Collect. Czech. Chem. Commun. 1979, 44, 2032-2063

Study of properties of complexes of SNAZOXS and Naphthylazoxine 6S with copper(II), zinc(II) and lead(II) ions in solution by non-linear regression of spectrophotometric data

Milan Meloun and Jan Pancl

Department of Analytical Chemistry, Institute of Chemical Technology, 532 10 Pardubice


Complexation equilibria of two metallochromic indicators viz. 7-(4-sulpho-1-naphthylazo)-8-hydroxyquinoline-5-sulphonic acid (SNAZOXS) and 7-(6-sulpho-2-naphthylazo)-8-hydroxyquinoline-5-sulphonic acid (Naphthylazoxine 6S) with copper(II), zinc(II), and lead(II) ions have been studied by various spectrophotometric methods in 0.1M-NaClO4 medium at 25 °C. Number of the coloured complexes in solution, their stoichiometry, and their overall and conditional stability constants have been determined by computer-assisted non-linear regression of the curves of continuous variations, the curves of molar ratios, the absorbance-pH curves, the curves of corresponding solutions, and by regression matrix analysis of the spectra. Besides the yellow complexes ML and ML2 the orange protonated forms MLH and M(LH)2 have also been determined.