Chemical laboratory

Sodium Thiosulfate

Versatile Reducing Agent for Water Treatment & Photography

  • CAS 7772-98-7
  • Formula Na₂S₂O₃
  • Flash Pt N/A °C
  • Density 1.667 g/cm³
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Physical & Chemical Properties

Property Value Unit
Boiling point 100°C (decomposes) °C
Flash point N/A °C
Density 1.667 g/cm³ g/cm³
Solubility 70.1 g/100 mL (20°C) -
Ph 6.0 - 9.5 (1% solution) -
Molecular weight 158.11 g/mol g/mol
Melting point 48°C (pentahydrate) °C
Vapor pressure N/A mmHg
Autoignition temp N/A -
Appearance White crystalline solid -
Odor Odorless -
Vapor density N/A g/cm³

Overview

Sodium Thiosulfate (Na₂S₂O₃) is a white, crystalline, odorless compound that serves as one of the most versatile reducing agents in industrial and laboratory applications. With its excellent solubility in water (70.1 g/100 mL at 20°C) and stable chemical properties, this compound has become essential across multiple industries including water treatment, photography, mining, and analytical chemistry. Its unique ability to neutralize chlorine and other oxidizing agents makes it particularly valuable for environmental and safety applications.

Key Applications

  • Water Dechlorination: Effectively neutralizes chlorine in municipal water systems, swimming pools, and industrial processes, making water safe for discharge or further treatment
  • Photographic Processing: Functions as a photographic fixer, removing unexposed silver halides from film and paper during development processes
  • Mining Operations: Used in gold extraction processes and cyanide neutralization, providing safe handling of toxic mining byproducts
  • Analytical Chemistry: Serves as a standard reagent in iodometric titrations and other quantitative analysis procedures

Safety & Handling

Sodium Thiosulfate is generally considered safe to handle, with no flash point or autoignition temperature due to its non-flammable nature. The compound decomposes at 100°C rather than boiling, releasing sulfur dioxide gas. Standard laboratory personal protective equipment including safety glasses, gloves, and lab coats should be worn when handling. Ensure adequate ventilation when heating or processing large quantities to prevent inhalation of decomposition products. The pH of a 1% solution ranges from 6.0 to 9.5, making it relatively neutral and safe for most applications.

Storage & Shelf Life

Store Sodium Thiosulfate in a cool, dry location away from direct sunlight and heat sources. Keep containers tightly sealed to prevent moisture absorption and contamination. The pentahydrate form has a melting point of 48°C, so storage temperatures should remain well below this threshold. Avoid contact with strong acids and oxidizing agents, which can cause decomposition. When stored properly in original packaging, the product maintains its quality and effectiveness for extended periods.

Why Alliance Chemical

Alliance Chemical provides high-quality Sodium Thiosulfate with same-day shipping from our Taylor, Texas facility. We offer flexible shipping options including UPS for smaller quantities and LTL/FTL freight for bulk orders. Every shipment includes comprehensive Safety Data Sheets (SDS) and Certificates of Analysis (COA) to ensure you receive consistent, laboratory-grade material that meets your specifications. Our technical support team stands ready to assist with application questions and product selection.

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

Same-day pickup at our Taylor, TX warehouse for Texas customers.

SDS, COA, and TDS available for every product • Same-day shipping on orders before 1 PM CT

Available Sizes

Sodium Thiosulfate - 1 Pack (2 lbs.)

1 Pack (2 lbs.)

$16.98

 Sodium Thiosulfate - 1 Pack (5 lbs.)

1 Pack (5 lbs.)

$23.53

 Sodium Thiosulfate - 1 Bag (55 lbs.)

1 Bag (55 lbs.)

$191.82
View all sizes →

Frequently Asked Questions

What is sodium thiosulfate and what is it used for?
Sodium thiosulfate (Na2S2O3) is a white crystalline salt commonly supplied as anhydrous or pentahydrate. It is used industrially and in laboratories as a reducing/complexing agent, photographic fixer, titrant in iodometry, cyanide neutralizer in mining waste treatment, and in metal finishing and water treatment applications.
How should I store sodium thiosulfate and what is its typical shelf life?
Store in a cool, dry, well‑ventilated area in a tightly closed container away from acids and oxidizers to prevent decomposition and moisture uptake. Typical shelf life ranges from 1–3 years depending on grade, packaging and storage conditions; verify potency with the supplier's COA or perform assay if long‑stored.
Is sodium thiosulfate hazardous and what personal protective equipment (PPE) is recommended?
Sodium thiosulfate is generally of low acute toxicity but can cause skin and eye irritation and respiratory irritation from dust; consult the SDS for hazards. Use standard laboratory PPE—gloves, safety goggles and lab coat—and employ local exhaust or dust control when handling powders, plus spill containment procedures.
What concentrations and grades of sodium thiosulfate are available?
Available forms include anhydrous and pentahydrate solids and aqueous solutions in custom concentrations; common grades are ACS/reagent, technical and industrial. For analytical work, standardized solutions (e.g., 0.1 N) are prepared from accurately weighed reagent-grade material and should be standardized against a primary standard.
What documentation comes with sodium thiosulfate shipments?
Suppliers typically provide a Safety Data Sheet (SDS), Certificate of Analysis (COA), and a technical data sheet (TDS) on request, plus packing lists and any regulatory compliance documentation required for transport or customs. Ask your supplier for batch-specific COA and stability/handling notes when purchasing.
How is sodium thiosulfate packaged and shipped?
It is commonly packaged in sealed plastic-lined paper bags (25 kg), drums, bottles for lab scale, or IBCs for bulk liquid solutions; custom packaging is available. Sodium thiosulfate is usually shipped as a non‑hazardous solid/solution but must be transported per local and international regulations and protected from moisture.
Which materials and chemicals are compatible or incompatible with sodium thiosulfate?
Compatible materials include glass, polyethylene, polypropylene and many stainless steels (316/304) under normal conditions. It is incompatible with strong acids (decomposes, releasing sulfur‑containing gases), strong oxidizers, and certain reactive metals; avoid mixing with acidic or oxidizing agents.
What are the key technical specifications for sodium thiosulfate I should check?
Check chemical formula (Na2S2O3), common physical form (white crystalline solid—anhydrous or pentahydrate), molecular weight (anhydrous ~158.11 g·mol−1, pentahydrate ~248.18 g·mol−1), assay/purity, and solubility (readily soluble in water). Also verify moisture content, chloride/sulfate impurities and heavy metal specifications on the COA for critical applications.
Which industries and applications commonly use sodium thiosulfate?
Common industries include photographic processing, mining (cyanide destruction and leaching alternatives), water and wastewater treatment, metal finishing and electroplating, textiles, and analytical/laboratory chemistry (titrations). It is valued where reducing, complexing, or neutralizing chemistry is required at industrial scale or in analytical workflows.
How can I purchase sodium thiosulfate and what should I ask the supplier?
Sodium thiosulfate is available from chemical distributors in laboratory bottles, 25 kg bags, drums or bulk shipments; lead times and MOQs vary by supplier and grade. When ordering, request the grade (anhydrous vs pentahydrate), COA, SDS, packing options, storage recommendations, and any custom concentration or quality controls needed for your application.

Documentation & Downloads

Safety Data Sheet
SDS / MSDS
Request COA
Certificate of Analysis
Technical Data Sheet (TDS)
Available for all products

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