| Popis: |
Results obtained in potentiometric titrations of Fe(II), Mn(II), Fe(CN)64-, C2O42- and As(III) with standard potassium permanganate solution, are presented. The titration end point (TEP) was detected with a universal electrode whose sensor is natural crystalline pyrite. The titrations of As(III) were carried out in HCl (1.2 M) and H2SO4 solutions (0.1- 4.5 M), whereas oxalate was determined in H2SO4 (0.1-4.5 M). Iron(II) and hexacyanoferrate(II) were titrated in H2SO4 and also in H3PO4 solutions (0.1-4.5 M). The titrations of Mn(II) were performed in H2P2O72- media at pH 4.0, 5.0, 6.0 and 7.0. The results obtained by using the pyrite electrode were compared with those obtained by the application of a Pt-electrode, and good agreement, reproducibility and accuracy were obtained. The potentials in the course of the titration and at the end-point (TEP) are rapidly established. The potential changes at the TEP ranged from 90 to 330 mV/0.1 mL, depending on the titrated system. The highest changes were observed in titrations of Fe(II) in H3PO4 (240-330 mV/0.1 mL). Reversed titrations were also performed and accurate and reproducible results were obtained. |
