A numerical method developed by Verteeg (1989, Chem. Engng Sci.44, 2295–2310; 1990, Chem Engng Sci.45, in press) is applied to some specific problems in gas—liquid mass transfer. The experimental results of Chakraborty (1986, Chem. Engng Sci.41, 997–1003) and Zioudas and Dadach (1986, Chem. Engng Sci.41, 405–408) on the absorption of Co2 into aqueous solutions of sterically hindered amines are evaluated with the numerical model. It is shown that studying the absorption of CO2 into aqueous solutions of sterically hindered amines requires a rigorous numerical solution of the differential equations describing the mass transfer instead of analytical and numerical approximations based on a reduction of the number of reactions by neglecting or lumping reactions. It is demonstrated that the absorption rates of CO2 into sterically hindered amine solutions can be explained in terms of the established reactions rates of CO2 in amine solutions alone, and no new reaction paths are necessary to explain the observed behaviour.