electrocapillary equation

A form of the Gibbs adsorption equation which includes an expression of the phenomenon of electrocapillarity:

$s d T − τ d p + d γ + σ α d E + ∑ Γ j d μ j = 0$

where $s$ is the surface excess of entropy of unit area of interphase, $T$ is the temperature, $τ$ is the thickness or excess volume of unit area of the interphase, $p$ is the external pressure, $γ$ is the interfacial tension, $σ α$ is the free surface charge density on phase $α$ (areal amount of charge on the surface of phase $α$ ), $E$ is the generalized potential, $Γ j$ is the surface excess, $μ j$ is the chemical potential and $j$ is an electrically neutral component of one or other of the phases; the sum is over all the components but one in each phase.

Source:

PAC, 1986, 58, 437 (Interphases in systems of conducting phases (Recommendations 1985)) on page 446