The ac and dc polarographic reduction of bismuth(III) in acidic halide and other media

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Abstract

Some aspects of the ac and dc polarographic reduction of Bi(III) in acidic perchlorate, nitrate and halide media have been examined and results from this and investigations by other workers have been used to elucidate the electrode processes occuring in non-complexing and complexing media. The equivalence of the ac and dc electrode processes is suggested, and the dependence of ac-wave height and independence of dc-wave height upon ligand concentration is used as a guide to the role of complex formation in altering the rate of the electrode process. In acidic perchloric acid, the major species is thought to be Bi(aq)3+ and the electrode process Bi(aq)3e⇄ Bi(amalgam) + aq is believed to be slow due to kinetically slow removal of co-ordinated water. Formation of covalently bonded ligands can increase the rate of removal of water and the rate of the electrode process increases substantially. Evidence for this comes from addition of nitrate to perchloric acid solutions. Bismuth(III) forms uncommonly stable nitrate complexes and the unusual ability of nitrate to catalyse strongly the bismuth(III) electrode process would appear to be related to nitrate complex formation. The halides also form strong bismuth(III) complexes, but because they are strongly adsorbed at mercury electrodes complex formation in the double layer can occur as well as in the bulk solution. For chloride, as with nitrate, complex formation at the electrode is not thought to be significant; however for the other halides, complex formation both in solution and the double layer appear to be important.

Original languageEnglish
Pages (from-to)769-785
Number of pages17
JournalElectrochimica Acta
Volume17
Issue number4
DOIs
Publication statusPublished - Apr 1972
Externally publishedYes

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