Molar enthalpy of condensation

The way in which these factors operate to produce Type III isotherms is best appreciated by reference to actual examples. Perhaps the most straightforward case is given by organic high polymers (e.g. polytetra-fluoroethylene, polyethylene, polymethylmethacrylate or polyacrylonitrile) which give rise to well defined Type III isotherms with water or with alkanes, in consequence of the weak dispersion interactions (Fig. S.2). In some cases the isotherms have been measured at several temperatures so that (f could be calculated in Fig. 5.2(c) the value is initially somewhat below the molar enthalpy of condensation and rises to qi as adsorption proceeds. In Fig. 5.2(d) the higher initial values of q" are ascribed to surface heterogeneity. 

Apart from the inherent interest in the gas phase ion clusters, the accumulation of solvent molecules around an ion should yield at the limit of very large values of n to a constant value of j H°(S,g). This would be the molar enthalpy of condensation of a solvent molecule into the bulk liquid solvent, because at this limit, the ion has no influence any more on the energetics of the process. Thus ... 

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