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The aqueous phase in contact with the mercury and the mercury(I) chloride (Hg 2 Cl 2, "calomel") is a saturated solution of potassium chloride in water. The electrode is normally linked via a porous frit (sometimes coupled to a salt bridge) to the solution in which the other electrode is immersed. In cell notation the electrode is written as:
Reference electrodes generally used are hydrogen electrodes, calomel electrodes, and silver chloride electrodes. The indicator electrode forms an electrochemical half-cell with the interested ions in the test solution. The reference electrode forms the other half-cell. The overall electric potential is calculated as
Mercury(I) chloride is the chemical compound with the formula Hg 2 Cl 2. Also known as the mineral calomel [4] (a rare mineral) or mercurous chloride, this dense white or yellowish-white, odorless solid is the principal example of a mercury(I) compound. It is a component of reference electrodes in electrochemistry. [5] [6]
Common reference electrodes and potential with respect to the standard hydrogen electrode (SHE): Standard hydrogen electrode (SHE) (E = 0.000 V) activity of H + = 1 Molar; Normal hydrogen electrode (NHE) (E ≈ 0.000 V) concentration H + = 1 Molar; Reversible hydrogen electrode (RHE) (E = 0.000 V - 0.0591 × pH) at 25 °C
The most common types of reference electrodes used in analytical chemistry include the standard hydrogen electrode, the saturated calomel electrode, and the Ag/AgCl electrode. [3] The standard hydrogen electrode (SHE) is the primary reference electrode that has a potential of 0 volts at all temperatures and a pressure of 1 atm. The figure on ...
A typical modern pH probe is a combination electrode, which combines both the glass and reference electrodes into one body. The combination electrode consists of the following parts (see the drawing): A sensing part of electrode, a bulb made from a specific glass. Internal electrode, usually silver chloride electrode or calomel electrode.
The data below tabulates standard electrode potentials (E°), in volts relative to the standard hydrogen electrode (SHE), at: Temperature 298.15 K (25.00 °C; 77.00 °F); Effective concentration (activity) 1 mol/L for each aqueous or amalgamated (mercury-alloyed) species; Unit activity for each solvent and pure solid or liquid species; and
This isolates the undesired redox events taking place at the auxiliary electrode. During bulk electrolysis, the analyte undergoes a redox event at the working electrode. If the system was open, then it would be possible for the product of that reaction to diffuse back to the auxiliary electrode and undergo the inverse redox reaction.