Sodium thiosulfate

Sodium Thiosulfate (also known as sodium hyposulfite or "hypo") is an inorganic compound represented by the formula Na2S2O3. It is a colorless, crystalline solid that is more commonly encountered as a pentahydrate, Na2S2O3•5H2O. Sodium thiosulfate has a wide range of uses in various industries, including photography, medicine, and water treatment.

Chemical Properties[edit | edit source]

Sodium thiosulfate is an ionic compound made up of two sodium ions (Na+) and one thiosulfate ion (S2O3-). The thiosulfate ion is a polyatomic ion in which two sulfur atoms are bonded to three oxygen atoms. One of the sulfur atoms has an oxidation state of +6 and the other has an oxidation state of +2. The overall charge of the ion is -2.

Production[edit | edit source]

Sodium thiosulfate is produced industrially by the reaction of sodium sulfite with sulfur. Alternatively, it can be produced by boiling sodium sulfide with sulfur.

Uses[edit | edit source]

Photography[edit | edit source]

In photography, sodium thiosulfate is used as a fixing agent to dissolve unaltered silver salts from exposed photographic film or photographic paper.

Medicine[edit | edit source]

In medicine, sodium thiosulfate is used as an antidote to cyanide poisoning. It works by converting the poisonous cyanide into thiocyanate, a compound that is less toxic and can be excreted in urine.

Water Treatment[edit | edit source]

In water treatment, sodium thiosulfate is used to dechlorinate tap water including lowering chlorine levels for use in aquariums.

Safety[edit | edit source]

Sodium thiosulfate is generally considered safe for handling. However, exposure to large amounts can cause irritation to the eyes, skin, and respiratory tract.