Theories Regarding Interaction Between Solvent and Solute

In conjunction with the preceding sections, in which experimental evidence on the effect of concentration and temperature upon vapor and osmotic pressure has been described, it seems fitting to discuss the ideas which have been evolved as to the molecular mechanism of interaction between dissolved chain-like particles and solvent. Although we are at present still far distant from the stage of quantitative and detailed data, a few fundamental principles are already making their appearance. 

It seems legitimate to consider two separate possibilities in the interaction between solvent and solute. 

Hartley, Aqueous Solutions of Paraffin Chain Salts, Paris 1936, p. 23ff. 

There is, of course, the further possibility that strongly polar solvent molecules seek out easily polarizable points on the dissolved particles and remain fixed there because of strong interaction. Finally, the dispersion effect may be regarded as still a third reason for this attraction. 

In the case of large, compact particles, these force effects usually lead to the formation of monomolecular adsorption layers but they arc also able to form, in certain circumstances, adsorption films of several layers. In these films the binding strength of the individual solvent particle declines continuously from the surface of the adsorbent outwards, so that, in these cases, a variable adsorption or solvation potential has to be taken into account. 

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