A numerical method developed by Verteeg (1989, Chem. Engng Sci.44, 2295–2310; 1990, Chem. Engng Sci.45, in press) is applied to the absorption of CO2 into amine-promoted carbonate solutions. The experimental results of Savage (1984, Faraday Discuss. Chem. Soc.77, 17–31) are evaluated with the numerical model. It is shown that a rigorous numerical solutions of the differential equations describing the mass transfer gives more insight into the actual process than analytical and numerical approximations based on a reduction of the number of reactions by neglecting or lumping reactions.