Aqueous salting-out effect of inorganic cations and anions on non-electrolytes

The salting-out effects of 27 lithium, sodium, potassium, ammonium and magnesium salts and HCl on chloroform, benzene, chlorobenzene and anisole were characterized in aqueous solutions at 303 K by measuring the Henry's law constants. The concentration of the salt solutions was 0.5 mol dm(-3), i.e., similar to the salinity of sea water. The solubility change was described in terms of the Setschenow constant, K-S(salt, solute). The highest salting-out effects were observed for the solutions of salts involving doubly charged anions, and the smallest for NO3-. The individual ionic Setschenow constants, K-S(cation, solute) and K-S(an ion, solute), were determined by multilinear regression, using the assumption of additivity for the ions. Cl- was selected as the reference ion for calculation of the K-S(ion,solute) values of the other ions. The estimations resulted systematically in significant positive K-S(cation, solute) values, ranging from 0.13 +/- 0.026 (NH4+) to 0.28 +/- 0.032 (Mg2+), which were hardly affected by the accompanying anion in solution, and only slightly affected by the non-electrolytes present. NO3- resulted in a slight salting-in effect: K-S(NO3- solute) = -0.083 +/- 0.019; the other anions displayed salting-out effect for all of the non-electrolytes studied, with K-S(anion, solute) ranging between 0.090 +/- 0.008 (HCO3-) and 0.21 +/- 0.035 (CO32-). (c) 2006 Elsevier Ltd. All rights reserved.