Abstract

Chlorosulfuric acid, more widely known as chlorosulfonic acid, is a strong mineral acid made by reacting equimolar quantities of hydrogen chloride and sulfur trioxide. Its structure is analogous to sulfuric acid: the chloride replaces a hydroxyl group. Chlorosulfuric acid is a highly reactive chemical used principally in organic synthesis as a sulfating, sulfonating, or chlorosulfonating agent. Its main applications are an intermediate in the production of synthetic detergents, surfactants, and pharmaceuticals. It is also used in the production of dyes and pigments, ion-exchange resins, pesticides, and plasticizers.

Commercial-grade chlorosulfuric acid has a purity of 99+%. When exposed to the atmosphere, it reacts with the moisture present to form dense white clouds of sulfuric acid and hydrochloric acid mists. It has been used as a smoke screen in wartime.