Can anhydrous sodium thiosulfate be substituted by sodium thiosulfate pentahydrate on the same weight basis?

No. CAS 7772-98-7 identifies anhydrous sodium thiosulfate, while the pentahydrate is CAS 10102-17-7 and contains five waters of crystallization. Equal weights do not deliver the same amount of thiosulfate. Recalculate on an active or molar basis and confirm the hydration state, assay basis and moisture limit.

Which specification points should be compared for industrial anhydrous sodium thiosulfate?

Define assay on the stated basis, moisture, water-insoluble matter, pH or alkalinity method, sulfite and sulfate limits where relevant, trace metals required by the process, particle form and packaging integrity. Because the anhydrous material is hygroscopic, also confirm sampling, storage and the maximum moisture allowed at use.

Anhydrous Sodium Thiosulfate CAS 7772-98-7

Sodium Thiosulfate , CAS 7772-98-7 and EC 231-867-5 , refers on this page to the anhydrous salt Na2S2O3 , with molecular weight 158.11 g/mol. It must be distinguished from sodium thiosulfate pentahydrate, CAS 10102-17-7, and from the isolated thiosulfate ion. Commercial comparison therefore requires the hydrate form, assay basis, water content and application-specific impurity limits to be stated explicitly. Industrial or analytical supply is available against an agreed specification and lot-specific COA.

CAS: 7772-98-7
Synonyms: Sodium Thiosulfate, Sodium thiosulphate, Disodium thiosulfate, Sodium hyposulfite, Anhydrous sodium thiosulfate
Einecs: 231-867-5
Molecular Formula: Na₂S₂O₃
Grade: Confirm hydration state or concentration, assay basis, key ions, insolubles or trace metals, physical form and intended-use documents against the current COA or TDS.
Package: State required form, quantity and destination; confirm the current bag or container, liner, net weight, moisture or corrosion controls, palletization and transport requirements before quotation.

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Product Description

1 Identity and physicochemical profile

2 Applications and grade selection

3 Storage and handling

4 Safety, documentation and procurement

Identity and physicochemical profile

Item	Technical guidance
Correct identity	Anhydrous sodium thiosulfate; disodium thiosulfate
CAS / EC	7772-98-7 / 231-867-5
Formula / molecular weight	Na₂S₂O₃ / 158.11 g/mol
Hydrate boundary	The pentahydrate Na₂S₂O₃·5H₂O is a different commercial form identified by CAS 10102-17-7
Key purchase controls	Assay basis, water, pH, water-insoluble matter, sulfite or sulfate and application-specific metals
Grade boundary	Industrial or analytical identity does not establish pharmaceutical, injectable or medical-use suitability

Applications and grade selection

Anhydrous Sodium Thiosulfate is used or evaluated in dechlorination, photographic processing, analytical titration, chemical reduction and selected metal-processing or water-treatment operations. Grade choice depends on assay basis, dissolution behavior and impurities that matter to the specific process; dosage should be established from water chemistry or process trials.

State whether anhydrous material or pentahydrate is required and compare quotations on the same active-content basis.
Define assay method, water, pH, insolubles, sulfur oxyanion impurities and any route-critical metal limits.
Check dissolution, dosing, filtration and downstream performance in the buyer’s actual water or process conditions.

Storage and handling

Store in sealed moisture-protective packaging in a dry, ventilated area away from incompatible acids and oxidizing agents. Prevent cross-contamination and follow the current SDS and grade documentation for stacking, shelf life and handling.

Safety, documentation and procurement

Use dust control, gloves and eye protection in accordance with the current SDS and workplace assessment. A procurement request should identify hydrate form, assay basis, grade, application, quantity, packaging, destination and required analytical or compliance documents.

FAQ - Technical & Supply Chain

Q:
Can anhydrous sodium thiosulfate be substituted by sodium thiosulfate pentahydrate on the same weight basis?

A: No. CAS 7772-98-7 identifies anhydrous sodium thiosulfate, while the pentahydrate is CAS 10102-17-7 and contains five waters of crystallization. Equal weights do not deliver the same amount of thiosulfate. Recalculate on an active or molar basis and confirm the hydration state, assay basis and moisture limit.
Q:
Which specification points should be compared for industrial anhydrous sodium thiosulfate?

A: Define assay on the stated basis, moisture, water-insoluble matter, pH or alkalinity method, sulfite and sulfate limits where relevant, trace metals required by the process, particle form and packaging integrity. Because the anhydrous material is hygroscopic, also confirm sampling, storage and the maximum moisture allowed at use.

Ordering & Documentation

Key information for document requests, quotations, and supply planning.

Documents

COA, TDS, SDS/MSDS and packing details are available on request.

Quotation

Send the CAS number, grade, quantity, packing preference and destination.

Sample & Supply

Support is available for samples, trial orders, bulk and repeat supply.

Storage & Shipping

Product-specific conditions are confirmed before order.

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