Mercury (element)



80 thallium
Uub
General
Number mercury, Hg, 80
transition metals
Block d
Appearance silvery
(2)  g·mol−1
Xe] 4f14 5d10 6s2
shell 2, 8, 18, 32, 18, 2
Physical properties
Phase liquid
r.t.) (liquid) 13.534  g·cm−3
F)
F)
K, 172.00 MPa
kJ·mol−1
kJ·mol−1
Heat capacity (25 °C) 27.983  J·mol−1·K−1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 315 350 393 449 523 629
Atomic properties
Crystal structure rhombohedral
basic oxide)
Electronegativity 2.00 (Pauling scale)
Ionization energies 1st: 1007.1 kJ/mol
2nd: 1810 kJ/mol
3rd: 3300 kJ/mol
Atomic radius 150  pm
Atomic radius (calc.) 171  pm
Covalent radius 149  pm
Van der Waals radius 155 pm
Miscellaneous
diamagnetic
Electrical resistivity (25 °C) 961 nΩ·m
Thermal conductivity (300 K) 8.30  W·m−1·K−1
Thermal expansion (25 °C) 60.4  µm·m−1·K−1
Speed of sound (liquid, 20 °C) 1451.4 m/s
CAS registry number 7439-97-6
Selected isotopes
Main article: Isotopes of mercury
iso NA half-life DM DE (MeV) DP
194Hg syn 444 y ε 0.040 194Au
195Hg syn 9.9 h ε 1.510 195Au
196Hg 0.15% Hg is neutrons
197Hg syn 64.14 h ε 0.600 197Au
198Hg 9.97% Hg is neutrons
199Hg 16.87% Hg is neutrons
200Hg 23.1% Hg is neutrons
201Hg 13.18% Hg is neutrons
202Hg 29.86% Hg is neutrons
203Hg syn 46.612 d β- 0.492 203Tl
204Hg 6.87% Hg is neutrons
References

Mercury(standard conditions for temperature and pressure.

Mercury is used in cinnabar.

Mercury occurs in deposits throughout the world and it is harmless in an insoluble form, such as mercuric sulfide, but it is poisonous in soluble forms such as methylmercury.

History

Mercury was known to the ancient Chinese and Hindus, and was found in Egyptian tombs that date from 1500 BC.[citation needed] In China, India, and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. China's first emperor, Qin Shi Huang Di — said to have been buried in a tomb that contained rivers of flowing mercury, representative of the rivers of China — Qin was driven insane and killed by mercury pills (failing liver, poison, brain death) intended to give him eternal life.[citation needed] The ancient Greeks used mercury in ointments and the Romans used it in cosmetics. By 500 BC mercury was used to make Rasavātam which means "the way of mercury".

gold, and mercury was required for the transmutation of base (or impure) metals into gold as was the goal of many alchemists.

Hg is the modern chemical symbol for mercury. It comes from hydrargyrum, a Latinized form of the Greek word `Υδραργυρος (hydrargyros), which is a compound word meaning "water" and "silver" — since it is liquid, like water, and yet has a silvery metallic sheen. The element was named after the Roman god Mercury, known for speed and mobility. It is associated with the planet Mercury. The astrological symbol for the planet is also one of the alchemical symbols for the metal. Mercury is the only metal for which the alchemical planetary name became the common name.

Occurrence

  Mercury is an extremely rare element in the earth's crust, having an average crustal abundance by mass of only 0.08 parts per million. However, because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be extraordinarily concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance).

It is found either as a native metal (rare) or in volcanic regions.

Over 100,000 tons of mercury were mined from the region of Huancavelica, Peru, over the course of three centuries following the discovery of deposits there in 1563; mercury from Huancavelica was crucial in the production of silver in colonial Spanish America. Many former ores in Italy, Slovenia, the United States and Mexico which once produced a large proportion of the world's supply have now been completely mined out. The metal is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is

HgS + O2 → Hg + SO2

In 2005, China was the top producer of mercury with almost two-thirds global share followed by Kyrgyzstan, reports the British Geological Survey.[citation needed] Several other countries are believed to have unrecorded production of mercury from copper electrowinning processes and by recovery from effluents.

Due to minimal surface disruption, mercury mines lend themselves to constructive re-use. For example, in 1976 Santa Clara County, California purchased the historic Almaden Quicksilver Mine and proceeded to create a county park on the site, after conducting extensive safety and environmental analysis of the property.

See also Category:Mercury minerals, .

Releases in the environment

  Preindustrial deposition rates of mercury from the atmosphere may be in the range of 4 ng/L in the western USA. Although that can be considered a natural level of exposure, regional or global sources have significant effects. Volcanic eruptions can increase the atmospheric source by 4–6 times.[2]

Mercury enters the environment as a pollutant from various industries:

  • coal-fired power plants are the largest aggregate source (40% of USA emissions in 1999).[3]
  • large gold mines — the three largest point sources for mercury emissions in the US are the three largest gold mines[4]
  • gas fired power plants fueled with gas from mercury prone reservoirs where the mercury has not been removed
  • small-scale gold mining
  • industrial processes
    • gold production
    • metal smelting
    • manufacture & repair of weather and electronic devices
    • incineration of municipal waste streams
  • medical applications, including vaccinations
    • dentistry
    • cosmetic industries
  • laboratory work involving mercury compounds

  Mercury also enters into the environment through the disposal (e.g., landfilling, incineration) of certain products. Products containing mercury include: auto parts, thermometers now use pigmented alcohol instead of mercury. Mercury thermometers are still occasionally used in the medical field because they are more accurate than alcohol thermometers, though both are being replaced by electronic thermometers. Mercury thermometers are still widely used for certain scientific applications because of their greater accuracy and working range.

The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants that need to be controlled to the greatest possible extent. Thus, industries that release high concentrations of mercury into the environment agreed to install maximum achievable control technologies (MACT). In March 2005 EPA rule[6] added power plants to the list of sources that should be controlled and a national cap and trade rule was issued. States were given until November 2006 to impose stricter controls, and several States are doing so. The rule was being subjected to legal challenges from several States in 2005.

Historically, one of the largest releases was from the Colex plant, a lithium-isotope separation plant at Oak Ridge. The plant operated in the 1950s and 1960s. Records are incomplete and unclear, but government commissions have estimated that some two million pounds of mercury are unaccounted for.[7]

One of the worst industrial disasters in history was caused by the dumping of mercury compounds into Minamata Bay, Japan. The Minamata disease.

Applications

  Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures (In the United States, non-prescription sale of mercury fever thermometers is banned by a number of different states and localities). Other uses:

  • Mercury was used inside wobbler (fishing) lures. Its heavy, liquid form made it useful since the lures made an attractive irregular movement when the mercury moved inside the plug. Such use was stopped due to environmental concerns, but illegal preparation of modern fishing plugs has occurred.
  • Mercury sphygmomanometers.
  • Mercury barometers, coulometers, and many other laboratory instruments. As an opaque liquid with a high density and a nearly linear thermal expansion, it is ideal for this role.
  • The ITS-90).
  • In some gaseous electron tubes, including ignitrons, thyratrons, and mercury arc rectifiers
  • Gaseous mercury is used in fluorescent lamps.
  • Mercury is used to construct liquid-mirror telescopes. The mirror is formed by rotating liquid mercury on a disk, the parabolic form of the liquid thus formed reflecting and focusing incident light. Such telescopes are cheaper than conventional large mirror telescopes by up to a factor of 100, but the mirror cannot be tilted and always points straight up.
  • Liquid mercury was sometimes used as a coolant for nuclear reactors; however, sodium is proposed for reactors cooled with liquid metal, because the high density of mercury requires much more energy to circulate as coolant.
  • Liquid mercury has been proposed as a working fluid for a heat pipe type of cooling device for spacecraft heat rejection systems or radiation panels.
  • Mercury was a propellant for early ion engines in electric propulsion systems. Advantages were mercury's high molecular weight, low ionization energy, low dual-ionization energy, high liquid density and liquid storability at noble gas nature, and has a high liquid density under mild cryogenic storage.
  • Experimental Mercury vapour turbines were proposed to increase the efficiency of fossil-fuel electrical power plants.
  • Mercury was once used in the silver ores. This polluting practice is still used by the garimpeiros (gold miners) of the Amazon basin in Brasil and by illegal miners in South Africa.
  • Mercury is still used in some cultures for folk medicine and ceremonial purposes which may involve ingestion, injection, or the sprinkling of elemental mercury around the home. It must be emphasized that the former two procedures, especially, are extremely hazardous and the latter is nearly as so because mercury spreads easily and is therefore ingested.
  • Alexander Calder built a mercury fountain for the Spanish Pavilion at the 1937 World's Fair in Paris. The fountain is now on display at the Fundació Joan Miró in Barcelona.
  • Used in electrode potential of half cells.
  • Used in Cold Cathode (also generalised under the Neon Sign Industry) lighting to increase the success of Neon filled tubes the light produced will be inconsistent red/blue spots until the initial burning-in process is completed; eventually it will light a consistent dull off-blue colour.
  • Mercury was once used as a gun barrel bore cleaner.

Miscellaneous uses: dental amalgams/preparations and liquid mirror telescopes.

  Historical uses: preserving wood, developing daguerreotypes, corrode. This would cause mysterious structural failures.

In Islamic Spain it was used for filling decorative pools.[9]

In some applications, mercury can be replaced with less toxic but considerably more expensive galinstan alloy.

A new type of atomic clock, using mercury instead of caesium, has been demonstrated. Accuracy is expected to be within one second in 100 million years.[10][11]

Hat making

From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution of the mercury compound mercuric nitrate, Hg(NO3)2·2H2O.[12] This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. Its use resulted in widespread cases of hallucinations. The United States Public Health Service banned the use of mercury in the felt industry in December 1941. The psychological symptoms associated with mercury poisoning may have inspired the phrase "mad as a hatter"; see hatter on the origin of the phrase. Lewis Carroll's "Mad Hatter" in his book Alice's Adventures in Wonderland was based on this.

Production of chlorine and caustic soda

membrane cell or diaphragm cell technologies to produce chlorine.

Dentistry

The element mercury is the main ingredient in dental amalgam controversy. A recent review by an FDA-appointed advisory panel rejected, by a margin of 13-7, the current FDA report on amalgam safety,[citation needed] stating the report's conclusions were unreasonable given the quantity and quality of information currently available. Panelists said remaining uncertainties about the risk of so-called silver fillings demanded further research; in particular, on the effects of mercury-laden fillings on children and the fetuses of pregnant women with fillings, and the release of mercury vapor on insertion and removal of mercury fillings.[citation needed]

Medicine

Mercury and its compounds have been used in medicine for centuries, although they are much less common today than they once were, now that the toxic effects of mercury and its compounds are more widely understood.

Mercurochrome is still widely used but has been banned in some countries such as the U.S.

Since the 1930s some vaccines have contained the preservative ethyl mercury. Although it was widely speculated that this mercury-based preservative can cause or trigger autism in children, scientific studies showed no evidence supporting any such link.[19] Nevertheless thiomersal has been removed from or reduced to trace amounts in all U.S. vaccines recommended for children 6 years of age and under, with the exception of inactivated influenza vaccine.[20]

Mercury in the form of one of its common ores, Chinese, Tibetan, and Ayurvedic medicine. As problems may arise when these medicines are exported to countries that prohibit the use of mercury in medicines, in recent times, less toxic substitutes have been devised.

Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries. FDA has “inadequate data to establish general recognition of the safety and effectiveness,” of the mercury ingredients in these products.[22] Mercury is still used in some diuretics, although substitutes now exist for most therapeutic uses.

Isotopes

Main article: isotopes of mercury

There are seven stable NMR-active nuclei, having spins of 1/2 and 3/2 respectively.

Reactivity

Mercury dissolves to form amalgams with gold, zinc and many metals. Because iron is an exception to this rule, iron flasks have been traditionally used to trade mercury. When heated, mercury also reacts with oxygen in air to form mercury oxide, which then can be decomposed by further heating to higher temperatures.

Since it is below hydrogen in the hydrogen sulfide. Mercury even reacts with solid sulfur flakes, which is used in mercury spill kits to absorb mercury vapors (spill kits also use activated charcoal and powdered zinc).

Compounds

The most important salts are

Laboratory tests have found that an electrical discharge causes the noble gases to combine with mercury vapor. These compounds are held together with pollutant in water bodies and streams.

The discovery of Mercury(IV) fluoride (HgF4) was announced in September 2007.

See also Category:Mercury compounds.

Safety

See also: mercury poisoning

Mercury and most of its compounds are extremely toxic and are generally handled with care; in cases of spills involving mercury (such as from certain methylmercury.

Occupational exposure

Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization, OSHA, and NIOSH all treat mercury as an occupational hazard, and have established specific occupational exposure limits. Environmental releases and disposal of mercury are regulated in the U.S. primarily by the United States Environmental Protection Agency.

Case control studies have shown effects such as tremors, impaired cognitive skills, and sleep disturbance in workers with chronic exposure to mercury vapour even at low concentrations in the range 0.7–42 μg/m3.[24][25]

A study has shown that acute exposure (4-8 hours) to calculated elemental mercury levels of 1.1 to 44 mg/m3 resulted in chest pain, dyspnea, cough, hemoptysis, impairment of pulmonary function, and evidence of interstitial pneumonitis.[26]

Acute exposure to mercury vapor has been shown to result in profound central nervous system effects, including psychotic reactions characterized by delirium, hallucinations, and suicidal tendency. Occupational exposure has resulted in broad-ranging functional disturbance, including erethism, irritability, excitability, excessive shyness, and insomnia. With continuing exposure, a fine tremor develops and may escalate to violent muscular spasms. Tremor initially involves the hands and later spreads to the eyelids, lips, and tongue. Long-term, low-level exposure has been associated with more subtle symptoms of erethism, including fatigue, irritability, loss of memory, vivid dreams, and depression.[27][28]

Treatment

Research on the treatment of mercury poisoning is limited. Currently available drugs for acute mercurial poisoning include chelators N-acetyl-D,L-penicillamine (NAP), dimercaptosuccinic acid (DMSA). In one small study including 11 construction workers exposed to elemental mercury, patients were treated with DMSA and NAP.[29] Chelation therapy with both drugs resulted in the mobilization of a small fraction of the total estimated body mercury. DMSA was able to increase the excretion of mercury to a greater extent than NAP.

Mercury in fish

 

Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of Minamata disease.

The complexities associated with mercury fate and transport are relatively succinctly described by USEPA in their 1997 Mercury Study Report to Congress. Because methylmercury and high levels of elemental mercury can be particularly toxic to unborn or young children, organizations such as the U.S. EPA and FDA recommend that women who are pregnant or plan to become pregnant within the next one or two years, as well as young children avoid eating more than 6 ounces (one average meal) of fish per week.[30] In the United States the FDA has an action level for methyl mercury in commercial marine and freshwater fish that is 1.0 parts per million (ppm), and in Canada the limit for the total of mercury content is 0.5 ppm.

Species with characteristically low levels of mercury include shrimp, tilapia, salmon, pollock, and catfish (FDA March 2004). The FDA characterizes shrimp, catfish, pollock, salmon, and canned light tuna as low-mercury seafood, although recent tests have indicated that up to 6 percent of canned light tuna may contain high levels.[31]

Mercury and aluminium

Mercury readily combines with aluminium to form a mercury-aluminum amalgam when the two pure metals come into contact. However, when the amalgam is exposed to air, the aluminium oxidizes, leaving behind mercury. The oxide flakes away, exposing more mercury amalgam, which repeats the process. This process continues until the supply of amalgam is exhausted, and since it releases mercury, a small amount of mercury can “eat through” a large amount of aluminium over time, by progressively forming amalgam and relinquishing the aluminium as oxide.

Aluminium in air is ordinarily protected by a molecule-thin layer of its own oxide, which is not porous to oxygen. Mercury coming into contact with this oxide does no harm. However, if any elemental aluminium is exposed (even by a recent scratch), the mercury may combine with it, starting the process described above, and potentially damaging a large part of the aluminium before it finally ends.[32]

For this reason, restrictions are placed on the use and handling of mercury in proximity with aluminium. In particular, mercury is not allowed aboard aircraft under most circumstances because of the risk of it forming amalgam with exposed aluminium parts in the aircraft.

Regulations

In the European Union, Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (See ppm.[33]

Besides, in the European Union there are restriction for mercury concentration in packaging (the limit is 100 ppm for sum of mercury, cadmium) and batteries (the limit is 5 ppm).[34].

In July 2007, European Union also banned mercury in non-electrical measuring devices, such as thermometers and barometers. The ban applies to new devices only, and contains exemptions for the healthcare sector and a two-year grace period for manufacurers of barometers. [35]

In Norway, there is a total ban on use of mercury in the manufacturing as well as import or export of mercury products. The ban is efficient since January 1, 2008.[36] Lakes in Norway are already polluted by mercury.[37]

References

  • Kolev, S.T. Bates, N. Mercury (UK PID). National Poisons Information Service: Medical Toxicology Unit (London Centre).
  • Jahn, Robert G. "Physics of Electric Propulsion" McGraw-Hill Series in Missile and Space Technology, McGraw-Hill, (1968)
  1. ^ Fred Senese. Why is mercury a liquid at STP?. General Chemistry Online at Frostburg State University. Retrieved on 1 May 2007.
  2. ^ Glacial Ice Cores Reveal A Record of Natural and Anthropogenic Atmospheric Mercury Deposition for the Last 270 Years. United States Geological Survey (USGS). Retrieved on 1 May 2007.
  3. ^ What is EPA doing about mercury air emissions?. United States Environmental Protection Agency (EPA). Retrieved on 1 May 2007.
  4. ^ Rebecca Solnit (September/October 2006). Winged Mercury and the Golden Calf. Orion Magazine. Retrieved on 2007-12-03.
  5. ^ Mercury-containing Products. United States Environmental Protection Agency (EPA). Retrieved on 1 May 2007.
  6. ^ Clean Air Mercury Rule. United States Environmental Protection Agency (EPA). Retrieved on 1 May 2007.
  7. ^ Introduction. Y-12 Mercury Task Force Files: A Guide to Record Series of the Department of Energy and its Contractors. Department of Energy.
  8. ^ FDA. Thimerosal in Vaccines. Retrieved on 25 October 2006.
  9. ^ Tor Eigeland. "The City of Al-Zahra". Saudi Aramco World 27 (5) Retrieved on 1 May 2007.
  10. ^ "World's most precise clock developed", BBC, 2001-07-12. Retrieved on 2007-05-01. 
  11. ^ (July 23, 2001) "NIST New Atomic Clock Could Be 1,000 Times Better Than Today’s Best". NIST update Retrieved on 1 May 2007.
  12. ^ Concise Inorganic Chemistry- J.D.Lee
  13. ^ The CRB Commodity Yearbook (annual) 2000, p. 173, ISSN 1076-2906
  14. ^ a b Leopold, Barry R. (2002). "Chapter 3: Manufacturing Processes Involving Mercury" Use and Release of Mercury in the United States. National Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio. Retrieved on 1 May 2007.
  15. ^ Chlorine Online Diagram of mercury cell process. Euro Chlor. Retrieved on 2006-09-15.
  16. ^ Statement on Dental Amalgam. American Dental Association. Retrieved on 1 May 2007.
  17. ^ Pimple, K.D. Pedroni, J.A. Berdon, V. (2002, July 09). Syphilis in history. Poynter Center for the Study of Ethics and American Institutions at Indiana University-Bloomington. Retrieved on April 17, 2005.
  18. ^ Hillary Mayell (July 17, 2001). "Did Mercury in "Little Blue Pills" Make Abraham Lincoln Erratic?". National Geographic Retrieved on 1 May 2007.
  19. ^ Parker SK, Schwartz B, Todd J, Pickering LK (2004). "Thimerosal-containing vaccines and autistic spectrum disorder: a critical review of published original data". Pediatrics 114 (3): 793–804. doi:10.1542/peds.2004-0434. PMID 15342856. Erratum (2005). Pediatrics 115 (1): 200. doi:10.1542/peds.2004-2402 PMID 15630018.
  20. ^ Thimerosal in vaccines. Center for Biologics Evaluation and Research, U.S. Food and Drug Administration (2007-09-06). Retrieved on 2007-10-01.
  21. ^ Two States Pass First-time Bans on Mercury Blood Pressure Devices. Health Care Without Harm (June 2, 2003). Retrieved on 1 May 2007.
  22. ^ Title 21—Food and Drugs Chapter I—Food and Drug Administration Department of Health and Human Services Subchapter D—Drugs for Human Use Code of federal regulations. United States Food and Drug Administration. Retrieved on 1 May 2007.
  23. ^ Mercury: Spills, Disposal and Site Cleanup. Environmental Protection Agency. Retrieved on 2007-08-11.
  24. ^ Ngim CH, Foo SC, Boey KW, and Keyaratnam J (1992). "Chronic neurobehavioral effects of elemental mercury in dentists". British Journal of Industrial Medicine 49: 782-790.
  25. ^ Liang YX, Sun RK, Chen ZQ, and Li LH. "Psychological effects of low exposure to mercury vapor: Application of computer-administered neurobehavioral evaluation system". Environmental Research 60: 320-327.
  26. ^ McFarland, RB and H. Reigel. J Occup Med. 1978 Aug;20(8):532-4.
  27. ^ WHO (1976) Environmental Health Criteria 1: Mercury, Geneva, World Health Organization, 131 pp.
  28. ^ WHO. Inorganic mercury. Environmental Health Criteria 118. World Health Organization, Geneva, 1991.
  29. ^ Bluhm, RE, et. Al. Hum Exp Toxicol 1992 May;11(3):201-10.
  30. ^ FDA/EPA (2004). What You Need to Know About Mercury in Fish and Shellfish. Retrieved on 25 October 2006.
  31. ^ "FDA tests show risk in tuna", Chicago Tribune, January 27, 2006. Retrieved on 2007-05-01. 
  32. ^ Ornitz, Barry L. (15 December 1998). Aluminium Alloys and Mercury and FEATHERS. USENET sci.engr.chem. Retrieved on 2006-01-29.
  33. ^ Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment 2002/95/EC, Article 4 Paragraph 1. "Member States shall ensure that, from 1 July 2006, new electrical and electronic equipment put on the market does not contain lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) or polybrominated diphenyl ethers (PBDE)." http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2003:037:0019:0023:EN:PDF
  34. ^ Mercury compounds in European Union
  35. ^ EU bans mercury in barometers, thermometers
  36. ^ Norway to ban mercury
  37. ^ Mercury in lake sediments, map
 
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