Abstract An analysis is presented for the absorption and reaction of a pulse of reactant gas introduced into a column containing a stationary liquid phase. This type of process is of interest for separation of gases such as H 2S and CO 2 using a liquid amine. For first-order reactions in the liquid, measured moments of the effluent curve can be used to evaluate rate and equilibrium parameters for the system. The theory for the moments is based upon a model which accounts for the rates of axial dispersion in the gas, of gas-to-liquid mass transfer, and of diffusion and reaction in the liquid layer. The equilibrium parameters are the Henry's law constant for the solubility of the reactant and the reaction equilibrium constant.