Comparative study on molecular associations in solid and liquid phases of aqueous solutions. I. Presentation of high resolution mixing calorimetry, differential scanning calorimetry, dynamic thermal densimetry, and thermomechanical analysis

Abstract

The comparative study on the composite structure of water and aqueous solutions is initiated both by a series of measuring systems and for a series of standard solutes (Na, Cu, Ni and Mn sulfates) in view of better identifying the nature and the amplitude of molecular associations in the solid and liquid states of these systems. This paper deals with the detailed description of high resolution mixing calorimetry (HRMC), differential scanning calorimetry (DSC), dynamic thermal densimetry analysis (DTDA) and thermo‐mechanical analysis (TMA) as measuring systems. The data for solution and dilution processes obtained by HRMC and the melting behavior according to DSC, DTDA and TMA as function of the nature of the solute and of the solute/water ratio, allow to make clear distinction between the solutes and to conclude that the “chemical” treatment of water by addition of a solute makes clearer the separation of pure water from the hydrogen bound molecular associations. These results are similar with the recently ones on crystalline composites in which the defects and/or impurities coherently precipitate by forming two ordered phases for which two order‐disorder transitions in the melting behaviour occur.