hydrosulfites

Hydrosulfites are salts containing the hydrosulfite anion, S2O4^2−, most commonly encountered as sodium hydrosulfite (Na2S2O4). They are typically referred to as dithionites and are valued for their reducing power, enabling them to donate electrons to oxidized substrates. In aqueous solution, hydrosulfites are generally stable under alkaline conditions and readily oxidize in air, forming sulfite or sulfate species.

Industrially, hydrosulfites are produced and sold as salts such as sodium hydrosulfite, calcium hydrosulfite, and potassium hydrosulfite. They are prepared by controlled chemical routes that generate the S2O4^2− anion, and several hydrates are used in commercial formulations. The compounds are usually stored and handled as solid salts or solutions, where they are sensitive to air and moisture.

Applications of hydrosulfites center on their role as mild, effective reducing agents. They are used in the textile and paper industries for decolorizing and bleaching procedures, including reduction of oxidized dyes and whitening of pulp. They can also serve as reducing agents in various chemical syntheses and in certain photographic and metallurgical processes.

Safety and handling considerations are important: hydrosulfites can release sulfur dioxide upon acidification and can pose irritation to eyes, skin, and the respiratory tract. They should be kept away from acids and oxidizing agents, stored in sealed containers, and used with appropriate ventilation and personal protective equipment. Proper disposal requires neutralization and adherence to local regulations.