Solubility, Phase Equilibria, and Critical Phenomena in the Ternary KBr + H2O + C5H5N System from T=283.15 to 363.15 K

The solubility of components, phase equilibria, and critical phenomena in the potassium bromide + water + pyridine system were investigated from T = 283.15 to 363.15 K by the visual polythermal method. KBr delaminates water-pyridine solutions above 323.75 K. The formation temperature of the critical tie line of the monotectic state (323.75 K) and the compositions of the solutions corresponding to the critical solubility points of liquid-liquid equilibrium at three temperatures were determined. The distribution coefficients K-d of pyridine between the organic and aqueous phases of the monotectic state at 328.15, 343.15, and 363.15 K were calculated. The salting-out effect of KBr relative to pyridine from solutions is shown to be enhanced with an increase in the temperature. A comparative analysis of the results of our polythermal study of the salting-out action of potassium salts (iodide, bromide, nitrate, and chloride) on the binary water + pyridine system was done. It has been found that a decrease in the crystallographic radius of the salt anion in the KI-KBr-KNO3-KCl series leads to a decreased formation temperature of the critical tie line of the monotectic state of the ternary salt + water + pyridine systems and an enhanced salting-out effect of pyridine from aqueous solutions.