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

Abstract

A general model of structural and molecular-kinetic changes in transition from dilute electrolyte solutions to aqueous melts of crystal hydrates and salts 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 electrostatic hydration effects and an abrupt decrease in the dielectric permittivity of electrolyte solutions beyond the concentration range of the first structural 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 properties and other physicochemical properties of solutions (electric conductivity, viscosity, density, etc.), as well as phase equilibria in water-salt systems are interpreted in terms of the concepts developed.