Name: Sodium Thiosulfate
CAS No: Sodium thiosulfate anhydrous [7772-98-7], Sodium thiosulfate pentahydrate [10102-17-7]
BP: Sodium Thiosulphate JP: Sodium Thiosulfate Hydrate PhEur: Sodium Thiosulfate USP-NF: Sodium Thiosulfate
Ametox; disodium thiosulfate; disodium thiosulfate pentahydrate; natrii thiosulfas; natrium thiosulfuricum; sodium hyposulfite; sodium subsulfite; Sodothiol; Sulfothiorine; thiosulfuric acid disodium salt.
Sodium thiosulfate anhydrous [7772-98-7], Sodium thiosulfate pentahydrate [10102-17-7]
Na2S2O3 158.11 (for anhydrous) Na2S2O35H2O 248.2 (for pentahydrate)
Sodium thiosulfate is used as an antioxidant in pharmaceuticals (ophthalmic, intravenous, and oral preparations). It has also been used for its antifungal properties(1) and as a reagent in analytical chemistry.
Sodium thiosulfate occurs as odorless and colorless crystals, a crystalline powder or granules. It is efflorescent in dry air and deliquescent in moist air.
See Table I.
Acidity/alkalinity Aqueous solution practically neutral at pH 6.5–8.0 (pentahydrate). Density 1.69 g/cm3 (pentahydrate) Hygroscopicity Slightly deliquesces in moist air (pentahydrate). Melting point 488C (pentahydrate) Solubility Soluble in water; practically insoluble in ethanol (95%)
Sodium thiosulfate decomposes on heating. The bulk powder should be stored in a cool place, and the container should be kept tightly closed in a dry and well-ventilated place. It should not be stored near acids.
Sodium thiosulfate is incompatible with iodine, with acids, and with lead, mercury, and silver salts. It may reduce the activity of some preservatives, including bronopol, phenylmercuric salts, and thimerosal.(1)
On an industrial scale, sodium thiosulfate is produced chiefly from liquid waste products of sodium sulfide or sulfur dye manufacture. Small-scale synthesis is done by boiling an aqueous solution of sodium sulfite with sulfur.(2,3)
Sodium thiosulfate is used in ophthalmic, intravenous, and oral pharmaceutical preparations. Apart from osmotic disturbances, sodium thiosulfate is relatively nontoxic. It is moderately toxic by the subcutaneous route and mildly irritating to respiratory tract and skin. Large oral doses have a cathartic action.(1) LD50 (IP, mouse) 5.6 g/kg(4) LD50 (IV, mouse) 2.4 g/kg
Observe normal precautions appropriate to the circumstances and quantity of the material handled. Protective gloves are recommended for prolonged or repeated contact use. Hazardous products (sulfur oxides) are formed when heated to decomposition.
GRAS listed. Included in the FDA Inactive Ingredients Database (IV solutions; ophthalmic solutions and suspensions; oral capsules, solutions, and tablets). Included in the Canadian List of Acceptable Non-medicinal Ingredients.
Sodium thiosulfate has been used as an antidote to cyanide poisoning.(5,6) Thiosulfate acts as a sulfur donor for the conversion of cyanide to thiocyanate (which can then be safely excreted in the urine), catalyzed by the enzyme rhodanase. There is a specification for sodium thiosulfate in the Food Chemicals Codex (FCC).(7) The EINECS number for sodium thiosulfate is 231-867-5. The PubChem Compound ID (CID) for sodium thiosulfate pentahydrate is 516922