Results of the investigations of the electrical double layer (edl) at manganese oxides/ aqueous solution of alkali metal chlorides interface are presented. The solid phase in the experiments consists of Mn₂O₃ or MnO₂. Dzeta potential (ζ) and surface charge (σ0) measurements for the mentioned oxides were performed in 0.1- 0.001M solutions of LiCl, NaCl and CsCl. On the basis of surface charge density as a function of pH and ionic strength data the ionization and complexation constants of surface hydroxyl groups were calculated. The surface charge measurements and cation adsorption data indicated that the sequence of the adsorption of alkali metal cations is Li> Na>Cs.