Background: Triangular phase diagrams are important to understand the phase
behaviors in ternary systems. The salting out of alcohol from water by kosmotropic salt has
long been known, but the molecular interactions and the mechanism of bond breaking and
making processes has not yet been fully understood.
Objective: To understand the salting-out of 2-propanol from water using kosmotropic salts
(Na2S2O3, Na2SO4 and Na2SO3). To study the phase equilibria of liquid-liquid, liquid-solid
and liquid-liquid-solid system by constructing ternary phase diagrams. To determine the
solute-solute, solute-solvent, and solvent-solvent molecular interactions to resolve the salting-
Methods: The solubility data of Na2S2O3/Na2SO4/Na2SO3 salts have been reported in pure
water, 2-propanol and water + 2-propanol mixtures in different concentrations at 298.15 ±
1 K. The ternary phase diagrams have been constructed from the obtained solubility data.
The volumetric and acoustic data of binary and ternary systems of water + 2-propanol, water
+ salt and water + 2-propanol + salt has been determined using density meter and interferometer.
Results: The ternary phase diagrams have been constructed for water+2-propanol+
Na2S2O3/Na2SO4/Na2SO3 system. The rise in sound velocity signifies more structural interactions
in binary water-alcohol and water-salt systems, while the relation is rather change
with the ternary system, as the water-alcohol sheath will be broken by the kosmotropic salt
which results in to salt-water sheath.
Conclusion: The density, sound velocity and adiabatic compressibility results suggest that
phase separation phenomenon is due to the bond breaking and bond making process along
with hydrophobic hydration and hydrophobic interactions. The anion S2O3
2- promote salting-out effect and the strength of these effects decreases in the order