The Dow Chemical Company

Dow Deutschland Inc.

Bernd Wottawa

Jeff H Stultz

Edmund R Nettersheim

Heinz Rorup

Siegfried Unger

Aqueous hydrochloric acid of very high purity can be obtained in a process for purifying crude aqueous 5 to 20 wt. % hydrochloric acid. In the purification, process water or a water/HCl mixture is evaporated from the crude aqueous hydrochloric acid at a pressure of from 0.01 to 1.0 bar and a temperature of from 10.degree. to 100.degree. C. until a crude, azeotropic mixture of water and HCl is obtained. The crude, azeotropic mixture of water and HCl is distilled in a distillation apparatus at a pressure of from 0.1 to 1.5 bar and a temperature of from 50.degree. to 110.degree. C. A purified gaseous, azeotropic mixture of water and HCl is recovered from the head of the distillation apparatus and a liquid mixture is left at the bottom of the distillation apparatus. The liquid mixture which is left at the bottom of the distillation apparatus is distilled at a pressure of from 0.5 to 2.5 bar and a temperature of from 80.degree. to 130.degree. C.

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Himmelpforten, Germany

Bernd Wottawa