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Sodium thiosulfate crystal

GOST 244-76
Na2S2O3 • 5H2O


Crystalline sodium thiosulfate is for photography, film industry, leather, fur, pulp and paper, chemical and other industries.

Safety requirements

Sodium thiosulfate fire and explosion proof. The dust is toxic.


Sodium thiosulfate is packed in four-, five-, six-layer paper bags or plastic bags, liners, enclosed in paper bags or flax, jute bags kenafnye or wooden barrels with a capacity of up to 100 dm³. Sodium thiosulfate is also packaged in a special soft disposable containers.

Guaranteed shelf life

1 year from date of manufacture.

Physical and chemical properties
Item Norm
Photocal Technical
Top First
Appearance Non-caking colorless crystals or granules, may be off-white, yellow, pink.
Mass fraction of sodium thiosulfate in terms of Na2S2O3•5H2O, %, not less 99.0 98.5 98.0
Total iron (Fe2 +), %, not more 0.001 0.002 0.003
Insoluble in water, %, not more 0.01 0.03 0.03
Mass fraction of sodium sulfide (Na2S), %, not more 0.001 0.001 0.001
Calcium, magnesium, and substances that are not soluble in the ammonium solution, %, not more 0.02
Heavy metals (Pb2 +), %, not more 0.001
pH of the aqueous solution at 20 °C 6.5–9.5
Appearance of an aqueous solution Colorless, transparent
Safety requirements
Class of danger
Basic properties and hazards
Basic properties Non-caking colorless crystals or granules, may be off-white, yellow, pink. Non-volatile, soluble in water. Water and acids can decompose to form toxic and flammable gases. Corrosive. Pollutes water.
Explosion and fire Fire-and explosion-proof. Fire resistant. Upon contact with the flame, forms toxic gases (sulfur oxides, etc.).
The risk to humans Can kill is ingested!
Harmful by inhalation and if swallowed (a burning sensation in the mouth, nose and throat, metallic taste, nausea, vomiting, weakness, in severe cases of poisoning — gasp, fainting, seizures), in contact with skin (redness, dryness, itching) and in the eyes (слезотечие, pain in the eyes.) Possible chemical burn.
The dust is toxic. When injected into the human body, it can cause vomiting, lethargy, circulatory disorders, heart palpitations.
Under the action of acid, sodium thiosulfate decomposes with the release of sulfur dioxide (4th class of danger). Sulfur dioxide (SO 2) — a colorless gas with a pungent odor, irritating to mucous membranes. Prolonged exposure causes acute inflammation of the mucous membranes and bronchial (cough, sore throat and chest, tearing).
Individual protection means RC-3 (for 20 minutes). Insulating protective clothing FIR 5 complete with an insulating mask IP-4M. Special clothing, respirator type Y-2K, SB-1 "Petal".