Gibbs isotherm
The Gibbs adsorption isotherm for multicomponent systems is an equation used to relate the changes in concentration of a component in contact with a surface with changes in the surface tension, which results in a corresponding change in surface energy. For a binary system, the Gibbs adsorption equation in terms of surface excess is − d γ = Γ 1 d μ 1 + Γ 2 d μ 2 , {\displaystyle -\mathrm {d} \gamma =\Gamma _{1}\,\mathrm {d} \mu _{1}+\Gamma _{2}\,\mathrm {d} \mu _{2},} where γ {\displaystyle \gamma } is the surface tension, Γ i {\displaystyle \Gamma _{i}} is the surface excess concentration of component i, μ i {\displaystyle \mu _{i}} is the chemical potential of component i.