On the possibility of the formation of a NaCl–KCl solid-solution crystal from an aqueous solution at room temperature in small-volume systems

Phase transitions in binary and ternary small-volume systems have been simulated by the methods of equilibrium chemical thermodynamics. Considerable dissimilarities of the equilibrium phase compositions of the systems of macroscopic and microscopic sizes have been revealed. A change in the system’s volume is accompanied by a change in the heterogeneity region in the phase diagram. This can increase considerably the solubility of small systems and lead to the emergence of phases that are thermodynamically unstable in macroscopic systems. Such size effects have been considered by the example of phase transformations in NaCl–KCl–H$_2$O and NaCl–KCl systems.