SOLUBILITY, DISSOCIATION AND COMPLEXATION WITH ND(III) AND TH(IV) OF OXINE, THENOYLTRIFLUOROACETONE AND 1,10-PHENANTHROLINE IN 5.0 M NACL

Equilibria in the system of Nd(III) and Th(IV) with 8-hydroxyquinoline (oxine), thenoyltrifluoroacetone (HTTA) and 1,10-phenanthroline (phen ) in 5.0 m NaCl solution have been investigated by spectroscopy and po tentiometry. The solubility and deprotonation constants of the three o rganics were measured to be: pK(s) = 3.09 +/- 0.01, pK(a1) = 5.82 +/- 0.02, pK(a2) = 10.00 +/- 0.01 for oxine; pK(s) = 2.49 +/- 0.01, pK(a2) = 6.47 +/- 0.03 for HTTA; pK(s) = 2.86 +/- 0.02, pK(a2) = 5.82 +/- 0. 05 for phen. The stabilities of the corresponding metal complexes are in the order M(oxine) > M(TTA) > M(phen), where M = Nd(III), Th(IV). F or all three organic ligands, the Th(IV) complexation is stronger than that of Nd(III).