Donnan dialysis with ion-exchange membranes was investigated experimentally. The equation derived theoretically in the previous paper was fitted to the results of a Donnan dialytic experiment, and the diffusion coefficients of various kinds of ions and in various kinds of ion-exchange membranes were obtained. The flux of monovalent ions in Donnan dialysis was much larger than that of bivalent ions. Thus, monovalent drive ions are the best kind of drive ions to employ. It was found that the ratio of the diffusion coefficient in the ion-exchange membrane to that in the solution remained constant at 70 for monovalent feed and drive ions except for H+ ions, and at 175 for bivalent feed and drive ions. It became apparent that the fundamental equation derived from Fick’s equation and no electric current might be used for Donnan dialysis instead of the Nernst-Planck equation.