Аннотация:The adsorption behavior of dimethylbenzimidazole on mercury in neutral, acidic, and alkaline aqueous-ethanolic solutions has been analyzed on the basis of its adsorption energy as function of electrode potential. The adsorption parameters have been calculated directly from the experimental values of interfacial-tension depression; the virtual isotherm was used for the calculations in acidic solution, the Frumkin isotherm was used in neutral and alkaline solutions. Dimethylbenzimidazole was shown to exhibit two adsorption states depending on electrode potential; in the transition between these states, the potential dependence of the adsorption energy and attraction constant can change.