What are sulfur trioxide and sulfuric acid?
Sulfur trioxide is generally a colorless liquid but can also exist as ice- or fiber-like crystals or as a gas. When sulfur trioxide is exposed to air, it rapidly takes up water and gives off white fumes. It combines with water, releasing considerable heat while forming sulfuric acid. It also reacts violently with some metal oxides. Sulfur trioxide is also called sulfuric oxide and sulfuric anhydride. It is used as an intermediate in the production of sulfuric acid, other chemicals, and explosives. Sulfur trioxide is unlikely to exist in the environment except for very short periods when it may be present in the air as a gas. In the air, sulfur trioxide can be formed slowly from sulfur dioxide. Once formed, sulfur trioxide will react with water in the air to form sulfuric acid. Both sulfur dioxide and sulfuric acid are more likely to be found in air than sulfur trioxide. If you are interested in learning more about sulfur dioxide, the Agency for Toxic Substances and Disease Registry has
