POTENTIOMETRIC AND EXTRACTIVE SPECTROPHOTOMETRIC STUDIES ON MIXED-LIGAND COMPLEXES OF COPPER(II) WITH 3-HYDROXYPICOLINAMIDE AND A FEW ALIPHATIC AND AROMATIC-ACIDS

The equilibria involved in the formation of the mixed-ligand complexes of the type CuAL, where A = 3-hydroxypicolinamide (Hpa); L = phthalic (pha), salicylic (sa); thiosalicylic (tsa); anthranilic (ant), maleic (mal) and succinic acid (succ) have been studied by pH-titration tech nique in 40% (v/v) ethanol-water medium at I = 0.1 M (NaClO4) and 25-d egrees-C. The formation constants of the binary and ternary complexes have been evaluated and the various complexation equilibria in solutio n are demonstrated and characterized. The discriminating and stability increasing properties of 3-hydroxypicolinamide in the mixed complexes are discussed. After considering all the parameters, the Cu-Hpa-tsa t ernary system has been utilized as a suitable, rapid and sensitive spe ctrophotometric method for the microdetermination of copper. The metho d has been used in the determination of copper in some white metal all oys.