Electrocapillary phenomena at polarizable and reversible interfaces between two immiscible liquids: the generalized electro-capillary equation in hansen's representation

The thermodynamic theory of electrocapillary phenomena at the interface between two immiscible electrolyte solutions is considered. A generalized electrocapillary equation for polarizable and reversible interfaces is derived based on Hansen's method. The Gibbs equation for electrolytic systems is obtained both in variables corresponding to ion concentrations and concentrations of neutral ion combinations. The relationship between the ion concentrations in the system and EMF of the circuit consisting of immiscible electrolyte solutions whose terminals are made of identical metals is discussed. The formulae for the thermodynamic charge and the free charge of the interface between two immiscible electrolyte solutions (ITIES) are analysed. The cases of both perfectly and ideally polarizable, and also reversible (non-polarizable) interfaces are considered. Relationship between thermodynamic charges in different sets of variables is obtained.