WATER-INDUCED SELF-OSCILLATORY PROCESSES IN COLLOIDAL SYSTEMS BY THE EXAMPLE OF INSTANT COFFEE

Abstracts

Slow long-lived fluctuations of mechanical properties of drying drops of instant coffee water solutions have been found by means of the Drying Drop Technology developed earlier. Parameters of the fluctuations depended on the extent of dilution and were not affected by additional hashing of the solution, closing by a cover and shielding from external electromagnetic fields [1-3]. Here we compared dynamics of physicochemical and morphological processes in bulk. We observed microscopically periodic emergence, growth, aggregation and disappearance of spherical cavities (50-250 µm in diameter) in bulk of dispersion, which was followed by agreed fluctuations of physicochemical parameters of the colloidal system. We have shown that those spheres were huge hydrate covers of liquid crystal water around colloidal particles. Phase transitions between free and bound (liquid crystal) water in a bulk of a colloidal system is a pacemaker of fluctuations of its physicochemical properties. These changes are regulated and coordinated by the value of osmotic pressure. At low osmotic pressure hydrate covers grow, forcing out particles and ions into the bulk; at high osmotic pressure they collapse to small size, reducing osmotic pressure. Existence of self-oscillatory processes was confirmed by a mathematical model.

Keywords : Colloidal systems; spatial inhomogeneities; free and bound water; self-oscillatory processes.

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