Density, viscosity, and refractive index measurements of pure formamide and of formic, acetic, and propionic acids in the temperature range (298.15 to 313.15) K were made. Additionally, measurements of the same properties and in the same temperature range were made on the following mixtures: formamide + (formic acid, or + acetic acid, or + propionic acid). The results were fitted to empirical equations, whose calculated values are in agreement with the experimental ones.

The influence of the addition of CaCl2 to the water + propionic acid + 1-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 + 1-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 1-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.

Tie-line data for the water, methyl tert-butyl ether, and cyclohexane [w 1H2O + w 2C5H12O + (1 − w 1 − w2)C6H12] and water, methyl tert-butyl ether, and benzene [w 1H2O + w 2C5H12O + (1 − w 1 − w 2)C6H6] ternary systems (where w is the mass fraction) were investigated at a temperature of T = 303.15 K. A quaternary system containing these four compounds [w 1H2O + w 2C5H12O + w 3C6H6 + (1 − w 1 − w 2 − w 3)C6H12] was also studied at the same temperature. Data for the other partially miscible ternary system [w 1H2O + w 3C6H6 + (1 − w 1 − w 3)C6H12] were taken from the literature, whereas the fourth ternary system [w 2C5H12O + w 3C6H6 + (1 − w 2 − w 3)C6H12] was completely miscible. The mutual hydrocarbon−water solubility with the addition of methyl tert-butyl ether was investigated. The equilibrium data of the three ternary systems (including that taken from the literature) were used to determine interaction parameters for the UNIQUAC and NRTL equations. The UNIQUAC parameters were then averaged to predict equilibrium data for the quaternary system using this model. The liquid−liquid equilibrium (LLE) were also predicted with the UNIFAC group contribution method. The UNIQUAC equation seems to be more accurate than the other methods both for the ternary systems and the quaternary system, as can be observed from the values of both residuals. However, its predicted distribution coefficients have high deviation percentages. On the other hand, the solubility curves are well-correlated by the UNIQUAC and NRTL equations for these ternary systems.