Two‐Dimensional Second Virial Coefficient in Physical Adsorptions

Abstract

Recently Sinanoğlu and Pitzer have shown that a third‐order perturbation calculation of the three‐body system consisting of two interacting nonpolar molecules and an adsorbent surface leads to a three‐body term for the intermolecular interaction in addition to the pairwise interaction. We investigate the effect of this additional force on the thermodynamic properties of the adsorbed phase by calculating the two‐dimensional second virial coefficient. The statistical‐mechanical model assumed lateral interactions and small oscillations normal to the plane. An expression given by Everett and Barker in terms of the two‐dimensional virial coefficient and empirical data is used to calculate the area for the case of argon on carbon black. It is found that the additional term leads to better agreement with values obtained by means of electron‐microscope measurements.