Chronoamperometry and electrochemical impedance spectroscopy were employed to determine the diffusion coefficients in the solid state D-S for anions HSO4- (from H2SO4- in three protic solvents) and ClO4- (from LiClO4 in three aprotic solvents), which are intercalated in graphite. Strong convection in the electrolyte was provided to minimize the time constant for the transport in the electrolyte diffusion layer. D-S approximate to 10(-5) and 10(-6) cm(2) s(-1) were found for these categories. The Walden products eta . D-S were identified to be constant (eta = specific viscosity in the bulk liquid). It is concluded, that the anions move in the solid in an environment which is similar to the liquid electrolyte due to cointercalation of solvent molecules.