Different definitions of standard thermodynamic functions of proton adsorption on oxides are discussed in terms of distinguishing between the temperature variations of acidity of the surface and those of pK(w). Inert electrolyte titration was proposed as an accurate method for the determination of pH(o) of oxides. The temperature dependence of pH(o) of gamma-alumina was similar to other oxides notwithstanding some literature data (Akratopulu et al. 1986). The standard enthalpy of proton adsorption on gamma-alumina is more sensitive to dioxane admixtures in water relative to methanol.