PHYSICOCHEMICAL STUDIES OF NICKEL AND COPPER COMPLEXES WITH TAR AND SIMULTANEOUS DETERMINATION OF THE METAL IONS IN MIXTURES BY DERIVATIVE SPECTROPHOTOMETRY

Nickel(II) and Copper(II) chelates of 4-(2̀–thiazolylazo)resorcinol (TAR) were reported. The dissociation constants of the ligand and the stability constants of the metal complexes were calculated pH-metrically and spectrophotometrically at 25 ◦C, in 50% (v/v) ethanol and 0.1 M ionic strength. The effects of an acid or a base on the visible absorption behaviour of the ligand and complexes has been investigated. Nickel and copper react with 4-(2̀–thiazolylazo)resorcinol (TAR) to form a binary complexes. The equilibria occurring in solution were established and the basic characteristics of the complexes formed were determined. The complexation reaction in the systems investigated were demonstrated and characterized using graphical logarithmic analysis of the absorbance versus pH graph. The composition of the formed complexes with the reagent have been determined. The molar absorptivity of the binary system is investigated. The binary systems obeyed beer's law up to 0.23 and 0.25 µg/ml for Ni2+ and Cu2+ respectively. A simple and highly sensitive procedure for spectrophotometric determination of Ni2+ and Cu2+ has been developed. A method for the simultaneous determination of nickel and copper in mixtures by first-derivative spectrophotometry is described. Zero-crossing measurement technique is found suitable for the simultaneous determination of the metal ions. The method has been applied to direct determination of copper and nickel in dome synthetic mixtures without any separation.