ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Potentiometrie Study of Tungsten(VI) Complex Formation with Tartrate

P. Lubal, J. Perutka, and J. Havel

Department of Analytical Chemistry, Faculty of Science, Masaryk University, CZ-611 31 Brno, Czech Republic

E-mail: havel@chemi.muni.cz

Abstract: Complexation of tungstate with tartrate has been investigated by potentiometry in the pH range 2.5-7.5 in 1 M-KNO₃ at 25°C. The experimental data were evaluated with ESAB (for the calculation of protonation constants of tartrate) and OPIUM (for the calculation of formation constants of complexes) computer programs. A high number of chemical models including polynuclear complexes were considered and tested on a computer. The final model comprises five complexes that have a tungsten(VI) : tartrate ratio of 2 : 2 and 1 : 2. The following formation constants (β_p,q,r) were calculated: log β₂₁₂ = 16.6 +/- 0.1, log β₃₁₂ = 20.4 +/- 0.2, log β₄₁₂ = 23.9 +/- 0.1, log β₃₂₂ = 26.68 +/- 0.08, and log β₄₂₂ = 30.7 +/- 0.1, where p, q, r refer to stoichiometric coefficients in general formula (H)_p(WO₄)_q(C₄H₄O₆)_r^p-2q-2r. Structures of the complexes were proposed.

Full paper in Portable Document Format: 545a289.pdf

Chemical Papers 54 (5) 289–295 (2000)