Sodium Metabisulfite (Na2S2O5)

Sodium metabisulfite (Na₂S₂O₅) is an important inorganic compound widely recognized for its properties as a preservative, antioxidant, and reducing agent. This white crystalline powder, which emits a faint sulfurous odor, plays a crucial role in numerous industries, including food processing, pharmaceuticals, and water treatment. Its ability to release sulfur dioxide (SO₂) when dissolved in water or heated makes it particularly effective for applications requiring preservation or reduction. This article will explore its definition, various grades, production process, and applications in more detail.

Nobel Trading Co. is a trusted supplier of sodium metabisulfite (Na₂S₂O₅), offering a reliable source for industries that require high-quality chemical products. The company stands out due to its advanced production facilities, which adhere to strict quality standards, ensuring consistent purity and efficacy of sodium metabisulfite. Additionally, Nobel Trading Co. provides flexible packaging and logistics options, making it convenient for customers to receive the product in the quantities and formats that best suit their needs. Their dedication to quality, customer support, and reliable supply chain management has made them a preferred partner for many businesses worldwide.

 

What is Sodium Metabisulfite?

Sodium metabisulfite (Na₂S₂O₅) is an inorganic compound that is widely used as a preservative, antioxidant, and reducing agent in many industries, including food processing, pharmaceuticals, and water treatment. It appears as a white crystalline powder with a faint sulfurous odor, and it is known for its ability to release sulfur dioxide (SO₂) when dissolved in water or heated.

Chemical Properties

Sodium metabisulfite has the chemical formula Na₂S₂O₅ and a molecular weight of 190.10 g/mol. It comprises two sodium ions (Na⁺) ionically bonded to a metabisulfite anion (S₂O₅²⁻). The anion features two sulfur atoms connected by an oxygen bridge, with each sulfur bonded to additional oxygen atoms.

Regarding reactivity, sodium metabisulfite functions as a strong reducing agent in chemical reactions. It reacts with strong acids to produce sulfur dioxide (SO₂), water, and sodium salts, according to the equation:

Na₂S₂O₅ + 2 HCl → 2 NaCl + H₂O + 2 SO₂ ↑

When heated, it decomposes to release sulfur dioxide and form sodium sulfate (Na₂SO₄):

Na₂S₂O₅ → Na₂SO₄ + SO₂ ↑

Additionally, when exposed to air and moisture, it slowly oxidizes to sodium sulfate:

2 Na₂S₂O₅ + O₂ → 2 Na₂SO₄ + 2 SO₂ ↑

Physical Properties

Sodium metabisulfite is a white crystalline powder with a faint sulfurous odor, similar to sulfur dioxide. It has a density of approximately 1.48 g/cm³. The compound decomposes before melting at temperatures around 150°C (302°F), meaning it does not have a true melting point.

It is highly soluble in water, with about 65.3 g dissolving in 100 mL of water at 20°C (68°F), forming an acidic solution. It is also soluble in glycerol and slightly soluble in ethanol. A 10% aqueous solution of sodium metabisulfite has a pH ranging from 4.0 to 5.5, resulting from sulfur dioxide release and bisulfite ions’ formation.

Sodium metabisulfite is hygroscopic, meaning it absorbs moisture from the air. Unlike sodium sulfite, it does not form hydrates, which necessitates storing it in airtight containers to prevent caking and ensure effectiveness.

Stability and Storage

To maintain its stability, sodium metabisulfite should be stored in a cool, dry place in tightly sealed containers to avoid exposure to air and moisture. It is sensitive to air and moisture, which can lead to gradual oxidation and reduce its potency over time.

Safety Considerations

Handling sodium metabisulfite requires personal protective equipment (PPE) such as gloves, goggles, and face masks to avoid skin contact or inhalation. It can cause irritation to the eyes, skin, and respiratory system. In some individuals, sodium metabisulfite may also trigger allergic reactions or asthma symptoms, particularly if inhaled.

From an environmental standpoint, sodium metabisulfite generally poses a low risk when used properly. However, it must be disposed of by local regulations to prevent contamination.

 

Different Grades of Sodium Metabisulfite

Sodium metabisulfite (Na₂S₂O₅) is a widely used inorganic compound that functions as an antioxidant, preservative, and reducing agent across different industries, such as food processing, pharmaceuticals, and water treatment. The diverse needs of these industries require sodium metabisulfite to be available in various grades, each with specific characteristics and regulatory compliance. Below are the main grades of sodium metabisulfite and their features:

Technical Grade

Technical-grade sodium metabisulfite is primarily used in general industrial applications where ultra-high purity is not required. It has a lower level of purity compared to other grades, allowing for acceptable levels of impurities in non-critical applications.

This grade is cost-effective and often used in large-scale industrial operations. It is applied in industrial processes like water treatment, textile processing, and chemical manufacturing as a reducing agent, as well as in the mining industry for metal extraction, including gold. Due to its impurity content, the technical grade is unsuitable for food or pharmaceutical use.

Food Grade (E223)

Food-grade sodium metabisulfite meets the stringent safety and purity requirements necessary for additives used in food products. It has a higher purity level than technical grade and controlled impurity levels to ensure it is safe for human consumption. In the European Union, this grade is designated as E223 and complies with Commission Regulation (EU) No 231/2012 specifications.

This grade also meets international standards the Joint FAO/WHO Expert Committee on Food Additives (JECFA) sets. Food-grade sodium metabisulfite is used to prevent browning and spoilage in dried fruits, vegetables, and juices and to inhibit unwanted microbial activity and oxidation in winemaking. It must be used within regulated limits to avoid health issues, as excessive intake may lead to allergic reactions in some individuals. Foods containing E223 must be labeled appropriately for consumer awareness.

Pharmaceutical Grade

The highest purity characterizes pharmaceutical-grade sodium metabisulfite, meeting strict standards for medicinal applications. It conforms to specifications outlined by major pharmacopeias, including the United States Pharmacopeia (USP), European Pharmacopoeia (Ph. Eur.), British Pharmacopoeia (BP), and Japanese Pharmacopoeia (JP).

This grade is used as an antioxidant and preservative in injectable medications, ophthalmic solutions, and tablets, stabilizing active pharmaceutical ingredients (APIs) against oxidation. It undergoes rigorous quality testing to ensure compliance and full documentation and batch traceability are maintained for pharmaceutical use.

FCC Grade

FCC (Food Chemicals Codex) grade sodium metabisulfite adheres to the standards set by the Food Chemicals Codex, which defines quality and purity criteria for food ingredients. It is highly pure, making it suitable for use in food and beverage applications where FCC compliance is required. Adherence to FCC standards ensures international acceptance, facilitating trade across borders. Manufacturers using FCC-grade sodium metabisulfite must conduct appropriate testing to verify that their products meet the required specifications.

Kosher Grade

Kosher-grade sodium metabisulfite matches the purity of food grade but comes with additional certification to comply with Jewish dietary laws. It is certified by recognized Kosher certification agencies after ensuring that both the product and manufacturing processes meet Kosher requirements.

Kosher grade sodium metabisulfite is used by manufacturers producing food for consumers who observe kosher dietary practices. Regular audits and inspections are conducted to maintain kosher certification, assuring consumers about the product’s compliance with their nutritional needs.

 

Sodium Metabisulfite Production Process

The production of sodium metabisulfite involves several chemical processes, starting from sulfur burning and leading to the crystallization of sodium metabisulfite. The process can be broken down into four main stages: sulfur dioxide generation, absorption of sulfur dioxide in sodium hydroxide, conversion to sodium metabisulfite, and separation and drying.

Sulfur Dioxide Generation

The first step in the production of sodium metabisulfite is generating sulfur dioxide (SO₂) gas by burning elemental sulfur.

  • Chemical Reaction:

S (s) + O₂ (g) → SO₂ (g)

Elemental sulfur, in its solid form and of high purity, is burned in the presence of air to produce sulfur dioxide. The process is carried out in a sulfur burner or furnace at a temperature of approximately 250–400°C to ensure complete combustion. The air supply is controlled to provide the correct ratio of oxygen to sulfur. Safety precautions are crucial as the combustion process produces heat and sulfur dioxide, both of which are hazardous. Maintaining efficient combustion also helps minimize the formation of unwanted byproducts like sulfur trioxide (SO₃).

Absorption of Sulfur Dioxide in Sodium Hydroxide Solution

The next step involves absorbing sulfur dioxide gas into an aqueous solution of sodium hydroxide (NaOH) to form sodium bisulfite (NaHSO₃).

  • Chemical Reaction:

SO₂ (g) + NaOH (aq) → NaHSO₃ (aq)

Sulfur dioxide, obtained from the previous stage, is absorbed in sodium hydroxide using an absorption tower or scrubber. Gas dispersers are used to ensure uniform distribution of sulfur dioxide in the solution. The temperature is maintained between 40–60°C to optimize absorption efficiency, while pH is monitored to keep the solution in an acidic range that favors the formation of sodium bisulfite. The gas flow rate and the concentration of the sodium hydroxide solution are adjusted to ensure effective absorption and to prevent the formation of sodium sulfite (Na₂SO₃).

Conversion to Sodium Metabisulfite

Once sodium bisulfite is formed, the next objective is to concentrate it and induce the formation of sodium metabisulfite.

  • Chemical Transformation:

2 NaHSO₃ (aq) → Na₂S₂O₅ (s) + H₂O (l)

The sodium bisulfite solution is concentrated by evaporating excess water. This process is carried out using evaporators, often with multiple effects to conserve energy. The temperature and pressure are carefully controlled to avoid decomposition. After sufficient concentration, the solution is cooled to form sodium metabisulfite crystals. This step involves using crystallizers that allow for controlled cooling to achieve the desired crystal formation. Temperature control and maintaining appropriate concentration levels are crucial for effective crystallization.

Separation and Drying

The final stage is the separation of sodium metabisulfite crystals from the remaining solution and their subsequent drying.

The crystals are separated using filtration or centrifugation, with equipment like filter presses or centrifuges commonly employed. The separated crystals are then washed with a small amount of cold distilled water to remove any impurities or residual liquid. Drying is carried out using tray dryers, rotary dryers, or fluidized bed dryers to remove residual moisture from the crystals. The temperature is kept below 150°C to prevent decomposition, and sometimes, an inert gas atmosphere is used to reduce oxidation risk. Throughout this stage, product quality is monitored to ensure sodium metabisulfite’s purity and desired physical properties. Dust control is also important, as fine particles can irritate when inhaled.

Product Quality and Safety

Ensuring the purity and physical properties of the final product is essential. The production process is closely monitored to meet the required specifications, and any impurities are removed during the washing and drying stages. Dust control measures are also crucial, as fine sodium metabisulfite particles can be irritating if inhaled. Proper handling and protective equipment are necessary to minimize exposure risks.

 

Sodium Metabisulfite Applications

Sodium metabisulfite is a multi-purpose chemical that finds applications across a variety of industries. Below are the key uses of sodium metabisulfite in different sectors:

Food Industry

  • Preservative and Antioxidant:

Sodium metabisulfite is commonly used as a preservative in food products to prevent browning and discoloration. It inhibits both enzymatic and non-enzymatic oxidation, thereby extending the shelf life of items like dried fruits, juices, and wines.

  • Winemaking:

In winemaking, it is essential to both sanitize equipment and preserve the wine itself. Sodium metabisulfite inhibits the growth of wild yeast and bacteria, thus preventing unwanted fermentation and oxidation, which helps maintain the wine’s flavor and quality.

  • Shelf Life Extension:

By controlling microbial growth and oxidation, sodium metabisulfite helps maintain the freshness of food products during storage and distribution.

Pharmaceutical Industry

  • Antioxidant in Formulations:

It acts as an antioxidant in various pharmaceutical formulations, including oral, topical, and injectable products. Sodium metabisulfite helps protect active ingredients from oxidative degradation, ensuring the stability and efficacy of the medication.

  • Preservative in Medications:

It is often used as a preservative in medications, such as those containing adrenaline (epinephrine), to prevent oxidation and maintain the effectiveness of the medication over its shelf life.

  • Excipient in Tablets:

In tablet formulations, it serves as an excipient, aiding in the manufacturing process and improving the stability of the final product.

Water Treatment

  • Dechlorination Agent:

Sodium metabisulfite is used in water treatment processes to remove excess chlorine and chloramine from water. Dechlorination is important for preventing harmful effects on aquatic life and ensuring water quality.

  • Oxygen Scavenger:

In boiler systems, sodium metabisulfite acts as an oxygen scavenger, reacting with dissolved oxygen to prevent corrosion of metal components, thus extending the lifespan of boilers and piping systems.

Chemical Industry

  • Reducing Agent:

It is used as a reducing agent in chemical processes, such as the reduction of aldehydes and ketones.

  • Gold Extraction:

In the mining industry, sodium metabisulfite is used to precipitate gold from chloroauric acid (gold chloride) solutions. It reduces the gold ions to elemental gold, facilitating the extraction and purification process.

  • Reagent in Organic Synthesis:

Sodium metabisulfite is used in organic synthesis for forming carbon-sulfur (C-S) bonds, which is critical in the production of sulfur-containing compounds.

Other Applications

  • Photography:

In photographic development, sodium metabisulfite is used to protect developer solutions from oxidation, helping maintain their effectiveness for consistent image quality.

  • Textile Industry:

It is used in the textile industry to break sulfide bonds in damaged woolen fabrics, allowing restoration. Additionally, it acts as a reducing agent to remove excess dye from textiles.

  • Pulp and Paper Manufacturing:

Sodium metabisulfite is used in the delignification process to break down lignin in wood pulp, which helps improve the brightness and quality of paper products.

  • Wastewater Treatment:

It is effective in reducing hexavalent chromium (Cr⁶⁺) to trivalent chromium (Cr³⁺), which is less toxic and easier to remove from wastewater. This application is crucial for industries that generate chromium-containing effluents.

  • Rust Stain Removal:

Sodium metabisulfite, often combined with sodium hydrosulfite, is used to remove rust stains from fabrics and surfaces due to its reducing properties.

 

About Nobel Trading Co’s Sodium Metabisulfite

Nobel Trading Co, based in China, is a well-established and trusted supplier of sodium metabisulfite, catering to a wide range of industries. The company has ownership in several production facilities, ensuring the highest quality standards and reliable supply of sodium metabisulfite to meet diverse industrial requirements. Strong global connections with raw material sources enable them to offer competitive pricing, making them an ideal partner for customers seeking both quality and value.

Production, Quality, and Competitive Advantage

Nobel Trading Co’s production facilities are equipped with advanced technology that ensures consistent product quality and rigorous adherence to quality control measures. The production process is overseen by a team of highly skilled professionals who are committed to producing sodium metabisulfite with high purity and consistency, meeting international standards. With substantial production capacity, the company can meet the demands of both small and large-scale customers, ensuring a continuous supply of the product.

The company also benefits from strong relationships with raw material suppliers worldwide, allowing for efficient sourcing at competitive rates. Operating multiple production facilities results in cost-effective production, which enables Nobel Trading Co. to offer competitive pricing. Additionally, an efficient supply chain contributes to minimizing operational costs, providing further pricing advantages for customers.

Packaging, Shipping, and Logistics

Nobel Trading Co offers customized packaging options to meet specific customer requirements, including moisture-resistant bags, drums, and bulk containers. To ensure timely and secure delivery, the company provides multiple shipping solutions, such as sea and air freight, which are managed by a dedicated logistics team. This team handles all aspects of the shipping process, including documentation and compliance with international regulations, ensuring smooth delivery to customers worldwide.

Industrial Applications of Sodium Metabisulfite

Sodium metabisulfite supplied by Nobel Trading Co. is used in a broad spectrum of industries. In the food industry, it functions as a preservative and antioxidant, preventing discoloration and extending the shelf life of products such as dried fruits, juices, and wines. In water treatment, it serves as a dechlorinating agent to remove excess chlorine, ensuring water quality and protecting aquatic life. In the textile industry, sodium metabisulfite is used for dye removal and treatment, enhancing fabric quality. In the chemical industry, it acts as a reducing agent in various processes and is used in the production of sulfur-containing compounds. Additionally, it plays a role in photography by preventing oxidation and maintaining the quality of developer solutions.

Customer Support, Services, and Value Proposition

Nobel Trading Co provides comprehensive customer support and services to help clients optimize their use of sodium metabisulfite. Technical support and guidance are available, and all products meet international quality standards. Detailed safety data sheets (SDS) are provided to customers for reference. The company is dedicated to prompt and efficient communication, addressing customer inquiries and concerns effectively.

Nobel Trading Co has a proven track record of delivering high-quality products while maintaining a dependable supply chain. With robust logistics capabilities, the company is capable of serving customers worldwide. Their customer-focused approach prioritizes building strong, long-term relationships by understanding and meeting each client’s specific needs.