mercuryelectrode

A mercury electrode is an electrochemical working electrode that uses mercury as the conductive surface, either as a pool, a rebirthable drop, or as a thin film on an inert substrate. Mercury’s liquid state at room temperature allows the surface to be renewed easily, reducing fouling and providing a smooth, well-defined interface. In aqueous solutions, mercury offers a wide cathodic potential window, high hydrogen overpotential, and the ability to form amalgams with many metals, features that historically made mercury electrodes versatile for redox studies and analytical measurements.

Common variants include the hanging mercury drop electrode (HMDE), the mercury pool electrode, and the mercury film electrode (MFE). The HMDE forms reproducible drops at the end of a capillary, enabling continuous surface regeneration during measurements such as polarography. The mercury pool electrode uses a stationary pool of mercury, while the MFE deposits a thin layer of mercury on an inert substrate (for example glassy carbon or gold), combining the benefits of mercury’s electrochemistry with improved mechanical stability.

In operation, mercury electrodes are used in voltammetric techniques. Polarography, based on a dropping mercury electrode, yields polarographic waves whose heights relate to analyte concentration. Mercury electrodes are also employed in stripping voltammetry for trace metal analysis and in studies of various redox couples.

Safety and environmental concerns limit widespread use of mercury electrodes due to mercury’s toxicity and regulatory restrictions. Many laboratories seek mercury-free alternatives, though mercury electrodes have historical significance in electrochemistry.

Historically, mercury electrodes were central to the development of polarography by Jaroslav Heyrovský, who received the Nobel Prize in Chemistry in 1959 for this work.

See also: polarography, voltammetry, drop electrode, mercury film electrode.