The Hill-de Boer equation in the adsorption of water on quartz

Within the limitations imposed by the number of experimental points, it has been possible to establish that the system of water adsorbed on pure and methylated quartz has adsorption isotherms in which the quantity adsorbed increases with increasing temperature when plotted in terms of relative pressure. This behavior can be adequately described by the Hill-de Boer equation, even though the interpretation of the data by means of parameter K₁ of the equation suggests that the water shows only dispersion interactions with the silica surface. This rather anomalous behavior of the system is in agreement with the previously published values of parameter S of the Frenkel-Halsey-Hill equation.