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mercury

 
Dictionary: mer·cu·ry   (mûr'kyə-rē) pronunciation
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n.
  1. (Symbol Hg) A silvery-white poisonous metallic element, liquid at room temperature and used in thermometers, barometers, vapor lamps, and batteries and in the preparation of chemical pesticides. Atomic number 80; atomic weight 200.59; melting point −38.87°C; boiling point 356.58°C; specific gravity 13.546 (at 20°C); valence 1, 2. Also called quicksilver.
  2. Temperature: The mercury had fallen rapidly by morning.
  3. Any of several weedy plants of the genera Mercurialis or Acalypha.

[Middle English mercurie, from Medieval Latin mercurius, from Latin Mercurius, Mercury.]


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Britannica Concise Encyclopedia: mercury
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Metallic chemical element, chemical symbol Hg, atomic number 80. Mercury is the only elemental metal that is liquid at ordinary temperatures, with a freezing point of -38 °F (-39 °C) and a boiling point of 674 °F (356.9 °C). Silvery white, dense, toxic (see mercury poisoning), and a good conductor of electricity, mercury is occasionally found free in nature but usually occurs as the red sulfide ore, cinnabar (HgS). It has many uses — in dental and industrial amalgams, as a catalyst, in electrical and measuring apparatus and instruments (e.g., thermometers), as the cathode in electrolytic cells, in mercury-vapour lamps, and as a coolant and neutron absorber in nuclear power plants. Many of mercury's compounds, in which it has valence 1 or 2, are pigments, pesticides, and medicinals. It is a dangerous pollutant because it concentrates in animal tissues in increasing amounts up the food chain.

For more information on mercury, visit Britannica.com.

How Products are Made: How is mercury made?
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Background

Mercury is one of the basic chemical elements. It is a heavy, silvery metal that is liquid at normal temperatures. Mercury readily forms alloys with other metals, and this makes it useful in processing gold and silver. Much of the impetus to develop mercury ore deposits in the United States came after the discovery of gold and silver in California and other western states in the 1800s. Unfortunately, mercury is also a highly toxic material, and as a result, its use has severely declined over the past 20 years. Its principal applications are in the production of chlorine and caustic soda, and as a component of many electrical devices, including fluorescent and mercury-vapor lamps.

Mercury has been found in Egyptian tombs dating to about 1500 B.C., and it was probably used for cosmetic and medicinal purposes even earlier. In about 350 B.C., the Greek philosopher and scientist Aristotle described how cinnabar ore was heated to extract mercury for religious ceremonies. The Romans used mercury for a variety of purposes and gave it the name hydrargyrum, meaning liquid silver, from which the chemical symbol for mercury, Hg, is derived.

Demand for mercury greatly increased in 1557 with the development of a process that used mercury to extract silver from its ore. The mercury barometer was invented by Torricelli in 1643, followed by the invention of the mercury thermometer by Fahrenheit in 1714. The first use of a mercury alloy, or amalgam, as a tooth filling in dentistry was in 1828, although concerns over the toxic nature of mercury prevented the widespread use of this new technique. It wasn't until 1895 that experimental work by G.V. Black showed that amalgam fillings were safe, although 100 years later scientists were still debating that point.

Mercury found its way into many products and industrial applications after 1900. It was commonly used in batteries, paints, explosives, light bulbs, light switches, pharmaceuticals, fungicides, and pesticides. Mercury was also used as part of the processes to produce paper, felt, glass, and many plastics.

In the 1980s, increasing understanding and awareness of the harmful health and environmental effects of mercury started to greatly outweigh its benefits, and usage began to drop sharply. By 1992, its use in batteries had dropped to less than 5% of its level in 1988, and overall use in electrical devices and light bulbs had dropped 50% in the same period. The use of mercury in paints, fungicides, and pesticides has been banned in the United States, and its use in the paper, felt, and glass-manufacturing processes has been voluntarily discontinued.

Worldwide, production of mercury is limited to only a few countries with relaxed environmental laws. Mercury mining has ceased altogether in Spain, which until 1989 was the world's largest producer. In the United States, mercury mining has also stopped, although small quantities of mercury are recovered as part of the gold refining process to avoid environmental contamination. China, Russia (formerly the USSR), Mexico, and Algeria were the largest producers of mercury in 1992.

Raw Materials

Mercury is rarely found by itself in nature. Most mercury is chemically bound to other materials in the form of ores. The most common ore is red mercury sulfide (HgS), also known as cinnabar. Other mercury ores include corderoite (Hg3S2Cl2), livingstonite (HgSb4S8), montroydite (HgO), and calomel (HgCl). There are several others. Mercury ores are formed underground when warm mineral solutions rise towards the earth's surface under the influence of volcanic action. They are usually found in faulted and fractured rocks at relatively shallow depths of 3-3000 ft (1-1000 m).

Other sources of mercury include the dumps and tailing piles of earlier, less-efficient mining and processing operations.

The Manufacturing
Process

The process for extracting mercury from its ores has not changed much since Aristotle first described it over 2,300 years ago. Cinnabar ore is crushed and heated to release the mercury as a vapor. The mercury vapor is then cooled, condensed, and collected. Almost 95% of the mercury content of cinnabar ore can be recovered using this process.

Here is a typical sequence of operations used for the modern extraction and refining of mercury.

Mining

Cinnabar ore occurs in concentrated deposits located at or near the surface. About 90% of these deposits are deep enough to require underground mining with tunnels. The remaining 10% can be excavated from open pits.

  • Cinnabar is dislodged from the surrounding rocks by drilling and blasting with explosives or by the use of power equipment. The ore is brought out of the mine on conveyor belts or in trucks or trains.

Roasting

Because cinnabar ore is relatively concentrated, it can be processed directly without any intermediate steps to remove waste material.

  • The ore is first crushed in one or more cone crushers. A cone crusher consists of an interior grinding cone that rotates on an eccentric vertical axis inside a fixed outer cone. As the ore is fed into the top of the crusher, it is squeezed between the two cones and broken into smaller pieces.
  • The crushed ore is then ground even smaller by a series of mills. Each mill consists of a large cylindrical container laying on its side and rotating on its horizontal axis. The mill may be filled with short lengths of steel rods or with steel balls to provide the grinding action.
  • The finely powdered ore is fed into a furnace or kiln to be heated. Some operations use a multiple-hearth furnace, in which the ore is mechanically moved down a vertical shaft from one ledge, or hearth, to the next by slowly rotating rakes. Other operations use a rotary kiln, in which the ore is tumbled down the length of a long, rotating cylinder that is inclined a few degrees off horizontal. In either case, heat is provided by combusting natural gas or some other fuel in the lower portion of the furnace or kiln. The heated cinnabar (HgS) reacts with the oxygen (02) in the air to produce sulfur dioxide (SO2), allowing the mercury to rise as a vapor. This process is called roasting.

Condensing

  • The mercury vapor rises up and out of the furnace or kiln along with the sulfur dioxide, water vapor, and other products of combustion. A considerable amount of fine dust from the powdered ore is also carried along and must be separated and captured.
  • The hot furnace exhaust passes through a water-cooled condenser. As the exhaust cools, the mercury, which has a boiling point of 675° F (357° C), is the first to condense into a liquid, leaving the other gases and vapors to be vented or to be processed further to reduce air pollution.
  • The liquid mercury is collected. Because mercury has a very high specific gravity, any impurities tend to rise to the surface and form a dark film or scum. These impurities are removed by filtration, leaving a liquid mercury that is about 99.9% pure. The impurities are treated with lime to separate and capture any mercury, which may have formed compounds.

Refining

Most commercial-grade mercury is 99.9% pure and can be used directly from the roasting and condensing process. Higher purity mercury is needed for some limited applications and must be refined further. This ultrapure mercury commands a premium price.

  • Higher purity can be obtained through several refining methods. The mercury may be mechanically filtered again, and certain impurities may be removed through oxidation with chemicals or air. In some cases the mercury is refined through an electrolytic process, in which an electric current is passed through a tank of liquid mercury to remove the impurities. The most common refining method is triple distillation, in which the temperature of the liquid mercury is carefully raised until the impurities either evaporate or the mercury itself evaporates, leaving the impurities behind. This distillation process is performed three times, with the purity increasing each time.

Shipping

  • Commercial-grade mercury is poured into wrought-iron or steel flasks and sealed. Each flask contains 76 lb (34.5 kg) of mercury. Higher purity mercury is usually sealed in smaller glass or plastic containers for shipment.

Quality Control

Commercial-grade mercury with 99.9% purity is called prime virgin-grade mercury. Ultrapure mercury is usually produced by the triple-distillation method and is called triple-distilled mercury.

Quality control inspections of the roasting and condensing process consist of spot checking the condensed liquid mercury for the presence of foreign metals, since those are the most common contaminants. The presence of gold, silver, and base metals is detected using various chemical-testing methods.

Triple-distilled mercury is tested by evaporation or spectrographic analysis. In the evaporation method, a sample of mercury is evaporated, and the residue is weighed. In the spectrographic analysis method, a sample of mercury is evaporated, and the residue is mixed with graphite. Light coming from the resulting mixture is viewed with a spectrometer, which separates the light into different color bands depending on the chemical elements present.

Health and Environmental Effects

Mercury is highly toxic to humans. Exposure may come from inhalation, ingestion, or absorption through the skin. Of the three, inhalation of mercury vapor is the most dangerous. Short-term exposure to mercury vapor can produce weakness, chills, nausea, vomiting, diarrhea, and other symptoms within a few hours. Recovery is usually complete once the victim is removed from the source. Long-term exposure to mercury vapor produces shaking, irritability, insomnia, confusion, excessive salivation, and other debilitating effects.

In normal situations, most exposure to mercury comes from the ingestion of certain foods, such as fish, in which the mercury has accumulated at high levels. Although mercury is not absorbed in great quantities when passing through the human digestive system, ingestion over a long period of time has been shown to have cumulative effects.

In industrial situations, mercury exposure is a far more serious hazard. Mining and processing mercury ore can expose workers to mercury vapor as well as to direct contact with the skin. The production of chlorine and caustic soda can also cause significant mercury exposure hazards. Dentists and dental assistants can be exposed to mercury while preparing and placing mercury amalgam fillings.

Because mercury poses a serious health hazard, its use and release to the environment has come under increasingly tight restrictions. In 1988, it was estimated that 24 million lb/yr (11 million kglyr) of mercury were released into the air, land, and water worldwide as the result of human activities. This included mercury released by mercury mining and refining, various manufacturing operations, the combustion of coal, the discarding of municipal refuse and sewage sludge, and other sources.

In the United States, the Environmental Protection Agency (EPA) has banned the use of mercury for many applications. The EPA has set a goal of reducing the level of mercury found in municipal refuse from 1.4 million Ib/yr (0.64 million kg/yr) in 1989 to 0.35 million lb/yr (0.16 million kg/yr) by 2000. This is to be accomplished by decreasing the use of mercury in products and increasing the diversion of mercury from municipal refuse through recycling.

The Future

Mercury is still an important component in many products and processes, although its use is expected to continue to decline. Improved handling and recycling of mercury are expected to significantly reduce its release to the environment and thereby reduce its health hazard.

Where to Learn More

Books

Brady, George S., Henry R. Clauser, and John A. Vaccari. Materials Handbook, 14th Edition. McGraw-Hill, 1997.

Heiserman, David L. Exploring Chemical Elements and Their Compounds. TAB Books, 1992.

Kroschwitz, Jacqueline I., executive editor, and Mary Howe-Grant, editor. Encyclopedia of Chemical Technology, 4th edition. John Wiley and Sons, Inc., 1993.

Stwertka, Albert. A Guide to the Elements. Oxford University Press, 1996.

Periodicals

Raloff, J. "Mercurial Airs: Tallying Who's to Blame." Science News (February 19, 1994): 119.

Spencer, Peter, and G. Murdoch. "Mercury in Paint." Consumers' Research Magazine (January 1991): 2.

Stone, R. "Mercurial Debate." Science (March 13, 1992): 1356-1357.

Other

http://www.intercorr.com/periodic/80.htm [This website contains a summary of the history, sources, properties, and uses of mercury.]

[Article by: Chris Cavette]


Sci-Tech Encyclopedia: Mercury
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A chemical element, Hg, atomic number 80 and atomic weight 200.59. Mercury is a silver-white liquid at room temperature (melting point −38.89°C or −37.46°F); it boils at 357.25°C (675.05°F) under atmospheric pressure. It is a noble metal that is soluble only in oxidizing solutions. Solid mercury is as soft as lead. The metal and its compounds are very toxic. With some metals (gold, silver, platinum, uranium, copper, lead, sodium, and potassium, for example) mercury forms solutions called amalgams. See also Transition elements.

In its compounds, mercury is found in the 2+, 1+, and lower oxidation states, for example, HgCl2, Hg2Cl2, or Hg3(AsF6)2. Often the mercury atoms are doubly covalently bonded, for example, ClHgCl or ClHgHgCl. Some mercury(II) salts, for example, Hg(NO3)2 or Hg(ClO4)2, are quite soluble in water and dissociate normally. The aqueous solutions of these salts react as strong acids because of hydrolysis. Other mercury(II) salts, for example, HgCl2 or Hg(CN)2, also dissolve in water, but exist in solution as only slightly dissociated molecules. There are compounds in which mercury atoms are bound directly to carbon or nitrogen atoms, for example, H3CHgCH3 or H3CCONHHgNHCOCH3. In complex compounds, for example, K2(HgI4), mercury often has three or four bonds.

Metallic mercury is used as a liquid contact material for electrical switches, in vacuum technology as the working fluid of diffusion pumps, for the manufacture of mercury-vapor rectifiers, thermometers, barometers, tachometers, and thermostats, and for the manufacture of mercury-vapor lamps. It finds application for the manufacture of silver amalgams for tooth fillings in dentistry. Of importance in electrochemistry are the standard calomel electrode, used as the reference electrode for the measurement of potentials and for potentiometric titrations, and the Weston standard cell.

Mercury is commonly found as the sulfide, HgS, frequently as the red cinnabar and less often as the black metacinnabar. A less common ore is the mercury(I) chloride. Occasionally the mercury ore contains small drops of metallic mercury.

The surface tension of liquid mercury is 484 dynes/cm, six times greater than that of water in contact with air. Hence, mercury does not wet surfaces with which it is in contact. In dry air metallic mercury is not oxidized. After long standing in moist air, however, the metal becomes coated with a thin layer of oxide. In air-free hydrochloric acid or in dilute sulfuric acid, the metal does not dissolve. Conversely, it is dissolved by oxidizing acids (nitric acid, concentrated sulfuric acid, and aqua regia).

Encyclopedia of Public Health: Mercury
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Mercury (Hg) is a naturally occurring silvery metal that has been associated with adverse health effects throughout history. Elemental mercury is a liquid at room temperature, and, because of this, Aristotle named mercury "quicksilver." There are three forms of mercury: elemental mercury (Hg0), organic mercury (e.g., methylmercury), and inorganic mercury (e.g., Hg+, Hg2+). Many different organic and inorganic mercury compounds are found in nature because of mercury's ability to form covalent or ionic bonds with other chemicals. Mercury has numerous commercial uses—including its use in the extraction of gold from ores—and is an ingredient in alkaline batteries (approximately 0.025% of battery content), mercury vapor lamps, thermostats, and mercury amalgam fillings (in the United States, 50% of a dental filling is made of mercury). Humans can be exposed to mercury compounds via the oral, inhalation, and dermal routes. The primary source of exposure to mercury compounds is attributed to the ingestion of fish and other seafood (marine mammals, crustaceans) that have bioaccumulated mercury compounds. Dental amalgams, which leach mercury, are another source.

Adverse health effects from elemental and inorganic mercury compounds have been observed, particularly in occupational settings. Health consequences commonly observed from exposure to compounds such as elemental mercury vapor and mercuric chloride include tremors, bleeding gums, abdominal pain, vomiting, and kidney damage.

Health effects from organic mercury compounds have also been well-documented, primarily because of the tragic mass poisonings from organic mercurials in locations such as Minamata, Japan, and in Iraq. These mass poisonings were primarily associated with central nervous system toxicity and death. Adverse health effects observed in poisoned individuals and their offspring included ataxia, dysarthria, impaired vision and hearing, and death. Methylmercury is particularly toxic because 95 percent of an ingested dose is absorbed into the bloodstream and can cross the blood-brain and placental barriers, causing adult and fetal neurotoxicity. One of the reasons that offspring are particularly susceptible is that methylmercury can accumulate at 30 percent higher levels in fetal red blood cells than in maternal red blood cells. Besides damaging the brain and peripheral nervous system, methylmercury may also adversely affect the adult and fetal cardiovascular systems.

Research continues to be performed on the potential neurodevelopment effects of ingesting low levels of mercury in seafood. Three particularly important, ongoing studies involve residents of New Zealand and the Seychelles and Faroe Islands who consume significant portions of seafood as part of their normal diets. Analyses performed to date on mother-offspring pairs from the Seychelles identified adverse neurodevelopmental impact in offspring attributable to maternal methylmercury exposure from seafood. Mild developmental effects were also reported among offspring of New Zealand and Faroe Island residents who ingested seafood containing relatively high levels of methylmercury. These studies are particularly pertinent to assessing potential health effects among Native Arctic populations who consume marine mammals (beluga whales, ringed seals) as part of their normal diet. An increased level of mercury has been noted in the Arctic environment since the 1970s, possibly due to anthropogenic sources such as fossil fuel combustion, or possibly from increased natural releases of mercury from geologic sources. It is hypothesized that the cold Arctic climate acts as a sink for mercury; a particularly troublesome prospect for Native Arctic populations who continue to consume mercury-laden mammals and seafood.

(SEE ALSO: Environmental Determinants of Health; Foods and Diets; Heavy Metals; Minamata Disease; Occupational Safety and Health)

Bibliography

Agency for Toxic Substances and Disease Registry (1999). Toxicological Profile for Mercury (Update). Washington, DC: U.S. Department of Health and Human Services.

Arctic Monitoring and Assessment Programme (1999). Arctic Pollution Issues: A State of the Arctic Environment Report. Available at http://www.amap.no.

National Research Council (2000). Toxicological Effects of Methyl Mercury. Washington, DC: Committee on the Toxicological Effects of Mercury. Board on Environmental Studies and Toxicology. Commission on Life Sciences.

Tenenbaum, D. J. (1998). "Northern Overexposure." Environmental Health Perspective 106(2): A64–A69.

U.S. Environmental Protection Agency (1997). Report to Congress on Mercury. Available at http://www.epa.gov/oar/mercury.html.

World Health Organization (1990). Methyl Mercury, Vol. 101. Geneva: International Programme on Chemical Safety, WHO.

—— (1990). Inorganic Mercury, Vol. 118. Geneva: International Programme on Chemical Safety, WHO.

— MARGARET H. WHITAKER; BRUCE A. FOWLER


 
Columbia Encyclopedia: mercury
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mercury or quicksilver [from the Roman god Mercury], metallic chemical element; symbol Hg [Lat. hydrargyrum=liquid silver]; at. no. 80; at. wt. 200.59; m.p. −38.842°C; b.p. 356.58°C; sp. gr. 13.55 at 20°C; valence +1 or +2. Mercury was discovered in antiquity, and was known to the ancient Chinese, Hindus, and Egyptians, but was not recognized as an element. It was used as a medicine by Paracelsus. It was first recognized as a chemical element (in the modern sense) by A. L. Lavoisier about the end of the 18th cent.

Properties

Mercury is the only common metal existing as a liquid at ordinary temperatures. The pure metal has a silver-white mirrorlike appearance. Mercury is below cadmium in Group 2 of the periodic table. It is relatively stable in dry air, but in moist air slowly forms a gray oxide coating. Mercury has high surface tension; when spilled, it breaks up into tiny beads which often become lodged in cracks.

Compounds

Mercury forms numerous compounds, assuming +1 valence in mercurous compounds and +2 valence in mercuric compounds. Mercury is not attacked by dilute hydrochloric or sulfuric acid. It reacts with hot nitric acid to form mercuric nitrate, Hg(No3)2. An excess of mercury reacts with nitric acid to form mercurous nitrate, HgNO3. Mercury reacts with hot concentrated sulfuric acid to form mercuric sulfate, HgSO4; with excess mercury, mercurous sulfate, Hg2SO4, is formed. Mercury reacts directly with the halogens to form mercuric salts. At elevated temperatures mercury reacts slowly with oxygen to form mercuric oxide, HgO. A mercurous oxide may be formed chemically but is unstable, decomposing to a mixture of mercury and mercuric oxide.

Natural Occurrence and Uses

Mercury occurs uncombined in nature to a limited extent. The metal is obtained commercially from cinnabar, a mercuric sulfide ore; it is easily separated by roasting the ore in air. The metal is usually purified by repeated vacuum distillation.

Mercury metal has many uses. Because of its high density, it is used in barometers and manometers. Because it has a high rate of thermal expansion that is fairly constant over a wide temperature range, it is used extensively in thermometers. Mercury is important as a liquid contact material for electric switches. It is used in mercury-vapor lamps, which emit light rich in ultraviolet radiation; various kinds of such lamps are used for street lighting, as sun lamps, and in "black lights" (see lighting). Mercury is used as an electrode in the production of chlorine and sodium hydroxide. It is also used in certain electric batteries. With some other metals mercury forms a special type of alloy called an amalgam; a special amalgam (mostly mercury, silver, and tin) is used in dentistry for filling teeth.

Mercury compounds have many uses. Calomel (mercurous chloride, Hg2Cl2) is used as a standard in electrochemical measurements and in medicine as a purgative. Mercuric chloride (corrosive sublimate, HgCl2) is used as an insecticide, in rat poison, and as a disinfectant. Mercuric oxide is used in skin ointments. Mercuric sulfate is used as a catalyst in organic chemistry. Vermilion, a red pigment, is mercuric sulfide; another crystalline form of the sulfide (also used as a pigment) is black. Mercury fulminate, Hg(CNO)2, is used as a detonator. Mercury forms many organic compounds. Mercurochrome (in 2% aqueous solution) is used in medicine as a topical antiseptic. Mercury compounds were formerly used in the treatment of syphilis.

See also mercury poisoning.

Food & Culture Encyclopedia: Mercury
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Possible carcinogen. May cause brain, kidney, or fetal damage. Highest concentration is in fish. Grains and meat account for half of the dietary intake.

Occultism & Parapsychology Encyclopedia: Mercury
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Also popularly known as quicksilver. Known for many centuries, the metal has played an important part in the history of alchemy. In its refined state it forms a coherent, very mobile liquid that at ordinary room temparature was a well-known unique substance. The early alchemists believed that nature formed all metals from mercury, and that it was a living and feminine principle. It went through many processes, and the metal that evolved was pure or impure according to the locality of its production.

The mercury of the philosophers' stone needed to be a purified and revivified form of the ordinary metal; as the Arabian alchemist Geber stated in his Summa perfectionis: "Mercury, taken as Nature produces it, is not our material or our physic, but it must be added to."

Mercury seems to have been an entirely different substance than any ordinary metal or chemical element. Depending upon one's interprepation of alchemy as a system of spiritual growth, mercury could be one of several substances or states of consciousness.

Science Dictionary: mercury
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In chemistry, a heavy, silvery metallic element, a liquid at normal temperatures. Mercury expands or contracts rapidly in response to changes in temperature and therefore was once widely used in thermometers.

  • The term mercury is used figuratively in such expressions as “The mercury's rising” to mean that the temperature is going up.

    • Rock & Mineral Guide: mercury
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    Hg
    Hexagonal -- rhombohedral

    Environment

    Often in or close to volcanic regions, in low-temperature veins.

    Crystal description

    Mercury is the only metal that is liquid at normal temperatures. It does not become solid until the temperature falls to -40°F (which equals -40°C). Hence, we find it in nature only in the form of liquid metallic drops or as thin metallic films on small cavities and surfaces of rocks.

    Physical properties

    Silvery white. Luster metallic; specific gravity 13.6. Liquid, whence the name "quicksilver."

    Composition

    Mercury, sometimes with a little silver. Poisonous and instantly amalgamates with gold, so caution is recommended in any utilization or testing. Avoid breathing any fumes.

    Tests

    Volatilizes (disappears as fumes) under a blowpipe; dissolves in nitric acid.

    Distinguishing characteristics

    The liquid droplets cannot be confused with anything else. The silvery films are more confusing but can easily be burned off with a blowpipe. The usual association with cinnabar (HgS) helps in identification.

    Occurrence

    Native mercury is almost invariably associated with the red sulfide of mercury, cinnabar. It is often found in cavities and cracks in cinnabar-impregnated rocks and sometimes forms as a result of the weathering of cinnabar, which leaves little holes lined with drops and films of mercury. Mercury and cinnabar will be found in rocks of regions where there has been some volcanic or hot-spring activity, though the deposits may lie some distance from any obvious source.

    Remarks

    Found in the U.S. in California, Oregon, Texas, and Arkansas. The most notable occurrences are the Almadén (Spain) and the Idrija, in the former Yugoslavia, cinnabar mines. It is never an ore alone, but often enriches the mercury sulfide ores.


    Veterinary Dictionary: mercury
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    A chemical element, atomic number 80, atomic weight 200.59, symbol Hg.
    Mercury forms two sets or classes of compounds: mercurous, in which a single atom of mercury combines with a monovalent radical, and mercuric, in which a single atom of mercury combines with a bivalent radical. Mercury and its salts have been employed therapeutically as purgatives; as alternatives in chronic inflammations; and as intestinal antiseptics, disinfectants and astringents. They are absorbed by the skin and mucous membranes, causing chronic mercurial poisoning, or hydrargyria. The mercuric salts are more soluble and irritant than the mercurous. See also mercurous, mercuric.

    • ammoniated m. — used as an antiseptic skin and ophthalmic ointment.
    • organic m. — includes the fungistats phenylmercurials, ethyl and methyl mercurials, e.g. methoxyethylmercury silicate; poisonous to animals and cause unacceptable residues in animal products.
    • m. plant — mercurialis annua.
    • m. poisoning — by inorganic compounds causes gastritis and kidney damage manifested by diarrhea and terminal uremia. Organic mercury compounds were until recently extensively used as fungistatic agents in stored grain. They cause poisoning manifested by nervous signs, including incoordination, blindness and recumbency. With larger doses there are convulsions.
    Wikipedia: Mercury (element)
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    gold ← Mercury → thallium
    Cd
    ↑
    Hg
    ↓
    Uub
    Appearance
    silvery
    General properties
    Name, symbol, number Mercury, Hg, 80
    Element category transition metal
    Group, period, block 12, 6, d
    Standard atomic weight 200.59(2) g·mol−1
    Electron configuration [Xe] 4f14 5d10 6s2
    Electrons per shell 2, 8, 18, 32, 18, 2 (Image)
    Physical properties
    Phase liquid
    Density (near r.t.) (liquid) 13.534 g·cm−3
    Melting point 234.32 K, -38.83 °C, -37.89 °F
    Boiling point 629.88 K, 356.73 °C, 674.11 °F
    Critical point 1750 K, 172.00 MPa
    Heat of fusion 2.29 kJ·mol−1
    Heat of vaporization 59.11 kJ·mol−1
    Specific 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
    Oxidation states 4, 2 (mercuric), 1 (mercurous)
    (mildly basic oxide)
    Electronegativity 2.00 (Pauling scale)
    Ionization energies 1st: 1007.1 kJ·mol−1
    2nd: 1810 kJ·mol−1
    3rd: 3300 kJ·mol−1
    Atomic radius 151 pm
    Covalent radius 132±5 pm
    Van der Waals radius 155 pm
    Miscellanea
    Crystal structure rhombohedral
    Magnetic ordering diamagnetic
    Electrical resistivity (25 °C) 961nΩ·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
    Most stable 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% 196Hg is stable with 116 neutrons
    197Hg syn 64.14 h ε 0.600 197Au
    198Hg 9.97% 198Hg is stable with 118 neutrons
    199Hg 16.87% 199Hg is stable with 119 neutrons
    200Hg 23.1% 200Hg is stable with 120 neutrons
    201Hg 13.18% 201Hg is stable with 121 neutrons
    202Hg 29.86% 202Hg is stable with 122 neutrons
    203Hg syn 46.612 d β− 0.492 203Tl
    204Hg 6.87% 204Hg is stable with 124 neutrons
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    Mercury (pronounced /ˈmɜrkjʊri/ MER-kyə-ree), also called quicksilver (/ˈkwɪksɪlvər/) or hydrargyrum (/haɪˈdrɑrdʒɨrəm/ hye-DRAR-ji-rəm), is a chemical element with the symbol Hg (Latinized Greek: hydrargyrum, meaning watery or liquid silver) and atomic number 80. A heavy, silvery d-block metal, mercury is one of six chemical elements that are liquid at or near room temperature and pressure,[1][2] the others being caesium, francium, gallium, bromine, and rubidium. Mercury is the only metal that is liquid at standard conditions for temperature and pressure. With a melting point of −38.83 °C and boiling point of 356.73 °C, mercury has one of the narrowest ranges of its liquid state of any metal.

    Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide), which is the source of the red pigment vermilion, and is mostly obtained by reduction from cinnabar. Cinnabar is highly toxic by ingestion or inhalation of the dust. Mercury poisoning can also result from exposure to soluble forms of mercury (such as mercuric chloride or methylmercury), inhalation of mercury vapor, or eating fish contaminated with mercury.

    Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, and other scientific apparatus, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor of alcohol-filled, digital, or thermistor-based instruments. It remains in use in a number of other ways in scientific and scientific research applications, and in amalgam material for dental restoration. It is used in lighting; electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce, making visible light.

    Contents

    Properties

    Physical

    A pound coin (density ~7.6 g/cm3) floats in mercury due to the combination of the buoyant force and surface tension.

    Mercury is a heavy, silvery-white metal. As compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity. [3] Mercury has an exceptionally low melting temperature for a d-block metal. A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s subshells. As such configuration strongly resists removal of an electron, mercury behaves similarly to noble gas elements, which form weakly bonded and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus (see lanthanide contraction). The absence of a filled inner f shell is the reason for the much higher melting temperature of cadmium. Metals such as gold have atoms with one less 6s electron than mercury. Those electrons are more easily removed and are shared between the gold atoms forming relatively strong metallic bonds.[2][4] At the melting point (-38.86 °C) its density is[5] 14.1 g/cm3.

    Reactivity and compounds

    See also: Category:Mercury compounds

    Mercury dissolves to form amalgams with gold, zinc and many other metals. Because iron is an exception, iron flasks have been traditionally used to trade mercury. Other metals that do not form amalgams with mercury include tantalum, tungsten and platinum. When heated, mercury also reacts with oxygen in air to form mercury oxide, which then can be decomposed by further heating to higher temperatures.[6]

    Since it is below hydrogen in the reactivity series of metals, mercury does not react with most acids, such as dilute sulfuric acid, though oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate, nitrate, and chloride salts. Like silver, mercury reacts with atmospheric hydrogen sulfide. Mercury even reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury vapors (spill kits also use activated charcoal and powdered zinc).[6]

    Some important mercury salts include:

    In these compounds, mercury displays two oxidation states: +1 and +2. The +1 state oxidation involves the dimeric cation, Hg2+2. Solutions of Hg2+2 are in equilibrium with Hg2+ and metallic mercury:

    Hg2+ + Hg is in equilibrium with Hg2+2

    This equilibrium causes solutions of Hg2+2 to have a small amount of Hg2+ present. Consuming the Hg2+ by another reaction, such as complexation with strong ligands or precipitation of an insoluble salt, will cause all the Hg2+2 to fully disproportionate to Hg2+ and elemental mercury.[9]

    Besides Hg2+2, mercury also forms other mercury polycations such as Hg2+3.[10]

    Higher oxidation states of mercury were confirmed in September 2007, with the synthesis of mercury(IV) fluoride (HgF4) using matrix isolation techniques.[11]

    Laboratory tests have found that an electrical discharge causes the noble gases to combine with mercury vapor. These compounds are held together with van der Waals forces and result in Hg·Ne, Hg·Ar, Hg·Kr, and Hg·Xe (see exciplex). Organic mercury compounds are also important. Methylmercury is a dangerous compound that is widely found as a pollutant in water bodies and streams.[12]

    Mercury and aluminium

    Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. However, when the amalgam is exposed to air, the aluminium oxidizes, leaving mercury behind. The oxide flakes away, exposing more mercury amalgam, which repeats the process. This process continues until the supply of amalgam is exhausted. Because this process 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.[13]

    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.[13][14] 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 an amalgam with exposed aluminium parts in the aircraft.[13]

    Isotopes

    Main article: Isotopes of mercury

    There are seven stable isotopes of mercury with 202Hg being the most abundant (29.86%). The longest-lived radioisotopes are 194Hg with a half-life of 444 years, and 203Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. 199Hg and 201Hg are the most often studied NMR-active nuclei, having spins of 1⁄2 and 3⁄2 respectively.[3]

    History

    The symbol for the planet Mercury (☿) has been used since ancient times to represent the element

    Mercury was known to the ancient Chinese[15] and was found in Egyptian tombs that date from 1500 BC.[16] In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. One of China's emperors, Qín Shǐ Huáng Dì — allegedly buried in a tomb that contained rivers of flowing mercury on a model of the land he ruled, representative of the rivers of China — was killed by drinking a mercury and powdered jade mixture (causing liver failure, poisoning, and brain death) intended to give him eternal life.[17][18] The ancient Greeks used mercury in ointments; the ancient Egyptians and the Romans used it in cosmetics which sometimes deformed the face. By 500 BC mercury was used to make amalgams with other metals.[19] The Indian word for alchemy is Rasavātam which means "the way of mercury".[20]

    Alchemists thought of mercury as the First Matter from which all metals were formed. They believed that different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. The purest of these was gold, and mercury was called for in attempts at the transmutation of base (or impure) metals into gold, which was the goal of many alchemists.[21]

    Hg is the modern chemical symbol for mercury. It comes from hydrargyrum, a Latinized form of the Greek word Ύδραργυρος (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.[21]

    The mines in Almadén (Spain), Monte Amiata (Italy), and Idrija (now Slovenia) dominated the mercury production from the opening of the mine in Almadén 2500 years ago until new deposits were found at the end of the 19th century.[22]

    Occurrence

    See also: :Category:Mercury minerals and :Category:Mercury mines
    Mercury output in 2005

    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 (ppm).[23] 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 cinnabar, corderoite, livingstonite and other minerals, with cinnabar (HgS) being the most common ore. Mercury ores usually occur in very young orogenic belts where rock of high density are forced to the crust of the Earth, often in hot springs or other volcanic regions.[24]

    Beginning in 1558, with the invention of the patio process to extract silver from ore using mercury, mercury became an essential resource in the economy of Spain and its American colonies. Mercury was used to extract silver from the lucrative mines in New Spain and Peru. Initially, the Spanish Crown's mines in Almaden in Southern Spain supplied all the mercury for the colonies.[25] Mercury deposits were discovered in the New World, and more than 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. The patio process and later pan amalgamation process continued to create great demand for mercury to treat silver ores until the late 1800s.[26]

    Former mines in Italy, the United States and Mexico which once produced a large proportion of the world supply have now been completely mined out or, in the case of Slovenia (Idrija) and Spain (Almadén), shut down due to the fall of the price of mercury. Nevada's McDermitt Mine, the last mercury mine in the United States, closed in 1992. The price of mercury has been highly volatile over the years and in 2006 was $650 per 76-pound (34.46 kg) flask.[27]

    Mercury 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.[28] Several other countries are believed to have unrecorded production of mercury from copper electrowinning processes and by recovery from effluents.

    Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning. In China, prison labor was used by a private mining company as recently as the 1950s to create new cinnabar mercury mines. Thousands of prisoners were used by the Luo Xi mining company to establish new tunnels.[29] In addition, worker health in functioning mines is at high risk.

    The European Union directive calling for compact fluorescent bulbs to be made mandatory by 2012 has encouraged China to re-open deadly cinnabar mines to obtain the mercury required for CFL bulb manufacture. As a result, new generations of Chinese, their livestock, and their crops are being poisoned, particularly in the southern cities of Foshan and Guangzhou, and in the Guizhou province in the southwest.[29]

    Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines. Water runoff from such sites is a recognized source of ecological damage. Former mercury mines may be suited for constructive re-use. For example, in 1976 Santa Clara County, California purchased the historic Almaden Quicksilver Mine and created a county park on the site, after conducting extensive safety and environmental analysis of the property.[30]

    Releases in the environment

    Amount of atmospheric mercury deposited at Wyoming's Upper Fremont Glacier over the last 270 years

    Preindustrial deposition rates of mercury from the atmosphere may be in the range of 4 ng /(1 L of ice deposit). 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.[31]

    Natural sources such as volcanoes are responsible for approximately half of atmospheric mercury emissions. The human-generated half can be divided into the following estimated percentages:[32][33][34]

    • 65% from stationary combustion, of which coal-fired power plants are the largest aggregate source (40% of U.S. mercury emissions in 1999). This includes power plants fueled with gas where the mercury has not been removed. Emissions from coal combustion are between one and two orders of magnitude higher than emissions from oil combustion, depending on the country.[32]
    • 11% from gold production. The three largest point sources for mercury emissions in the U.S. are the three largest gold mines. Hydrogeochemical release of mercury from gold-mine tailings has been accounted as a significant source of atmospheric mercury in eastern Canada.[35]
    • 6.8% from non-ferrous metal production, typically smelters.
    • 6.4% from cement production.
    • 3.0% from waste disposal, including municipal and hazardous waste, crematoria, and sewage sludge incineration. This is a significant underestimate due to limited information, and is likely to be off by a factor of two to five.
    • 3.0% from caustic soda production.
    • 1.4% from pig iron and steel production.
    • 1.1% from mercury production, mainly for batteries.
    • 2.0% from other sources.

    The above percentages are estimates of the global human-caused mercury emissions in 2000, excluding biomass burning, an important source in some regions.[32]

    Current atmospheric mercury contamination in outdoor urban air is (0.01 – 0.02 µg/m3 ) indoor concentrations are significantly elevated over outdoor concentrations, at a range of 0.0065 – 0.523 µg/m3 (average 0.069 µg/m3) [36]

    Mercury also enters into the environment through the disposal (e.g., land filling, incineration) of certain products. Products containing mercury include: auto parts, batteries, fluorescent bulbs, medical products, thermometers, and thermostats.[37] Due to health concerns (see below), toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, most 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[38] 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 and decision was made in 2008. The Clean Air Mercury Rule was struck down by a Federal Appeals Court on February 8, 2008. The rule was deemed not sufficient to protect the health of persons living near coal-fired power plants. The court opinion cited the negative impact on human health from coal fired power plants' mercury emissions documented in the EPA Study Report to Congress of 1998.[39]

    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.[40]

    One of the worst industrial disasters in history was caused by the dumping of mercury compounds into Minamata Bay, Japan. The Chisso Corporation, a fertilizer and later petrochemical company, was found responsible for polluting the bay from 1932 — 1968. It is estimated that over 3,000 people suffered various deformities, severe mercury poisoning symptoms or death from what became known as Minamata disease.[41]

    Applications

    The bulb of a mercury-in-glass thermometer

    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. A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other applications are slowly phased out due to health and safety regulations and is in some applications replaced with less toxic but considerably more expensive Galinstan alloy.

    Present use

    Medicine

    Amalgam filling
    The deep violet glow of a mercury vapor discharge in a germicidal lamp, whose spectrum is rich in invisible ultraviolet radiation.
    See also: Amalgam (dentistry)

    Mercury and its compounds have been used in medicine, 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. The element mercury is an ingredient in dental amalgams. Thiomersal (called Thimerosal in the United States) is an organic compound used as a preservative in vaccines, though this use is in decline.[42] Another mercury compound Merbromin (Mercurochrome) is a topical antiseptic used for minor cuts and scrapes is still in use in some countries.

    Mercury(I) chloride (also known as calomel or mercurous chloride) has traditionally been used as a diuretic, topical disinfectant, and laxative. Mercury(II) chloride (also known as mercuric chloride or corrosive sublimate) was once used to treat syphilis (along with other mercury compounds), although it is so toxic that sometimes the symptoms of its toxicity were confused with those of the syphilis it was believed to treat.[43] It was also used as a disinfectant. Blue mass, a pill or syrup in which mercury is the main ingredient, was prescribed throughout the 1800s for numerous conditions including constipation, depression, child-bearing and toothaches.[44] In the early 20th century, mercury was administered to children yearly as a laxative and dewormer, and it was used in teething powders for infants. The mercury-containing organohalide merbromin (sometimes sold as Mercurochrome) is still widely used but has been banned in some countries such as the U.S.[45]

    Since the 1930s some vaccines have contained the preservative thiomersal, which is metabolized or degraded to 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.[46] 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.[47]

    Mercury in the form of one of its common ores, cinnabar, remains an important component of 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. Thermometers and sphygmomanometers containing mercury were invented in the early 18th and late 19th centuries, respectively. In the early 21st century, their use is declining and has been banned in some countries, states and medical institutions. In 2002, the U.S. Senate passed legislation to phase out the sale of non-prescription mercury thermometers. In 2003, Washington and Maine became the first states to ban mercury blood pressure devices.[48] Mercury compounds are found in some over-the-counter drugs, including topical antiseptics, stimulant laxatives, diaper-rash ointment, eye drops, and nasal sprays. The FDA has “inadequate data to establish general recognition of the safety and effectiveness,” of the mercury ingredients in these products.[49] Mercury is still used in some diuretics, although substitutes now exist for most therapeutic uses.

    Cosmetics

    Mercury, as thiomersal, is widely used in the manufacture of mascara. In 2008, Minnesota became the first state in the US to ban intentionally added mercury in cosmetics, giving it a tougher standard than the federal government.[50]

    Production of chlorine and caustic soda

    Chlorine is produced from sodium chloride (common salt, NaCl) using electrolysis to separate the metallic sodium from the chlorine gas. Usually the salt is dissolved in water to produce a brine. By-products of any such chloralkali process are hydrogen (H2) and sodium hydroxide (NaOH), which is commonly called caustic soda or lye. By far the largest use of mercury[51][52] in the late 1900s was in the mercury cell process (also called the Castner-Kellner process) where metallic sodium is formed as an amalgam at a cathode made from mercury; this sodium is then reacted with water to produce sodium hydroxide.[53] Many of the industrial mercury releases of the 1900s came from this process, although modern plants claimed to be safe in this regard.[52] After about 1985, all new chloralkali production facilities that were built in the United States used either membrane cell or diaphragm cell technologies to produce chlorine.

    Gold and silver mining

    Historically, mercury was used extensively in hydraulic gold mining in order to help the gold to sink through the flowing water-gravel mixture. Thin mercury particles may form mercury-gold amalgam and therefore increase the gold recovery rates.[3] Large scale use of mercury stopped in the 1960s. However, mercury is still used in small scale, often clandestine, gold prospection. It is estimated that 45,000 metric tons of mercury used in California for placer mining have not been recovered.[54] Mercury was also used in silver mining.[55]

    Other present uses

    Skin tanner containing a low-pressure mercury vapor lamp and two infrared lamps, which act both as light source and electrical ballast
    Assorted types of fluorescent lamps.

    Gaseous mercury is used in mercury-vapor lamps and some "neon sign" type advertising signs and fluorescent lamps. Those low-pressure lamps emit very spectrally narrow lines, which are traditionally used in optical spectroscopy for calibration of spectral position. Commercial calibration lamps are sold for this purpose; however simply reflecting some of the fluorescent-lamp ceiling light into a spectrometer is a common calibration practice.[56] Gaseous mercury is also found in some electron tubes, including ignitrons, thyratrons, and mercury arc rectifiers.[57] It is also used in specialty medical care lamps for skin tanning and desinfection (see pictures).[58] Gaseous mercury is added to cold cathode argon-filled lamps to increase the ionization and electrical conductivity. An argon filled lamp without mercury will have dull spots and will fail to light correctly. Lighting containing mercury can be bombarded/oven pumped only once. When added to 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 color.[59]

    Some medical thermometers, especially those for high temperatures, are filled with mercury, however, they are gradually disappearing. In the United States, non-prescription sale of mercury fever thermometers has been banned in 2003.[60] Mercury is also found in 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.[61][62]

    Liquid mercury is a part of popular secondary reference electrode (called the calomel electrode) in electrochemistry as an alternative to the standard hydrogen electrode. The calomel electrode is used to work out the electrode potential of half cells.[63] Last, but not least, the triple point of mercury, -38.8344 °C, is a fixed point used as a temperature standard for the International Temperature Scale (ITS-90).[3]

    Proposed uses

    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.[64] 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.[65][66]

    Historic uses

    Old mercury switches
    Mercury manometer to measure pressure

    Mercury was used for preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), handheld maze games, cleaning, and road leveling devices in cars. Mercury compounds have been used in antiseptics, laxatives, antidepressants, and in antisyphilitics. It was also allegedly used by allied spies to sabotage German planes. A mercury paste was applied to bare aluminium, causing the metal to rapidly corrode. This would cause structural failures.[14]

    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 (the term "carroting" arose from this color) of the mercury compound mercuric nitrate, Hg(NO3)2·2H2O.[78] This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. 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 are said by some to have inspired the phrase "mad as a hatter", though etymological study suggests that the phrase is actually much older and unrelated to hatters - see hatter for commentary on the origin of the phrase. Lewis Carroll's "Mad Hatter" in his book Alice's Adventures in Wonderland was a play on words based on the older phrase, but the character himself does not exhibit symptoms of mercury poisoning.[79]

    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 thermometers or fluorescent light bulbs) specific cleaning procedures are used to avoid toxic exposure.[80] It can be inhaled and absorbed through the skin and mucous membranes, so containers of mercury are securely sealed to avoid spills and evaporation. Heating of mercury, or compounds of mercury that may decompose when heated, are always carried out with adequate ventilation in order to avoid exposure to mercury vapor. The most toxic forms of mercury are its organic compounds, such as dimethylmercury and methylmercury. However, inorganic compounds, such as cinnabar are also highly toxic by ingestion or inhalation of the dust.[81] Mercury can cause both chronic and acute poisoning.

    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 vapor even at low concentrations in the range 0.7–42 μg/m3.[82][83] 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.[84] 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.[85][86]

    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), British Anti-Lewisite (BAL), 2,3-dimercapto-1-propanesulfonic acid (DMPS), and dimercaptosuccinic acid (DMSA). In one small study including 11 construction workers exposed to elemental mercury, patients were treated with DMSA and NAP.[87] 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.[88]

    Fish

    Main article: Mercury in fish

    Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organic compound of mercury. Species of fish that are high on the food chain, such as shark, swordfish, king mackerel, albacore tuna, and tilefish contain higher concentrations of mercury than others. As mercury and methylmercury are fat soluble, they primarily accumulate in the viscera, although they are also found throughout the muscle tissue. When this fish is consumed by a predator, the mercury level is accumulated. Since fish are less efficient at depurating than accumulating methylmercury, fish-tissue concentrations increase over time. Thus species that are high on the food chain amass body burdens of mercury that can be ten times higher than the species they consume. This process is called biomagnification. Mercury poisoning happened this way in Minamata, Japan, now called Minamata disease. As a result, those consuming high levels of fish should be aware of the symptoms of mercury poisoning.[89]

    Regulations

    In the United States, the Environmental Protection Agency is charged with regulating and managing mercury contamination. Several laws give the EPA this authority, including the Clean Air Act, the Clean Water Act, the Resource Conservation and Recovery Act, and the Safe Drinking Water Act. Additionally, the Mercury-Containing and Rechargeable Battery Management Act, passed in 1996, phases out the use of mercury in batteries, and provides for the efficient and cost-effective disposal of many types of used batteries.[90] North America contributed approximately 11% of the total global anthropogenic mercury emissions in 1995.[91]

    In the European Union, the directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (see RoHS) bans mercury from certain electrical and electronic products, and limits the amount of mercury in other products to less than 1000 ppm.[92] There are restriction for mercury concentration in packaging (the limit is 100 ppm for sum of mercury, lead, hexavalent chromium and cadmium) and batteries (the limit is 5 ppm).[93] In July 2007, the 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 health care sector and a two year grace period for manufacturers of barometers. [94]

    Norway enacted a total ban on the use of mercury in the manufacturing and import/export of mercury products, effective January 1, 2008.[95] In 2002, several lakes in Norway were found to have a poor state of mercury pollution, with an excess of 1 mg/g of mercury in their sediment.[96]

    References

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    2. ^ a b Norrby, L.J. (1991). "Why is mercury liquid? Or, why do relativistic effects not get into chemistry textbooks?". Journal of Chemical Education 68: 110. 
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    7. ^ Banus, Mg (1941). "A design for a saturated calomel electrode". Science (New York, N.Y.) 93 (2425): 601–602. doi:10.1126/science.93.2425.601-a. PMID 17795970. 
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    Translations: Mercury
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    Home > Library > Literature & Language > Translations

    Dansk (Danish)
    1.
    n. - kviksølv

    2.
    n. - Merkur (planet)

    Nederlands (Dutch)
    kwik, Mercurius, levendigheid, boodschapper

    Français (French)
    1.
    n. - (Chim) mercure, mercure (d'un thermomètre)

    2.
    n. - (Bot) mercuriale

    Deutsch (German)
    1.
    n. - Quecksilber

    2.
    n. - (bot.) Bingelkraut

    Ελληνική (Greek)
    n. - (μυθολ., αστρον.) Ερμής, (χημ.) υδράργυρος

    Italiano (Italian)
    Mercurio

    Português (Portuguese)
    n. - mercúrio (m) (Quím.)

    Русский (Russian)
    ртуть, бог Меркурий, планета Меркурий

    Español (Spanish)
    1.
    n. - Mercurio

    2.
    n. - mercurio, azogue

    Svenska (Swedish)
    n. - kvicksilver

    中文（简体）(Chinese (Simplified))
    水银, 使者, 汞

    中文（繁體）(Chinese (Traditional))
    n. - 水銀, 使者, 汞

    한국어 (Korean)
    1.
    n. - 수은

    2.
    n. - 수성

    日本語 (Japanese)
    n. - マーキュリー, 水星

    العربيه (Arabic)
    ‏(الاسم) زئبق‏

    עברית (Hebrew)
    n. - ‮כספית (יסוד, GH, מספר אטומי 08)‬
    n. - ‮כוכב-חמה (כוכב לכת)‬

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