Sodium thiosulfate is a chemical compound with the formula Na2S2O3. It appears as a white crystalline powder and is commonly used in various applications, including photography, where it acts as a fixer to remove unexposed silver halides from film. It is also utilized in water treatment to neutralize chlorine and in medicine as an antidote for cyanide poisoning. In addition to its industrial uses, sodium thiosulfate plays a role in analytical chemistry as a reducing agent. It can be used in titrations to determine the concentration of certain substances. Its safety profile is generally favorable, but it should still be handled with care.