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Mercury (element)
Notable CharacteristicsMercury is a heavy, silvery-white univalent and bivalent transition metal that is a relatively poor conductor of heat but a decent conductor of electricity and is the only common metal that is liquid at room temperature (forming an opaque glistening liquid).Mercury easily forms alloys with almost all common metals, including gold and silver but not iron. These alloys are collectively called amalgams. The freezing point of mercury is -40 ° Celsius which is the same as -40 ° Fahrenheit. This is the only point at which these two temperature scales coincide. This metal also has uniform volumetric thermal expansion, is less reactive than zinc and cadmium and does not displace hydrogen from acids. Common oxidation states of this element are; mercurous, or +1, and mercuric, or +2. Rare instances of +3 mercury compounds exist. ApplicationsMost mercury is used for the manufacture of industrial chemicals and for electrical and electronic applications. In addition, mercury is widely used in thermometers, especially ones which are used to measure high temperatures. Other uses;
Miscellaneous uses; mercury switches, pesticides, dental amalgams/preparations, cercury cells for caustic soda and chlorine production, anti-fouling paint, electrode in some types of electrolysis, batteries (mercury cells), and catalysts. HistoryMercury was known to the ancient Chinese and Hindus and was found in Egyptian tombs that date from 1500s BC. By 500 BC it was used to make amalgams with other metals. The ancient Greeks used this toxic metal in ointments and the Romans used it in cosmetics. Alchemists thought it to be the stuff from which all matter was formed and they also thought that when it hardened it turned into gold.In the 18th and 19th centuries, mercury nitrate was used to remove fur from the animal skins from which felt hats were made. This caused many cases of brain-damage among hatters, or milliners, leading, it is claimed, to the simile "as mad as a hatter". It was named by alchemists after the Roman god Mercury. Its symbol Hg comes from hydrargyrum, a Latinised form of the Greek word hydrargyros, which was a compound word whose Greek roots meant 'water' and 'silver'. Mercury is one of the few elements that has an alchemical symbol[?]. If you have the right browser and font to support Unicode, you should see the symbol here: ☿.
OccurrenceA rare element in the earth's crust, mercury is found either as a native metal (rare) or in cinnabar, corderoite[?], livingstonite[?], and other minerals with cinnabar (HgS) being the most common ore. Approximately 50% of the global supply comes from Spain and Italy with much of the rest coming from Yugoslavia, Russia, and North America. The metal is extracted by heating cinnabar in a current of air and by condensing the vapor.CompoundsThe most important salts are;
Organic mercury compounds are also important. Laboratory test have found that electrical discharge causes the noble gases neon, argon, krypton, and xenon to combine with mercury vapor. The products of this combination are held together with van der Waals' forces[?] and result in; HgNe, HgAr, HgKr, and HgXe. Methyl mercury[?] is a dangerous compound that is widely found as a pollutant in water bodies and streams. IsotopesThere are seven stable isotopes of mercury with Hg-202 being the most abundant (26.86%). The longest-lived radioisotopes are Hg-194 with a half-life of 444 years, and Hg-203 with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lifes that are less than a day.PrecautionsMercury is highly toxic in both liquid and gaseous forms. This is a toxic heavy metal, that causes brain and liver damage if it is ingested. For this reason, thermometers which are only intended to measure typical climatic temperatures now use pigmented alcohol instead. The commercial unit for handling mercury is the "flask," which weighs 76 lb.Mercury is a very dangerous bioacumulative toxin that is easily absorbed through skin, respiratory and gastrointestinal tissues. Mercury attacks the central nervous system and adversely affects the mouth, gums, and teeth. High exposure over long periods of time will result in brain damage and ultimately death. Air saturated with mercury vapor at room temperature is at a concentration many times the toxic level (the danger is increased at higher temperatures). Mercury should therefore be handled with great care. Containers of mercury need to be covered securely to avoid spillage and sublimation. Heating of mercury or mercury compounds should always be done under a well-ventilated hood.
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