A computational procedure is presented for the rigorous calculation of multicomponent multistage separation for systems involving equilibria in ionization and chemical reactions in addition to the usual phase equilibrium. This procedure can be used for calculations applied to distillation with and without chemical reaction for systems consisting of both ionizing and non-ionizing species. For ionizing volatile weak electrolytes, the phase equilibrium is computed on the basis of the model of Edwards et al. For distillation calculations the tridiagonal matrix algorithm is used with the modified Muller's method or the step-limited Newton—Raphson method for the convergence of column temperature profiles. The computational procedure has been successfully used to simulate urea hydrolyserstrippers and sour-water strippers. The method converges rapidly and stably. The major limitation is the applicability of the phase equilibrium relationships used for weak electrolyte systems, which is valid in the concentration range below 10 molal.