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Sodium Thiosulfate

CAS 7772-98-7 · Formula Na2O3S2 · MW 158.11 g/mol

Inorganic thiosulfate for photographic fixing, dechlorination, and chrome reduction. HSDB documents its use as a photographic fixer that dissolves silver halides, as an antichlor for dechlorinating bleached paper and textiles, in wastewater treatment to reduce chlorine and chromium, in chrome leather tanning, and as a mordant in dyeing and printing.

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HS Code
2832.30
At a Glance
Material Family
Acids & Salts
Record Type
Pure compound
Primary Role
Preservation
Functional Roles
SODIUM THIOSULFATE
REDUCING
Applications & Use Cases
  • Dechlorination: Antichlor in water and wastewater treatment.
  • Photographic fixer: Dissolves silver halides in film and print processing.
  • Leather: Reducer in chrome tanning.
  • Textiles: Mordant in dyeing and printing.
  • Metal recovery: Agent in silver extraction from ores.
Physical Properties
Melting Point
48.5 °C
Density
1.667
Solubility
PRACTICALLY INSOL IN ALCOHOL
Vapor Pressure
Vapor pressure at 20 °C: negligible
Safety & Handling
Full SDS available on request

A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.

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HS / Tariff Classification
Harmonized System (HS) Code — 6-digit international heading
2832 . 30
Chapter 28
Inorganic chemicals; compounds of precious metals and rare-earth metals
Heading 28.32
Internationally harmonized (WCO HS)
Subheading 2832.30
6-digit international code — national tariff line adds further digits
Chemical Identity
CAS Number
7772-98-7
Molecular Formula
Na2O3S2
Molecular Weight
158.11 g/mol
IUPAC Name
disodium;dioxido-oxo-sulfanylidene-lambda6-sulfane
INCI Name
SODIUM THIOSULFATE
PubChem CID
InChI Key
AKHNMLFCWUSKQB-UHFFFAOYSA-L
Synonyms & Trade Names
SODIUM THIOSULFATE Sodium thiosulphate Disodium thiosulfate Sodothiol Hypo Chlorine Control Chlorine Cure Sodium thiosulfate, anhydrous Thiosulfuric acid, disodium salt Sodium thiosulfate (Na2S2O3) Sodium thiosulphate (Na2S2O3) Sodium oxide sulfide (Na2S2O3) Thiosulfuric acid (H2S2O3), disodium salt Ins no.539 Ins-539 Sodium thiosulphate, anhydrous
Full Description

Sodium thiosulfate (CAS 7772-98-7) is an inorganic thiosulfate salt. HSDB documents its use as a photographic fixer that dissolves silver halides, as an antichlor for dechlorinating bleached paper and textiles, in wastewater treatment to reduce chlorine and chromium, in chrome leather tanning, and as a mordant in dyeing and printing. It also serves as a sequestrant in salt.

Frequently Asked Questions

What is sodium thiosulfate used for?

Sodium thiosulfate (CAS 7772-98-7) is an inorganic thiosulfate salt used as an antichlor for dechlorinating water and wastewater, as a photographic fixer that dissolves silver halides, as a reducer in chrome leather tanning, as a mordant in textile dyeing and printing, and as an agent in silver extraction from ores.

What is another name for Na2S2O3?

Sodium thiosulfate (CAS 7772-98-7) is historically known as hypo or sodium hyposulfite, a name carried over from its long use as a photographic fixer. It is commonly supplied as the pentahydrate. Each lot ships with a Certificate of Analysis.

Is sodium thiosulfate soluble in water?

Yes. Sodium thiosulfate is highly water-soluble, and the pentahydrate dissolves with a cooling (endothermic) effect. Its solubility underpins its use in dechlorination and photographic fixing. See the SDS for handling details.

What HS code is used for sodium thiosulfate?

Sodium thiosulfate is classified under HS heading 2832.30 (Sulfites; thiosulfates: thiosulfates). Verify the destination-country tariff line with your broker prior to export.

What is the cost of bulk sodium thiosulfate?

Bulk pricing depends on form (pentahydrate crystal vs. anhydrous), assay, and volume. Submit a bulk RFQ with quantity and destination and we will return a current quote with CoA and SDS.

Disclaimer. Information on this page — including properties, identifiers, hazard, transport (DOT/UN) and tariff (HS) classifications, and applications — is provided for general reference and is compiled from authoritative public sources (e.g. PubChem/ECHA, 49 CFR 172.101, the Harmonized Tariff Schedule). Values are typical and are not a guaranteed specification; the Certificate of Analysis (CoA) for the lot purchased governs. Products are sold for industrial and professional use only. Nothing here is a medical, health, or efficacy claim or advice. Always consult the current Safety Data Sheet (SDS) before handling, storage, transport or disposal, and confirm regulatory status, classification and suitability for your application and jurisdiction. Hazard, transport and tariff classifications must be verified for your specific shipment. RawSource makes no warranty, express or implied, and assumes no liability for use of this information. Trademarks. Third-party trademarks and brand names are the property of their respective owners; any reference is nominative — used only to identify a comparable product — and does not imply affiliation with, sponsorship by, or endorsement by the trademark owner.