Abstract: An absorbent composition that is useful in the selective removal of hydrogen sulfide relative to carbon dioxide from gaseous mixtures that comprise both hydrogen sulfide and carbon dioxide and the use thereof. The absorbent composition includes an aqueous solvent that comprises an amine mixture, comprising an amination reaction product of tert-butylamine and a polydispersed polyethylene glycol mixture, and water with a concentration of an added strong acid to inhibit phase separation of the aqueous solvent. The operation of certain gas absorption processes can be improved by the use of the absorbent composition.