INFLUENCE OF TEMPERATURE ON THE PHASE FORMATION IN THE TERNARY SYSTEM Cа(NO3)2–H2O–n-C3H7OH

The paper presents the results of the study of three-component system calcium nitrate-propanol-1-water at negative temperatures (–5, –10, –15, –20 oС) and determining of its optimal composition with the prospect of its use as a coolant. Solubility diagrams of calcium nitrate-water-propanol-1 systems are constructed on the basis of the study of components of three sections mixtures on each of two concentration triangles and are presented in concentration triangles of Gibbs–Rosebom. Each section is a set of points with variable salt content and constant water and alcohol ratio. As the parameter measured, the refractive index was chosen. The solubility of calcium nitrate in the three-component system under study decreases as the mass fraction of alcohol increases. If the limited concentration is exceeded, the excess salt falls out in the form of calcium nitrate tetrahydrate. A separation area is formed. It is divided into 2 parts: an aqueous calcium nitrate solution (L1) and a calcium nitrate alcoholic solution (L2). It was found that when the temperature decreases, an increase in the solid phase S2 (the ice crystallization fi eld) is observed, the salt solubility in the water decreases, the area of the stably existing homogeneous three-component solution (L3) also decreases. According to the experimental data obtained and the phase diagrams constructed, the solution optimal composition is determined, suitable for use as a coolant: propanol-1 mass fraction – 5 %, water – 55 % and salt – 40 %.