Solid-liquid separation after liquid-liquid extraction Distribution of oxine (a-hydroxyquinoline) and copper oxinate between naphthalene and aqueous phase at 90°C

The distribution equilibria of oxine or copper oxinate between naphthalene and aqueous phase were studied by the method of liquid-liquid extraction followed by solid-liquid separation using naphthalene as the solvent, and compared with the result obtained by the conventional method of liquid-liquid extraction using chloroform as the solvent. In a previous paper, Fujinaga, Kuwamoto, Nakayama and the author showed that the copper oxinate was extracted quantitatively into naphthalene at 90°C in the pH range larger than 4. This extraction behavior is quite identical to that into chloroform at room temperature, in spite of the difference in the experimental temperature and of the solvent used. The present investgation was performed to elucidate the reason of this similarity of both method in the extraction of copper oxinate and to determine the equilibrium data of oxine and copper oxinate at 90°C