A study of structural organization of water and aqueous solutions by means of optical microscopy

TL;DR

This study reveals that water and aqueous solutions inherently contain microcrystals of NaCl surrounded by hydrated water, which influence their physicochemical properties and are observable via optical microscopy.

Contribution

It introduces the concept of microcrystals as elementary microparticles in water and solutions, explaining their formation, aggregation, and impact on water's properties.

Findings

Microcrystals of NaCl are intrinsic to water and solutions.

Microcrystals form coacervates that affect physicochemical properties.

Aggregation of microcrystals varies with ionic strength and temperature.

Abstract

It is shown that structuring at the microlevel, a previously not described in detail phenomenon, is the intrinsic property of water and aqueous solutions. At room conditions water (including "ultrapure" one) and aqueous solutions are dispersed systems in which microcrystals of NaCl, surrounded by a layer of hydrated water (average diameter - 10-15 microns), are "elementary microparticles", which form the basis of the dispersed phase. Possible ways of formation of these microparticles and their evolution in the process of evaporation of unstructured part of water - dispersion medium - are considered. It is shown, in particular, that they are present in the air as aerosol contaminants. When the ionic strength of the solution increases, the water-salt particles aggregate, forming a new phase - coacervates, remaining on the substrate after evaporation of the liquid part of the water. The aggregates of coacervate structures, formed in a liquid medium, are disordered during heating, which can cause a change in a number of physicochemical properties of water at the temperatures of 50{\deg}-60{\deg}C range that have not been correctly explained in the framework of atomic-molecular concepts.