Sodium Thiosulfate (Sodium Thiosulphate)

What Is Sodium Thiosulfate?

Sodium thiosulfate, also spelled sodium thiosulphate, is a water-soluble inorganic sodium salt with strong reducing and chlorine-neutralizing properties. It is widely used in water treatment, analytical chemistry, photographic processing, textiles and selected industrial processes.

The product is commonly supplied as anhydrous sodium thiosulfate or sodium thiosulfate pentahydrate. Buyers should distinguish between the two forms because their CAS numbers, molecular weights, appearance and active content per kilogram are different.

Sodium Thiosulfate Product Information

Appearance and specification limits may vary according to grade and contract requirements.

Anhydrous vs Pentahydrate: Which Grade Should You Choose?

Sodium thiosulfate pentahydrate is the traditional crystalline form. It is commonly selected for solution preparation, laboratory work and general industrial use.

Anhydrous sodium thiosulfate contains no crystal water, providing more sodium thiosulfate per unit weight. It may be preferred when buyers want reduced crystal-water content, compact transportation or a dry powder formulation.

The two forms should not be substituted kilogram-for-kilogram without recalculating the required active amount. When requesting a quotation, specify the required form, assay basis, application and annual consumption.

How Does Sodium Thiosulfate Remove Chlorine?

Sodium thiosulfate acts as a reducing agent and reacts with residual chlorine and related oxidizing species. This makes it useful for dechlorinating process water, wastewater and laboratory water samples.

Required dosage depends on the chlorine species, residual concentration, pH, temperature, contact time and other oxidants present in the system. Excess dosing should be avoided because it can create unnecessarily reducing conditions or affect downstream testing.

Final dosing should be confirmed by residual-chlorine testing under actual process conditions.

Main Sodium Thiosulfate Applications

Water and Wastewater Treatment

Used to neutralize residual chlorine after disinfection and to protect chlorine-sensitive downstream processes.

Analytical Chemistry

Used as a standard reducing and titration reagent, particularly in iodometric analytical methods.

Photographic Processing

Forms soluble complexes with silver halides and has traditionally been used in photographic fixing solutions.

Textile and Pulp Processing

Used as a reducing or antichlor agent to remove residual oxidants following bleaching operations.

Industrial Processing

May be used in selected metal-processing, mineral-processing and chemical manufacturing applications where controlled reducing action is required.

Application suitability must be confirmed through process testing. Pharmaceutical or regulated uses require the appropriate qualified grade and supporting documentation.

Key Specifications Buyers Should Compare

Specifications should be confirmed using the current batch Certificate of Analysis rather than relying only on general website values.

Packaging, Storage and Handling

Sodium thiosulfate is commonly packed in moisture-resistant bags, drums or other industrial packaging according to grade and order quantity.

Store the product tightly closed in a cool, dry and well-ventilated location. Protect it from moisture, excessive heat, strong acids and strong oxidizing materials. Contact with acids may result in decomposition and the release of sulfur dioxide.

Use suitable protective equipment and review the current Safety Data Sheet before handling.

Why Source Sodium Thiosulfate from AOZUN?

AOZUN supports international buyers requiring sodium thiosulfate for water treatment, industrial processing and chemical distribution.

Available services may include:

• Anhydrous and pentahydrate sourcing options

• Specification and application review

• Batch COA and SDS documentation

• Sample evaluation before bulk purchasing

• Flexible packaging and export logistics

• Support for recurring industrial orders

Product form, grade, specification and packaging should be confirmed in the official quotation.

Sodium Thiosulfate FAQ

Is sodium thiosulfate the same as sodium sulfite?

No. Sodium thiosulfate is Na₂S₂O₃, while sodium sulfite is Na₂SO₃. Both can act as reducing agents, but their composition, reaction behavior and dosage requirements are different.

Which CAS number should be used?

Use CAS 7772-98-7 for anhydrous sodium thiosulfate and CAS 10102-17-7 for sodium thiosulfate pentahydrate. Always verify that the CAS number matches the ordered form.

Can sodium thiosulfate remove residual chlorine?

Yes. It is widely used as a dechlorinating agent. However, dosage should be calculated for the specific water chemistry and confirmed by residual-chlorine testing.

Can anhydrous sodium thiosulfate replace the pentahydrate form?

It may be possible after recalculating the active amount and verifying dissolution, dosing and process performance. Direct kilogram-for-kilogram substitution is not recommended.

Are “thiosulfate” and “thiosulphate” different products?

No. “Thiosulfate” is the preferred American spelling, while “thiosulphate” is commonly used in British English and some international markets.

Request a Sodium Thiosulfate Quote

Contact AOZUN with the required form, specification, quantity, packaging, destination port and application. Our team will review product availability and provide the relevant commercial and technical documents.