Liquid-Liquid Equilibria of Aqueous Two-Phase Systems Containing Poly (ethylene Glycols) of Different Molecular Weight and Potassium Citrate

The phase diagrams corresponding to systems of potassium citrate and poly (ethylene glycol) of different molecular weights (4000, 6000 and 10000) were determined at varying temperature. Moreover, the medium pH (5, 7 and 9) effect was also studied. The binodal curves were described using a three parameter equation and the tie-lines were satisfactorily described using the Othmer-Tobias and Bancroft equations. An increase in pH caused the expansion of the two-phase area. The binodal curves became more asymmetric and close to the origin with an increase in poly (ethylene glycol) molecular weight.