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 ?
According to this method, if the potential of steel rebar becomes more negative than -270 mV when saturated calomel electrode is used as reference electrode, the probability of corrosion is 90% [22].
The potential of bare steel in seawater is approximately -650mV SCE (Saturated Calomel Electrode) and zinc has a potential of approximately -1050 mV SCE.
Calomel was used to purge patients of poor health and evil "humors" until the substance was found to be harming more than helping.
First, a laxative of rhubarb or calomel or an emetic, ipecac, to be followed up with a mixture of rust of iron, powdered columbo root, and orange peel twice a day for four weeks.
The author records an 1822 practitioner's recommendation for treating sick headache: First, a laxative of rhubarb or calomel or an emetic, ipecac, to be followed up with a mixture of rust of iron, powdered columbo root, and orange peel twice a day for four weeks.
02 V (vs saturated calomel electrode) as indicated by the long arrows in panels A, C, and E of Fig.
6) "In diarrhoea, [opium] was a major remedy, sometimes combined with camphor, sometimes with nitric acid or calomel Its use in dysentery was common, although it was argued that the constipation it produced could mask other, more serious symptoms" (Berridge and Edwards 1987, 67).
University researchers are testing DNA from his hair for traces of mercury chloride which would reveal if he used calomel.
Most doctors prescribed large doses of calomel (mercury) or quinine (a kind of tree bark widely used to treat malaria) and then tea, broth, cordials, wine, blisters, hot mustard baths, iced champagne, cold baths, or vinegar wraps.
4) Inorganic mercury salts such as calomel and ammoniated mercury chloride have been used in the past for the treatment of certain skin disorders, such as psoriasis.
Just before John's much noted (spiritually cleansing) sermon in Chapter 24, rot and purgation find poignant expression: "He felt inside as if he had been taking calomel.