Concentration transition from water-electrolyte to electrolyte-water solvents and ionic clusters in solutions

A general model of structural and molecular-kinetic changes in transition f rom dilute electrolyte solutions to aqueous melts of crystal hydrates and s alts is suggested. The model corresponds to the scheme: ions and complexes in the water structure --> ionic and ion-water clusters --> polymeric melt structures. The structural transition is caused by a decrease in electrosta tic hydration effects and an abrupt decrease in the dielectric permittivity of electrolyte solutions beyond the concentration range of the first struc tural region where the water structure persists. The appearance of cluster nanostructures is considered to be a common property of highly concentrated solutions of electrolytes. Analysis of concentration structural changes is based on X-ray diffraction and spectroscopic data. Microwave dielectric pr operties and other physicochemical properties of solutions (electric conduc tivity, viscosity, density, etc,), as well as phase equilibria in water-sal t systems are interpreted in terms of the concepts developed. (C) 2001 Else vier Science B.V. All rights reserved.