Process for purifying crude hydrochloric acid

A process for purifying crude aqueous 5 to 20 wt. % hydrochloric acid comprising the steps of

• a) evaporating water or a water/HCl mixture from said crude aqueous hydrochloric acid at a pressure of from about 0.05 to about 0.5 bar and a temperature of from about 20 to about 80.degree. C. until a crude, azeotropic mixture of water and HCl is obtained;
• b) distilling said crude, azeotropic mixture of water and HCl obtained in step a) in a distillation apparatus containing a head and a bottom at a pressure of from about 0.1 to about 1.5 bar and a temperature of from about 50.degree. to about 110.degree. C. wherein 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;
• and
• c) distilling the liquid mixture left at the bottom of the distillation apparatus used in step b) at a pressure of from about 0.5 to about 2.5 bar and a temperature of from about 80.degree. to about 130.degree. C.