Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Summary 1. The adsorption energy of nonpolar molecules is calculated by a method which takes into consideration three terms in the potential of the dispersive forces by means of constants calculated on the basis of the polarizabilities and magnetic susceptibilities, Other factors taken into consideration in the development of the method are inductive potential (through the mean polarizability of the adsorbate and the mean electrostatic field of the adsorbent) and the repulsion potential (through an exponential constant calculated from the individual constants of adsorbent and adsorbate and with summation of all of the interactions of the given energy center of the molecule of adsorbate over all of the centers of the lattice of the adsorbent). The exponential repulsion constant was determined from the minimum condition of the summed energy of all of the interactions at the equilibrium distance from the adsorbent surface. 2. The calculated values of the energy of adsorption of noble gases, nitrogen and thirteen hydrocarbons of various structures (normal and isomeric alkanes, an alkene, cyclanes and aromatics) on graphite are close to the measured heats of adsorption on graphitized carbon blacks. 3. The calculated values of the energy of adsorption of n-alkanes, benzene and toluene on magnesia are likewise close to the measured heats of adsorption. 4. In the case of adsorption on graphite the contributions of the first, second and third terms of the energy of the dispersive forces and the absolute value of the repulsion energy constitute 90–95, 5–10, 0.5–1 and 35–40%, respectively, of the total energy of the dispersive forces for the investigated adsorbates. In the case of adsorption of MgO the contributions of the first, second, and third terms of the energy of the dispersive forces, the energy of the inductive forces and the absolute magnitude of the repulsion energy constitute about 81–83, 12–14, 3, 2 and 42–48%, respectively, of the total energy of the attractive forces (dispersive and inductive).
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