Sulfur trioxide (also spelled sulphur trioxide) is the chemical compound with the formula SO3. In the gaseous form, this species is a significant pollutant, being the primary agent in acid rain. It is prepared on massive scales as a precursor to sulfuric acid.
Read more about Sulfur Trioxide: Structure and Bonding, Chemical Reactions, Preparation, Structure of Solid SO3, Application, Safety, Sources