Product Overview
Sodium thiosulfate is an inorganic salt (Na2O3S2, CAS 7772-98-7) offered in reagent grade. It is a strong reducing agent with high water solubility, making it a workhorse across water treatment, analytical laboratories, and industrial processing. This listing is carried in reagent grade — the designation buyers in QC labs, titration workflows, and water-treatment operations specify when their process demands documented purity control.
Available in sizes from 2 lb bench quantities through 55 lb bulk pails, sodium thiosulfate from Alliance Chemical ships with full documentation including an SDS and lot-specific Certificate of Analysis.
Why This Grade
Reagent grade sodium thiosulfate is the grade most commonly requested for volumetric titrations (particularly iodometric methods), dechlorinating municipal water, and photographic processing where residual impurities can interfere with results or downstream product quality. Buyers who need traceable purity for analytical procedures or regulated water-treatment dosing typically specify reagent grade over technical or industrial alternatives.
If your operation is large-scale dechlorination of cooling-tower blowdown or wastewater, a technical grade may serve at lower cost. But for any application where quantitative accuracy matters — standardized titrant preparation, laboratory reagent prep, or processes subject to QC audits — reagent grade is the appropriate selection.
Chemical Profile
Sodium thiosulfate has the molecular formula Na2O3S2 and a molecular weight of 158.11 g/mol (CAS 7772-98-7). In its anhydrous form it is a solid, supplied as dry powder, pellets, or large crystals. Its density is 1.667 g/cm³. The compound is highly soluble in water but practically insoluble in alcohol — an important handling note for labs using mixed-solvent systems. Vapor pressure at 20 °C is negligible, so no significant off-gassing occurs at ambient storage conditions.
Industrial Applications
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Water Treatment & Dechlorinating — Sodium thiosulfate neutralizes free chlorine and chloramines in municipal discharge, cooling-tower blowdown, and aquaculture systems. Operators dose it directly into the effluent stream where it reduces residual chlorine to chloride, bringing discharge into permit limits. It is the ideal dechlorinating agent for many facilities because it reacts quickly and does not introduce problematic byproducts.
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Analytical Chemistry — In iodometric titrations, sodium thiosulfate serves as the standard reducing titrant. The reaction with iodine is stoichiometric and fast, giving a sharp endpoint that labs rely on for dissolved-oxygen, sulfite, and hypochlorite determinations.
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Photographic Processing — Known historically as "hypo," sodium thiosulfate fixes photographic images by dissolving unreacted silver halides from the emulsion. Film and print processors still depend on it wherever silver-halide chemistry is in use.
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Textile Processing — After chlorine-based bleaching, residual chlorine can weaken fibers and cause uneven dye uptake. Sodium thiosulfate is dosed in the rinse bath to neutralize that residual chlorine before the dyeing step.
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Pharmaceutical Manufacturing — Sodium thiosulfate is used as a process intermediate in the synthesis of certain pharmaceutical compounds, where its reducing properties drive specific reaction steps.
Handling & Storage
Sodium thiosulfate is not classified as hazardous under GHS based on available data (per the product's GHS classification). No GHS signal word applies. That said, standard chemical-handling practice still governs: wear chemical-splash goggles and nitrile or HDPE gloves when handling dry powder or preparing solutions. Avoid generating airborne dust.
Store in a cool, dry area away from strong oxidizers and acids, which can decompose thiosulfate to sulfur dioxide. HDPE containers are ideal for long-term storage because they resist moisture transmission. Keep containers sealed — sodium thiosulfate is hygroscopic enough that uncovered product will absorb atmospheric moisture over time, affecting weighing accuracy and reagent preparation. Avoid prolonged exposure to heat or direct sunlight.
Hazmat & Shipping
Sodium thiosulfate is not regulated as a hazardous material for transport under DOT/49 CFR. No UN number, hazard class, packing group, or proper shipping name is assigned (per 49 CFR 172.101). This classification simplifies logistics compared to many industrial chemicals, though specific carrier policies and receiver requirements may still apply.
Documentation
An SDS ships with every order and is available in English, Spanish, French, and Japanese. A lot-specific Certificate of Analysis (COA) is also available for each shipment, giving buyers the traceability that reagent-grade workflows require. A Technical Data Sheet (TDS) is on file for reference.
Why Buy from Alliance Chemical
This sodium thiosulfate is available in sizes from 2 lb bench packs to 55 lb bulk pails — each shipped with an SDS and lot-specific COA so your receiving team has documentation in hand on arrival. Alliance Chemical has operated from our Taylor, Texas warehouse since 1998, serving over 50,000 customers across industrial, municipal, and laboratory markets. Shipping and handling guidance on this listing is reviewed by Andre Taki, DOT Hazmat Specialist.
