Electrocapillarity, electrical double-layer structure

Electrocapillarity and the Electric Double Layer Structure at Oil/Water Interfaces... 

The thermodynamic theory of electrocapillarity considered above is simultaneously the thermodynamic theory of the electrical double layer and yields, in its framework, quantitative data on the double layer. However, further clarification of the properties of the double layer must be based on a consideration of its structure. 

Electrocapillary phenomena at the interface between two immiscible electrolyte solutions, which we will call the oil/water (O/W) interface for short, were studied first by Guastalla [1], then by Blank and Feig [2,3], Watanabe et al. [4, 5], Dupeyrat et al. [6, 7], Joos et al. [8,9], Gavach et al. [10-12], and Spumy [13]. Watanabe et al. applied the electrocapillary equations such as the Lippmann-Helmholtz equation to elucidate the double layer structure of the interface, whereas others [2,3,6,7] made a distinction between electrocapillarity and electroadsorption. Koryta et al. [14] have discussed the electric polarizability of the oil/water interface on the basis of the transfer Gibbs energies of ions from one solvent (the aqueous phase) to the other (the oil or organic phase). 

Experimentally, the electrical double-layer affect is manifest in the phenomenon named electrocapillarity. The phenomenon has been studied for many years, and there exist thermodynamic relationships that relate interfacial surface tension between electrode and electrolyte solution to the structure of the double layer. Typically the metal used for these measurements is mercury since it is the only conveniently available metal that is liquid at room temperature (although some work has been carried out with gallium. Wood s metal, and lead at elevated temperature). 

---