The phase diagrams of the L35 + sodium sulfate + water, L35 + lithium sulfate + water, and L35 + magnesium sulfate + water systems were determined at ( 298.15 and 313.15) K. The phase diagrams of the F68 + sodium magnesium sulfate + water system was determined at ( 283.15, 298.15, and 313.15) K. In all ATPS systems, the binodal position was influenced by temperature change, while an increase in polymer molecular weight makes the separation process occur at lower salt and copolymer concentration. It was observed that the hydrophobic/ hydrophilic balance affects mainly the water content of the top phase.