Adsorption Isotherms and Equations of State of Insoluble Vapors at the Water-Gas Interface as Studied by Gas Chromatography

摘要

In continuation of previous work on the study of water at interfaces by gas chromatography, the gas-liquid interfacial adsorption isotherms of six insoluble vapors (three n-alkanes and three branched alkanes) have been determined in the range of 4000 sq A /molecule to 500 sq A/ molecule. From these isotherms, isosteric heats of adsorption have been derived, and it has been shown that over the whole concentration range examined the isosteric heat of adsorption is equal to or less than the heat of liquefaction. This points to the fact that water is a low energy surface for hydrocarbons. The free energy of adsorption and the entropy of adsorption at constant surface coverage have been also calculated. Equations of state have been determined. Finally, calculations of thickness of the surface films indicate that the hydrocarbons can be considered to lie flat on the water surface in most cases over the whole concentration range studied. (Author)