Ammonium thiosulfate is a white crystalline solid with the chemical formula (NH4)2S2O3. It is also sometimes called ammonium hyposulfite. The compound is a salt that is soluble in water and is commonly used in photography as a fixing agent to dissolve unexposed silver halide from photographic film or paper.Ammonium thiosulfate can also be used as a source of sulfur or as a fertilizer for crops that require a high sulfur content, such as onions, garlic, and broccoli. In agriculture, it is often used in combination with other nutrients such as nitrogen, phosphorus, and potassium.
The compound is also used in the treatment of cyanide poisoning as it can form a stable complex with cyanide ions, which can then be excreted from the body.