Construction and working of Dropping mercury electrode
A Dropping Mercury Electrode (DME) is a type of electrode commonly used in electrochemistry for polarography, voltammetry, and other electroanalytical techniques. The DME is composed of a mercury droplet that is suspended at the end of a capillary tube. The mercury droplet serves as the working electrode, while a reference electrode and a counter electrode are used to complete the electrochemical cell.
Construction of Dropping Mercury Electrode: The DME is typically made by heating a glass capillary tube and drawing it out to a fine tip. A small amount of mercury is then placed into the capillary, and the tip is heated until the mercury droplet forms. The droplet is then allowed to fall under the influence of gravity, and a stream of argon gas is used to stabilize the droplet and remove any impurities.
Working of Dropping Mercury Electrode: During the electrochemical analysis, a potential is applied to the mercury droplet, and the resulting current is measured. The droplet is continuously replenished as it evaporates, by allowing a small amount of mercury to flow down the capillary tube and form a new droplet. This ensures that the surface area of the working electrode remains constant during the analysis.
The DME is particularly useful for the analysis of metal ions, as the mercury droplet can readily amalgamate with many metal ions, resulting in a well-defined and reproducible signal. The DME can also be used for the analysis of organic compounds and other non-metallic species, by modifying the mercury droplet with a suitable modifier.
In summary, the Dropping Mercury Electrode is a versatile and widely used electrode in electrochemistry, with a construction that involves the formation of a mercury droplet at the end of a capillary tube. The droplet serves as the working electrode, and is continuously replenished during the analysis to ensure a constant surface area.
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