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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:
The name calomel is thought to come from the Greek καλός "beautiful", and μέλας "black"; or καλός and μέλι "honey" from its sweet taste. [4] The "black" name (somewhat surprising for a white compound) is probably due to its characteristic disproportionation reaction with ammonia, which gives a spectacular black coloration due to the finely dispersed metallic mercury formed.
Calomel is a powder that is white when pure, and it has been used as a pigment in painting in 17th century South Americas art and in European medieval manuscripts. [14] When it is exposed to light or contains impurities it takes on a darker tint. [7] Calomel is made up of mercury and chlorine with the chemical formula Hg 2 Cl 2. Depending on ...
A reference electrode is an electrode that has a stable and well-known electrode potential. The overall chemical reaction taking place in a cell is made up of two independent half-reactions , which describe chemical changes at the two electrodes.
Download as PDF; Printable version; ... This category is for electrodes used in electrochemistry and physical chemistry. ... Saturated calomel electrode;
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.
Potentiometric titrations were first used for redox titrations by Crotogino. He titrated halide ions with potassium permanganate using a shiny platinum electrode and a calomel electrode. He said that if an oxidizing agent is added to a reducing solution then the equilibrium between the reducing substance and reaction product will shift towards ...
The silver chloride electrode is most commonly used as a reference electrode in pH meters, although some designs use the saturated calomel electrode. The silver chloride electrode is simple to manufacture and provides high reproducibility. The reference electrode usually consists of a platinum wire that has contact with a silver/silver chloride ...