PHASE EQUILIBRIA, SOLUBILITY AND SALTING-OUT EFFECT IN THE TERNARY SYSTEM POTASSIUM NITRATE- WATER- BUTYRIC ACID IN THE RANGE OF 5-100 °C

Phase equilibria, solubility and the salting-out effect of butyric acid were studied by the visual-polythermal method in mixtures of the components of the ternary system potassium nitrate - water - butyric acid in the range of 5-100 & DEG;C. Polytherms of phase states in twelve sections of the triangle composition were plotted. The following phase states were found in mixtures of compo-nents: homogeneous and saturated solutions, monotectic and delamination. The formation tem-perature of the critical tie line of monotectic state (18.0 & DEG;C) is determined. It is the minimum tem-perature of existence of two liquid phases in three-component mixtures. The temperature depend-ence of the compositions of solutions corresponding to the critical solubility points were found by the phase-volume ratio method. The solubility of the components was determined at thirteen tem-peratures and isothermal phase diagrams were plotted at 5.0, 18.0, 25.0, 50.0, 70.0 and 100.0 & DEG;C. The topological transformation of the phase diagram of a ternary system with a temperature change is characteristic of these systems with the salting-out of a binary homogeneous liquid system. The compositions of the liquid phases of monotectic state were graphically determined. The butyric acid distribution coefficient between these phases was calculated at five temperatures as the ratio of acid concentrations in the organic and aqueous phases. It was found that the effect of salting-out butyric acid increases significantly with rising temperature, which is associated with a change in the solu-bility of potassium nitrate in solutions. The efficiency of potassium nitrate as a salting-out agent of butyric acid from its aqueous solution is compared with the previously studied salt - water - butyric acid systems. The possibility of the successful application of potassium nitrate for the concentration of butyric acid in the biochemical method of production from fermentation solutions is noted.