Capacitance-potential dependences for gold electrode in molten KNO3-KCl mixtures were obtained at various concentrations of KCl and ac frequencies. It was shown that chloC ride addition to nitrate melts causes capacitance drop at a certain anodic potential. This potential is almost the same for 5 and 10 mol % KCl, and it shifts to a more positive value for 1 mol % KCl. An explanation of this effect is suggested. According to it, the anodic maximum of capacitance is observed at the critical potential of the phase transition from chaotic distribution of Cl2- anions to formation of AuCl2- complexes on the electrode surface.