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Calomel is a mercury chloride mineral with formula Hg 2 Cl 2 (see mercury(I) chloride). It was used as a medicine from the 16th to early 20th century, despite frequently causing mercury poisoning in patients.
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.
The saturated calomel electrode (SCE) is a reference electrode based on the reaction between elemental mercury and mercury(I) chloride. It has been widely replaced by the silver chloride electrode , however the calomel electrode has a reputation of being more robust.
Calomel/horn quicksilver/horn mercury – mercury(I) chloride, a very poisonous purgative formed by subliming a mixture of mercuric chloride and metallic mercury, triturated in a mortar and heated in an iron pot. The crust formed on the lid was ground to powder and boiled with water to remove the calomel.
Mercury compounds like calomel were historically used for various medical purposes: as laxatives, diuretics, antiseptics or antimicrobial drugs for syphilis, typhus and yellow fever. [3] Teething powders were a widespread source of mercury poisoning until the recognition of mercury toxicity in the 1940s. [4]
Internal electrode, usually silver chloride electrode or calomel electrode. Internal solution, usually a pH=7 buffered solution of 0.1 mol/L KCl for pH electrodes or 0.1 mol/L MCl for pM electrodes. When using the silver chloride electrode, a small amount of AgCl can precipitate inside the glass electrode.
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 ...
Above the mercury a little calomel washed with concentrated KCl solution, C, is placed, and the rest of the glass tube packed with moist KC1 crystals, D, and the hole, E, stuffed with cotton soaked in KC1 solution. This forms a calomel electrode, and is separated off from the remainder of the tube by a short piece of glass rod, F.