Potentiometric studies of mixed ligand complexes of lanthanum(III) and thorium(IV) with nitrilotriacetic acid and ethylenediaminetetraacetic acid as primary ligands

Formation constants of mixed ligand complexes of lanthanum(III) and thorium(IV) with nitrilotriacetic acid (NTA) and ethylenediamine-tetraacetic acid (EDTA) as primary ligands, and anthranilic acid (ANA) as secondary ligand have been investigated potentiometrically. The values of log Ksub(MAL)sup(MA) have been found in the order log Ksub(MAL)sup(NTA) < log Ksub(MAL)sup(EDTA). The trends in stability constants of ternary complexes with respect to metal ion have been found in the order La(III) > Th(IV). (author)