Sodium Thiosulfate BP

Sodium Thiosulphate also known as sodium hyposulphite is an efflorescent crystalline substance that dissolves readily in water. It occurs in the anhydrous and pentahydrate forms.


It is used to dechlorinate tap water including lowering chlorine levels for use in aquariums, swimming pools, and spas and other chemical heating pads, in the tanning of leather, in pharmaceutical preparations as an anionic surfactant and as an antidote to cyanide poisoning. Also used as Processing Aids and Additive


Chemical Name: Sodium Thiosulphate
Synonyms: Sodium Hyposulphite
Mol. Formula: Na2S2O3.5H2O
Mol. Weight: 248.19 g/mol
CAS No.: 10102-17-7


General Specifications

Test Specification…BP
Description It occurs as transparent, colorless crystals, efflorescent in dry air

Test A

Test B


Test C


Test D


1.      It decolorizes iodinated potassium iodide solution R.

2.      Specified test. A white precipitate is formed which rapidly becomes yellowish and then black.

3.      Specified test. A precipitate of sulfur is formed, and gas is evolved which gives a blue color to starch iodate paper R.

4.      It gives reaction of sodium

Solubility Very soluble in water, practically insoluble in ethanol 96 per cent. It dissolves in its water of crystallization at about 49°C
Appearance of solution A freshly prepared solution is clear and colorless.
pH 6.0 to 8.4 for the freshly prepared solution
Sulfates and sulfites Not more than 0.2%
Sulfides Specified test. The solution does not become violet.
Heavy metals Not more than 10 ppm
Assay Not less than 99.0% and not more than 101.0% of Na2S2O3.5H2O


Shelf life, Storage and Packing

It should be stored in a segregated area in a cool and ventilated place away from combustible materials. Keep in a tightly closed container, sealed until ready for use. It is packed in 25kg or 50kg HDPE bags or drums as required.


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We observe WHO Good manufacturing practice and Good laboratory practice.

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