The hydrocomplexation in the system Cr{3+}– Cu{2+} – NO[3]{-} – H[2]O

Abstract

The hydrolysis processes in the system Cr{3+}– Cu{2+} – NO[3]{-} – H[2]O have been investigated by potentiometric titration and dialysis methods. The solutions of the chromium (III) nitrates and copper (II) nitrates obtained by dissolving chromium (III) nitrate and copper in nitric acid were used in the work. The experimental data have been obtained under following conditions: metal ions concentration – 0.01 mol/l, molar ratio Cr{3+}:Cu{2+} = 1:1, ionic strength – 0.3 mol/l (NaNO[3]), temperature – (25 ± 0.1) ° С, pH-range – 1.5–3.6. The results of potentiometric titration do not allow one to establish the possibility of heteropolymeric hydroxocomplexes formation. According to the results obtained by dialysis, polynuclear complexes of cromium (III) in the system Cr{3+}– Cu{2+} – NO[3]{-} – H[2]O are formed when the pH is 2.0. Copper (II) does not forms a polynuclear hydroxocomplexes. The distribution of different Cr(III) and Cu(II) forms upon pH value in the region before formuation of hydroxides sedimenys has been calculated upon experimental data. It was established that Cr (III) and Cu (II) do not form hetero-nuclear hydroxocomplexes.