Solubility and diffusion data have been used to describe absorption of chlorine into water. When the gas dissolves in water, hydrochloric acid produced by partial hydrolysis of molecular chlorine diffuses rapidly into the bulk liquid. Because the surface of the absorbent is depleted in hydrochloric acid, the solubility of chlorine in the interfacial liquid is significantly higher than the equilibrium solubility at the same chlorine partial pressure. During desorption of dissolved chlorine, hydrochloric acid diffuses from the interior and collects in the interfacial region. Differential equations for absorption and desorption with coupled flow of a second solute component are solved numerically. Calculated concentration profiles are in good agreement with profiles estimated by chemical analysis of layers of absorbent.