The CO absorption in CuCl solution, acidified with hydrochloric acid, or alkaline ammonium Cu(1) carbonate or formate solution is conducted at a pressure of up to ca. 300 bar. The desorption takes place at reduced pressure and ca. 40-50°C. There are essential differences in the concentrations of the Cu salt solutions depending on whether CO is to be recovered from gas mixtures or whether gases are to be freed from small amounts of co.