Derivative Spectrophotometry as a Tool for Determination of Stability Constants of Some 4-2(-Pyridylazo)-resorcinol Complexes with Divalent Metal Ions

Abstract The suitability of derivative spectrophotometry for examination of complexation equilibria was elaborated by the determination of stability constants of Zn-PAR and Pd-PAR complexes. Derivatization minimized the influence of an excess of a colored reagent on the absorbance of the complex and allowed the direct measurement of its true value. The stability constants determined using two different methods were compared with available published data. In the case of the Zn(PAR)2 complex the error of determination did not exceed ± 5%.