Chlorosulfonic acid is the hygroscopic, inorganic sulfonic acid of chlorine. Commonly used to prepare alkyl sulfates, chlorosulfonic acid should be used with caution as it reacts violently with water to yield sulfuric acid and hydrogen chloride.
Chlorosulfonic acid is used as detergent and as an anti-contrail agent. It is used as an intermediate in the production of other substances such as pharmaceuticals and chemicals. It finds application in producing smoke screens.