Ion penetration into an 'unfriendly medium' and the double layer capacitance of the interface between two immiscible electrolytes

We develop a theory of the double layer at electrolyte I electrolyte interf aces with account for the finite thickness of the interfacial region. This includes the distribution of ions between the two phases and smooth variati on of dielectric properties across the interface. The theory offers simple laws for the dependence of the double layer capacitance on the nature of io ns, ionic concentrations and potential, which are in line with experimental observations. The theory shows which parameters reflect the nature of ions and the structure of the interface, and how these parameters can be extrac ted from the capacitance data. (C) 2001 Elsevier Science B.V. All rights re served.