Product Introduction
Sodium Metabisulfite (abbreviated SMBS), CAS No. 7681-57-4, is a white or slightly yellow crystalline powder with a strong sulfur dioxide odor. Industrially, it is produced by absorbing sulfur dioxide into sodium carbonate solution to form sodium bisulfite, followed by crystallization and dehydration. Sodium metabisulfite possesses strong reducing, deoxidizing, and antioxidant properties, and can also slowly release sulfur dioxide to provide an antibacterial and bleaching effect, making it one of the most commonly used bleaching agents and preservatives in food processing (must be used strictly within permitted limits). In the water treatment field, it is the standard residual chlorine reducing agent for reverse osmosis membrane systems; in the printing/dyeing, papermaking, and photography industries, it serves as a dechlorinating agent and developing aid.
Basic Product Specifications
- CAS No.: 7681-57-4
- UN No.: None
- HS Code: 2832100000
- Hazard Class: General Cargo
- Density: approx. 1.4 g/cm³ (20°C, solid)
- Purity: ≥96.5% (Industrial grade; Food grade ≥97.0%, as Na₂S₂O₅. Sulfur dioxide content ≥65.0%, Iron ≤0.003%, Selenium ≤0.001%, Arsenic ≤0.0001%)
For complete and detailed specifications of this product, please contact our staff to obtain the latest test report for the corresponding batch.
Product Applications
- Water treatment: Used as a residual chlorine reducing agent and deoxidizer in reverse osmosis (RO) systems, protecting membrane elements from oxidative damage;
- Food processing: Used as a bleaching agent, preservative, and antioxidant in preserved fruits, dried fruits, starch, bamboo shoots, and wine (food grade, must strictly comply with GB 2760 usage limits);
- Printing/dyeing and papermaking: Used as a dechlorinating agent, reducing agent, and bleaching agent for textile desizing, dechlorination, and pulp bleaching;
- Chemical and pharmaceutical: Used as a reducing agent and sulfonating agent in dye intermediates, pharmaceutical synthesis, and rubber coagulation;
- Other applications: Used in photographic developing solutions, leather processing, mineral processing depressants, and agricultural product preservation (must comply with applicable regulations).
Packaging, Storage, and Transportation
Packaging: Standard packaging in 25kg woven bags or paper-plastic composite bags with plastic liners; for large volumes, 500kg or 1000kg jumbo bags are available, with food-grade product using food-grade inner liner bags.
Storage: Not classified as a hazardous chemical; store as general cargo. Must be stored in a cool, dry, well-ventilated warehouse, with strict sealing and moisture protection — this product will slowly oxidize into sodium sulfate and release sulfur dioxide when exposed to moisture or prolonged air exposure, causing a decrease in content and caking. Keep away from heat sources, ignition sources, oxidizers, and acids (contact with acids will cause a violent release of highly toxic sulfur dioxide gas). The warehouse must be well-ventilated to avoid accumulation of sulfur dioxide gas. Food-grade product must be stored in a dedicated warehouse.
Transportation: Transport as general cargo, protected from rain exposure and moisture throughout. During loading and unloading, handle gently to prevent packaging damage and dust dispersion; the work area must be well-ventilated, and operators must wear dust/gas masks, protective goggles, and gloves to avoid inhaling sulfur dioxide gas and dust. Food-grade product transportation must use clean, dedicated transport vehicles, with previous cargo and cleaning records retained.
Product Advantages
- Stable supply sources with long-term spot availability, suitable for large-volume foreign trade orders;
- Consistent product purity with minimal batch-to-batch variation, suitable for downstream deep-processing production;
- Backed by a comprehensive chemical supply chain system, enabling one-stop procurement across multiple categories of chemical raw materials.
