The ion exchange kinetics of polycrystalline material soaked in H2SO4 were studied. The rate of ion exchange in hot concentrated acid was determined by monitoring the change in dissolved alkali content. The H3O+ diffusion coefficient was estimated from the resultant time dependence data (table 15).

Ion Exchange Kinetics of Polycrystalline Na/Kβ/β”-Al2O3. M.Nagai, P.S.Nicholson: Solid State Ionics, 1985, 15[4], 311-6