Description

Sodium Thiosulfate USP

Na2S2O3·5H2O **8.*9
Sodium Thiosulfate USP
Contains not less than *9.0 percent and not more than **0.5 percent of Na2S2O3, calculated on the anhydrous basis.

Packaging and storage— Preserve in tight containers.
Identification—
A: To a solution (1 in *0) add a few drops of iodine TS: the color is discharged.
B: A solution (1 in *0) responds to the tests for Sodium and for Thiosulfate.
Water— Dry about 1.0 g, accurately weighed, in vacuum at *0 o to *5o for *6 hours: it loses between *2.0% and *7.0% of its weight.
Calcium— Dissolve 1 g  Sodium Thiosulfate in *0 mL of water, and add a few mL of ammonium oxalate TS: no turbidity is produced.
Heavy metals—: the limit is 0.**2%.

Sodium Thiosulphate BP

Na2S2O3,5H2O
Sodium Thiosulphate BP

DEFINITION
Content
*9.0 per cent to **1.0 per cent of Na2S2O3,5H2O.

CHARACTERS
Appearance
Transparent, colorless crystals, efflorescent in dry air.
Solubility
Very soluble in water, practically insoluble in ethanol *6 per cent. It dissolves in its water of crystallization at about *9°C.

IDENTIFICATION
A. It decolorizes iodinated potassium iodide solution.
B. To 0.5 ml of solution S (see Tests) add 0.5 ml of water R and 2 ml of silver nitrate solution. A white precipitate is formed which rapidly becomes yellowish and then black.
C. To 2.5 ml of solution S add 2.5 ml of water and 1 ml of hydrochloric acid. A precipitate of sulphur is formed and gas is evolved which gives a blue colour to starch iodate paper.
D. 1 ml of solution S gives reaction of sodium.

TESTS
Solution S
Dissolve *0.0 g in carbon dioxide-free water R prepared from distilled water R and dilute to **0 ml with the same solvent.
Appearance of solution
The freshly prepared solution is clear and colourless.
Dissolve *0.0 g in *0 ml of distilled water, add 1 ml of 0.1 M sodium hydroxide and dilute to **0 ml with the same solvent.
pH
6.0 to 8.4 for the freshly prepared solution S.
Sulphates and sulphites
Maximum 0.2 per cent.
Sulphides
To *0 ml of solution S add 0.*5 ml of a freshly prepared *0 g/l solution of sodium nitroprusside. The solution does not become violet.
Heavy metals
Maximum *0 ppm.

ASSAY
Dissolve Sodium Thiosulfate 0.**0 g in *0 ml of water and titrate with 0.*5 M iodine, using 1 ml of starch solution, added towards the end of the titration, as indicator.
1 ml of 0.*5 M iodine is equivalent to *4.*2 mg of Na2S2O3,5H2O.

Sodium Thiosulfate FCC Food Grade, US Food Chemical Codex

Sodium Thiosulfate
Sodium Hyposulfite
Na2S2O3·5H2O Formula wt **8.*9

DESCRIPTION

Sodium Thiosulfate or Sodium Thiosulphate occurs as large, colorless crystals or as a coarse, crystalline powder. It is deliquescent in moist air and effloresces in dry air at a temperature above *3°. Its solutions are neutral or faintly alkaline to litmus. One gram dissolves in 0.5 mL of water. It is insoluble in alcohol.
Function: Sequestrant; antioxidant.

REQUIREMENTS

Identification
A. Add a few drops of iodine TS to a 1:*0 aqueous solution. The color disappears.
B. A 1:*0 aqueous solution gives positive tests for Sodium and for Thiosulfate.
Assay: Not less than *9.0% and not more than **0.5% of Na2S2O3 after drying.
Lead: Not more than 2 mg/kg.
Selenium: Not more than 0.**3%.
Water: Between *2.0% and *7.0%.

Sodium Thiosulfate Pentahydrate ACS Sodium Thiosulphate ACS Analytical Reagent

American Chemical Society Reagent Grade
Na2S2O3 . 5H2O
Formula Wt **8.*9
CAS Number *********7

REQUIREMENTS
Assay: *9.****1.0% Na2S2O**5H2O
pH of a 5% solution: 6.**8.4 at *5C

MAXIMUM ALLOWABLE
Insoluble matter: 0.**5%
Nitrogen compounds (as N): 0.**2%
Sulfate and sulfite (as SO4): 0.1%
Sulfide (S): Passes test