ᐊ P1-81
Open Readings 2019 • P1-82
P1-83 ᐅ

EQUILIBRIA OF INDIVIDUAL ISOPOLY TUNGSTATE ANIONS FORMATION IN PHYSIOLOGICAL SOLUTIONS

Oleksii Yuliia A.1, Mishchanchuk Karyna V.2, Mariichak Oleksandra Yu.1, Rozantsev Georgiy M.1, Radio Serhii V.1

1 Educational and Scientific Institute of Chemistry, Vasyl' Stus Donetsk National University, Vinnytsia, UKRAINE

2 University College London, London, UNITED KINGDOM

[email protected]

By means of continuous pH-metric titration the state of the individual isopoly tungstate anions in the «Na2WO4 – HCl – PS» systems (PS – physiological solution; PS = Ringer's solution, Ringer-Locke's solution, Trisol solution; $C_W = 0.01$ mol L-1) at different temperatures (25 and 36.6°C) in the range of acidity $Z=v(H^+)/v(WO_4^{2-})=0.0-2.5$ was studied and herein reported.

The results of pH-potentiometry were used as a background for subsequent mathematical modeling of equilibria processes in the investigated solutions and for calculation of logarithms of concentration constants (lgKC) of isopoly tungstate anions formation (quasi-Newton procedure, CLINP 2.1 software [1]). Thus, mathematical models describing complexation processes were built and checked for excessiveness and sufficiency. Calculation of formation constants allowed us to build the diagrams of distribution of different ionic forms related to acidity Z and were used to define areas of existence for individual isopoly tungstate anions in physiological solutions (see Fig. 1).

It was found out that in the «Na2WO4 – HCl – PS» systems like in the «Na2WO4 – HCl – H2O» [2] or aqueous-organic solutions [3] hexatungstate ([W6O20(OH)2]6-), paratungstate B (Hx[W12O40(OH)2](10-x)-, x = 0–3), heptatungstate (H[W7O24]5-), metatungstate (H2[W12O40(OH)2](4-x)-, x = 0–2) anions are formed. And processes of protonation and deprotonation of HCO3- also are occurred.

Figure 1
Fig. 1. Calculated diagrams of isopoly tungstate anions distribution $α$, mol.% = $φ(Z)$ in the system «Na2WO4 – HCl – Ringer's solution» at 25 and 36.6°C: 1 – WO42-; 2 – W6O20(OH)26-; 3 – W12O40(OH)210-; 4 – H2W12O40(OH)28-; 5 – H3W12O40(OH)27-; 6 – W12O38(OH)26-; 7 – HW7O245-; 8 – HW12O38(OH)25-; 9 – H2W12O40(OH)24-; I – HCO3-; II – CO2·H2O; III – CO32-.

Acknowledgments: The study was carried out within the Fundamental Research Programme funded by the Ministry of Education and Science of Ukraine (Project No. 0119U100025).

[1] Yu. V. Kholin, Quantitative physicochemical Analysis of Complex Formation in Solutions and on Chemically Modified Silicas: Content Models, Mathematical Methods, and Their Applications (Folio, Kharkov, 2000) (in Russian).

[2] S.V. Radio, M.A. Kryuchkov, E.G. Zavialova et al., Equilibrium in the acidified aqueous solutions of tungstate anion: synthesis of Co(II) isopolytungstates. Crystal structure of Co(II) paratungstate B Co5[W12O40(OH)2]·37H2O, J. Coord.Chem., 63, 1678-1689 (2010).

[3] E.Yu. Poimanova, S.V. Radio, E.E. Belousova et al., Isopoly tungstate anions in water-dimethyl sulfoxide solutions, Russ. J. Inorg. Chem., 63, 1243-1250 (2018).