Na2S2O7

Sodium disulfite, also known as sodium pyrosulfite or sodium metabisulfite, has the chemical formula Na2S2O7. It is the sodium salt of disulfuric acid. This compound typically appears as a white crystalline solid. It is soluble in water, where it hydrolyzes to form sodium bisulfite. Sodium disulfite is a strong oxidizing agent and can react with reducing agents. It is an important intermediate in the industrial production of sulfur dioxide. Historically, it has been used in photographic processes and as a preservative in some food products, although its use in food is now restricted in many regions due to concerns about sulfite sensitivity. It can also be found as a component in some cleaning agents. The synthesis of sodium disulfite often involves the dehydration of sodium bisulfite or the reaction of sodium sulfite with sulfur dioxide under specific conditions. Care should be taken when handling sodium disulfite as it can be irritating to the skin, eyes, and respiratory tract.