In this work, we systematically studied the salting-out or salting-in effects of ammonium salts on the aqueous polymer solutions. For this purpose the liquid – liquid and vapor – liquid equilibria behaviors of aqueous polymer solutions in the absence and presence of different organic and inorganic ammonium salts were investigated. In the first part of this work, cloud point temperatures for binary system of polypropylene glycol 1000 (PPG1000) in pure water and for ternary systems of PPG1000 in aqueous solutions with different molalities of ammonium salts have been determined. Our results show that cloud point temperatures of PPG1000 aqueous solutions increase (salting-in) in the presence of tetra alkyl ammonium salts (tetra ethyl ammonium bromide (TEABr), tetra propyl ammonium bromide (TPABr), tetra butyl ammonium bromide (TBABr), tetra butyl ammonium chloride (TBACl) and dodecyl tri methyl ammonium bromide (DTABr)), while those decrease (salting-out) in the presence of NH4Cl and NH4Br which are inorganic ammonium salts. The salting-in effect of organic ammonium salts becomes more appreciable by decreasing hydrophilicity nature and by increasing molality of them. The salting-out effect of inorganic ammonium salts is strengthened by increasing hydrophilicity and molality of them. The calculation of clouding thermodynamic functions shows that the rise in entropy is the driving force for spontaneous phase separation in all the investigated systems. In the second part of this work, the isopiestic equilibrium has been investigated for different ternary H2O + polymer + salt systems at 298.15 K. The polymers are PPG400, PEG400 and PEG10000 and the salts are TEABr, TPABr, TBABr, TBACl, DTABr, NH4Cl and NH4Br. In order to study the salting effects, deviations of constant water activity lines from the semi-ideal behavior (linear isopiestic relation) have been evaluated. In the case of the salting-in effect, the constant water activity lines show positive deviations from the s
