Abstract
The solvent extraction of lanthanum(III), praseodymium(III), neodymium(III), samarium(III), europium(III), gadolini-um(III), thulium(III), ytterbium(III), lutetium(III), scandium(III), and indium(III) (M(III)) in 0.1 mol dm-3 sodium nitrate solutions with 4-isopropyltropolone (Hipt) into chloroform was studied. From the dependence of extraction on the concentration of 4-isopropyltropolonate anions in the aqueous phase and also on the concentration of metal ions, it was concluded that scandium(III) and indium(III) were always extracted in the mononuclear form, M(ipt)3. But dinuclear lanthanoid(III) chelate complexes, M2(ipt)6·nHipt where n=0 or 1, were also extracted with mononuclear ones even when the metal concentration in the organic phase was higher than about 10-6 mol dm-3. The degree of dinuclear species formation was greater in the following order: lutetium(III) to samarium(III)>neodymium(III)>praseodymium(III)>lanthanum(III)»scandium(III) - indium(III). On the other hand, the stability of the self-adduct dinuclear chelate complexes in the organic phase was higher in the order: lanthanum(III) to gadolinium(III)>thulium(III)>ytterbium(III)>lutetium(III).
