“…To do so, as a first step, let us note that varying T and a 2 under constant ϵ does not change the isotherm because of eq . Consequently Applying the implicit function theorem , on eq yields Noting the equivalence between constant ϵ and constant ⟨ n 2 ⟩/ n 1 and using again the definition (eq ), we obtain This left-hand side of eq is reminiscent of the procedure for obtaining the energy from the free energy (ϵ in this case). This derivative is also ϵ; hence, eq signifies the purely energetic nature of the adsorption potential, ϵ, ,− ,, which is in agreement with the original assumption by Polanyi. − ,− …”