable in water treatment, gold mining, food preservation, pulp bleaching, and textiles. Understanding the disulfite anion (S2O52−) unlocks insights into reactivity, shelf life, safety, and why not all sodium metabisulfite suppliers deliver equal quality. In this deep dive, we decode the structure of sodium metabisulfite (Na2S2O5, CAS 7681-57-4) and show how it translates into real-world performance, helping you make smarter sourcing decisions from a sodium metabisulfite supplier in India or anywhere in South Asia, including the growing sodium metabisulfite price in Sri Lanka market.
At its core, sodium metabisulfite (SMBS) is an inorganic compound of sodium, sulfur, and oxygen with the formula Na2S2O5. The sodium metabisulfite chemical structure features two sodium cations (Na+) and one disulfite dianion (S2O52−). The disulfite ion consists of two sulfur atoms linked by a direct sulfur–sulfur bond, with three oxygen atoms bonded to each sulfur in a tetrahedral arrangement. The S–S bond length is approximately 2.17 Å, significantly longer than typical S–O bonds, making it the reactive hinge of the molecule. In crystalline form, SMBS adopts a monoclinic crystal system at room temperature, with the disulfite anions arranged in layers separated by sodium ions.
This structure explains why sodium metabisulfite is not just a simple sulfite salt. When dissolved in water, the disulfite ion readily hydrolyses to form bisulfite (HSO3−) and sulfite (SO32−) ions, creating an equilibrium that acts as a powerful reducing agent. The reversible nature of this hydrolysis is the chemical basis for its effectiveness as a preservative, oxygen scavenger, and dechlorination agent.
The S–S bridge is the defining feature. Each sulfur atom is sp3 hybridized, with a lone pair and three S–O bonds. The O–S–O bond angles are close to 109.5°, but the S–S–O angles are slightly compressed. This strained geometry makes the S–S bond susceptible to cleavage, releasing sulfite species that can react with chlorine, oxygen, and heavy metals. The structure’s sensitivity to heat and moisture is directly tied to this labile S–S bond—above 65°C in air, SMBS begins to decompose, releasing sulfur dioxide (SO2) and forming sodium sulfate. That’s why proper storage and packaging are critical considerations when sourcing from a supplier, especially in humid tropical climates like those in India and Sri Lanka.
The benefits of sodium metabisulfite are not just a list of applications; they are a direct consequence of its molecular architecture. By understanding the structure, buyers can better evaluate product specifications, compare technical data sheets, and troubleshoot process inefficiencies.
In municipal and industrial water treatment, chlorine is widely used to disinfect potable water or treat wastewater. But residual chlorine must be removed before discharge or further processing to protect membranes, ion-exchange resins, and aquatic life. Sodium metabisulfite reacts stoichiometrically with chlorine: 1.34 mg of pure Na2S2O5 removes 1 mg of Cl2. This efficiency comes from the rapid reduction of hypochlorous acid (HOCl) by sulfite/bisulfite ions produced upon dissolution. The S–S bond cleavage provides two moles of sulfite per mole of SMBS, giving it a higher dechlorination capacity than sodium sulfite on a weight basis. For a water treatment plant operator or a procurement manager evaluating a sodium metabisulfite supplier, specifying a minimum purity of 97% (as per Hailei’s typical grades) ensures consistent chlorine removal rates.
The gold mining industry relies on sodium metabisulfite for the detoxification of cyanide-containing tailings. The SO2/air process (or INCO process) uses SMBS as a source of sulfur dioxide, which, in the presence of a copper catalyst, oxidizes free cyanide (CN−) and weakly bound metal–cyanide complexes to cyanate (OCN−). Here, the disulfite ion’s ability to release SO2 upon acidification or thermal activation is key. In aqueous solution, SMBS generates bisulfite, which decomposes to yield SO2. The controlled delivery of SO2 from a solid, easy-to-handle powder is a major advantage over compressed sulfur dioxide gas. For mining chemical buyers in regions like India or Southeast Asia, the logistics and safety profile of powdered SMBS often tip the balance in procurement decisions.
As a food preservative (E223), sodium metabisulfite is permitted in dried fruits, wine, fruit juices, and some processed vegetables. Its preservative action stems from the release of sulfite ions, which inhibit enzymatic and non-enzymatic browning, scavenge oxygen, and suppress microbial growth. The sulfur–sulfur bond in the disulfite ion provides a slow-release mechanism for sulfite, making it more stable during storage than sodium sulfite alone. However, food-grade SMBS must meet strict purity and heavy metal limits — typically >98% purity with iron, selenium, and lead in low ppm. Understanding the molecular structure helps food safety auditors and quality managers appreciate why impurities can catalyze decomposition and affect shelf life.
In pulp and paper mills, sodium metabisulfite is used as a bleaching agent for mechanical pulps (brightening) and as an antichlor to neutralize residual hydrogen peroxide or chlorine after bleaching stages. The structure’s rapid hydrolysis yields bisulfite, which reacts immediately with oxidizers, preventing fiber degradation. Similarly, in textile processing, after chlorine bleaching of cotton or synthetic blends, SMBS is applied to remove trace chlorine and halting further oxidation. This preserves fabric strength and dye receptivity. The instant reactivity is directly linked to the disulfite ion’s high reduction potential and the labile S–S bond.
Any B2B buyer or end-user handling chemicals must ask: is sodium metabisulfite bad for you? The answer depends on exposure route, concentration, and individual susceptibility. The chemical structure itself holds clues. In acidic environments (like the stomach or in the presence of moisture on skin), SMBS releases sulfur dioxide gas, which is a respiratory irritant. The sulfite ions can trigger asthmatic reactions in sensitive individuals — an estimated 3–10% of asthmatics may experience sulfite sensitivity. That’s why food labeling regulations (e.g., FDA 21 CFR 182.3766, EU Regulation (EC) 1333/2008) require clear declaration of sulfites above 10 mg/L (as SO2).
For industrial workers handling bulk sodium metabisulfite, the key hazards are dust inhalation and skin/eye contact. The powder is classified as harmful if swallowed (H302) and causes serious eye irritation (H319) under GHS. Proper PPE — nitrile gloves, safety goggles, and dust masks — mitigates risks. In well-ventilated areas, airborne SO2 levels remain below occupational exposure limits. A reputable sodium metabisulfite supplier in India or elsewhere will provide comprehensive Safety Data Sheets (SDS) that detail handling, first aid, and environmental precautions, aligning with the structure-derived reactivity.
Environmentally, sodium metabisulfite rapidly oxidizes to sulfate in water and soil, which is non-toxic to aquatic life at typical industrial dilution levels. Its widespread use in wastewater dechlorination and cyanide destruction actually reduces environmental harm compared to leaving chlorine or cyanide untreated. So, while direct contact can be harmful, SMBS is an indispensable tool for environmental protection when properly managed.
The sodium metabisulfite price in Sri Lanka and other South Asian markets fluctuates based on global sulfur pricing, freight costs, and local demand from tea processing, water treatment, and rubber industries. Sri Lanka’s tea estates historically use small quantities of SMBS as a post-harvest preservative and for cleaning equipment. Water treatment plants in Colombo and beyond rely on it for dechlorination. Understanding the chemical structure ties back to price because higher purity grades (>98%, low heavy metals) command a premium due to stricter process controls during manufacturing. For buyers monitoring sodium metabisulfite price in Sri Lanka, it’s critical to compare not just CIF Colombo rates but the landed quality — moisture pickup during shipment can degrade the product, reducing effective purity.
India is both a large producer and consumer of sodium metabisulfite. When vetting a sodium metabisulfite supplier in India, look for ISO 9001 certification, adherence to IS 248:1978 or international specs, and the ability to provide Certificates of Analysis (CoA) with full impurity profiles. The chemical structure’s vulnerability to moisture means packaging should be in 25 kg HDPE bags with inner liners, or 1,000 kg FIBCs with moisture barriers. Hailei Chemical, as a leading exporter from China, supports buyers across South Asia with consistent 97%–98% food grade and industrial grade material. We help Indian and Sri Lankan importers reduce supply chain risk through stable quality and reliable logistics.
Beyond price per metric ton, total cost of ownership includes freight, port handling, customs clearance, and potential spoilage. A supplier that understands the sodium metabisulfite chemical structure and its storage needs will pre-dry product, use anti-caking agents sparingly (if at all), and recommend the right packaging for monsoon season deliveries. Hailei’s technical team can guide you on optimal storage conditions and shelf-life extension — small insights that save thousands in operational delays.
When heated, sodium metabisulfite decomposes before melting, starting at 150°C. The disulfite ion loses SO2 and leaves sodium sulfite and then sodium sulfate. This decomposition pathway is critical when using SMBS in hot environments — for instance, in gold cyanidation where pulp temperatures can reach 40–50°C. Understanding the structure helps engineers adjust dosing to compensate for partial thermal loss. High-quality SMBS with low chloride and iron impurities exhibits slower thermal decomposition, a detail not obvious from a basic assay but apparent to those who truly understand the chemical structure.
Exposure to UV light can accelerate the breakdown of the S–S bond through radical mechanisms. That’s why sodium metabisulfite is stored in opaque packaging and kept away from direct sunlight. In tropical warehouses common in India and Sri Lanka, unshielded storage can reduce product potency by several percent per month. Hailei’s production process minimizes trace metals that catalyze this photodegradation, a direct benefit of premium manufacturing informed by the sodium metabisulfite chemical structure.
For industrial users, the CoA is the practical fingerprint of the chemical structure. Key parameters include:
A supplier mastering the sodium metabisulfite chemical structure delivers product that consistently meets these specs batch after batch. For example, excess sodium sulfate or chloride by-products indicate sloppy manufacturing that can skew the pH and reduce dechlorination efficiency.
From an engineering standpoint, the chemical structure dictates dissolution heat and feed system design. Dissolving SMBS in water is endothermic; the solution cools, which can slow dissolution in cold climates. In tropical settings, this cooling is negligible. The solution must be prepared fresh because sulfite ions oxidize in air; a structured understanding of the S–S bond’s hydrolysis rate helps determine maximum holding time for prepared tanks. Typically, a 10% solution should be used within 24 hours to maintain full dechlorination potency.
For gold mining, the INCO process requires precise SO2 dosing. While SMBS is a solid SO2 source, engineers must account for the 67% SO2 equivalent by weight (1 g Na2S2O5 liberates ~0.67 g SO2). This stoichiometry, rooted in the chemical structure, is non-negotiable for cyanide detoxification efficiency. Under-dosing can leave residual cyanide; over-dosing wastes reagent and can lower pH excessively.
Precious few procurement teams look beyond the product name and price per kilogram. Yet the sodium metabisulfite chemical structure is the ultimate quality spec. It explains why a cheap SMBS from an unreliable source might lose 50% of its SO2 content before arrival, or why it cakes solid in the bag due to moisture absorption facilitated by structural impurities. It tells you why food-grade material must be virtually free of selenium — a structural contaminant that substitutes for sulfur in the disulfite ion, altering its toxicological profile. And it reassures you that when you dose your water treatment plant or CIP system, the reaction will be fast, complete, and safe.
Hailei Chemical leverages this structural knowledge to produce sodium metabisulfite that meets stringent international standards. Our sodium metabisulfite product line is manufactured under ISO 9001, with dedicated food-grade and tech-grade production runs to eliminate cross-contamination. For buyers from India, Sri Lanka, or anywhere seeking a reliable sodium metabisulfite supplier in India alternative, we offer technical support on storage, dosing, and regulatory compliance.
Sodium sulfite (Na2SO3) contains the sulfite ion SO32− only, while sodium metabisulfite contains the disulfite ion S2O52−, which is essentially a dimer of bisulfite with a S–S bond. In water, SMBS forms an equilibrium mixture of sulfite and bisulfite, providing more SO2 equivalents per weight than sodium sulfite. This structural advantage makes SMBS the more concentrated reducing agent.
Yes, the disulfite ion is employed in the reduction of aldehydes to alcohols (e.g., in the synthesis of hydroxymethyl derivatives) and in sulfonation reactions. Its mild reducing ability, derived from the S–S bond, is preferred when harsher reagents might cause over-reduction.
The primary concerns: release of SO2 gas in acidic conditions, respiratory sensitization, and eye/skin irritation. Proper engineering controls (ventilation, dust collection) and PPE address these risks. The sodium metabisulfite chemical structure provides a predictable release profile, enabling safe design of handling systems.
Request a CoA from your sodium metabisulfite supplier and perform independent testing if needed. Key methods: iodometric titration for assay, ICP-MS for trace metals, and pH measurement of a 5% solution. Hailei encourages third-party verification to build trust.
The sodium metabisulfite chemical structure is far more than an academic curiosity. It is the blueprint for the compound’s reducing power, its hydrolysis dynamics, its thermal sensitivity, and its role across industries from water treatment to food preservation. For B2B buyers, this molecular understanding translates into better specs, safer handling, and a stronger negotiation position when comparing suppliers. Whether you’re monitoring the sodium metabisulfite price in Sri Lanka for a new water project or looking for a consistent sodium metabisulfite supplier in India for gold mining reagents, look beyond the label. Understand the structure, and you’ll understand the quality.
Ready to secure a reliable supply of high-purity sodium metabisulfite backed by technical expertise? Request your customized quote today and let Hailei Chemical’s team support your operational success with product consistency and deep structural knowledge.
At the heart of every effective water dechlorination process, gold leaching operation, or food preservation system lies a compound with a seemingly simple identity: sodium metabisulfite molecular formula Na2S2O5. For procurement managers, chemical engineers, and quality control specialists, understanding this formula is far more than an academic exercise. It’s the key to predicting product behavior, verifying supplier claims, and ensuring consistent operational results. When you source sodium metabisulfite – whether for a municipal water plant in Southeast Asia or a gold mine in Africa – the molecular structure directly dictates how the chemical will perform under your specific pH, temperature, and process conditions.
The sodium metabisulfite molecular formula is Na2S2O5, representing a white crystalline or granular powder with a pungent sulfur dioxide odor. Its molar mass is 190.107 g/mol. In solid form, sodium metabisulfite exists as a disulfite ion (S2O52−) paired with two sodium cations. However, the moment it dissolves in water, the compound begins to tell a different chemical story—one that matters immensely for real-world applications.
When dissolved, Na2S2O5 readily hydrolyzes to form sodium bisulfite (NaHSO3), releasing sulfur dioxide (SO2) and generating a mildly acidic solution. This equilibrium between metabisulfite, bisulfite, and free SO2 is what makes the product so versatile. From an industrial buyer’s perspective, recognizing this transformation ensures you purchase a material that delivers the correct active species for your intended reaction—whether that’s the dechlorinating power of sulfite ions or the antimicrobial effect of molecular SO2.
Beyond the sodium metabisulfite chemical structure, the real-world functionality comes from the disulfite anion. Two sulfur atoms are connected by a central oxygen bridge, each also bonded to three oxygen atoms—one with a double bond. This arrangement is highly reactive, making the material an excellent reducing agent. In practical terms:
Because these reactions are stoichiometrically governed by the chemical structure, accurate molecular knowledge translates directly into dosage precision and cost efficiency. For example, 1 kg of pure Na2S2O5 can theoretically reduce approximately 0.74 kg of chlorine. An informed buyer uses this ratio to verify supplier quality and optimize chemical consumption—a topic we cover in our Sodium Metabisulfite product guide.
Commercial sodium metabisulfite typically comes in two main purity grades: food grade (≥97.5% as Na2S2O5) and industrial grade (≥96%). However, the molecular formula alone doesn’t tell the full purity story. The presence of other sodium sulfur oxyanions—such as sulfate (Na2SO4) or thiosulfate—can arise from manufacturing or improper storage. These impurities dilute the effective disulfite content, meaning that a product with 96% assay might deliver significantly less reactive SO2 equivalent than a high-purity 98% material from a quality-focused producer.
When evaluating a sodium metabisulfite supplier, always request a certificate of analysis (COA) that specifies not only the Na2S2O5 content but also iron (Fe), heavy metals (as Pb), and water-insoluble matter. For water treatment plants, iron levels above 30 ppm can cause discoloration or staining issues. For food-grade applications, compliance with FCC or E223 monographs is mandatory, and the iron limit is even tighter. Weifang Hailei Fine Chemical Co., Ltd. provides detailed COAs with every shipment, ensuring your procurement team can map the molecular formula guarantee directly to your process requirements.
While the sodium metabisulfite molecular formula remains constant, its performance across industries varies with process parameters and the specific form delivered (powder, granular, or solution). Let’s examine how three major sectors capitalize on the compound’s redox chemistry.
In reverse osmosis plants, free chlorine must be removed before water contacts polyamide membranes to prevent oxidative damage. Sodium metabisulfite is the go-to reagent because it’s cost‐effective, stable when made up as a dosing solution, and leaves no harmful residuals. The active species—sulfite—converts chlorine to chloride in a rapid reaction:
Na2S2O5 + H2O + 2Cl2 → 2NaHSO4 + 2HCl
Procurement teams for large municipal works often buy 1-ton bulk bags or 25-kg woven bags, with on-site testing of the SO2 gas evolution rate to verify consistent molecular activity. Granular forms from our industrial-grade line dissolve quickly without dusting, a critical safety consideration.
Gold mines worldwide face strict cyanide discharge limits. The INCO SO2/air process uses sodium metabisulfite as the source of sulfur dioxide. When injected into a tailings slurry, the released SO2 oxidizes free cyanide to cyanate (OCN−) in the presence of a copper catalyst. This application directly exploits the disulfite bond cleavage that the sodium metabisulfite molecular formula implies. Buyers seeking compliance with the International Cyanide Management Code demand a product with minimal inert diluents because every percentage point of impurity reduces the available SO2, forcing an increase in chemical consumption and freight volume. Weifang Hailei’s mining-grade product guarantees ≥96% Na2S2O5, a specification earned through years of supplying gold operations in West Africa and Central Asia.
In textile mills and paper plants, hydrogen peroxide-based bleaching is often followed by a chlorine or hypochlorite stage. Residual chlorine attacks cellulose or protein fibers, causing yellowing and loss of tensile strength. An antichlorine agent—sodium metabisulfite—is applied as a reducing rinse. Its molecular structure allows a clean reaction that neutralizes chlorine without introducing new contaminants. Mills that switch from cheaper but less stable sodium sulfite to metabisulfite benefit from longer shelf life and more predictable dosage, because crystalline Na2S2O5 resists oxidation far better than sulfite salts.
For high-stakes industries, the sodium metabisulfite molecular formula serves as a quality anchor. In water treatment, the stoichiometric consumption of chlorine can be directly correlated with the assay. A plant manager who receives a batch with an assay of 95% instead of 98% would need roughly 3% more product to achieve the same dechlorination target—a hidden cost that affects the annual chemical budget. Similarly, in gold mining, the required SO2 dosage per ton of tailings is set by the cyanide concentration. If the metabisulfite supplied has a lower Na2S2O5 content, the mine operator must either increase the feed rate or risk exceeding cyanide discharge limits. This molecular-level accountability is why leading buyers insist on third-party testing against USP or equivalent monographs, even for industrial grades.
The question “how to use sodium metabisulfite as preservative” often arises in small-scale food processing, but even large manufacturers need to understand the underlying chemistry to avoid over-sulfiting or under-dosing. When Na2S2O5 is added to an acidic food system (pH <4.5), the hydrolysis equilibrium shifts, liberating molecular SO2—the true preservative agent. This SO2 disrupts microbial enzymes, prevents Maillard browning, and scavenges dissolved oxygen. The effective preservative dose is expressed as total SO2 (free plus bound) and regulated by food authorities like the FDA (residual SO2 limit <10 ppm for most categories).
To calculate the required sodium metabisulfite, you start with the molecular formula: 1 gram of pure Na2S2O5 liberates approximately 0.67 grams of SO2. Therefore, if a food product requires 200 ppm SO2, you need about 300 ppm of pure sodium metabisulfite. However, process losses (evaporation, binding to sugars) mean a 10–15% excess is normally added. At an industrial scale, pre-dissolving the powder in chilled water (to limit SO2 loss) and applying by spray or immersion ensures uniform distribution. Our food-grade sodium metabisulfite (view food-grade specs) is certified to meet the highest purity standards, with iron ≤10 ppm and arsenic ≤1 ppm, making it suitable for export markets that follow EU E223 regulations.
Winemaking is a prime example of how the sodium metabisulfite uses in winemaking hinge on molecular transformation. The compound is typically used in powdered form to add sulfites to must, juice, or wine. Once dissolved, it shifts the SO2 equilibrium, protecting the wine from oxidation and unwanted microbes. However, sodium-based sulfite additions increase the sodium content of the wine, which is why potassium metabisulfite (K2S2O5) is often preferred for premium wines. Nevertheless, large-volume commercial wineries and juice concentrate producers still use sodium metabisulfite for cost reasons, particularly for products destined for distillation or where sodium content is less critical.
Understanding the molecular weight difference is essential: to add the same amount of SO2 as 1 kg of potassium metabisulfite, you need only about 0.86 kg of sodium metabisulfite because sodium’s lower atomic mass yields a higher proportion of active SO2 per unit mass. This technical detail is frequently discussed by buyers in India and other wine-producing regions when sourcing an economical but reliable sodium metabisulfite supplier in India or the Middle East. Weifang Hailei serves these markets with food-grade sodium metabisulfite in 25 kg PE-lined bags, offering full traceability back to the batch molecular assay.
When you search for a sodium metabisulfite supplier in India or any other major market, the molecular formula itself can be your first filter. A supplier’s agility in providing a comprehensive COA that reports the product not just as “sodium metabisulfite 96%” but as Na2S2O5 with specific limits for sulfate, chloride, and arsenic is a strong indicator of quality management. At Weifang Hailei Fine Chemical Co., Ltd., we go further. Our sodium metabisulfite is manufactured in an ISO 9001-certified facility in China’s Shandong province, using food-grade sulfur and soda ash to minimize heavy metal carryover. The output is packed in multi-wall bags or bulk bags with moisture-barrier liners, ensuring stability during long ocean shipments to India, the Middle East, and Latin America.
For buyers, the most overlooked factor is shelf life. Because the disulfite ion can slowly oxidize to sulfate in the presence of moisture and air, the assay can degrade by up to 1% per year under poor storage. Reputable suppliers mitigate this risk through vacuum packaging or filling bags under nitrogen. Always ask for a shelf-life statement backed by accelerated stability studies when you order container loads. We provide a guaranteed shelf life of 24 months from production date for material stored in unopened original packaging under cool, dry conditions—a direct outcome of molecular-level expertise.
You can learn more about our quality standards and download typical COA examples by visiting the Sodium Metabisulfite dedicated product page. For bulk inquiries or formulation support, our technical team is available to provide dosage calculations based on your specific water chemistry, tailings composition, or food matrix.
The sodium metabisulfite molecular formula is not just a notation on a specification sheet—it is a predictive tool. By understanding how Na2S2O5 dissociates, releases SO2, and reduces target contaminants, procurement teams can move beyond simple price-per-kilogram comparisons to assess the total delivered value. A product with a verifiable high assay, minimal impurities, and reliable logistics enables you to hit environmental targets, protect product quality, and control total chemical expenditure. Whether you need food-grade sodium metabisulfite for winemaking or industrial-grade for a large-scale dechlorination plant, the first step is always a rigorous chemical specification rooted in the molecular truth.
Ready to source high-purity sodium metabisulfite with full transparency on assay and trace impurities? Request a quote today and let our technical specialists help you select the optimal grade for your application.
If you are sourcing sodium metabisulfite for water dechlorination, gold leaching, food preservation, or pulp bleaching, you have very likely come across the pressing question: is sodium metabisulfite bad for you? Buyers across the chemical supply chain—from mine managers to food plant QC supervisors—want to understand exactly what hazards this white crystalline powder brings to the workplace and the end product. In this evidence‑based guide we dissect the toxicity profile, review food‑grade safety, explain why sodium metabisulfite can be harmful without proper controls, and detail how choosing a high‑purity, fully documented supply from Hailei Chemical’s sodium metabisulfite product line keeps people and processes safe.
When sourcing chemicals for large-scale water treatment, procurement managers sometimes stumble upon the search “calcium hypochlorite vs sodium metabisulfite” while trying to decide which product to order. The very comparison is a red flag—because these two compounds perform completely opposite functions. Calcium hypochlorite (Ca(OCl)2) is a powerful oxidizer used to disinfect water by releasing free chlorine. Sodium metabisulfite (Na2S2O5), on the other hand, is a reducing agent whose primary water treatment job is to neutralize that same chlorine after disinfection. Mistaking one for the other can lead to serious process failures, safety incidents, and regulatory noncompliance. This article clears up the confusion, explains where and how each chemical is correctly applied, and gives industrial buyers the technical insight they need to specify the right material for their facility.
Calcium hypochlorite is a solid chlorine carrier typically supplied as a white granular powder or tablets, containing about 65% available chlorine by weight. When dissolved in water, it releases hypochlorous acid (HOCl) and hypochlorite ions (OCl−), the active species that destroy bacteria, viruses, and biofilm in municipal water systems, cooling towers, swimming pools, and industrial process water. It is valued for its high chlorine content, long shelf life, and lower transportation cost compared to liquid sodium hypochlorite (bleach). In many regions, calcium hypochlorite is the disinfectant of choice for potable water treatment in remote locations because it remains stable in hot climates and can be precisely dosed using erosion feeders.
Sodium metabisulfite, also known as sodium pyrosulfite (CAS 7681-57-4), is a white to slightly yellowish crystalline powder with a sharp sulfur dioxide odor. Its chemical formula Na2S2O5 reveals a strong reducing agent that reacts rapidly with dissolved oxygen and oxidizing agents such as chlorine, chloramines, and bromine. In water treatment, the primary reaction for dechlorination is:
Na2S2O5 + 3 Cl2 + 3 H2O → 2 NaHSO4 + 4 HCl
The stoichiometric ratio is roughly 1.47 parts sodium metabisulfite to neutralize 1 part chlorine, though practical dosing often includes a slight excess to ensure complete chlorine removal. Beyond water treatment, industrial-grade sodium metabisulfite is widely used in gold mining (cyanide detoxification), pulp bleaching (reductive bleaching after chlorine dioxide stages), textile processing (anti-chlorine agent), and as a food preservative (E223) in dried fruits, wine, and shrimp.
At the molecular level, the calcium hypochlorite vs sodium metabisulfite debate is resolved by their electrochemical character. Calcium hypochlorite is an oxidizing biocide; it kills microorganisms by transferring oxygen or chlorine atoms that damage cell walls and enzymes. Sodium metabisulfite is a reducing agent; it donates electrons to neutralize oxidative compounds like chlorine. This fundamental difference means the two chemicals are never substitutes. Using sodium metabisulfite where calcium hypochlorite is needed would provide zero disinfection. Conversely, adding calcium hypochlorite to a dechlorination step would reintroduce chlorine and possibly create toxic chlorine gas if mixed directly with metabisulfite under acidic conditions.
Why would anyone ask “calcium hypochlorite vs sodium metabisulfite”? Often it stems from seeing both names on a supplier’s product list or reading generic “water treatment chemicals” categories. New procurement officers in industries like food processing or beverage bottling may assume that any chlorine-related powder is interchangeable. Another source of confusion is the similar packaging—both are sold in 25 kg or 50 kg bags or drums—and the fact that sodium metabisulfite is occasionally labeled “sodium pyrosulfite,” which can be misread.
The consequences of mixing them up are serious:
Calcium hypochlorite is the go-to for shock chlorination of wells, municipal water treatment, and routine sanitation of cooling towers. It provides a stable chlorine residual that protects distribution systems from recontamination. Its granular form is easily handled in dry feeders, and briquettes can be used in automatic dosing skids. Operators value its high chlorine yield: one kilogram of 65% calcium hypochlorite can deliver roughly 650 grams of available chlorine, equivalent to several liters of liquid bleach.
Sodium metabisulfite used for dechlorination is the standard in RO pretreatment, boiler feedwater, and wastewater discharge. Immediately after disinfection, excess chlorine must be removed to protect downstream equipment and to comply with effluent limits (often <0.1 mg/L total residual chlorine). Sodium metabisulfite reacts instantaneously at ambient temperatures, and residual sulfite can be monitored by oxidation-reduction potential (ORP) measurement. A typical dosing rate for municipal wastewater is 2–3 mg/L of 97% Na2S2O5 solution per mg/L of chlorine residual.
Outside of water treatment, the mining industry uses food-grade sodium metabisulfite for cyanide destruction in gold extraction, while pulp and paper mills apply it in the bleach plant to eliminate residual chlorine from kraft pulp, improving brightness and reducing chlorinated organic compounds in effluent. These high-volume applications rely on the consistent purity and reactivity of the metabisulfite.
Understanding sodium metabisulfite side effects is essential for safe handling, and this knowledge also helps clarify why it cannot be used as a disinfectant like calcium hypochlorite. Sodium metabisulfite releases sulfur dioxide gas (SO2) upon contact with water or acid. Exposure to dust or vapor can cause severe respiratory irritation, bronchospasm, and allergic reactions in sulfite-sensitive individuals. Industrial hygiene data recommend an airborne exposure limit of 2 mg/m3 (8-hour TWA) for respirable SO2. Skin and eye contact cause irritation; prolonged contact may result in dermatitis. Storage must be in a cool, dry, well-ventilated area away from acids and oxidizers—never store near calcium hypochlorite, as accidental mixing could generate heat and toxic chlorine/SO2 gases. Personnel should wear chemical goggles, protective gloves, and a dust mask or respirator during handling.
By contrast, calcium hypochlorite is a strong oxidizer itself, classified as a 5.1 hazardous substance. It can react violently with reducing agents like metabisulfite, ammonium compounds, and organic materials. The safety profiles of the two chemicals explain exactly why they are stored and handled in separate chemical feed areas in modern plants.
Another related search often appears alongside the primary topic: “what is potassium metabisulfite used for?” Potassium metabisulfite (K2S2O5) is the potassium analog of sodium metabisulfite and also functions as a reducing agent and antioxidant. However, it finds its niche almost exclusively in the food and beverage industry—particularly in winemaking and brewing, where it serves as a sanitizer and antioxidant without adding sodium. In the industrial sphere, sodium metabisulfite is overwhelmingly preferred because it is more economical, has a higher effective SO2 content per kilogram, and is readily available in large volumes. Potassium metabisulfite is rarely, if ever, used for water treatment dechlorination or gold mining. For industrial procurement, the choice is clear: sodium metabisulfite provides the best cost-performance ratio.
Sodium metabisulfite price is driven by raw material costs (soda ash and sulfur), energy prices, and global supply-demand balances. In the B2B market, industrial grade (97% min purity) is the volume leader, while food-grade (98% min, compliant with FCC/GB standards) commands a premium. Bulk pricing per metric ton FOB China typically fluctuates between USD 350 and USD 550, depending on packaging, purity, and order volume. Key procurement considerations:
If your facility uses chlorine disinfection and requires a chemical to remove residual chlorine, sodium metabisulfite is the correct, cost-effective choice. If your goal is to kill pathogens and maintain a chlorine residual, you need calcium hypochlorite (or another chlorine donor). The two chemicals are never part of a “vs” decision in the sense of direct substitution; rather, they are complementary tools that many plants use sequentially—first dosing calcium hypochlorite for disinfection, then sodium metabisulfite for dechlorination. Understanding this sequence and the chemistry behind it will help you avoid ordering errors, protect your equipment, and maintain compliance with discharge permits.
At Hailei Chemical, we specialize in high-purity sodium metabisulfite manufactured under strict quality control. Our product meets the exacting requirements of water treatment plants, gold mines, and food processors worldwide. We supply both industrial and food-grade powders with reliable packaging and documentation. Whether you need a single container or a regular bulk shipment, our team can support your technical and logistic needs.
To discuss your sodium metabisulfite requirements or request a current price quote, click here to get a quote or explore detailed product specifications on our sodium metabisulfite product page.
If you’re procuring sodium metabisulfite for gold mining, municipal water treatment, or food processing in East Africa, understanding the current sodium metabisulfite price in Kenya is critical for budgeting and supplier evaluation. As Kenya accelerates its industrial and infrastructure projects—from new gold mines in Kakamega and Migori to expanding urban water treatment plants—demand for this versatile chemical continues to rise. This comprehensive guide provides procurement managers, chemical engineers, and industrial buyers with insights into pricing factors, solution preparation, product comparisons, safety data, and the advantages of sourcing directly from a reliable Chinese manufacturer like Weifang Hailei Fine Chemical Co., Ltd.
When benchmarking the sodium metabisulfite price in Kenya, buyers must look beyond a single CIF Mombasa quote. The final landed cost per metric ton is influenced by a chain of international and local variables. Understanding these factors helps you negotiate better terms and avoid supply chain surprises.
China produces over 70% of the world’s sodium metabisulfite. The FOB (Free On Board) price from major ports like Qingdao or Shanghai typically fluctuates between USD 350 and USD 500 per metric ton for industrial grade (97–98% purity) in bulk. Regional production costs, soda ash feedstock pricing, and environmental policies directly shape this baseline. As a buyer in Kenya, your supplier’s proximity to the port and export volume discounts also matter.
Sea freight from China to the Port of Mombasa adds approximately USD 1,200–1,800 per 20-foot container (20 MT) depending on seasonal surcharges and bunker fuel costs. This translates to an additional USD 60–90 per ton. Importers should always include marine insurance (roughly 0.3–0.5% of the CIF value). Delays at the port and demurrage charges can further inflate landed costs, so partnering with a supplier experienced in East African logistics is a serious advantage.
Kenya applies the East African Community (EAC) Common External Tariff on sodium metabisulfite (HS Code 2832.10.00). The import duty is typically 10% on the CIF value, plus a standard 16% VAT on the duty-inclusive value. Working with a supplier who provides a transparent commercial invoice and a Certificate of Origin can sometimes open preferential rates under trade agreements, so always verify the latest KRA tariff book.
Food grade sodium metabisulfite (≥98% purity, meeting FCC or E223 standards) commands a price premium of 10–15% over industrial grade (97% min). For gold mining and water dechlorination, industrial grade is sufficient, but sensitive food processing applications require food grade. Buyers should evaluate whether the higher cost of food grade can be recouped through product certification or export market advantages.
Standard 25 kg woven polypropylene bags are the most economical. However, purchasing in 1,000 kg big bags or loose bulk reduces the unit price per kg by up to 8%. A full container load (20–27 MT) always yields a better per-ton rate compared to less-than-container-load (LCL) shipments. When comparing the sodium metabisulfite price in Kenya, always request pricing for your exact annual volume and preferred packaging format.
A realistic landed cost range for industrial grade sodium metabisulfite in Kenya (CIF Mombasa, excluding local clearance) falls between USD 580 and USD 720 per metric ton, depending on order size and market conditions. Local distributors may add a markup of 15–25% for warehousing and break-bulk services. Direct sourcing from a major Chinese exporter like Hailei Chemical eliminates these intermediate margins, offering significant procurement savings.
Correct sodium metabisulfite solution preparation is essential to achieve effective chemical reactions while maintaining operator safety. Whether you’re pretreating process water or detoxifying cyanide in a mining operation, following proven protocols ensures you maximize the reducing power of Na2S2O5.
Sodium metabisulfite dissolves readily in cold water (solubility about 540 g/L at 20°C). To prepare a stock solution:
For neutralizing chlorine in municipal or industrial water, the stoichiometric ratio is 1.4 mg of sodium metabisulfite per 1 mg of chlorine (Cl2). In practice, a slight excess (10–15%) is used to ensure complete dechlorination. A 10% solution fed via a metering pump can be easily adjusted based on online ORP (oxidation-reduction potential) or chlorine residual monitoring. Typical dosing for a 5 mg/L chlorine residual would be 7.5–8.0 mL of 10% stock solution per cubic meter of water.
In the gold mining sector, sodium metabisulfite is widely employed to destroy residual cyanide in tailings slurry through the INCO process (SO2/air). The metabisulfite is dissolved and mixed with the tailings, often in combination with a copper catalyst. Preparation of a 15–20% solution, stored in HDPE tanks, allows controlled addition to the detox circuit. Operators should verify solution strength daily via iodometric titration to maintain process stability and comply with effluent discharge limits.
For site-specific guidance, consult our technical team and download the full application notes from our Sodium Metabisulfite product page.
Procurement teams often face the choice between sodium sulfite vs sodium metabisulfite for water treatment, mining, and industrial processes. While both chemicals deliver the sulfite ion (SO32-) needed for reduction, their differences in molecular weight, effective SO2 content, and storage stability have major cost and handling implications.
Sodium metabisulfite (Na2S2O5) is a dimer that releases two molecules of SO2 per molecule when dissolved in water, yielding an effective SO2 content of approximately 67.4%. In contrast, anhydrous sodium sulfite (Na2SO3) provides a theoretical SO2 content of only 50.8%. This means you need roughly 33% less sodium metabisulfite by weight to achieve the same reduction capacity—a direct cost advantage per ton of finished product.
Sodium metabisulfite is far more stable under ambient storage conditions. Sodium sulfite tends to oxidize gradually to sulfate when exposed to air, losing its reducing strength. For hot and humid climates like Kenya’s coastal regions, metabisulfite’s superior shelf-life (2 years when properly stored vs. about 1 year for sulfite) reduces waste and re-testing costs.
While sodium sulfite sometimes carries a lower FOB price per ton, its lower activity makes the delivered cost per unit of SO2 less competitive. For large-scale dechlorination in Nairobi’s water treatment plants or for cyanide destruction in Western Kenya’s gold mines, sodium metabisulfite consistently offers better value. The only scenarios where sodium sulfite may be preferred are niche applications that explicitly demand a higher pH or a sodium-based additive without any bisulfite character—rare in East Africa’s bulk chemical markets.
Source your next supply from our proven industrial grade sodium metabisulfite and lock in both technical and financial efficiency.
Some buyers researching sulfite-based sanitizers may come across potassium metabisulfite for sanitizing applications, particularly in winemaking and craft brewing. Understanding the difference helps you select the right product and avoid costly substitutions.
Potassium metabisulfite (K2S2O5) is chemically analogous to sodium metabisulfite but releases potassium ions instead of sodium. This makes it the preferred choice for beverage sanitation because excess potassium does not affect flavor or fermentability, whereas sodium additions can alter taste. In Kenya’s growing craft beer and wine sector, potassium metabisulfite is used to sanitize equipment and to protect against microbial spoilage.
However, for all large‑volume industrial applications—water treatment, gold mining cyanide detox, textile anti‑chlorine treatment, and pulp bleaching—sodium metabisulfite remains the overwhelmingly dominant and economical choice. The product is less than half the price of the potassium salt and provides identical SO2 release per mole. Unless your operation specifically requires a sodium‑free process, sourcing sodium metabisulfite from a reliable Chinese supplier like Hailei Chemical will consistently deliver the best return on investment.
Thorough knowledge of the sodium metabisulfite msds (Material Safety Data Sheet) is mandatory for every importer and end-user. Kenya’s regulatory agencies, including NEMA and the Directorate of Occupational Safety and Health, require that a current SDS accompanies all chemical shipments and is accessible to workers.
Store sodium metabisulfite in a dry, well-ventilated area away from heat, moisture, and incompatible materials—especially strong acids, oxidizers, and alkalis. Pallets should be kept off the floor to prevent water damage. Always use personal protective equipment: chemical splash goggles, nitrile gloves, and a dust mask or NIOSH-approved respirator when handling large quantities. Eating, drinking, and smoking must be prohibited in storage and handling zones.
For customs clearance in Kenya, a complete sodium metabisulfite msds in English must be submitted along with the Bill of Lading and commercial invoice. Hailei Chemical provides up‑to‑date SDS documents with every shipment. You can download a consolidated safety data sheet directly from our sodium metabisulfite product page.
Partnering with a vertically integrated manufacturer like Weifang Hailei Fine Chemical Co., Ltd. removes layers of risk and cost from your Kenyan supply chain. Here’s what sets us apart:
When you’re ready to compare the current sodium metabisulfite price in Kenya and receive a tailored quote, reach out to our sales team. Let us demonstrate how our quality and service can strengthen your supply chain.
Visit Get a Quote or explore the full specification on our sodium metabisulfite product page. We look forward to serving your chemical needs in Kenya.
If you’re a procurement manager or chemical engineer, you may have come across the search query sodium metabisulfite vs potassium nitrate. At first glance, both are white crystalline powders used in industry, but their chemical identities and functions are worlds apart. Confusing them can lead to failed processes, serious safety hazards, and costly downtime. This comprehensive guide breaks down the differences, applications, and procurement best practices so you can make the right choice every time.
Sodium metabisulfite (Na₂S₂O₅) is a powerful reducing agent, while potassium nitrate (KNO₃) is a strong oxidizer. Mixing them unintentionally could result in dangerous reactions. In the following sections, we’ll examine their profiles, clarify the common confusion, and highlight where each chemical truly excels. We’ll also cover related queries such as sodium metabisulfite cas no, sodium metabisulfite vs sodium sulfite, uses of sodium sulfite, and how does sodium metabisulfite remove chlorine—giving you a complete resource for informed sourcing.
Sodium metabisulfite, often abbreviated as SMBS, is an inorganic compound with the formula Na₂S₂O₅. It exists as a white or yellowish crystalline powder with a pungent sulfur dioxide odor. Its CAS number is 7681-57-4. Industrial grades typically offer a purity of 97–98%, while food-grade variants (E223) meet stricter limits on heavy metals and arsenic.
When dissolved in water, sodium metabisulfite releases sulfur dioxide, which is responsible for its preservative and dechlorinating properties. This reaction makes it a workhorse across water treatment, gold mining, food processing, pulp & paper, and textiles. Hailei Chemical supplies both food-grade and technical-grade sodium metabisulfite in 25 kg bags, 1000 kg big bags, or custom packaging to suit global logistics requirements.
Potassium nitrate (KNO₃, CAS 7757-79-1), also known as saltpeter, is an ionic salt of potassium and nitrate ions. It appears as a white, crystalline solid with a cooling, saline taste. Highly soluble in water, it is best known as an oxidizer in gunpowder, fireworks, and rocket propellants. In agriculture, it serves as a premium chloride-free N-K fertilizer (13-0-46). Food-grade potassium nitrate (E252) is used in meat curing to preserve color and inhibit botulism.
Unlike sodium metabisulfite, potassium nitrate supports combustion—a critical safety distinction. It does not release SO₂ and cannot be used for dechlorination or oxygen scavenging. Industrial buyers must never substitute one for the other, even if they look superficially similar.
The following comparison highlights why a sodium metabisulfite vs potassium nitrate evaluation leads to a clear-cut decision based on application:
The takeaway is simple: these two chemicals are functionally incompatible. If your process requires oxygen removal or chlorine neutralization, potassium nitrate is not an option. Conversely, if you need a controlled oxidizer for pyrotechnics, sodium metabisulfite would be dangerously ineffective.
Sodium metabisulfite’s versatility stems from its reducing ability. Let’s explore the major industrial segments that rely on it.
Municipal water treatment plants and industrial facilities use sodium metabisulfite to neutralize residual chlorine before discharge or further processing. The reaction with free chlorine is instantaneous and stoichiometric: Na₂S₂O₅ + 2Cl₂ + 3H₂O → 2NaHSO₄ + 4HCl. Typically, 1.34 mg SMBS removes 1 mg of chlorine. This is why we’ll answer how does sodium metabisulfite remove chlorine in depth later.
In gold leaching circuits, excess cyanide must be destroyed before tailings discharge. SMBS is used in the Inco SO₂/air process to oxidize cyanide to harmless cyanate. The reducing environment created by sulfur dioxide (from SMBS) combined with air and a copper catalyst efficiently detoxifies cyanide-bearing slurries. Mining chemical buyers prefer high-purity technical-grade sodium metabisulfite to ensure consistent performance.
As food additive E223, SMBS inhibits microbial growth and prevents enzymatic browning in dried fruits, wines, and fruit juices. Food-grade sodium metabisulfite must meet stringent limits for arsenic (<3 mg/kg) and lead (<5 mg/kg). Hailei’s food-grade product is certified to international standards, including EU and FDA requirements.
In pulp mills, SMBS acts as a reducing bleaching agent for mechanical pulps. In textile dyeing, it serves as an anti-chlorine agent to neutralize residual chlorine on fabrics after bleaching, preventing yellowing and fiber damage.
To avoid confusion, here’s where potassium nitrate is truly indispensable:
Each application exploits KNO₃’s oxidizing nature—a characteristic totally absent in sodium metabisulfite.
Attempting to replace sodium metabisulfite with potassium nitrate (or vice versa) can lead to process failure, equipment damage, or even catastrophic explosions. Consider these real-world risks:
Always verify chemical identity, CAS number, and specification sheet before use. Sodium metabisulfite CAS no 7681-57-4 and potassium nitrate CAS 7757-79-1 should be double-checked against your inventory and process needs.
While researching sodium metabisulfite vs potassium nitrate, buyers often encounter another sibling: sodium sulfite (Na₂SO₃). The query sodium metabisulfite vs sodium sulfite is common because both are used in similar applications. Here’s a quick breakdown:
If your application tolerates a slightly acidic pH, SMBS is usually the better value. Hailei Chemical stocks high-purity sodium metabisulfite and can also supply sodium sulfite upon request—talk to our team for a tailored recommendation.
A frequent technical question is how does sodium metabisulfite remove chlorine from water. The mechanism is a simple redox reaction. When dissolved, SMBS hydrolyzes to give sodium bisulfite (NaHSO₃) and ultimately sulfurous acid, which reacts with hypochlorous acid or free chlorine:
NaHSO₃ + HOCl → NaHSO₄ + HCl
In practice, a slight excess of SMBS is added to ensure complete dechlorination. The stoichiometric ratio is approximately 1.34 kg of pure sodium metabisulfite per 1 kg of chlorine removed. For industrial water treatment, a 10–20% solution of SMBS is metered into the water stream with a contact time of less than one minute. The reaction is so rapid that it is often used for emergency chlorine neutralization.
This powerful reducing ability is precisely why sodium metabisulfite is trusted worldwide. Our technical-grade product, with 97–98% purity, delivers consistent performance across thousands of municipal and industrial water plants. For details on packaging and shipping, visit our sodium metabisulfite product page.
When sourcing internationally, verifying the sodium metabisulfite cas no is your first line of defense against adulteration. The official CAS registry number is 7681-57-4. Hailei Chemical’s certificates of analysis (CoA) always include this identifier along with the following typical specifications:
We test every production batch against these parameters and share full documentation. Whether you require food-grade E223 for jam processing or technical-grade for cyanide detox, our quality management system ensures consistency and traceability.
As a leading Chinese chemical exporter, Weifang Hailei Fine Chemical Co., Ltd. combines manufacturing expertise with global logistics capability. Our sodium metabisulfite is produced under ISO 9001-certified quality control, with rigorous testing for purity, heavy metals, and particle size distribution. We offer flexible packaging options and can arrange sea, rail, or air freight to your destination port.
Procurement managers who choose Hailei Chemical benefit from:
If you are evaluating chemical suppliers for water treatment, mining, food processing, or pulp bleaching, contact us today for a tailored quotation. Our technical team can help you with dosage calculations, logistics planning, and sample approvals.
Ready to secure a reliable source of high-purity sodium metabisulfite? Request your personalized quote now and experience the Hailei Chemical difference.