H2S2O3, known as thiosulfuric acid, is a chemical compound composed of hydrogen, sulfur, and oxygen. It contains two sulfur atoms and three oxygen atoms, along with two hydrogen atoms. Thiosulfuric acid is often encountered in its salt forms, such as sodium thiosulfate, which is used in photography and water treatment. This compound is unstable and can decompose into sulfur dioxide and water. Thiosulfuric acid is important in various chemical reactions, particularly in the field of analytical chemistry and environmental science, where it plays a role in the reduction of heavy metals and the detoxification of certain pollutants.