Thermodynamics and kinetics investigation of ion exchange H+/M+ (M = Li, Na) in tin acid phosphate has been carried out. The equilibrium constants and the cation diffusion coefficients in the exchange products have been determined. It was shown that the diffusion coefficient value in MxH2 - xSn(PO4)(2).nH(2)O depends strongly on proton concentration in the solution. The cation mobility in tin acid phosphate and its ion exchange products has been investigated by impedance spectroscopy too. It was shown that the ion conductivity of these compounds is determined by the surface contribution and increases with increase in the hydration degree. (C) 2003 Elsevier B.V. All rights reserved.