It has been known for a long time that gases can be purified by a treatment with physically acting absorbent solutions and that particularly H.sub.2 S and COS, as well as CO.sub.2, can be removed from such gases. 
Processes of that kind have been described in German Patent No.  1,494,606 and in U.S. Pats.  Nos.  3,531,917 and 3,710,546. 
It is also known that the laden absorbent solution can be regenerated by pressure-relieving, heating or stripping treatments or by a combination thereof.  Suitable physically acting absorbent solutions are methanol and N-methylpyrrolidone (NMP).