Polarography of some anions in aqueous organic solvent mixtures: Part II. Reduction of bromate ions in aqueous mixtures of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, 1,3-propanediol and glycerol
✍ Scribed by B.K. Gupta; D.S. Jain; J.N. Gaur
- Publisher
- Elsevier Science
- Year
- 1974
- Weight
- 168 KB
- Volume
- 52
- Category
- Article
- ISSN
- 0022-0728
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✦ Synopsis
The reduction of bromate ion at the dropping mercury electrode has been studied by Rylich 1, who observed that the decomposition potential of the bromate (also iodate) becomes more positive with increase in the valency of the cation and with the increasing concentration of the supporting electrolyte. The current-voltage curves for bromate ion at different pH have been studied by Orlemann and Kolthoff 2 and Zykov and Zhdanov 3. The present studies are devoted to polarographic behaviour of bromate ions in aqueous organic mixtures of methanol, ethanol, n-pr0panol, isopropanol, ethylene glycol, propylene glycol, 1,3-propanediol and glycerol. Similar investigations on the reduction of chromate ions in different aqueous organic solvent mixtures have been made by the authors 4 7.
Stock solutions of BrO3 (0.01 M) and NaOH (1.0 M) were prepared by dissolving the required weight of reagent grade KBrO 3 and NaOH in twice distilled water and standardized as usual 8. Solvents supplied by commercial sources were purified and distilled by standard methods 9, and blank polarograms of solvent in 0.1 M NaOH were recorded to test the suitability of the solvents for polarographic measurements.
Solutions containing 1 mM BrO 3 and 0.1 M NaOH having different percentages of solvents (by volume) were prepared in 25 ml volumetric flasks. Solutions were also prepared having different BrO3 ion concentration in the same percentage of organic solvents without 0.1 M NaOH. The current-voltage curves were obtained by a Radiometer PO4. The dropping mercury electrode having m=l.15 mg s -1 and t=5.0 s (at 50 cm of mercury pressure in 0.1 M NaOH with applied potential of -1.0 V vs. SCE) was used for all the measurements. All the experiments were performed at 30°C, which was maintained by a Haake type ultrathermostat. All the reductions were carried out in a H-type cell with an agar-agar plug saturated with KC1. The solution was freed from dissolved oxygen by bubbling purified N2 gas, which was presaturated with the solution of the same solvent composition, for 30 min. The IR drop correction was applied wherever needed. For this purpose the resistance of the solution was measured with a L.P. conduscope. The viscosity and density of the solutions were measured by an Ostwald viscometer and pyknometer, respectively.