DIELECTRIC-SPECTROSCOPY OF AQUEOUS-SOLUTIONS - HYDRATION PHENOMENA AND HYDROGEN-BONDED NETWORKS

Results of dielectric relaxation studies in this laboratory on aqueous solutions are summarized to took for the relative merits and limitations of different solution models. The solutes include inorganic and organic electrolytes and low-molecular-weight organic molecules. It is shown that even these comparatively simple solutions exhibit a great variety of effects, Due to the preferential orientation of water molecules in the Coulombic field of small ions and also in clathrate-like structures around large ions for solutions of such solutes the hydration model seems to be justified. With solutions of predominantly hydrophobic molecules the idea of a hydration model appears to be also appropriate. Mainly hydrophilic molecules are obviously incorporated in a hydrogen-bonded network which, on many conditions, does not even allow the contributions of the solute and solvent molecules to the dielectric spectrum to be separated from another. With such mixtures it is the more inadequate to discriminate between differently affected water regions.