Chlorosulfonic acid (CSA), ClSO2OH, is a clear to straw-colored liquid with a pungent odor. It is a highly reactive chemical compound, containing equimolar quantities of HCl and SO3 with a molecular weight of 116.52.
It reacts violently with water, evolving heat and large quantities of white fumes of hydrochloric acid and sulfuric acid.
The uses are principally in organic synthesis as a sulfating, sulfonating or chlorosulfonating agent. It is also valuable in the dyes and pigments, pharmaceutical, agricultural chemical, and plasticizer industries.
It is preferred in many applications because it is a strong agent, but less destructive than sulfur trioxide.