Formation constants of ternary complexes of vanadium(IV) with picolinic acid and salicylic or 5-sulphosalicylic acid

The formation constants, beta(MAL), for the reaction VO(2+) + A(-) + L(2-) <==> VOAL(-) [where HA = picolinic acid and H(2)L = salicylic or 5-sulphosalicylic acid] have been determined at 30 +/- 1 degrees (mu = 0.1, KNO(3)). Potentiometric evidence is presented for the simultaneous addition of both ligands to the metal ion to form the 1:1:1 ternary complex.