Sulfur trioxide (SO3) is a chemical compound composed of one sulfur atom and three oxygen atoms. It is a colorless liquid at room temperature and is known for its strong acidic properties. SO3 is primarily used in the production of sulfuric acid, one of the most widely used industrial chemicals, through the contact process. When sulfur trioxide comes into contact with water, it reacts vigorously to form sulfuric acid (H2SO4). This reaction releases heat and can produce a mist of sulfuric acid, which is highly corrosive. Due to its reactivity, SO3 must be handled with care in industrial settings to prevent accidents and ensure safety.