S2O4

S2O4 refers to the chemical formula for dithionite, also known as hyposulfite. It is the anion with the chemical formula [S2O4]2-. Dithionite is a salt that contains the dithionite ion. Common examples include sodium dithionite (Na2S2O4) and potassium dithionite (K2S2O4).

Sodium dithionite is a white crystalline powder that is soluble in water. It is a powerful reducing agent, meaning it readily donates electrons to other substances. This property makes it useful in a variety of industrial applications. For instance, it is used in the textile industry as a reducing agent for vat dyes and in the paper industry as a bleaching agent for pulp. It also finds use in photography, in the production of certain chemicals, and as a food additive (E239) to prevent spoilage, although its use in food is regulated and varies by region.

The dithionite ion is relatively unstable and can decompose, particularly in acidic solutions or when exposed to heat and oxygen. This decomposition can produce sulfur dioxide and other sulfur compounds. Due to its reducing power, it is important to handle dithionite salts with care, avoiding contact with oxidizing agents. The synthesis of dithionites typically involves the reduction of sulfur dioxide or bisulfite.