Chlorosulfonic Acid

SO₂Cl(OH), a monochloroanhydride of sulfuric acid. A colorless, mobile liquid, chlorosulfonic acid has a melting point of – 80°C, a boiling point at atmospheric pressure of 155°C (with decomposition), and a density of 1.75 g/cm³. It is chemically very reactive. It reacts vigorously with water, forming sulfuric and hydrochloric acids, and it fumes in the presence of atmospheric moisture. It also reacts with many organic and inorganic compounds. Chlorosulfonic acid is produced by the reaction of hydrogen chloride with sulfur trioxide: HCl + SO₃ = SO₂Cl(OH). In the absence of moisture, it can be stored and transported in steel containers. Chlorosulfonic acid is used in the production of dyes, detergents, and drugs; it is also used as a smoke producer.