Liquid-liquid equilibrium data of aqueous two-phase systems (ATPSs) composed of the thermo-sensitive copolymer L31 and (NH4)(2)SO4 at 288.15 K, L31 and (NH4)(2)SO4/Na2SO4/Li2SO4/Na2C4H4O6 at 293.15 K were determined, respectively. The Othmer-Tobias and Bancroft equations were successfully used to correlate the tie-line data of the investigated systems. In the L31-(NH4)(2)SO4 ATPS, it was found that the size of the two-phase region of phase diagrams increased with an increase in temperature. Meanwhile, the salting out ability of cations followed the order: Na+ > NH4+ > Li+, and the salting out ability of SO42- is stronger than C4H4O62-. It was found that evaluating the salting outing ability of ions by using the Gibbs energy of hydration or Hofmeister series is not available for all of ATPSs. (C) 2014 Elsevier B.V. All rights reserved.