Salting-in and salting-out of polar nonelectrolytes

Abstract

The solubility of toluene and benzaldehyde was measured in NaBr and (n-Pr)4NBr aqueous solutions at 25 °C, and the solubility of benzoic acid and nitrobenzene was measured in the same systems at 10, 25, and 40 °C. The apparent molal volumes of the four nonelectrolytes were also determined from the densities of the saturated aqueous solutions.The volumes of mixing of the nonelectrolytes in water are all negative but become less so as their polarity increases. With the exception of benzoic acid, the salting-out by NaBr and the salting-in by (n-Pr)4NBr both decrease with increasing polarity of the nonelectrolytes. Both salting effects increase with temperature. These trends can be explained with existing theories of salting-out and salting-in.