ABSTRACT

The thermodynamic description of adsorption layers is important for the quantitative understandings of liquid/fluid interfaces in equilibrium. A thermodynamic analysis of adsorption layers provides the equation of state that expresses the surface tension (surface pressure) as a function of surface layer composition. Moreover, we get the adsorption isotherm, which determines the dependence of the adsorption of each component as a function of the bulk concentrations. The values of surface tension, adsorption, and dilational viscoelasticity calculated on the basis of these equations can be directly compared with experimental data. Various theoretical models for the description of adsorption layers at liquid interfaces have been proposed so far [1-30], using approaches based on surface thermodynamics. The analysis of chemical potentials of the surface layer components based on the Butler equation [31] turned out to be extremely productive in studies of interfacial layers for various systems [1-6,17-23]. It is very important to note here that the Butler equation for the chemical potential was derived in the framework of a rigorous Gibbs thermodynamics, for example, by Defay and Prigogine [2] and Rusanov [5].