Effect of addition of calcium chloride on the liquid-liquid equilibria of the water plus propionic acid plus 1-butanol system at 303.15 K

The influence of the addition of CaCl2 to the water + propionic acid + l-butanol ternary system was studied at (303.15 +/- 0.05) K. The quaternary system was represented projecting four sectional quaternary planes corresponding to 4.3%, 9.3%, 15.1%, and 20.3% CaCl2 in aqueous solution onto the face of the tetrahedron containing the ternary system water + propionic acid + l-butanol. Therefore, all compositions are given on a salt-free basis for the solubility curves and for tie-line data. The addition of salt always enhances significantly the distribution coefficients and selectivities, while the region of heterogeneity increases as compared to the no-salt condition. Band type curves were obtained for solubility curves above 4.3% CaCl2, and no salt precipitation was observed. The experimental results show that CaCl2 is not distributed in the same proportion between the phases at equilibrium and that l-butanol appears to be a good solvent for extraction purposes. A comparison between the influence of CaCl2 and NaCl on this ternary system is also made using these experimental results with earlier data. A high value of the Sestchenow's constant was obtained by a linear regression method, which is an indication that a great salting-out effect is produced by the addition of CaCl2, which is more important than for NaCl.