Reduction potentials bismuth

Bismuth (Z = 83) is the heaviest stable element in group 15 (VA) of the periodic table (see Periodic Table Trends in the Properties of the Elements). The Bi isotope, which is 100% abundant, has a 9/2 nuclear spin. Bi, an alpha emitter is used in nuclear medicine as a radiotherapeutic agent. Bismuth has two stable oxidation states Bi(V), corresponding to complete loss of the valence electrons, and Bi(III), a lower oxidation state that retains two valence electrons. Both oxidation states are diamagnetic. The latter is more stable and more common since Bi(V) has a large reduction potential ... 

Results obtained for the oxide film on bismuth illustrate this approach [29]. The oxide grows by the field-assisted migration of ions and Fig. 12 shows that the forward sweep of a cyclic voltammogram exhibits the plateau currrent characteristic of this mechanism. On the reverse sweep, where the field is insufficient to sustain further film growth, the current falls to zero until the potential is reached at which the film is reduced. The figure also shows the photocurrent observed under the same conditions when the electrode is illuminated. On the forward sweep, the photocurrent rises as the film thickens, but on the reverse sweep it falls and then changes sign before the reduction potential is reached. 

The reductive dimerization of nitroarenes is very dependent on the substitution in aromatic ring and electron-withdrawing groups (p-OCOMe, p-C02Me, and P-NO2) suppress the reaction (Table 6.17). Reaction was tested with several other metals (tin, manganese, copper, aluminum, antimony, and lead), and metal activity correlates with oxidation-reduction potentials of these metals in the order A1 > Mn > Sn > Pb > H > Sb > Bi > Cu (Table 6.18). The pathway for the deoxygenative dimerization of nitroarenes on the activated bismuth surface proceeds via the stepwise reduction processes from nitroarene to nitrosoarene and W-arylhydroxylamine, followed by dehydrative coupling. 

Differences in the reduction potentials for copper, bismuth, lead and cadmium with a dropping mercury electrode has been seen In Figure 12.. Similar differences exist If a platinum electrode Is used providing a suitable depolarizing agent Is employed to prevent excess polarization at the anode. Hydrazine hydrochloride or hydroxylamlne hydrochloride are the usual depolarizers (l4). 

Bismuth may be deposited on platinum electrodes from a number of different electrolytes. (See Table 3.) Lingane (24) also separated bismuth from other metals having reduction potentials differing by less than 0.2 V using a stirred mercury-pool cathode at —0.35 V vs. SCE. His work is noteworthy for its direct use of coulometers to... 

Promotion and deactivation of unsupported and alumina-supported platinum catalysts were studied in the selective oxidation of 1-phenyl-ethanol to acetophenone, as a model reaction. The oxidation was performed with atmospheric air in an aqueous alkaline solution. The oxidation state of the catalyst was followed by measuring the open circuit potential of the slurry during reaction. It is proposed that the primary reason for deactivation is the destructive adsorption of alcohol substrate on the platinum surface at the very beginning of the reaction, leading to irreversibly adsorbed species. Over-oxidation of Pt active sites occurs after a substantial reduction in the number of free sites. Deactivation could be efficiently suppressed by partial blocking of surface platinum atoms with a submonolayer of bismuth promoter. At optimum Bi/Ptj ratio the yield increased from 18 to 99 %. 

In this paper we report the application of bimetallic catalysts which were prepared by consecutive reduction of a submonolayer of bismuth promoter onto the surface of platinum. The technique of modifying metal surfaces at controlled electrode potential with a monolayer or sub-monolayer of foreign metal ("underpotential" deposition) is widely used in electrocatalysis (77,72). Here we apply the theory of underpotential metal deposition without the use of a potentiostat. The catalyst potential during promotion was controlled by proper selection of the reducing agent (hydrogen), pH and metal ion concentration. 

Paneth and Hevesy showed that the electrochemical potential from two cells made from different isotopes of the metal bismuth was the same as far as experimental techniques of the day could distinguish. E.R. Scerri, Realism, Reduction and the Intermediate Position, in N. Bhushan, S, Rosenfeld (eds.). Minds and Molecules, Oxford University Press, New York, 2000, pp. 51-72. 

The electrode potential for the reduction of bismuth sulfide to bismuth is more positive than that of the iron electrode reaction (Eq. 2.7) and thus the charging process conducted at -1 V facilitates the formation of elemental bismuth. 

Alfonsi (9,10,11,12,13) has carried out an extensive investigation of the controlled-potential separation and determination of antimony in alloys containing combinations of lead, tin, bismuth, and copper. Tanaka (14, 15), working mainly with synthetic samples, reports conditions for the separation of antimony from gold, silver, mercury, copper, bismuth, cadmium, zinc, and vanadium in a variety of common electrolytes. Very recently, Dunlap and Shults (18) have developed two coulometric procedures which permit the determination of antimony in each of its oxidation states as well as the total antimony present. After pre-reduction of antimony (V) with hydrazine hydrate, the antimony (III) is reduced to the amalgam at a mercury cathode with a potential of —0.28 V vs. SCE in a supporting electrolyte 0.4 m in tartaric add and 1 m in hydrochloric acid. In the... 

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