Sodium thiosulfate is a chemical compound with diverse uses across various sectors. This article covers its common forms, applications, and key considerations for purchase.
Common Forms and Applications
Sodium thiosulfate typically appears in two main physical forms: anhydrous and pentahydrate. The pentahydrate form (Na₂S₂O₃·5H₂O) is the most common, presenting as a white or colorless crystalline solid or granules that dissolve readily in water. Anhydrous sodium thiosulfate (Na₂S₂O₃) is an opaque crystalline powder. This chemical is also frequently sold in liquid solutions, such as a 30% concentration.
It is available in various grades, including technical, food, and photographic. Reagent grades like ACS (American Chemical Society), Lab Grade, and ReagentPlus are common. Pharmaceutical and food-grade variations, such as USP (United States Pharmacopeia), FCC (Food Chemicals Codex), EP (European Pharmacopoeia), and BP (British Pharmacopoeia), are also produced.
Sodium thiosulfate serves many purposes, including:
Water treatment, neutralizing chlorine in swimming pools, aquariums, and tap water, and treating industrial wastewater.
Photography, functioning as a “fixer” to stabilize images by dissolving unexposed silver halides, sometimes still referred to as “hypo.”
Laboratory use as a reducing agent, in iodometry, and as an antidote for cyanide poisoning.
Medicine for specific conditions.
Industrial applications in gold and silver extraction, as an antichlor in the textile and paper industries, as a fertilizer, and in leather production.
Where to Find Sodium Thiosulfate
You can acquire sodium thiosulfate from various sources, depending on your intended use and desired quantity. Online retailers offer a convenient purchasing avenue, with major e-commerce platforms like Amazon and eBay often listing smaller quantities. Many specialized chemical suppliers also maintain online stores, such as RND Center, ChemWorld, Lab Alley, and Carolina Biological Supply, providing various grades and quantities.
For larger volumes or specific industrial grades, specialty chemical suppliers are generally the primary source. Companies like Hawkins Inc., Lab Alley, and those listed on B2B platforms such as Thomasnet and go4WorldBusiness, cater to businesses and laboratories, offering bulk options and tailored solutions. These suppliers often specialize in particular grades, from technical to pharmaceutical.
Local retail options are more limited. Common sources include pool supply stores (for chlorine neutralization), some photography supply stores, garden centers or farm supply stores (for agricultural uses), and occasionally pharmacies or pet stores for specialized needs.
Purchasing decisions often involve considering wholesale versus retail. Wholesale options, usually available through specialty chemical suppliers, are suitable for large-scale industrial or laboratory needs and typically offer better per-unit pricing. Retail purchases, commonly found through online marketplaces or local stores, are geared towards individual consumers requiring smaller amounts.
Key Considerations Before Purchase
Before purchasing sodium thiosulfate, consider its purity and grade. Different applications require specific refinement levels; for instance, laboratory work needs ACS or Reagent grade, while medical or food uses require USP or FCC certified products. Always verify certifications (e.g., ISO 9001, REACH, GMP) and request batch-specific Certificates of Analysis (COAs) to confirm purity.
Evaluate the quantity and packaging options to match your requirements. Sodium thiosulfate is sold in sizes ranging from small bottles for hobbyists to large bags, pails, or drums for industrial use. Ensure the packaging is securely sealed and protects the product from moisture, as sodium thiosulfate can absorb water from the air.
Choosing a supplier with a good reputation is important. Look for suppliers with a track record of reliable service, consistent product quality, and responsive customer support. Checking their operational history, on-time delivery rates, and any available third-party audits can provide insight into their trustworthiness.
Review safety information, such as Safety Data Sheets (SDS), before handling. While sodium thiosulfate has low toxicity, it can cause irritation if it contacts skin, eyes, or is inhaled. It reacts with acids to produce sulfur dioxide gas, requiring proper storage away from incompatible materials. Pricing varies based on grade, quantity, and supplier, influenced by raw material costs and market supply and demand.