Chemical laboratory

Sodium Metabisulfite

Food-Grade Antioxidant and Water Treatment Chemical

  • CAS 7681-57-4
  • Formula Na₂S₂O₅
  • Flash Pt N/A °C
  • Density 1.48 g/cm³
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Physical & Chemical Properties

Property Value Unit
Boiling point N/A (Decomposes) °C
Flash point N/A °C
Density 1.48 g/cm³ g/cm³
Solubility Very soluble in water (65 g/100 mL at 20°C) -
Ph 4 - 5 (10% solution) -
Molecular weight 190.10 g/mol g/mol
Melting point N/A °C
Vapor pressure N/A mmHg
Autoignition temp N/A -
Appearance White or yellowish crystalline powder -
Odor Slight sulfur dioxide odor -
Vapor density N/A g/cm³

Overview

Sodium Metabisulfite (Na₂S₂O₅) is a white to yellowish crystalline powder widely used as an antioxidant, preservative, and reducing agent across multiple industries. With excellent water solubility (65 g/100 mL at 20°C) and a molecular weight of 190.10 g/mol, this versatile chemical compound decomposes rather than melts, releasing sulfur dioxide gas. Its slightly acidic nature (pH 4-5 in 10% solution) and characteristic sulfur dioxide odor make it easily identifiable in laboratory and industrial settings.

Key Applications

In the food and beverage industry, sodium metabisulfite serves as a critical antioxidant and preservative, preventing oxidation and microbial growth in processed foods. Winemakers rely on it to maintain wine quality and prevent spoilage during fermentation and storage processes. The chemical also functions as an effective oxygen scavenger in water treatment systems, removing dissolved oxygen that can cause corrosion in boiler systems and industrial equipment.

Chemical synthesis operations utilize sodium metabisulfite as a reducing agent, while the textile industry employs it as a bleaching agent for natural and synthetic fibers. Photography laboratories depend on this compound as a developer chemical, and research facilities use it as a reliable laboratory reagent for various analytical procedures.

Safety & Handling

As sodium metabisulfite decomposes rather than burns, it has no flash point or autoignition temperature. However, proper safety protocols are essential when handling this chemical. Workers should wear appropriate personal protective equipment including safety goggles, gloves, and dust masks to prevent inhalation of particles. Adequate ventilation is crucial, especially in enclosed spaces, as the compound can release sulfur dioxide gas upon decomposition or when mixed with acids.

Handle the material in well-ventilated areas and avoid contact with strong acids, which can accelerate gas release. In case of skin or eye contact, flush immediately with plenty of water and seek medical attention if irritation persists.

Storage & Shelf Life

Store sodium metabisulfite in tight, sealed containers in a cool, dry location away from heat sources and incompatible materials. The chemical should be kept separate from strong acids, alkalis, and oxidizing agents to prevent unwanted reactions. Moisture can cause clumping and gradual decomposition, so maintaining low humidity storage conditions is essential for product integrity.

When stored properly in original packaging, sodium metabisulfite maintains its effectiveness for extended periods. Regular inspection of containers for signs of deterioration or moisture intrusion helps ensure optimal product quality and safety.

Why Alliance Chemical

Alliance Chemical provides reliable access to high-quality Sodium Metabisulfite with same-day shipping from our Taylor, Texas facility. We offer flexible shipping options including UPS for smaller quantities and LTL/FTL freight services for bulk orders. Every shipment includes comprehensive Safety Data Sheets (SDS) and Certificate of Analysis (COA) documentation to support your compliance and quality assurance requirements.

Shipping & Availability

Parcel Shipping

UPS Ground supports pints, quarts, and most 1-gallon packages nationwide.

LTL Freight

5-gallon pails, drums, and totes move via LTL carriers such as ABF Freight, SEFL, Saia, and XPO.

Full Truckload

FTL available for palletized bulk orders. Competitive freight rates.

Local Pickup

Will-call pickup available at our Taylor, TX warehouse for Texas customers.

SDS, COA, and TDS available for every product • Most orders ship in 1-2 business days from Taylor, TX

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Frequently Asked Questions

What is sodium metabisulfite (Na2S2O5) and what is it used for?
Sodium metabisulfite (CAS 7681-57-4, formula Na2S2O5) is a white crystalline reducing agent and preservative used widely in industry and laboratories. Common uses include chemical synthesis, water treatment, textile and pulp processing, photographic and analytical chemistry applications.
How should sodium metabisulfite be stored and what is its typical shelf life?
Store in a cool, dry, well‑ventilated area in tightly sealed containers away from acids and oxidizers to prevent decomposition and SO2 release. Unopened material typically remains stable 1–2 years depending on grade and storage conditions; verify shelf life on the supplier Certificate of Analysis (COA).
What are the main safety hazards and recommended PPE when handling sodium metabisulfite?
Sodium metabisulfite can be an irritant to eyes, skin and respiratory tract and can release sulfur dioxide when exposed to acids. Use engineering controls (local exhaust), wear chemical‑resistant gloves, safety goggles and a dust respirator or NIOSH‑approved mask as indicated by the SDS.
What concentration and form options are available for sodium metabisulfite?
Available as technical or reagent grade solids (powder, granules) and as aqueous solutions in various strengths; solid assay is commonly 95–99% Na2S2O5 and solutions are typically supplied in ranges like 10–50% w/w. Choose the grade and concentration appropriate for analytical, laboratory or bulk industrial processes.
What documentation can suppliers provide for sodium metabisulfite orders?
Suppliers routinely provide a Safety Data Sheet (SDS), Certificate of Analysis (COA), Technical Data Sheet (TDS) and shipping paperwork; additional documents such as Certificate of Origin or custom test reports are available on request. Always review the SDS before use and retain the COA for quality records.
How is sodium metabisulfite packaged and shipped?
Common packaging includes multi‑wall kraft bags with polyethylene liner (25 kg or 50 lb), steel or plastic drums, intermediate bulk containers (IBCs) and bulk tanker deliveries for solutions. Transport classification and regulatory requirements vary by region, so suppliers will advise on labeling, placarding and any restrictions for hazardous shipments.
What materials is sodium metabisulfite compatible or incompatible with?
Avoid contact with acids, strong oxidizers, nitrites and halogens because these reactions can produce corrosive gases or heat. It is generally compatible with storage in HDPE, polyethylene‑lined containers and glass, but compatibility with specific metals or process materials should be confirmed by testing.
What technical specifications should I check for sodium metabisulfite before purchase?
Key specs include CAS number (7681-57-4), assay/purity (% Na2S2O5), moisture content, particle size or bulk density, impurity profile (sulfate, heavy metals), solubility and recommended storage conditions. Ask the supplier for the COA and TDS to confirm the batch meets your process requirements.
Which industries and applications commonly use sodium metabisulfite?
Industries include pulp & paper, textiles, water and wastewater treatment, photographic and imaging chemistry, chemical manufacturing and laboratory research, as well as certain mining and metal processing operations. It is used primarily as a reducing agent, antioxidant and oxygen scavenger in these applications.
How do I purchase sodium metabisulfite and what availability should I expect?
Sodium metabisulfite is sold worldwide in laboratory and industrial grades through chemical distributors and direct manufacturers; availability depends on grade and order size with typical lead times from immediate stock to several weeks for large bulk orders. Request a formal quote, COA, SDS and minimum order/packaging options from your supplier to finalize purchase.

Documentation & Downloads

Request SDS
Safety Data Sheet
Request COA
Certificate of Analysis
Technical Data Sheet (TDS)
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