What is disclosed is the use of metallic vessels having particularly high corrosion resistance which are made of(a) aluminum or alloys containing more than 95% aluminum, or of(b) nickel-chromium-iron alloys containing from 30 to 50% of nickel, from 20 to 30% of chromium, and from 18 to 50% of iron, by weight, in reacting or working up mixtures containing substantial amounts of hydrogen fluoride in addition to organic carboxylic acids and/or carbon monoxide and/or water.