The adsorption of tetraethylammonium (TEA(+)) ions on the (111) plane of the bismuth single crystal from solutions in ethanol has been investigated by impedance measurement method. It was found that the ionic charge due to the specific adsorption of TEA+ ions in ethanol can be obtained using the classical calculation methods for simple ions. The experimental data were obtained in 0.02 M mixed-electrolyte solutions and the calculations performed with electrode potential as the independent electrical variable. The Gibbs energy of adsorption of TEA+ ions has been calculated using the simple virial adsorption isotherm and it was found that the adsorption of TEA+ cations is weaker than the adsorption of halide anions. The electrosorption valency evaluated has a constant value in the potential region studied. It was concluded that the formed effective surface dipole is significantly screened by the solvent molecules and the metal electron gas. (c) 2005 Elsevier B.V. All rights reserved.