Sodium thiosulfate is a key inorganic compound used across industries such as mining, water treatment, photography, textiles and laboratories. Understanding the sodium thiosulfate formula, its properties and applications can help procurement and operations teams make better sourcing decisions.

For importers, distributors and manufacturers across Africa and beyond, reliable supply and consistent quality are essential. That’s where a specialist supplier like Wigmore Trading can help.

What Is the Sodium Thiosulfate Formula?

The chemical formula for sodium thiosulfate is Na₂S₂O₃.

In its most common commercial form – the crystalline solid used in industry – it is usually supplied as sodium thiosulfate pentahydrate, with the formula: Na₂S₂O₃·5H₂O

This means each formula unit contains:

• 2 sodium (Na) ions

• 2 sulfur (S) atoms

• 3 oxygen (O) atoms

• and 5 molecules of water of crystallisation in the pentahydrate form

Because of its structure and composition, sodium thiosulfate acts as a reducing agent, a complexing agent and a dechlorinating agent, making it extremely versatile in industrial processes.

Wigmore Trading can source both anhydrous sodium thiosulfate (Na₂S₂O₃) and sodium thiosulfate pentahydrate (Na₂S₂O₃·5H₂O) depending on your technical requirements.

Key Physical and Chemical Properties of Na₂S₂O₃

Understanding the basic properties of the sodium thiosulfate formula helps with safe handling, storage and process optimisation.

Basic Physical Properties

• Appearance: Colourless, transparent crystals or white crystalline powder

• Odour: Odourless

• Solubility: Highly soluble in water, practically insoluble in alcohol

• Taste: Slightly saline and cooling (not for consumption)

• Stability: Stable under normal conditions but decomposes when heated strongly or in acidic solutions

These properties make sodium thiosulfate easy to dissolve in process water, dosing systems and laboratory work.

Chemical Behaviour of the Sodium Thiosulfate Formula

The sodium thiosulfate formula Na₂S₂O₃ gives it several useful chemical behaviours:

• Redox behaviour: Acts as a reducing agent; commonly used in redox titrations (iodometric titration).

• Complex formation: Forms complexes with certain metals, especially silver; this is why it is widely used as a photographic “fixer”.

• Reaction with chlorine: Reacts with free chlorine, converting it to harmless chloride – essential in dechlorination of water and effluents.

• Acid decomposition: In acidic conditions, it can decompose to form sulfur, sulfur dioxide and other sulfur species, which is why pH control is important in many applications.

For customers in industries such as water treatment or mining, Wigmore Trading can help you select the right grade and concentration of sodium thiosulfate to match your process chemistry.

Common Industrial Uses of Sodium Thiosulfate (Na₂S₂O₃)

The versatility of the sodium thiosulfate formula means it is used in many sectors. Below are some of the most important commercial applications.

1. Water Treatment and Dechlorination

In water treatment plants, laboratories and aquaculture, sodium thiosulfate Na₂S₂O₃ is widely used to:

• Neutralise residual chlorine in treated water

• Dechlorinate wastewater before discharge

• Prepare chlorine-free water for sensitive processes or organisms

Because sodium thiosulfate reacts quickly with chlorine and chloramine, it is ideal for quality control testing and adjusting water samples.

Wigmore Trading supplies sodium thiosulfate suitable for municipal water boards, industrial water users and testing laboratories across Africa.

2. Mining and Metallurgy

In some gold recovery processes, the sodium thiosulfate formula is used as part of alternative leaching systems to cyanide. It can form soluble complexes with certain metals, offering:

• Potentially lower toxicity than cyanide systems

• Selective complexation under controlled conditions

While cyanide is still dominant in many operations, interest in sodium thiosulfate-based systems is growing, especially where environmental regulations are tightening.

Wigmore Trading works with mining and metallurgical clients to arrange consistent bulk supply, regional warehousing and efficient cross-border logistics.

3. Photography and Imaging

Historically known as “hypo”, sodium thiosulfate was a critical chemical in traditional film-based photography. It is used as a fixer:

• It dissolves unexposed silver halide from photographic film and paper

• Helps “fix” the image and make it permanent

Although digital imaging has replaced most film processes, sodium thiosulfate is still used in:

• Specialist darkroom work

• Educational institutions and art schools

• Some medical and scientific imaging archives

If your organisation still operates film-processing or archival facilities, Wigmore Trading can help you maintain a stable supply of sodium thiosulfate for your fixer solutions.

4. Laboratory Reagent and Analytical Chemistry

The sodium thiosulfate formula Na₂S₂O₃ is fundamental in titrimetric analysis, especially:

• Iodometric titrations for determining oxidising agents such as chlorine, iodine and certain metal ions

• Standard solutions used for calibration and quality control

Because purity and consistency are critical in analytical work, laboratories often require specific analytical-grade sodium thiosulfate. Wigmore Trading can source and supply lab-grade materials as part of broader lab chemical procurement.

5. Medical and Pharmaceutical Uses

Sodium thiosulfate also appears in medical applications, including:

• As part of certain antidote protocols for cyanide poisoning (in combination with other agents)

• In some formulations for treating calciphylaxis and other rare conditions

These uses typically require strict regulatory and quality standards (e.g., pharmaceutical or injection grades). While Wigmore Trading focuses primarily on industrial and technical grades, our team can help you navigate sourcing options where medical-grade material is required through approved channels.

Handling, Storage and Safety for Sodium Thiosulfate Products

While sodium thiosulfate is generally considered of low acute toxicity compared to many industrial chemicals, it still requires proper handling and storage.

Safe Handling Guidelines

• Avoid creating dust; use appropriate local exhaust ventilation.

• Wear standard PPE: gloves, safety goggles and suitable workwear.

• Handle solutions with care to avoid spills and contamination.

• Follow your site’s chemical handling procedures and risk assessments.

Storage Recommendations for Na₂S₂O₃

To maintain quality and stability of the sodium thiosulfate formula:

• Store in a cool, dry, well-ventilated area

• Keep containers tightly closed to avoid moisture uptake and caking

• Protect from strong acids and oxidising agents

• Avoid long-term exposure to high temperatures or direct sunlight

Wigmore Trading works with manufacturers that use robust packaging and labelling, helping you maintain product quality throughout transportation, warehousing and on-site storage.

Choosing the Right Sodium Thiosulfate Grade for Your Application

Not all sodium thiosulfate is the same. Depending on how you use it, you may need different grades, particle sizes or hydration levels.

Key considerations include:

• Form: Anhydrous (Na₂S₂O₃) vs pentahydrate (Na₂S₂O₃·5H₂O)

• Purity: Technical, industrial, analytical or pharmaceutical grade

• Packaging: Small bags, drums, IBCs or bulk shipments

• Documentation: COAs, MSDS, and compliance certificates

Wigmore Trading can help you match:

• Water treatment plants with reliable technical-grade sodium thiosulfate

• Laboratories and QA/QC departments with analytical-grade material

• Distributors and wholesalers with bulk volumes suitable for repacking or regional distribution

If you are unsure which version of the sodium thiosulfate formula best fits your process, Wigmore Trading can help you review technical data and recommend suitable options.

Why Partner with Wigmore Trading for Sodium Thiosulfate Supply?

Operating across Africa and global trade corridors, Wigmore Trading specialises in sourcing and distributing industrial chemicals, FMCG and raw materials.

When it comes to the sodium thiosulfate formula, working with Wigmore Trading offers several benefits:

• Reliable sourcing: Established relationships with vetted manufacturers

• Quality assurance: Products supplied with appropriate documentation and specifications

• Efficient logistics: Expertise in cross-border shipments, customs clearance and regional distribution

• Market understanding: Experience serving mining, water treatment, manufacturing and wholesale clients

Whether you need container-load shipments for industrial use or regular smaller consignments for laboratories and specialist facilities, Wigmore Trading can design a supply solution that fits your volumes, timelines and compliance needs.

Take the Next Step: Source Sodium Thiosulfate with Confidence

The sodium thiosulfate formula Na₂S₂O₃ underpins a wide range of industrial, laboratory and specialist applications. From dechlorinating water and supporting gold recovery to fixing photographic images and powering analytical chemistry, this versatile compound remains a staple of modern industry.

If you are looking to:

• Secure a dependable source of sodium thiosulfate

• Optimise your procurement for cost, reliability and quality

• Expand your product range as a chemical or industrial distributor

Wigmore Trading can help.

Contact Wigmore Trading today to streamline your sodium thiosulfate sourcing, improve supply chain reliability and support your operations across Africa and beyond.