AMmet-The principle of corresponding states is used to predict the adsorption isotherms of gases possessing small, nearly spherical molecules. Adsorption data for argon on graphitized carbon black are used to predict adsorption isotherms for nitrogen, neopentane and carbon tetrachloride on the same adsorbent; the predictions are in excellent agreement with experimental results. The parameters required for the prediction are Henry's constants, or initial slopes of the adsorption isotherms, and the critical properties of the gas. The results are restricted to the case of monolayer physical adsorption on a homogeneous surface.
PROGRFSS in the study of physical adsorption has been retarded in the past by the unknown nature of the adsorbent surface.
Recent work on homogeneous surfaces, however, has provided considerable insight into the nature of the adsorption process. The two-dimensional analog of the van der Waals equation of state has been used extensively in describing the adsorption isotherm below monolayer surface coverage [l-3]. But it is well known that the van der Waals equation is only qualitatively correct [4] and therefore, by analogy to the threedimensional case, it appeared desirable to investigate a more general treatment which describes the configurational properties of an adsorbed layer in terms of an unspecified two-parameter equation of state in a manner similar to the generalized compressibility factor diagrams so commonly used for non-ideal gases.