Quaternary phase equilibrium of water–carboxylic acid mixture (formic–propionic acid or acetic–propionic acid)–solvent liquid systems at 298.15 K

Liquid–liquid equilibrium data of water–acid mixture (formic–propionic acid or acetic–propionic acid)–solvent (amyl acetate, diisobutyl ketone, and diisopropyl ether) quaternary systems were measured at 298.15 K. Complete phase diagrams were obtained by determining solubility curves and tie-lines. A comparison of the extracting capabilities of the solvents was made with respect to distribution coefficients, separation factors and solvent-free selectivity bases. Reliability of the data was ascertained from Othmer–Tobias plots. It is concluded that the used solvents can be treated as suitable separating agents for dilute aqueous formic–propionic acid or acetic–propionic acid mixtures.

► LLE data of water–acid mixture-solvent were presented at 298.15 K.
► Solubility curves were constructed.
► Distribution coefficients were evaluated for the immiscibility region.
► Separation factors were calculated.