Aqueous biphasic systems formed by nonionic polymers I. Effects of inorganic salts on phase separation

The effect of salts KSCN, KI, KBr, KCl, KClO₄, KF, K₂SO₄ and NH₄Cl, LiCl, NaCl, KCl, CsCl on the binodials of the phase diagrams for aqueous biphasic dextranpolyvinylpyrrolidone, dextran-polyvinyl alcohol, dextran-ficoll and dextran-polyethylene glycol systems was studied. It is established that the K-salts present at the concentrations of 0.1 and 0.5 mol/kg alter the binodials of the phase diagrams for the above systems. The effect of a salt is found to be related to the lyotropy of the salt quantified by the salt molal surface tension increment. It is assumed that phase separation in an aqueous polymer biphasic system is affected by the presence of a salt mainly due to the effect of the salt on the structure and/or state of water in the system.