The adsorption of binary mixtures of cetyltrimethyl ammonium bromide (CTAB) and cetyldimethylbenzylammonium chloride (CDBACI) at the mercury/electrolyte interface was studied in various electrolyte systems. The optimum surfactant concentration and electrolyte ratio was searched for, to obtain the formation of a condensed film at as wide a potential range as possible at the highest temperature possible. The optimum conditions found were 2 x 10(-4) M CTAB and 2 x 10(-4) M CDBACI in 0.07 M KF and 0.03 M KBr at 2 degrees C. The capacitances vs time curves were used for the reconstruction of isochronous capacitance vs potential curves. These curves showed that in that system the condensed film was formed in the potential range from -0.4 to -1.9 V vs Ag/AgCl in less than 220 s. The stability of this film, following the removal of the mercury drop from the solution, was also studied. (c) 2006 Elsevier Inc. All rights reserved.