The absorption of hydrogen chloride in water is a very important operation in the manufacture of commercial hydrochloric acid. It is also important in the purification of exhaust gas from chemical operations which form HCL as a by-product, and from refuse incineration where HCL is formed by the combustion of chlorine-containing plastics and solvents. Where HCL vapor is present as an impurity in gas streams, it can readily be removed by washing with water.