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

Abstract

The paper presents the results of the study of three-component system calcium nitrate-propanol-1-water at negative temperatures (-5, -10, -15, -20 °С) 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 field) 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%.