The purpose of this study was to investigate a new model for the prediction of adsorption isotherms at various temperatures from known data at a given temperature. The systems under study consisted either of pure methane, pure n-butane, or mixtures thereof on Columbia Grade G activated charcoal. The proposed model is An + nx = Anxn where x represents an active center, n represents the number of these centers, and A represents the adsorbate. This model assumes that no dissociation occurs upon adsorption. Isotherm data were determined at 27°C for pure butane, pure methane, and three binary mixtures consisting of 0.537, 1.436, and 2.998 mole percent butane in methane. On the basis of the proposed model, an expression for the equilibrium constant was written employing n as defined above and a constant L, the total number of active sites on the surface. The value of n for methane was found to be 1 while while L was found to be 2.9 moles of sites per 100 moles charcoal. A satisfactory corresponding value for butane, however, was not found. Because of the greater adsorption capacity of butane, the value of 2.9 for L appeared to be too small. This apparent variation of L