SO3, or sulfur trioxide, is a chemical compound composed of one sulfur atom and three oxygen atoms. It is a colorless liquid at room temperature and has a strong, pungent odor. SO3 is highly reactive and can form sulfuric acid when it comes into contact with water, making it an important substance in the production of fertilizers and other chemicals. In industrial processes, SO3 is primarily produced through the Contact Process, which involves the oxidation of sulfur dioxide (SO2) in the presence of a catalyst. Due to its corrosive nature, SO3 must be handled with care, as it can cause severe burns and damage to materials.