Phase Separation Phenomena in Ternary Systems and Selective Solvation (II)

The phase separation temperatures of binary solvent systems can be measurably changed through the addition of small amounts of electrolytes. A relation between the shift of the coexistence curve to higher or lower temperatures and the solvation of electrolytes was investigated for the system acetonitrile‐water. The phase separation temperature was raised by addition of a homoselective solvated electrolyte the ions of which are preferentially surrounded by one component of the solvent mixture. This was proved for electrolytes being preferentially solvated by acetonitrile (e.g., silver picrate) or extensively hydrated (sodium benzoate). On the other hand, the region of immiscibility is shifted to lower temperatures, if cation and anion are not preferentially solvated by the same component. Experiments have been made for the different possibilities of heteroselective solvation (silver benzoate, sodium picrate).