Streaming Mercury Electrod

When the area A of the eleetrode/solution interface with a redox system in the solution varies (e.g. when using a streaming mercury electrode), the double layer capacity which is proportional to A, varies too. The corresponding double layer eharging current has to be supplied at open eireuit eonditions by the Faradaic current of the redox reaction. The associated overpotential can be measured with respect to a reference electrode. By measuring the overpotential at different capaeitive eurrent densities (i.e. Faradaic current densities) the current density vs. eleetrode potential relationship can be determined, subsequently kinetic data can be obtained [65Del3]. (Data obtained with this method are labelled OC.)... 

Voltammetry at other hydrodynamic electrodes The particular features of this technique are (a) plate, conical and tubular electrodes in contact with the flowing solutions and (b) vibrating dme and streaming mercury electrodes. 

One can imagine that to go from the VDME to a streaming mercury electrode would be another obvious step many experiments in this connection have been carried out, e.g., the use of a jet-type Hg electrode as depicted in Fig. 3.70. However, the results obtained so far are not sufficiently reliable, so that the streaming Hg electrode has not found general acceptance. 

Koryta, J., Diffusion and kinetic currents at the streaming mercury electrode, Coll. 

Recently, Fuchs etal. [15], using the streaming mercury electrode and applying the Henderson equation, have determined the pzc value in the solutions of tetraethy-lammonium perchlorate in DMSO as —0.515 0.001 V (versus Ag/0.01 M Ag+ (DMSO) reference electrode). This value was corrected for the liquid junction potential and was independent of tetraethyl ammonium perchlorate (TEAR) concentration within the range 0.02 to 0.75 M. Using the same methodology, KiSova et al. 

Gugala etal. [167] have studied adsorption of butyl acetate at mercury electrode in 1, 0.5, and 0.1 M NaCl04. The zero charge potential values at the streaming mercury electrode were found to shift to positive values with the increasing ester concentration, which indicated the hydrophilic part of the molecules to be directed toward the solution. 

Polarography and Voltammetry Both methods are the same in that current-potential curves are measured. According to the IUPAC recommendation, the tenn polarography is used when the indicator electrode is a liquid electrode whose surface is periodically or continuously renewed, like a dropping or streaming mercury electrode. When the indicator electrode is some other electrode, the term voltammetry is used. However, there is some confusion in the use of these terms. 

A natural extension of the VDME is the streaming mercury electrode [74] where a fine jet of mercury issues from the capillary and is limited by a glass plate. Although some theoretical treatments are available, the poor definition of the length, radius and surface velocity of the mercury... 

The following types of mercury electrodes have been widely used for voltammetry dropping mercury electrode (DME), hanging mercury drop electrode (HMDE), static mercury drop electrode (SMDE), streaming mercury electrode (SME), and mercury film electrode (MFE). We begin our discussion with a description of the construction and properties of the DME because this electrode has a long history and continues to be used for both analytical and fundamental studies. 

There are two types of streaming mercury electrodes (SMEs). The first type is used in the determination of the potential of zero charge, and the second was introduced for voltammetry by Heyrovsky. 

The streaming mercury electrode has been used in kinetic measurements [44,45]. Following introduction of the HMDE, streaming electrodes have become little more than historical curiosities. They are limited by the fact that the radius of the mercury stream and the flow rate are not exactly constant as a function of distance [46]. 

Streaming mercury electrode (mercury jet electrode) — Figure. In... 

Mercury cell process alkali chloride electrolysis Mercury jet electrode streaming mercury electrode... 

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