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Mercury(I) chloride

Mercury(I) chloride
Mercury Chloride.jpg
Calomel-2D.png
Calomel-xtal-3D-vdW.png
Names
IUPAC name
Dimercury dichloride
Other names
Mercurous chloride
Calomel
Identifiers
10112-91-1 YesY
3D model (Jmol) Interactive image
ChEBI CHEBI:33050 YesY
ChemSpider 16740467 YesY
ECHA InfoCard 100.028.574
EC Number 233-307-5
PubChem 24956
RTECS number OV8750000
UNII J2D46N657D N
UN number 3077
Properties
Hg2Cl2
Molar mass 472.09 g/mol
Appearance White solid
Density 7.150 g/cm3
Melting point 525 °C (977 °F; 798 K) (triple point)
Boiling point 383 °C (721 °F; 656 K) (sublimes)
0.2 mg/100 mL
Solubility insoluble in ethanol, ether
−26.0·10−6 cm3/mol
1.973
Hazards
Safety data sheet ICSC 0984
Harmful (Xn)
Dangerous for the environment (N)
R-phrases R22, R36/37/38, R50/53
S-phrases (S2), S13, S24/25, S46, S60, S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)
210 mg/kg (rat, oral)
Thermochemistry
196 J·mol−1·K−1
−265 kJ·mol−1
Related compounds
Other anions
Mercury(I) fluoride
Mercury(I) bromide
Mercury(I) iodide
Other cations
Mercury(II) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Mercury(I) chloride is the chemical compound with the formula Hg2Cl2. Also known as calomel (a mineral form, rarely found in nature) 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.

The name calomel is thought to come from the Greek καλός beautiful, and μέλας black; or καλός and μέλι honey from its sweet taste. 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. It is also referred to as the mineral horn quicksilver or horn mercury. Calomel was taken internally and used as a laxative, for example to treat George III in 1801, and disinfectant, as well as in the treatment of syphilis, until the early twentieth century. Until fairly recently it was also used as a horticultural fungicide, most notably as a root dip to help prevent the occurrence of clubroot amongst crops of the Brassicaceae family.

Mercury became a popular remedy for a variety of physical and mental ailments during the age of "heroic medicine." It was used by doctors in America throughout the eighteenth century, and during the revolution, to make patients regurgitate and release their body from "impurities". Benjamin Rush was one particular well-known advocate of mercury in medicine and used calomel to treat sufferers of yellow fever during its outbreak in Philadelphia in 1793. Calomel was given to patients as a purgative or cathartic until they began to salivate and was often administered to patients in such great quantities that their hair and teeth fell out. Shortly after yellow fever struck Philadelphia, the disease broke out in Jamaica. A war of words erupted in the press concerning the best treatment for yellow fever; bleeding or calomel. Anecdotal evidence indicates calomel was more effective than bleeding.


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