The simulation of an ion-exchange interdiffusion in a glass with allowance made for the mass transfer inertia is carried out on the basis of the generalized gradient transport law that leads to the wave diffusion equation with constant coefficients in simple cases. From the experimental data on the escape a substance from a glass into a solution, coefficients of this equation—the effective diffusion coefficient and the concentration relaxation time—are calculated. The model kinetic dependences adequately describe the experiment and make it possible to extrapolate this process to the time range preceding the measurements. Parameters of the attainment of a quasi-stationary regime are justified and calculated. With the procedure proposed, the leaching process is calculated for binary silicate glasses.