Water molecules in organic solvents involved in the synergistic extractionof europium(III) with beta-diketones and Lewis bases

To explain the difference in the magnitude of synergistic extraction among organic solvents, the water solubility in hexane, carbon tetrachloride, ben zene, and chloroform was measured, and then the residual hydration number o f europium(III) in the beta -diketonato chelate and in their adducts with 1 ,10-phenanthroline as well as the adduct formation constants were determine d. Using the data, the formation constants of the adduct according to a nov el definition, in which the water concentration in the organic phase is tre ated as one variable, were determined. The constants are approximately cons tant irrespective of the organic solvents, although those according to the conventional definition are different among the solvents. It has been concl uded that one of the most important factors controlling the magnitude of sy nergistic effects is the presence of water, such as the water content disso lved in organic solvents, and the hydration and dehydration of the relevant species, because water molecules compete with a Lewis base in complexation to the metal(III) chelates in the organic solvents.