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 NO(-)(3). The individual ionic Setschenow constants, K(S)(cation,solute) and K(S)(anion,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 (NH(+)(4)) to 0.28+/-0.032 (Mg(2+)), which were hardly affected by the accompanying anion in solution, and only slightly affected by the non-electrolytes present. NO(-)(3) resulted in a slight salting-in effect: K(S)(NO(-)(3),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 (HCO(-)(3)) and 0.21+/-0.035 (CO(2-)(3)).