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Heterocyclic azo dyes as analytical reagents. II. 2-(5,5-Dimethyl-4,5,6,7-tetrahydrobenzthiazolyl-2-azo)-5-hydroxyphenol and its complexes with copper(II), nickel(II), cadmium(II), zinc(II), and lead(II)

J. Kandráč and E. Kuchár

Department of Chemistry, Faculty of Pedagogics, Komenský University, 917 24 Trnava


Abstract: The optical and acid-base properties of 2-(5,5-dimethyl-4,5,6,7-tetrahydrobenzthiazolyl- 2-azo)-5-hydroxyphenol were studied. This substance occurs in 40% aqueous solution of ethyl alcohol over the pH range from 0.15 to 12.80 in four differently coloured acid-base forms with maximum absorbances of 500 nm (RH3+), 460 nm (RH2), 490 nm (RH-), and 510 nm (R2-). Furthermore, the complexes of this reagent with Cu(II), Ni(II), Cd(II), Zn(II), and Pb(II) were investigated. This reagent forms complexes with Cu(II) and Pb(II) in molar ratio 1 1, with Ni(II) and Zn(II) in molar ratio 1 : 2 while both these complexes are formed with Cd(II). The complexes formed with Cu(II), Ni(II), Pb(II), and Zn(II) in fairly acid region are protonized. The molar absorptivities of complexes and equilibrium constants were established by graphical analysis. The constants of stability of individual complexes were calculated.

Full paper in Portable Document Format: 272a204.pdf


Chemical Papers 27 (2) 204–217 (1973)

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