Volumetric and compressibility studies and phase equilibria of aqueous biphasic systems of alcohols using phase diagram

The solubility data of Na 2 S 2 O 3 ·5H 2 O in various concentrations of water and ethanol/1-propanol/2-propanol/2-methyl-2-propanol have been obtained to plot triangular phase diagrams and to determine the liquid–liquid–solid equilibria at 298.15 K. The density and sound velocity measurements were carried out for binary systems (water–salt, water–ethanol/1-propanol/2-propanol/2-methyl-2-propanol) and ternary systems (water–ethanol/1-propanol/2-propanol/2-methyl-2-propanol-Na 2 S 2 O 3 ) to investigate volumetric and compressibility properties. The obtained data was used to determine the acoustic parameters including adiabatic compressibility ( β s ), excess molar volume ( V E ), intermolecular free length ( L f ), specific acoustic impedance ( Z ), relative association ( R A ), solvation number ( S n ) of water–alcohols, water–salt and water–alcohol–salt at 298.15 ± 0.05 K to evaluate equilibrium effects. Based on which, the salting-out of studied alcohols and phase forming ability of Na 2 S 2 O 3 through its bond making and breaking properties, intermolecular interactions were reported. The density, sound velocity and adiabatic compressibility of ternary system suggest phase separation phenomenon is bond breaking and bond making process with hydrogen bonding and hydrophobic interaction. The phase formation ability of systems composed of different alcohols is in order of 2-methyl-2-propanol > 1-propanol > 2-propanol > ethanol.