Electrode, antimony hydrogen

The standard electrode potential for zinc reduction (—0.763 V) is much more cathodic than the potential for hydrogen evolution, and the two reactions proceed simultaneously, thereby reducing the electrochemical yield of zinc. Current efficiencies slightly above 90% are achieved in modem plants by careful purification of the electrolyte to bring the concentration of the most harmful impurities, eg, germanium, arsenic, and antimony, down to ca 0.01 mg/L. Addition of organic surfactants (qv) like glue, improves the quaUty of the deposit and the current efficiency. 

For some industrial operations an antimony electrode is used to measure hydrogen-ion concentrations. The electrode consists of a rod of antimony which invariably has a coating of oxide, and placed in an aqueous solution the equilibrium... 

Indicator Electrodes Hydrogen, Glass or Antimony electrodes ... 

Figure 2 shows the structure of this sensor which is similar to that of the potentiometric sensor reported earlier (10). The only difference is that in this sensor a short circuit current between the sensing electrode and the counter electrode is measured with an ammeter. The proton conductor, antimonic acid (Sb205 2H20), was prepared from antimony trioxide and hydrogen peroxide according to a method described elsewhere (7,14). The sample powder was mixed with... 

Kusaka et al. [760] generated the gaseous hydrides of antimony(III), arsenic(III) and tin by sodium borohydride reduction. The hydrides were swept from solution onto a Porapak Q column where they were separated and detected at a gold gas-porous electrode by measurement of the respective electro-oxidation currents. Detection limits for 5ml samples were As(III) (0.2pg L ) Sn(II) (0.8pg L 1) Sb(III) (0.2pg L 1). The order of elution is hydrogen, arsine, stannane, stibine and mercury, ie the order of increasing molecular weight. 

According to this equation the antimony electrode is reversible with respect to hydroxyl ions. The same can be said about the hydrogen ions too, because their concentration is indirectly proportionate to that of ions OH. Therefore, when substituting the activity of the hydrogen ion for that of the hydroxyl ion ... 

BRI/ROB] Britton, H. T. S., Robinson, R. A., The use of the antimony-antimonious oxide electrode in the determination of the concentration of hydrogen ions and in potentiometric titrations. The Prideaux-Ward universal buffer mixture, J. Chem. Soc., (1931), 458-473, Contains report of measurements by W. L. German. Cited on page 141. 

The Practical Determination of pH by Potentiometric Methods. There are four potentiometric methods in general use for determining pH values. These depend upon (a) the hydrogen electrode, (b) the quinhydrone electrode, (c) the antimony-antimony trioxide electrode, and (d) the glass "electrode. These will be discussed in the order... 

The grids of both flat-plate and tubular batteries should not contain antimony or any other additive that may decrease the hydrogen overpotential of the negative electrode. Indeed, it is recommended that ultra-pure lead be used to manufacture both the grids and the active material in order to avoid the possibility of excessive self-discharge at either the positive or the negative plates. 

Figure 4.16 shows the dependences of the rate of hydrogen evolution on electrode potential for pure Pb and Pb—Sb electrodes with different Sb content [8].Addition of antimony to the alloy lowers substantially the potential of hydrogen evolution on electrode polarization at 2.0 mA cm . Depending on the Sb content in the alloy, a reduction in hydrogen overpotential by 220 mV (Pb—2.2 wt% Sb) and by 380 mV (Pb—5.7 wt% Sb) is registered. These results speak... 

Benzaldehyde, benzoic acid and benzene also exhibit substantial inhibiting effect on the hydrogen reaction [45—47]. The hydrogen evolution inhibitors are adsorbed at the protons that are mainly present on the antimony sites (catalytic centres) of the electrode surface. Boehnsted et al. [45] propose a mechanism of the specific adsorption of aromatic aldehydes on these sites [45]. 

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