Calomel


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calomel

[′kal·ə·məl]
(mineralogy)
Hg2Cl2 A colorless, white, grayish, yellowish, or brown secondary, sectile, tetragonal mineral; used as a cathartic, insecticide, and fungicide. Also known as calomelene; calomelite; horn quicksilver; mercurial horn ore.

Calomel

 

(from the Greek kalos, “beautiful,” and melas, “black”), mercurous chloride, Hg2Cl2; a colorless powder. When treated with caustic alkalies or ammonia, it turns black (hence the name). The darkening occurs as result of the precipitation of finely powdered mercury according to the reactions

Hg2Cl2 + 2NaOH - Hg + HgO + 2NaCl + H2O

Hg2Cl2 + 2NH 4OH = HgNH2Cl + Hg + NH4C1 + 2H2O

Calomel has a density of 7, 160 kg/m3 and evaporates without fusion. Its sublimation point is 383.7°C. It is poorly soluble in water.

Calomel is used in the preparation of calomel electrodes and as a catalyst in organic reactions. In medicine it serves as an antibacterial agent, applied externally in ointment form in cases of wart infections and gonorrheal conjunctivitis and as a safeguard against venereal diseases (locally). Calomel is sometimes used internally as a cholagogue.

In nature calomel exists as a rare mineral of the halide group.It crystallizes in the tetragonal system and has an adamantineluster. Its hardness on the mineralogical scale measures 1.5.Native calomel exhibits very high double refraction. It is formedin the oxidation zone of mercury deposits.

References in periodicals archive ?
A saturated calomel electrode or other electrodes such as silver/silver chloride or mercury/mercury sulfate can also be used as the reference electrode.
Stimulants Only Brandy Bleeding and Salines Venesection (8 oz), salt and mustard emetics, mustard poultices, saline solution, (every half hour) brandy, calomel, opium (every two hours).
Using Volta Lab apparatus model PGZ 100 at the corrosion laboratory of engineering faculty at Cairo University, a standard calomel electrode and platinum electrode were used as a reference and counter electrode, respectively.
The experiments were conducted using a conventional electrochemical cell with three electrodes, where a saturated calomel electrode (SCE) was employed as reference electrode and a platinum wire was used as counter-electrode.
Soil pH was measured using a low conductivity glass calomel electrode in a soil suspension prepared by mixing 10g of moist soil with 20 ml of distilled water.
5 V for 24 h using saturated calomel (SCE) and a graphite rod as reference and counter electrodes, respectively, by a PAR versaSTAT MC instrument.
Calomel (which contained mercury) was used to produce the evacuation of so-called toxins: we are not told of its ill effects but they must have been common and serious.
A conventional three-electrodes cell with a pt sheet as counter electrode and saturated calomel (SCE) as reference electrode.
15 V as SCE An Elico digital pH meter 269 was used with glass and calomel electrode assembly Experimental sets, each having known amount of Se, & Te in appropriate quantity of BR buffer of pH 5.
Haad has urged the public to stop using any whitening product that may contain the words "mercurouschloride", calomel, mercuric, mercurio or mercury.
Haad advises the public to read posters or information on any whitening, or anti-aging product packaging thoroughly and to stop the use of any product that may contain the word 'mercurouschloride', calomel, mercuric, mercurio or mercury.