SO2

Sulfur dioxide, with the chemical formula SO2, is a colorless gas known for its sharp, pungent odor. It is the simplest oxide of sulfur and plays a central role in industrial chemistry. In water, it dissolves to form sulfurous acid (H2SO3) and can be further oxidized to sulfuric acid.

SO2 occurs naturally in volcanic emissions and hot springs. It is commonly released during the combustion of sulfur-containing fuels and during the roasting of sulfide ores. Industrially, it is produced on a large scale by burning elemental sulfur or by processing sulfur-containing minerals, and it is often captured from flue gases for use in chemical syntheses. A major downstream process converts SO2 to sulfur trioxide (SO3), which is then used to produce sulfuric acid via the contact process.

The principal use of SO2 is as an intermediate in the production of sulfuric acid, one of the most widely manufactured chemicals. Historically, it has been used as a preservative and antioxidant in foods and beverages, such as dried fruits and wines, though its use in foods is restricted in many jurisdictions due to health considerations. It has also served as a reducing agent in certain syntheses and, in some applications, as a fumigant or bleaching agent.

Health and environmental aspects: SO2 is a respiratory irritant that can affect the eyes, throat, and lungs at sufficient concentrations. It contributes to the formation of sulfuric acid aerosols in the atmosphere, playing a role in acid rain and impacting air quality, vegetation, and aquatic systems. Emissions are subject to regulatory controls, and exposure in occupational settings is managed with ventilation, monitoring, and protective equipment.

Safety and regulation: Handling follows standards for toxic gas, emphasizing containment, proper storage, and leak prevention. Monitoring and emission controls aim to minimize ambient concentrations and environmental impact.