Mercury (I) chloride is a chemical compound with the formula Hg 2 Cl 2 . Also known as mineral calomel (rare mineral) or mercurous chloride, white or yellowish white solid, this odorless solid is the prime example of mercury (I) compounds. It is a reference electrode component in electrochemistry.
Video Mercury(I) chloride
Histori
Name of calomel allegedly comes from the Greek ????? pretty , and ????? black ; or ????? and ???? honey of sweet taste. The name black (somewhat surprising for white compounds) may be due to the typical disproportionation reaction with ammonia, which gives the black color "spectacular" because of the finely dispersed metallic mercury formed. This is also called a quicksilver horn mineral or mercury horn .
Calomels are taken internally and used as laxatives, for example to treat George III in 1801, and disinfectants, as well as in the treatment of syphilis, until the early 20th century. Until fairly recently, it was also used as a horticultural fungicide, primarily as a rootstroke to help prevent the occurrence of clubroot among the plants of the Brassicaceae family.
Mercury is a popular remedy for various physical and mental illnesses during the age of "heroic medicine". It was used by American doctors throughout the 18th century, and during the revolution, to make patients vomit and release their bodies from "dirt". Benjamin Rush is one of the best known mercury advocates in medicine and uses calomel to treat yellow fever sufferers during the outbreak in Philadelphia in 1793. Calomels are given to patients as laxatives or catharsis until they begin to salivate and are often given to patients in large quantities such that their hair and teeth fall out.
Shortly after yellow fever struck Philadelphia, the disease erupted in Jamaica. War of words erupts in the media about the best treatment for yellow fever: bleeding; or calomel. Anecdotal evidence suggests that calomel is more effective than bleeding.
Mormon Prophet Joseph Joseph's eldest brother Alvin Smith died in 1823 of mercury poisoning from calomel.
Maps Mercury(I) chloride
Properties
Mercury is unique among groups of 12 metals because of its ability to form M-M bonds so easily. Hg 2 Cl 2 is a linear molecule. Mineral calomel crystallizes in tetragonal system, with group space I4/m 2/m 2/m. The unit cell of the crystal structure is shown below:
The length of the Hg-Hg bond is 253 μm (Hg-Hg in metal is 300 μm) and the length of the Hg-Cl bond in the subgroup Hg 2 linear 243 pm. The overall coordination of each Hg atom is octahedral as, in addition to the nearest two neighbors, there are four other Cl atoms at 321 pm. Longer mercury polarization exists.
Preparation and reaction
Mercurous chloride is formed by the elemental reactions of mercury and mercury chloride:
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- Hg HgCl 2 -> Hg 2 Cl 2
This can be prepared by a metathesis reaction involving aqueous mercury (I) nitrate using various sources of chloride including NaCl or HCl.
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- 2HCl Hg 2 (NO 3 ) 2 -> Hg 2 Cl 2 2HNO 3
Mercurous chloride is widely used in electrochemistry, taking advantage of the ease of oxidation and reduction reactions. The calomel electrode is a reference electrode, especially in older publications. Over the past 50 years, it has been replaced by silver/silver chloride electrodes (Ag/AgCl). Although mercury electrodes have been largely abandoned due to the dangerous mercury properties, many chemists believe they are still more accurate and harmless as long as they are handled properly. Differences in experimental potential differ slightly from literary values. Other electrodes can vary up to 70 to 100 millivolts.
Photochemistry
Mercurous chloride breaks down into mercury (II) chloride and mercury elements after exposure to UV rays.
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- Hg 2 Cl 2 -> HgCl 2 Hg
Hg formation can be used to calculate the number of photons in light beams, with actinometry techniques.
By utilizing light reactions in the presence of mercury (II) chloride and ammonium oxalate, mercury (I) chloride, ammonium chloride and carbon dioxide are produced.
- 2 < sub> 2 - sub (s) 2 [NH 4 ] [Cl - ] 2CO 2
This particular reaction was discovered by J.M. Eder (hence the name Eder reaction ) in 1880 and re-investigated by W. E. Rosevaere in 1929.
The mercury compound (I) is related
Mercury (I) bromide, Hg 2 Br 2 , greenish color. Both are difficult to dissolve. Mercury (I) fluoride is unstable in the absence of strong acids.
Security considerations
Mercurous chloride is toxic, although due to its low solubility in water, it is generally harmless compared to mercury chloride. It was used in medicine as a diuretic and laxative (laxative) in the United States from the late 1700s to the 1860s. Calomel was also a common ingredient in tooth-growing dust in England until 1954, causing extensive mercury poisoning in the form of pink disease, which at that time had a mortality rate of 1 in 10. The use of this drug was then discontinued when the toxicity of the compound was found.
It also finds usefulness in cosmetics as a skin lightening cream and soap, but these preparations are now illegal to be produced or imported in many countries including the US, Canada, Japan and the European Union. A study of workers involved in the production of this preparation showed that the sodium salt of 2,3-dimercapto-1-propanesulfonic acid (DMPS) was effective in lowering the body's mercury load and lowering urine mercury levels to normal levels.
References
External links
- International Chemical Safety Cards 0984
- National Pollutant Inventory - Mercury and Mixed Fact Sheet
- The NIOSH Pocket Guide for Chemical Hazards
Source of the article : Wikipedia
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