{{Protection padlock|small=yes}} {{Good article}} {{Redirect|Hg|other uses|HG (disambiguation){{!}}HG}} {{Use dmy dates|date=May 2017}} {{Infobox mercury}}
'''Mercury''' is a chemical element; it has symbol '''Hg''' and atomic number 80. It is commonly known as '''quicksilver'''. A heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure. As well as having the lowest freezing point, mercury has the lowest boiling point and subsequently the narrowest liquid state range of any metal at standard conditions.
Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is obtained by grinding natural cinnabar or synthetic mercuric sulfide. Exposure to mercury and mercury-containing organic compounds is toxic to the nervous system, immune system and kidneys of humans and other animals; mercury poisoning can result from exposure to water-soluble forms of mercury (such as mercuric chloride or methylmercury) either directly or through mechanisms of biomagnification.
Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices, but concerns about the element's toxicity have led to a reduction in the amount of mercury used in these instruments, or manufacturers not using it altogether. It remains in use in scientific research applications and in amalgam for dental restoration in some locales. It is also still used in fluorescent lighting, although the quantity of mercury used is now smaller. Electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light, which then causes the phosphor in the tube to fluoresce, making visible light.
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==Properties== ===Physical properties=== [[File:Pound-coin-floating-in-mercury.jpg|thumb|left|A round pound coin (density ~7.6 g/cm<sup>3</sup>) floats on mercury due to the buoyancy force upon it and appears to float higher because of the strong surface tension of the mercury.]]
Mercury is a heavy, silvery-white metal. It is the only metallic element that is known to be liquid at standard temperature and pressure;{{efn|Theoretical calculations indicate that copernicium, which lies directly beneath mercury on the periodic table, is likely a liquid at standard pressure and temperature.<ref>{{cite journal |last1=Mewes |first1=J.-M. |last2=Smits |first2=O. R. |last3=Kresse |first3=G. |last4=Schwerdtfeger |first4=P. |title=Copernicium is a Relativistic Noble Liquid |journal=Angewandte Chemie International Edition |date=2019 |volume=58 |issue=50 |pages=17964–17968 |doi=10.1002/anie.201906966 |pmid=31596013 |pmc=6916354 |bibcode=2019ACIE...5817964M }}</ref>}} the only other element that is liquid under these conditions is bromine, one of the halogens, though metals such as caesium,<!--Fr is not completely certain--> gallium, and rubidium melt just above room temperature.{{efn|A room can easily reach {{convert|29|C|K F}} to melt caesium, and {{convert|30|C|K F}} to melt gallium. However, rubidium at {{convert|39|C|K F}} is barely feasible unless on a hot summer day.}} Compared to other metals, mercury is a poor conductor of heat, but a fair conductor of electricity.<ref name="CRC">{{cite web|last=Hammond |first=C. R. |url=http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf |title=The Elements |archive-url=https://web.archive.org/web/20080626181434/http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elements.pdf |archive-date=26 June 2008}} in {{RubberBible86th}}</ref>
Mercury has a melting point of {{convert|−38.83|C|F K}} and a boiling point of {{convert|356.73|C|F K}}<ref name="Norrby">{{cite journal |last1=Norrby |first1=Lars J. |title=Why is mercury liquid? Or, why do relativistic effects not get into chemistry textbooks? |journal=Journal of Chemical Education |date=February 1991 |volume=68 |issue=2 |page=110 |doi=10.1021/ed068p110 |bibcode=1991JChEd..68..110N}}</ref><ref>{{cite web| url=http://antoine.frostburg.edu/chem/senese/101/periodic/faq/why-is-mercury-liquid.shtml| title=Why is mercury a liquid at STP?| access-date=1 May 2007| publisher=General Chemistry Online at Frostburg State University| author=Senese, F| archive-url=https://web.archive.org/web/20070404210838/http://antoine.frostburg.edu/chem/senese/101/periodic/faq/why-is-mercury-liquid.shtml| archive-date=4 April 2007| url-status=live}}</ref><ref>{{RubberBible86th|pages=4.125–4.126}}</ref> both the lowest of any stable metal, resulting in the lowest stable liquid-state range of any metal under standard conditions. This effect is due to lanthanide contraction and relativistic contraction reducing the orbit radius of the outermost electrons, and thus weakening the metallic bonding in mercury.<ref name="Norrby"/> Upon freezing, the volume of mercury decreases by 3.59% and its density changes from 13.69 g/cm<sup>3</sup> when liquid to 14.184 g/cm<sup>3</sup> when solid. The coefficient of volume expansion is 181.59 × 10<sup>−6</sup> at 0 °C, 181.71 × 10<sup>−6</sup> at 20 °C and 182.50 × 10<sup>−6</sup> at 100 °C (per °C). Solid mercury is malleable and ductile, and can be cut with a knife.<ref>{{cite book|author=Simons, E. N. |title=Guide to Uncommon Metals|date=1968|publisher=Frederick Muller|page=111}}</ref>
When expanded by heating near its critical point (around {{convert|1750|K|C F}} and {{convert|1720|bar|MPa}}), mercury exhibits a metal-nonmetal transition associated with sharp changes in its electronic conductivity and optical properties.<ref>{{cite journal|first1=F.|last1=Hensel|first2=E. U.|last2=Franck|title=Metal-nonmetal transition in dense mercury vapor|journal=Rev. Mod. Phys.|volume=40|pages=697–703|year=1968|issue=4 |doi=10.1103/RevModPhys.40.697 |bibcode=1968RvMP...40..697H }}</ref>
Mercury was the first known superconductor, discovered in 1911 by Heike Kamerlingh Onnes by cooling of mercury below {{convert|4|K|C F}} shortly after the discovery and production of liquid helium.<ref>{{Cite book|last1=Onnes|first1=Heike Kamerlingh|title=Further experiments with liquid helium. G. On the electrical resistance of pure metals, etc. VI. On the sudden change in the rate at which the resistance of mercury disappears|series=Through Measurement to Knowledge: The Selected Papers of Heike Kamerlingh Onnes 1853–1926|editor=K. Gavroglu and Y. Goudaroulis|publisher=Springer|location=Netherlands, Dordrecht|year=1991|pages=267–272}}</ref><ref>{{Cite journal |last1=van Delft |first1=Dirk |last2=Kes |first2=Peter |date=2010-09-01 |title=The discovery of superconductivity |url=https://pubs.aip.org/physicstoday/article/63/9/38/386608/The-discovery-of-superconductivityA-century-ago |url-status=live |archive-url=https://web.archive.org/web/20231114035120/https://pubs.aip.org/physicstoday/article/63/9/38/386608/The-discovery-of-superconductivityA-century-ago |archive-date=2023-11-14 |access-date=2023-12-06 |journal=Physics Today|volume=63 |issue=9 |pages=38–43 |doi=10.1063/1.3490499 |bibcode=2010PhT....63i..38V }}</ref> Its superconductive properties were later determined to be unusual compared to other later-discovered superconductors, such as the more popular niobium alloys.<ref>{{cite journal |last1=Tresca |first1=Cesare |last2=Profeta |first2=Gianni |last3=Marini |first3=Giovanni |last4=Bachelet |first4=Giovanni B. |last5=Sanna |first5=Antonio |last6=Calandra |first6=Matteo |last7=Boeri |first7=Lilia |title=Why mercury is a superconductor |journal=Physical Review B |date=3 November 2022 |volume=106 |issue=18 |article-number=L180501 |doi=10.1103/PhysRevB.106.L180501 |arxiv=2111.13867 |bibcode=2022PhRvB.106r0501T |hdl=11573/1659661 |hdl-access=free }}</ref><ref>{{cite journal |author=Berlincourt |first1=T. G. |last2=Hake |first2=R. R. |name-list-style=amp |date=1962 |title=Pulsed-Magnetic-Field Studies of Superconducting Transition Metal Alloys at High and Low Current Densities |journal=Bulletin of the American Physical Society |volume=II-7 |page=408}}</ref>
At room temperature ({{convert|20|C|K F}}), liquid mercury solidifies into a simple rhombohedral structure at approximately {{convert|1.2|GPa|bar}} of pressure. On further compression, mercury undergoes several structural phase transitions into at least four distinct solid allotropes as compression increases, where the δ-phase with an hexagonal-close-packed (hcp) structure is stable above {{convert|36|GPa|bar}} until at least {{convert|200|GPa|bar}}.<ref>{{cite journal|last1=Takemura|first1=K|first2=S|last2=Nakano|first3=Y|last3=Ohishi|first4=Y|last4=Nakamoto|first5=H|last5=Fujihisa|title=High-pressure structural study of solid mercury up to 200 GPa|year=2014|journal=Materials Research Express|volume=2|article-number=016502|doi=10.1088/2053-1591/2/1/016502}}</ref> The melting curve at high-pressure increases steeply on initial compression, but exhibits a pronounced flattening and a potential local maximum at around {{convert|9|GPa|bar}}.<ref name=Drewitt2026>{{Cite journal|title=Structure of liquid mercury at high pressure|author1=Drewitt, James W. E.|author2=Turci, Francesco|author3=Barnes, Adrian C.|author4=Heinen, Benedict J.|author5=Rogmann, Elena-Marie|author6=Lord, Oliver T.|author7=Wilson, Craig W.|author8=Macleod, Simon G.|author9=Kleppe, Annette K.|year=2026|journal=Physical Review B|volume=113|issue=17|article-number=174201 |doi=10.1103/nffz-z1g8}}</ref> At {{convert|1|atm|bar MPa}}), liquid mercury exhibits an anomalously low first-shell coordination number, with each Hg atom having around 6 to 10 nearest neighbours,<ref>{{Cite journal|journal=The Philosophical Magazine: A Journal of Theoretical Experimental and Applied Physics|title=The structure of liquid mercury|last1=Rivlin|first1=V. G.|last2=Waghorne|first2=R. M.|last3=Williams|first3=G. I.|pages=1169-1179|year=1966|doi=10.1080/14786436608213533}}</ref><ref>{{Cite journal|url=https://pubs.aip.org/jcp/article/11/7/330/182166/The-Structure-of-Liquid-Mercury|title=The Structure of Liquid Mercury|first1=J. A.|last1=Campbell|first2=J. H.|last2=Hildebrand|date=1 July 1943|journal=The Journal of Chemical Physics|volume=11|issue=7|pages=330–333|via=CrossRef|doi=10.1063/1.1723851}}</ref><ref>{{cite journal|last1=Waseda|first1=Y|last2=Miller|first2=W.A.|title=The structure of liquid mercury over a wide range of temperature (−30 to 290 °C)|journal=Phys. Status Solidi B|volume=91|pages=141–146|year=1979|issue=1|doi=10.1002/pssb.2220910114|bibcode=1979PSSBR..91..141W}}</ref> in contrast to simple metallic liquids in which atoms are densely-packed with 12 nearest neighbours.<ref>{{cite journal |last=Drewitt |first=James W. E.|year=2021|title=Liquid structure under extreme conditions: High-pressure x-ray diffraction studies|journal=Journal of Physics: Condensed Matter |volume=33 |issue=50 |doi=10.1088/1361-648X/ac2865 |pmid=34544063 |bibcode=2021JPCM...33X3004D |doi-access=free }}</ref> At simultaneous high-pressure and temperature conditions, the atomic arrangement in liquid mercury progresses towards a simple densely packed liquid structure. However, even at very high pressures (up to around {{convert|10|GPa|bar}}), liquid mercury retains more many-body clusters than expected for a simple hard-sphere liquid.<ref name=Drewitt2026/>
===Chemical properties=== Mercury does not react with most acids,{{cn|date=May 2026}} such as dilute sulfuric acid, although oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate, nitrate, and chloride.{{cn|date=May 2026}} Like silver, mercury reacts with atmospheric hydrogen sulfide. Mercury reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury (spill kits also use activated carbon and powdered zinc).<ref name="Greenwood" />
====Amalgams==== Mercury dissolves many metals such as gold and silver to form amalgams. Iron is an exception, and iron flasks have traditionally been used to transport the material.<ref>{{Cite web |last=Swackhamer |first=Barry |date=26 November 2011 |title=Mercury Storage Vault |url=https://www.hmdb.org/m.asp?m=49858 |access-date=11 December 2023 |website=The Historic Marker Database}}</ref> Several other first row transition metals (with the exception of manganese, copper and zinc) are also resistant in forming amalgams. Other elements that do not readily form amalgams with mercury include platinum.<ref>{{cite book |author=Gmelin, Leopold |title=Hand book of chemistry |url=https://books.google.com/books?id=1AI5AAAAMAAJ&pg=PA128 |access-date=30 December 2012|date=1852|publisher=Cavendish Society |pages=103 (Na), 110 (W), 122 (Zn), 128 (Fe), 247 (Au), 338 (Pt)|url-status=live|archive-url=https://web.archive.org/web/20130509033751/http://books.google.com/books?id=1AI5AAAAMAAJ&pg=PA128|archive-date=9 May 2013}}</ref><ref>{{cite book |last=Soratur|first=S. H.|title=Essentials of Dental Materials |url=https://books.google.com/books?id=-U5ztAEACAAJ|date=2002|publisher=Jaypee Brothers Publishers |isbn=978-81-7179-989-3|page=14}}</ref> Sodium amalgam is a common reducing agent in organic synthesis, and is also used in high-pressure sodium lamps.
Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact.<ref>{{Cite journal|title=The activation of aluminium by mercury ions in non-aggressive media|url=https://ui.adsabs.harvard.edu/abs/2006Corro..48.4243B/abstract|journal=Corrosion|date=2006|pages=4243–4256|volume=48|issue=12|doi=10.1016/j.corsci.2006.03.013|language=en|first=J. B.|last=Bessone |bibcode=2006Corro..48.4243B }}</ref> Since the amalgam destroys the aluminium oxide layer which protects metallic aluminium from oxidizing in-depth (as in iron rusting), even small amounts of mercury can seriously corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft.<ref name="CorrAl">{{cite book |author=Vargel, C. |author2=Jacques, M. |author3=Schmidt, M. P.| title=Corrosion of Aluminium| date=2004| isbn=978-0-08-044495-6 |publisher=Elsevier |url=https://books.google.com/books?id=NAABS5KrVDYC&pg=PA158 |page=158}}</ref>
Mercury embrittlement is the most common type of liquid metal embrittlement, as mercury is a natural component of some hydrocarbon reservoirs and will come into contact with petroleum processing equipment under normal conditions.<ref>{{cite conference|title=Mercury Liquid Metal Embrittlement Of Alloys For Oil And Gas Production And Processing|url=https://onepetro.org/NACECORR/proceedings-abstract/CORR10/All-CORR10/NACE-10294/126967|first1=Raymundo|last1=Case|first2=Dale R.|last2=McIntyre|date=14 March 2010}}</ref>
===Isotopes=== {{Main|Isotopes of mercury}} There are seven stable isotopes of mercury, with {{chem|202|Hg}} being the most abundant (29.86%). The longest-lived radioisotopes are {{chem|194|Hg}} with a half-life of 444 years, and {{chem|203|Hg}} with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. {{chem|206|Hg}} occurs naturally in tiny traces as an intermediate decay product of {{chem|238|U}}. {{chem|199|Hg}} and {{chem|201|Hg}} are the most often studied NMR-active nuclei, having spins of {{frac|2}} and {{frac|3|2}} respectively.<ref name="CRC" />
==Etymology== [[File:Mercury symbol (fixed width).svg|thumb|left|upright=0.55|The symbol for the planet Mercury (☿) has been used since ancient times to represent the element]] ''Hg'' is the modern chemical symbol for mercury.<ref>{{cite journal |last1=Blum |first1=Joel D. |title=Mesmerized by mercury |journal=Nature Chemistry |date=December 2013 |volume=5 |issue=12 |page=1066 |doi=10.1038/nchem.1803 |pmid=24256872 |bibcode=2013NatCh...5.1066B }}</ref> It is an abbreviation of {{lang|la|hydrargyrum}}, a romanized form of the ancient Greek name for mercury, {{wikt-lang|grc|ὑδράργυρος}} ({{transliteration|grc|hydrargyros}}). Hydrargyrum ({{IPAc-en|h|aɪ|ˈ|d|r|ɑr|dʒ|ər|ə|m}} {{respell|hy|DRAR|jər|əm}})<ref name="etym">{{Cite web |title=Definition of hydrargyrum {{!}} Dictionary.com |url=https://www.dictionary.com/browse/hydrargyrum |access-date=2022-12-22 |archive-url=https://web.archive.org/web/20140812203929/http://dictionary.reference.com/browse/hydrargyrum |archive-date=12 August 2014}} ''Random House Webster's Unabridged Dictionary''.</ref> has also been used in English, though the term is now dated. {{transliteration|grc|Hydrargyros}} is a Greek compound word meaning {{gloss|water-silver}}, from {{lang|grc|ὑδρ}}- ({{transliteration|grc|hydr}}-), the root of {{wikt-lang|grc|ὕδωρ}} ({{transliteration|grc|hydor}}) {{gloss|water}}, and {{wikt-lang|grc|ἄργυρος}} ({{transliteration|grc|argyros}}) {{gloss|silver}}.<ref name="etym" /> Like the English name quicksilver ({{gloss|living-silver}}), this name was due to mercury's liquid and shiny properties.<ref>{{cite book|url=http://www.websters1913.com/words/Quicksilver|title=Webster's Revised Unabridged Dictionary |location = Springfield, Mass. |publisher = G. & C. Merriam |year = 1913 |access-date = 27 December 2023 |oclc = 800618302}}</ref>
The modern English name ''mercury'' comes from the planet Mercury. In medieval alchemy, the seven known metals—quicksilver, gold, silver, copper, iron, tin, and lead—were associated with the seven classical planets (Mercury, the sun, moon, Venus, Mars, Jupiter, and Saturn respectively). Quicksilver was associated with the fastest planet, which had been named after the Roman god Mercury, who was associated with speed and mobility. The astrological symbol for the planet became one of the alchemical symbols for the metal, and ''Mercury'' became an alternative name for the metal. Mercury is the only metal for which the alchemical planetary name survives, as it was decided it was preferable to ''quicksilver'' as a chemical name.<ref name="Stillman" /><ref>Maurice Crosland (2004) ''Historical Studies in the Language of Chemistry''</ref>
==History== Mercury was found in Egyptian tombs that date from 1500 BC;<ref>{{cite web|title=Mercury and the environment — Basic facts|publisher=Environment Canada, Federal Government of Canada|date=2004|url=http://www.ec.gc.ca/mercure-mercury/default.asp?lang=En&n=9A4397AD-1|access-date=27 March 2008|url-status=live|archive-url=https://web.archive.org/web/20110916172302/http://www.ec.gc.ca/mercure-mercury/default.asp?lang=En&n=9A4397AD-1|archive-date=16 September 2011}}</ref> cinnabar, the most common natural source of mercury, has been in use since the Neolithic Age.<ref>{{cite journal |last1=Martín Gil |first1=J. |last2=Martín Gil |first2=F. J. |last3=Delibes de Castro |first3=G. |last4=Zapatero Magdaleno |first4=P. |last5=Sarabia Herrero |first5=F. J. |year=1995 |title=The first known use of vermillion |journal=Experientia |volume=51 |issue=8 |pages=759–761 |doi=10.1007/BF01922425 |pmid=7649232 |bibcode=1995Expea..51..759M }}</ref>
In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health, although it is now known that exposure to mercury vapor leads to serious adverse health effects.<ref>{{cite web|title=Mercury — Element of the ancients |publisher=Center for Environmental Health Sciences, Dartmouth College |url=http://www.dartmouth.edu/~toxmetal/mercury/history.html |access-date=9 April 2012|url-status=live|archive-url=https://web.archive.org/web/20121202092915/http://www.dartmouth.edu/~toxmetal/mercury/history.html|archive-date=2 December 2012}}</ref> The first emperor of a unified China, 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 reportedly killed by drinking a mercury and powdered jade mixture formulated by Qin alchemists intended as an elixir of immortality.<ref>{{cite web|title=Qin Shihuang|publisher=Ministry of Culture, People's Republic of China|date=2003 |url=http://www.chinaculture.org/gb/en_aboutchina/2003-09/24/content_22854.htm|access-date=27 March 2008|archive-url=https://web.archive.org/web/20080704151150/http://www.chinaculture.org/gb/en_aboutchina/2003-09/24/content_22854.htm|archive-date=4 July 2008}}</ref><ref name="wright">{{cite book|title=The History of China|date=2001|author=Wright, David Curtis |publisher=Greenwood Publishing Group|isbn=978-0-313-30940-3 |url=https://archive.org/details/historyofchina00wrig/page/49 |page=49|url-access=registration}}</ref> Khumarawayh ibn Ahmad ibn Tulun, the second Tulunid ruler of Egypt (r. 884–896), known for his extravagance and profligacy, reportedly built a basin filled with mercury, on which he would lie on top of air-filled cushions and be rocked to sleep.<ref>{{cite encyclopedia |title=Khumārawaih |first=Moritz |last=Sobernheim |encyclopedia=E.J. Brill's first encyclopaedia of Islam, 1913–1936, Volume IV: 'Itk–Kwaṭṭa |editor-first=Martijn Theodoor |editor-last=Houtsma |publisher=BRILL |location=Leiden |year=1987 |isbn=978-90-04-08265-6 |url=https://books.google.com/books?id=7CP7fYghBFQC&pg=PA973 |page=973 |url-status=live |archive-date=3 June 2016 |archive-url= https://web.archive.org/web/20160603004305/https://books.google.com/books?id=7CP7fYghBFQC&pg=PA973#v=onepage&q&f=false}}</ref>
Quantities of liquid mercury, ranging from {{convert|90|to|600|g|oz}} have been recovered from a chamber 60 feet below the 1800-year-old pyramid known as the Temple of the Feathered Serpent, the third-largest pyramid of Teotihuacan, Mexico, along with "jade statues, jaguar remains, a box filled with carved shells and rubber balls".<ref name="Yuhas">{{Cite news |last=Yuhas |first=Alan |title=Liquid mercury found under Mexican pyramid could lead to king's tomb |url=https://www.theguardian.com/world/2015/apr/24/liquid-mercury-mexican-pyramid-teotihuacan |date=24 April 2015 |newspaper=The Guardian |language=en-GB |access-date=22 November 2016 |url-status=live |archive-url=https://web.archive.org/web/20161201200540/https://www.theguardian.com/world/2015/apr/24/liquid-mercury-mexican-pyramid-teotihuacan |archive-date=1 December 2016}}</ref> In Lamanai, once a major city of the Maya civilization, a pool of mercury was found under a marker in a Mesoamerican ballcourt.<ref>{{cite journal |last=Pendergast |first=David M. |title=Ancient maya mercury |journal=Science |volume=217 |issue=4559 |pages=533–535 |date=6 August 1982 |bibcode=1982Sci...217..533P |doi=10.1126/science.217.4559.533 |pmid=17820542 }}</ref><ref>{{cite web |title=Lamanai |url=http://www.guidetobelize.info/en/maya/belize-mayan-lamanai-guide.shtml |access-date=17 June 2011 |url-status=live |archive-url=https://web.archive.org/web/20110611124757/http://www.guidetobelize.info/en/maya/belize-mayan-lamanai-guide.shtml |archive-date=11 June 2011}}</ref> This mercury may have been used in bowls as mirrors for divinatory purposes. Five of these date to the Classic Period of Maya civilization (c. 250–900) but one example predated this.<ref>{{cite journal |last1=Healy |first1=Paul F. |last2=Blainey |first2=Marc G. |title=Ancient Maya Mosaic Mirrors: Function, Symbolism, And Meaning |journal=Ancient Mesoamerica |date=2011 |volume=22 |issue=2 |pages=229–244 |doi=10.1017/S0956536111000241 }}</ref>
Aristotle recounts that Daedalus made a wooden statue of Aphrodite move by pouring quicksilver in its interior.<ref>{{cite book |last=Hicks |first=R. D. |year=1907 |title=Aristotle De Anima |chapter=Chapter 3 |place=Cambridge |publisher=Cambridge University Press |url=https://archive.org/details/aristotledeanima005947mbp/page/n7/mode/2up}} [https://archive.org/stream/aristotledeanima005947mbp/aristotledeanima005947mbp_djvu.txt Text]</ref> In Greek mythology Daedalus gave the appearance of voice in his statues using quicksilver. The ancient Greeks used cinnabar (mercury sulfide) in ointments; the ancient Egyptians and the Romans used it in cosmetics. By 500 BC mercury was used to make amalgams (Medieval Latin ''amalgama'', "alloy of mercury") with other metals.<ref>{{cite book |url=https://books.google.com/books?id=DIWEi5Hg93gC&pg=PA120 |page=120|title=Jewelrymaking through history |author=Hesse, R W |publisher=Greenwood Publishing Group|date=2007|isbn=978-0-313-33507-5}}</ref>
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.<ref name="Stillman">{{cite book|title = Story of Alchemy and Early Chemistry|author = Stillman, J. M.|publisher = Kessinger Publishing|date = 2003|isbn = 978-0-7661-3230-6|pages = 7–9|oclc = 233637688}}</ref>
The mines in Almadén (Spain), Monte Amiata (Italy), and Idrija (now Slovenia) dominated 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.<ref name="MercHz">{{cite book|title =Mercury hazards to living organisms|author= Eisler, R.| publisher = CRC Press|date = 2006|isbn = 978-0-8493-9212-2|url = https://books.google.com/books?id=gqc8wUvsI8cC}}</ref> {{Location map+|America|float=right|width=300|caption=The location of major 18th century Spanish silver mine districs (crossed pickaxes) and the mines involved in mercury supply needed for silver mining (purple dots).|places= <!-- North-East--> {{Location map~|America|lat=46.0025 |long=14.0275 |label=Idrija|position=left|mark=Purple pog.svg}} {{Location map~|America|lat=38.776389 |long=-4.836944 |label=Almadén|position=left|mark=Purple pog.svg}} {{Location map~|America|lat=-12.786389 |long=-74.975556 |label=Huancavelica|position=right|mark=Purple pog.svg}} {{Location map~|America|lat=24.025 |long=-104.6675 |label=Durango|position=top|mark=Schlaegel und Eisen nach DIN 21800.svg}} {{Location map~|America|lat=22.773611 |long=-102.573611 |label=Zacatecas|position=left|mark=Schlaegel und Eisen nach DIN 21800.svg}} {{Location map~|America|lat=21.0177784 |long=-101.256667 |label=Guanajuato|position=bottom|mark=Schlaegel und Eisen nach DIN 21800.svg}} {{Location map~|America|lat=22.21728 |long=-100.80012 |label=S.L. Potosí|position=right|mark=Schlaegel und Eisen nach DIN 21800.svg}} {{Location map~|America|lat=-6.7649 |long=-78.6065 |label=Hualgayoc|position=right|mark=Schlaegel und Eisen nach DIN 21800.svg}} {{Location map~|America|lat=-10.686389 |long=-76.2625 |label=C. de Pasco|position=left|mark=Schlaegel und Eisen nach DIN 21800.svg}} {{Location map~|America|lat=-17.966667 |long=-67.116667 |label=Oruro|position=left|mark=Schlaegel und Eisen nach DIN 21800.svg}} {{Location map~|America|lat=-19.618901 |long=-65.749687 |label=Potosí|position=right|mark=Schlaegel und Eisen nach DIN 21800.svg}} }} 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 Almadén in Southern Spain supplied all the mercury for the colonies.<ref>{{cite book |author=Burkholder, M.|author2=Johnson, L.|name-list-style=amp|title=Colonial Latin America|publisher=Oxford University Press|date= 2008 |pages=157–159|isbn=978-0-19-504542-0}}</ref> 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.<ref name=Jamieson/> In 1786 the main mine at Huancavelica suffered a sudden collapse that killed over 100 persons and greatly reduced the mine's output.<ref name=historica>{{Cite journal |title=El derrumbe de Huancavelica en 1786: Fracaso de una reforma borbónica |journal=Histórica |last=Lang |first=Mervyn |url= |volume=X |issue=2 |pages=213–226 |year=1986 |doi=10.18800/historica.198602.003 |language=es}}</ref> Through the legalization of scavenging known as ''pallaqueo'' mercury production rose again peaking in 1794–1796.<ref name=isabelm/><ref>{{Cite book |last=Povea Moreno |first=Isabel Povea |title=Minería y reformismo borbónico en el Perú. Estado, empresa y trabajadores en Huancavelica, 1784-1814 |publisher=Instituto de Estudios Peruanos |year=2014 |location=Peru |pages=143–209}}</ref> The French Revolutionary Wars disrupted European mercury supply to Spanish America leading to an increasing reliance for the mines in present-day Peru and Bolivia on mercury from Huancavelica but this mines production was clearly by 1799 not enough to supply the demand in the Andean mines.<ref name=isabelm>{{Cite journal|title=Los busconesde metal. El sistema de pallaqueoen Huancavelica (1793-1820)|trans-title=The buscones of metal. The pallaqueo system in Huancavelica (1793-1820)|year=2012|journal=Anuario de Estudios Americanos|url=https://estudiosamericanos.revistas.csic.es/index.php/estudiosamericanos/article/view/564/567|last=Povea Moreno|first=Isabel María|doi=10.3989/aeamer.2012.1.04|language=es|volume=69|issue=1|pages=109–138}}</ref> Spain abolished the royal mercury monopoly in 1813.<ref name=isabelm/>
Mercury poisoning in the mines left many people disabled through the early modern period but mercury itself was not the chief cause of deaths in the mines.<ref>{{Cite journal |title=La cadena del mercurio en la Monarquía Hispánica a partir de su historiografía |journal=Relaciones. Estudios de historia y sociedad |last=Laris Pardo |first=Jorge Alejandro |url=https://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0185-39292022000200071 |volume=43 |issue=170 |trans-title=Historiographical essay on the Commodity Chain of mercury in the Hispanic Monarchy |language=es|year=2022}}</ref>
The patio process and later pan amalgamation process continued to create great demand for mercury to treat silver ores until the late 19th century.<ref name=Jamieson>{{cite book|url=https://books.google.com/books?id=a4hPCX2XWDIC&pg=PA33|page=33|title=Domestic Architecture and Power |author=Jamieson, R W|publisher=Springer|date=2000|isbn=978-0-306-46176-7}}</ref>
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(NO<sub>3</sub>)<sub>2</sub>.<ref>{{cite book |title=Concise Inorganic Chemistry |author=Lee, J. D. |publisher=Wiley-Blackwell |date=1999 |isbn=978-0-632-05293-6}}</ref> 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 inspired the phrase "mad as a hatter".<ref>{{Cite journal |last=Crean |first=J. F. |date=1962 |title=Hats and the Fur Trade |journal=The Canadian Journal of Economics and Political Science |volume=28 |issue=3 |page=380 |doi=10.2307/139669 |jstor=139669 }}</ref> 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.<ref>{{cite journal |journal=Br. Med. J. (Clin. Res. Ed.) |date=1983 |volume=287 |page=1961 |title=Did the Mad Hatter have mercury poisoning? |author=Waldron, H. A. |pmid=6418283 |doi=10.1136/bmj.287.6409.1961 |issue=6409 |pmc=1550196}}</ref>
==Occurrence== Mercury is an extremely rare element in Earth's crust; it has an average crustal abundance by mass of only 0.08 parts per million (ppm)<ref>{{cite book |url=https://books.google.com/books?id=GerdDmwMTLkC&pg=PA265 |page=265|title=Geomicrobiology|author=Ehrlich, H. L. |author2=Newman, D. K.|publisher=CRC Press| date=2008|isbn=978-0-8493-7906-2}}</ref> and is the 66th most abundant element in the Earth's crust.<ref>{{cite journal |last1=Meyer |first1=Lorraine |last2=Guyot |first2=Stéphane |last3=Chalot |first3=Michel |last4=Capelli |first4=Nicolas |title=The potential of microorganisms as biomonitoring and bioremediation tools for mercury-contaminated soils |journal=Ecotoxicology and Environmental Safety |date=September 2023 |volume=262 |article-number=115185 |doi=10.1016/j.ecoenv.2023.115185 |pmid=37385017 |bibcode=2023EcoES.26215185M }}</ref> 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, metacinnabar, sphalerite, corderoite, livingstonite and other minerals, with cinnabar (HgS) being the most common ore.<ref>{{cite journal |last1=Rytuba |first1=James J. |title=Mercury from mineral deposits and potential environmental impact |journal=Environmental Geology |date=January 2003 |volume=43 |issue=3 |pages=326–338 |doi=10.1007/s00254-002-0629-5 |bibcode=2003EnGeo..43..326R }}</ref><ref name="metacinnabar">{{Cite web |url=https://www.mindat.org/min-2670.html |title=Metacinnabar |website=Mindat.org |access-date=2023-11-16}}</ref> Mercury ores often occur in hot springs or other volcanic regions.<ref>{{cite web|access-date=7 July 2009|title=Mercury Recycling in the United States in 2000 |publisher=USGS |url-status=live |url=https://pubs.usgs.gov/circ/c1196u/Circ_1196_U.pdf|archive-url=https://web.archive.org/web/20090326135650/http://pubs.usgs.gov/circ/c1196u/Circ_1196_U.pdf|archive-date=26 March 2009}}</ref>
[[File:Mercury-27128.jpg|thumb|Native mercury with cinnabar, Socrates mine, Sonoma County, California. Cinnabar sometimes alters to native mercury in the oxidized zone of mercury deposits.]] 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.<ref name="brooks_usgs">{{cite web |url=https://minerals.usgs.gov/minerals/pubs/commodity/mercury/mercumcs07.pdf|title=Mercury|author=Brooks, W. E.|date=2007|publisher=U.S. Geological Survey|access-date=30 May 2008|url-status=live|archive-url=https://web.archive.org/web/20080527203059/http://minerals.usgs.gov/minerals/pubs/commodity/mercury/mercumcs07.pdf|archive-date=27 May 2008}}</ref>
Mercury is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is: :HgS + O<sub>2</sub> → Hg + SO<sub>2</sub>
thumb|Evolution of mercury price (U.S.) and production (worldwide) In 2020, China was the top producer of mercury, providing 88% of the world output (2200 out of 2500 tonnes), followed by Tajikistan (178 t), Russia (50 t) and Mexico (32 t).<ref name="Anon. t636">{{cite web | title=World Mineral Production | url=https://nora.nerc.ac.uk/id/eprint/534464/1/WMP_2016_2020.pdf | page=48 | access-date=22 Nov 2023}}</ref>{{srn}}{{table alignment}} {| class="wikitable sortable static-row-numbers col1left" style="text-align:right;" |+Mercury production by country in 2022–24 (tonnes)<ref>{{Cite web |title=Mineral Commodity Summaries 2025 - Mercury |url=https://pubs.usgs.gov/periodicals/mcs2025/mcs2025-mercury.pdf |access-date=2025-09-17}}</ref><ref>{{Cite web |title=World mineral statistics data |url=https://www.bgs.ac.uk/mineralsuk/statistics/world-mineral-statistics/world-mineral-statistics-data-download/world-mineral-statistics-data/ |access-date=2025-09-17 |website=MineralsUK |language=en-GB}}</ref> |- class="static-row-header" style="text-align:center;vertical-align:bottom;" ! Country !! Production |- class="static-row-header " style="font-weight:bold;" | {{left}} World || 1,200 |- | {{flagg|us*eft|China|pref=Natural resources of}} || 1,000 |- | {{flagg|us*eft|Tajikistan|pref=Natural resources of}} || 100 |- | {{flagg|us*eft|Peru|pref=Natural resources of}} || 30 |- |{{Flag|Russia}} |30 |- | {{flagg|us*eft|Norway|pref=Natural resources of}} || 20 |- |{{Flag|United States}} |15 |- |{{Flag|Mexico}} |10 |- | {{flagg|us*eft|Kyrgyzstan|pref=Natural resources of}} || 6 |- |{{Flag|Morocco}} |2 |}
Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning.<ref>{{cite web |url=http://act.credoaction.com/campaign/thanks_mercury/?rc=fb_share1 |title=Thank President Obama and Administrator Jackson for protecting us from toxic mercury |archive-url=https://web.archive.org/web/20120501171523/http://act.credoaction.com/campaign/thanks_mercury/?rc=fb_share1 |archive-date=1 May 2012 |website=Act.credoaction.com |date=21 December 2011 |access-date=30 December 2012}}</ref> In China, prison labor was used by a private mining company as recently as the 1950s to develop new cinnabar mines. Thousands of prisoners were used by the Luo Xi mining company to establish new tunnels.<ref name="GREEN" /> Worker health in functioning mines is at high risk.
A newspaper claimed that an unidentified European Union directive calling for energy-efficient lightbulbs to be made mandatory by 2012 encouraged China to re-open cinnabar mines to obtain the mercury required for CFL bulb manufacture. Environmental dangers have been a concern, particularly in the southern cities of Foshan and Guangzhou, and in Guizhou province in the southwest.<ref name="GREEN">{{cite news|author=Sheridan, M.|title='Green' Lightbulbs Poison Workers: hundreds of factory staff are being made ill by mercury used in bulbs destined for the West|date=3 May 2009 |url=http://www.timesonline.co.uk/tol/news/world/asia/article6211261.ece|publisher=The Sunday Times (of London, UK) |archive-url=https://web.archive.org/web/20090517122911/http://www.timesonline.co.uk/tol/news/world/asia/article6211261.ece |archive-date=17 May 2009}}</ref>
Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines. Water run-off 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.<ref>{{Cite web |date=2015-03-12 |title=Almaden Quicksilver Park, then and now in pictures |url=https://www.mercurynews.com/2015/03/12/almaden-quicksilver-park-then-and-now-in-pictures/ |access-date=2025-01-02 |website=The Mercury News |language=en-US}}</ref><ref>{{cite book |author=Boulland M |date=2006 |title=New Almaden |url=https://books.google.com/books?id=C6N03Lww1YsC&pg=PA8 |page=8|publisher=Arcadia Publishing|isbn=978-0-7385-3131-1}}</ref>
==Chemistry== All known mercury compounds exhibit one of two positive oxidation states: I and II. Experiments have failed to unequivocally demonstrate any higher oxidation states: both the claimed 1976 electrosynthesis of an unstable Hg(III) species and 2007 cryogenic isolation of HgF<sub>4</sub> have disputed interpretations and remain difficult (if not impossible) to reproduce.<ref>For a general overview, see {{Cite journal|last1=Riedel |first1=S. |last2=Kaupp |first2=M. |doi=10.1016/j.ccr.2008.07.014 |title=The Highest Oxidation States of the Transition Metal Elements |journal=Coordination Chemistry Reviews |volume=253 |issue=5–6 |pages=606–624 |year=2009}}
The claimed 1976 synthesis is {{cite journal |last1=Deming |first1=Richard L. |last2=Allred |first2=A. L. |last3=Dahl |first3=Alan R. |last4=Herlinger |first4=Albert W. |last5=Kestner |first5=Mark O. |title=Tripositive mercury. Low temperature electrochemical oxidation of 1,4,8,11-tetraazacyclotetradecanemercury(II) tetrafluoroborate |journal=Journal of the American Chemical Society |date=July 1976 |volume=98 |issue=14 |pages=4132–4137 |doi=10.1021/ja00430a020 |bibcode=1976JAChS..98.4132D |postscript=; }} but note that Reidel & Kaupp cite more recent work arguing that the cyclam ligand is instead oxidized.
The claimed 2007 isolation is {{cite journal |author=Xuefang Wang |first2=Lester |last2=Andrews |first3=Sebastian |last3=Riedel |first4=Martin |last4=Kaupp |title=Mercury Is a Transition Metal: The First Experimental Evidence for HgF<sub>4</sub> |journal=Angew. Chem. Int. Ed. |date=2007 |volume=46 |issue=44 |pages=8371–8375 |doi=10.1002/anie.200703710 |pmid=17899620 |bibcode=2007ACIE...46.8371W |postscript=,}} but the spectral identifications are disputed in {{Cite journal |title=Mercury-fluorine interactions: a matrix isolation investigation of Hg⋯F<sub>2</sub>, HgF<sub>2</sub> and HgF<sub>4</sub> in argon matrices |last1=Rooms |first1=J. F. |last2=Wilson |first2=A. V. |last3=Harvey |first3=I. |last4=Bridgeman |first4=A. J. |last5=Young |first5=N. A. |journal=Phys Chem Chem Phys |year=2008 |volume=10 |issue=31 |pages=4594–605 |doi=10.1039/b805608k |pmid=18665309 |bibcode=2008PCCP...10.4594R|url=https://hull-repository.worktribe.com/output/399994 }}</ref>
===Compounds of mercury(I)=== Unlike its lighter neighbors, cadmium and zinc, mercury usually forms simple stable compounds with metal-metal bonds. Most mercury(I) compounds are diamagnetic and feature the dimeric cation, Hg{{su|b=2|p=2+}}. Stable derivatives include the chloride and nitrate. In aqueous solution of a mercury(I) salt, slight disproportion of Hg{{su|b=2|p=2+}} into Hg and {{chem|Hg|2+}} results in >0.5% of dissolved mercury existing as {{chem|Hg|2+}}. In these solutions, complexation of the {{chem|Hg|2+}} with addition of ligands such as cyanide causes disproportionation to go to completion, with all Hg{{su|b=2|p=2+}} precipitating as elemental mercury and insoluble mercury(II) compounds (e.g. mercury(II) cyanide if cyanide is used as the ligand).<ref name="henderson">{{cite book| title=Main group chemistry| author=Henderson, W.| location=Great Britain| publisher=Royal Society of Chemistry| date=2000| isbn=978-0-85404-617-1| url=https://books.google.com/books?id=twdXz1jfVOsC&pg=PA162| page=162| url-status=live| archive-url=https://web.archive.org/web/20160513101559/https://books.google.com/books?id=twdXz1jfVOsC&pg=PA162| archive-date=13 May 2016}}</ref> Mercury(I) chloride, a colorless solid also known as calomel, is really the compound with the formula Hg<sub>2</sub>Cl<sub>2</sub>, with the connectivity Cl-Hg-Hg-Cl. It reacts with chlorine to give mercury(II) chloride, which resists further oxidation. Mercury(I) hydride, a colorless gas, has the formula HgH, containing no Hg-Hg bond; however, the gas has only ever been observed as isolated molecules.<ref>{{cite journal|doi=10.1063/1.1676373|title=Hyperfine Interaction, Chemical Bonding, and Isotope Effect in ZnH, CdH, and HgH Molecules|year=1971|last1=Knight|first1=Lon B.|journal=The Journal of Chemical Physics|volume=55|issue=5|pages=2061–2070|bibcode=1971JChPh..55.2061K}}</ref>
Indicative of its tendency to bond to itself, mercury forms mercury polycations, which consist of linear chains of mercury centers, capped with a positive charge. One example is {{chem|Hg|3|(AsF|6|)}}{{su|b=2}} containing the {{chem|Hg|3|2+}} cation.<ref>{{Cite journal| last1=Brown| first1=I. D.| last2=Gillespie| first2=R. J.| last3=Morgan| first3=K. R.| last4=Tun| first4=Z.| last5=Ummat| first5=P. K.| title=Preparation and crystal structure of mercury hexafluoroniobate ({{chem|Hg|3|NbF|6}}) and mercury hexafluorotantalate ({{chem|Hg|3|TaF|6}}): mercury layer compounds| journal=Inorganic Chemistry| volume=23| issue=26| pages=4506–4508| year=1984| doi=10.1021/ic00194a020}}</ref>
===Compounds of mercury(II)=== Mercury(II) is the most common oxidation state and is the main one in nature as well. All four mercuric halides are known and have been demonstrated to form linear coordination geometry, despite mercury's tendency to form tetrahedral molecular geometry with other ligands. This behavior is similar to the Ag<sup>+</sup> ion. The best known mercury halide is mercury(II) chloride, an easily sublimating white solid.<ref name=EB1911>{{cite EB1911 |wstitle=Corrosive Sublimate |volume=7 |page=197}}</ref>
Mercury(II) oxide, the main oxide of mercury, arises when the metal is exposed to air for long periods at elevated temperatures. It reverts to the elements upon heating near 400 °C, as was demonstrated by Joseph Priestley in an early synthesis of pure oxygen.<ref name="Greenwood">{{Greenwood&Earnshaw2nd}}</ref> Hydroxides of mercury are poorly characterized, as attempted isolation studies of mercury(II) hydroxide have yielded mercury oxide instead.<ref>{{cite journal |doi=10.1002/hlca.19580410411|title=Monomolekular gelöstes Quecksilberhydroxyd und seine Basizität|year=1958|last1=Anderegg|first1=G.|last2=Schwarzenbach|first2=G.|last3=Padmoyo|first3=M.|last4=Borg|first4=Ö. F.|journal=Helvetica Chimica Acta|volume=41|issue=4|pages=988–996 |bibcode=1958HChAc..41..988A }}</ref>
Being a soft metal, mercury forms very stable derivatives with the heavier chalcogens. Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore cinnabar and is the brilliant pigment vermilion. Like ZnS, HgS crystallizes in two forms, the reddish cubic form and the black zinc blende form.<ref name="CRC" /> The latter sometimes occurs naturally as metacinnabar.<ref name="metacinnabar"/> Mercury(II) selenide (HgSe) and mercury(II) telluride (HgTe) are known, these as well as various derivatives, e.g. mercury cadmium telluride and mercury zinc telluride being semiconductors useful as infrared detector materials.<ref>{{cite book |url=https://books.google.com/books?id=4b3WLgomvd0C&pg=PA507 |page=507|title=Infrared detectors |author=Rogalski, A|publisher=CRC Press|date=2000|isbn=978-90-5699-203-3}}</ref>
Mercury(II) salts form a variety of complex derivatives with ammonia. These include Millon's base (Hg<sub>2</sub>N<sup>+</sup>), the one-dimensional polymer (salts of {{chem|HgNH|2|+}}){{su|b=n}}), and "fusible white precipitate" or [Hg(NH<sub>3</sub>)<sub>2</sub>]Cl<sub>2</sub>. Known as Nessler's reagent, potassium tetraiodomercurate(II) ({{chem|K|2|HgI|4}}) is still occasionally used to test for ammonia owing to its tendency to form the deeply colored iodide salt of Millon's base.<ref>{{VogelQualitative5th|page=319}} </ref>
Mercury fulminate is a detonator widely used in explosives.<ref name="CRC" />
===Organomercury compounds=== {{Main|Organomercury compound}} Organic mercury compounds are historically important but are of little industrial value in the western world. Mercury(II) salts are a rare example of simple metal complexes that react directly with aromatic rings. Organomercury compounds are always divalent and usually two-coordinate and linear geometry. Unlike organocadmium and organozinc compounds, organomercury compounds do not react with water. They usually have the formula HgR<sub>2</sub>, which are often volatile, or HgRX, which are often solids, where R is aryl or alkyl and X is usually halide or acetate. Methylmercury, a generic term for compounds with the formula CH<sub>3</sub>HgX, is a dangerous family of compounds that are often found in polluted water.<ref name="methylHg">{{cite book |url=https://books.google.com/books?id=BPvWJbBMd7wC |title=Toxicological effects of methylmercury |author1=Committee on the Toxicological Effects of Methylmercury |author2=Board on Environmental Studies and Toxicology |author3=Commission on Life Sciences |author4=National Research Council |publisher=National Academies Press |date=2000 |isbn=978-0-309-07140-6}}</ref> They arise by a process known as biomethylation.
==Use in medicine== thumb|right|Amalgam filling ===Historical and traditional=== Mercury and its compounds have historically 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. An example of the early therapeutic application of mercury was published in 1787 by James Lind.<ref>{{cite journal |last1=Lind |first1=James |title=An Account of the Efficacy of Mercury in the Cure of Inflammatory Diseases, and the Dysentery |journal=The London Medical Journal |date=1787 |volume=8 |issue=Pt 1 |pages=43–56 |pmc=5545546 |pmid=29139904 }}</ref> The first edition of ''The Merck Manuals'' (1899) featured many then-medically relevant mercuric compounds, such as mercury-ammonium chloride, yellow mercury proto-iodide, calomel, and mercuric chloride, among others.<ref>{{cite book|title=Merck's Manual 1899 |edition=1st |url=http://www.gutenberg.org/ebooks/41697|access-date=16 June 2013|url-status=live|archive-url=https://web.archive.org/web/20130824150245/http://www.gutenberg.org/ebooks/41697|archive-date=24 August 2013}}</ref> Blue mass, a pill or syrup in which mercury is the main ingredient, was prescribed throughout the 19th century for numerous conditions including constipation, depression, child-bearing and toothaches.<ref name="lincoln">{{cite news |title= Did Mercury in "Little Blue Pills" Make Abraham Lincoln Erratic? |author= Mayell, H. |url= http://news.nationalgeographic.com/news/2001/07/0717_lincoln.html |work= National Geographic News |date= 17 July 2007 |access-date= 15 June 2008 |archive-url= https://web.archive.org/web/20080522125650/http://news.nationalgeographic.com/news/2001/07/0717_lincoln.html |archive-date= 22 May 2008}}</ref> 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.<ref>{{cite web |url=http://www.straightdope.com/columns/read/2518/what-happened-to-mercurochrome |access-date=7 July 2009 |title=What happened to Mercurochrome? |date=23 July 2004 |url-status=live |archive-url=https://web.archive.org/web/20090411060622/http://www.straightdope.com/columns/read/2518/what-happened-to-mercurochrome |archive-date=11 April 2009}}</ref>
Mercury in the form of one of its common ores, cinnabar, is used in various traditional medicines, especially in traditional Chinese medicine. Review of its safety has found that cinnabar can lead to significant mercury intoxication when heated, consumed in overdose, or taken long term, and can have adverse effects at therapeutic doses, though effects from therapeutic doses are typically reversible. Although this form of mercury appears to be less toxic than other forms, its use in traditional Chinese medicine has not yet been justified, as the therapeutic basis for the use of cinnabar is not clear.<ref>{{cite journal |author=Liu J |author2= Shi JZ |author3=Yu LM |author4=Goyer RA |author5=Waalkes MP |title=Mercury in traditional medicines: is cinnabar toxicologically similar to common mercurials? |journal=Exp. Biol. Med. (Maywood) |volume=233 |issue=7 |pages=810–7 |date=2008 |pmid=18445765 |pmc=2755212 |doi=10.3181/0712-MR-336 |bibcode= 2008ExpBM.233..810L }}</ref> Mercury(I) chloride (also known as calomel or mercurous chloride) has been used in traditional medicine 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.<ref>{{cite news |vauthors=Pimple KD, Pedroni JA, Berdon V |date=9 July 2002 |url=http://www.indiana.edu/~poynter/sas/lb/syphilis.html |title=Syphilis in history |publisher=Poynter Center for the Study of Ethics and American Institutions at Indiana University-Bloomington |access-date=17 April 2005 |archive-url=https://web.archive.org/web/20050216215916/http://www.indiana.edu/~poynter/sas/lb/syphilis.html |archive-date=16 February 2005 }}{{self-published inline|date=April 2026}}</ref>
===Contemporary=== In contemporary medicine, mercury remains an ingredient in dental amalgams.<ref>{{cite web |title=Dental Amalgam Fillings |url=https://www.fda.gov/medical-devices/dental-devices/dental-amalgam-fillings |archive-url=https://web.archive.org/web/20200930040530/https://www.fda.gov/medical-devices/dental-devices/dental-amalgam-fillings |archive-date=30 September 2020 |date=2020-09-29 |publisher=U.S. Food and Drug Administration (FDA) |location=Silver Spring, MD}}</ref> Thiomersal (called ''Thimerosal'' in the United States) is an organic compound used as a preservative in vaccines, although this use is in decline.<ref name="FDA thimerosal">{{cite web |url=https://www.fda.gov/Cber/vaccine/thimerosal.htm |title=Thimerosal in Vaccines |publisher=Food and Drug Administration / Center for Biologics Evaluation and Research |date=6 September 2007 |access-date=1 October 2007 |archive-url=https://web.archive.org/web/20070929105040/https://www.fda.gov/Cber/vaccine/thimerosal.htm |archive-date=29 September 2007}}</ref> Although it was widely speculated that this mercury-based preservative could cause or trigger autism in children, no evidence supports any such link.<ref>{{cite journal |last1=Parker |first1=Sarah K. |last2=Schwartz |first2=Benjamin |last3=Todd |first3=James |last4=Pickering |first4=Larry K. |title=Thimerosal-Containing Vaccines and Autistic Spectrum Disorder: A Critical Review of Published Original Data |journal=Pediatrics |date=September 2004 |volume=114 |issue=3 |pages=793–804 |doi=10.1542/peds.2004-0434 |pmid=15342856 |bibcode=2004Pedia.114..793P }}<br />Erratum: {{cite journal |last1=Parker |first1=Sarah |last2=Todd |first2=James |last3=Schwartz |first3=Benjamin |last4=Pickering |first4=Larry |title=Thimerosal-Containing Vaccines and Autistic Spectrum Disorder: A Critical Review of Published Original Data |journal=Pediatrics |date=January 2005 |volume=115 |issue=1 |page=200 |doi=10.1542/peds.2004-2402 |pmid=15630018 }}</ref> 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 the inactivated influenza vaccine.<ref name="FDA thimerosal"/> Merbromin (Mercurochrome), another mercury compound, is a topical antiseptic used for minor cuts and scrapes in some countries. Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries.<ref>{{Cite web |date=30 April 2009 |title=Quantitative and Qualitative Analysis of Mercury Compounds in the List |url=https://www.fda.gov/RegulatoryInformation/LawsEnforcedbyFDA/SignificantAmendmentstotheFDCAct/FDAMA/ucm100219.htm |archive-url=https://web.archive.org/web/20170405001453/https://www.fda.gov/RegulatoryInformation/LawsEnforcedbyFDA/SignificantAmendmentstotheFDCAct/FDAMA/ucm100219.htm |archive-date=5 April 2017 |website=Federal Food, Drug, and Cosmetic Act (FD&C Act) |publisher=U.S. Food and Drug Administration}}</ref> Mercury is still used in some diuretics, although substitutes such as thiazides now exist for most therapeutic uses.<ref name="Chlorothiazide p.222">{{cite journal|vauthors=Beyer KH|date=September 1993|title=Chlorothiazide. How the thiazides evolved as antihypertensive therapy|journal=Hypertension|volume=22|issue=3|pages=388–91|doi=10.1161/01.hyp.22.3.388|pmid=8349332|doi-access=free}}</ref>
In 2003, mercury compounds were found in some over-the-counter drugs, including topical antiseptics, stimulant laxatives, diaper-rash ointment, eye drops, and nasal sprays. The FDA has{{Update inline|reason=This might have been true in 2007 but what does the current data say?|date=May 2026}} "inadequate data to establish general recognition of the safety and effectiveness" of the mercury ingredients in these products.<ref>{{cite web |url=http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=310.545&SearchTerm=mercury|title=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 |publisher=United States Food and Drug Administration|access-date=1 May 2007|archive-url=https://web.archive.org/web/20070313135424/http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=310.545&SearchTerm=mercury|archive-date=13 March 2007}}</ref> Mercury is effective as an active ingredient in skin whitening compounds used to depigment skin.<ref>{{cite journal |last1=Mohammed |first1=Terry |last2=Mohammed |first2=Elisabeth |last3=Bascombe |first3=Shermel |title=The evaluation of total mercury and arsenic in skin bleaching creams commonly used in Trinidad and Tobago and their potential risk to the people of the Caribbean |journal=Journal of Public Health Research |date=9 October 2017 |volume=6 |issue=3 |page=1097 |doi=10.4081/jphr.2017.1097 |pmid=29291194 |pmc=5736993 }}</ref> The Minamata Convention on Mercury limits the concentration of mercury in such whiteners to 1 part per million. However, as of 2022, many commercially sold whitener products continue to exceed that limit, and are considered toxic.<ref>Meera Senthilingam, "Skin whitening creams containing high levels of mercury continue to be sold on the world's biggest e-commerce sites, new report finds", 9 March 2022, CNN https://www.cnn.com/2022/03/09/world/zmwg-skin-whitening-creams-mercury-ecommerce-sites-intl-cmd/index.html</ref>
==Industrial, technological, and scientific uses== Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some liquid-in-glass thermometers, especially those 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 being phased out due to health and safety regulations.<ref>{{cite web|url=https://www.epa.gov/mercury|title=What is EPA doing about mercury air emissions?|publisher=United States Environmental Protection Agency (EPA)|access-date=1 May 2007|url-status=live|archive-url=https://web.archive.org/web/20070208013531/http://www.epa.gov/mercury/|archive-date=8 February 2007}}</ref> In some applications, mercury is replaced with less toxic but considerably more expensive Galinstan alloy.<ref>{{cite journal |last1=Surmann |first1=Peter |last2=Zeyat |first2=Hanan |title=Voltammetric analysis using a self-renewable non-mercury electrode |journal=Analytical and Bioanalytical Chemistry |date=November 2005 |volume=383 |issue=6 |pages=1009–1013 |doi=10.1007/s00216-005-0069-7 |pmid=16228199 }}</ref> ===Measuring instruments=== Thermometers containing mercury were invented in the early 18th century by Daniel Gabriel Fahrenheit, though earlier attempts at making temperature-measuring instruments filled with quicksilver had been described in the 1650s.<ref name="middleton">{{Cite book |last=Middleton |first=W. E. K. |url=http://archive.org/details/thermometer0000unse |title=A history of the thermometer and its use in meteorology |publisher=Johns Hopkins Press|year=1966|isbn=978-0-8018-7153-5}}</ref>{{rp|23}} Fahrenheit's mercury thermometer was based on an earlier design that used alcohol rather than mercury; the mercury thermometer was significantly more accurate than those using alcohol.<ref>{{cite book |last1=Grigull |first1=Ulrich |title=Proceeding of International Heat Transfer Conference 8 |chapter=Fahrenheit a Pioneer of Exact Thermometry |date=1986 |pages=9–18 |doi=10.1615/IHTC8.3910 |isbn=0-89116-559-2 }}</ref> Historically, mercury sphygmomanometers, barometers, diffusion pumps, coulometers, and many other laboratory instruments also took advantage of mercury's properties as a very dense, opaque liquid with a nearly linear thermal expansion.<ref>{{cite book |url=https://books.google.com/books?id=G8QyI1Nf0VQC&pg=PA251 |page=251 |title=AIEEE Chemistry |author=Ramanathan E. |publisher=Sura Books |isbn=978-81-7254-293-1}}</ref>
From the early 21st century onwards, the use of mercury thermometers has been declining, and mercury-containing instruments have been banned in many jurisdictions following the 1998 Protocol on Heavy Metals.<ref>{{cite web|url=http://www.unece.org/env/lrtap/hm_h1.html|title=Protocol on Heavy Metals|publisher=UNECE |access-date=10 August 2014}}</ref><ref>{{cite news|title = Mercury Reduction Act of 2003|url = https://openlibrary.org/b/OL17617678M|access-date = 6 June 2009|publisher = United States. Congress. Senate. Committee on Environment and Public Works}}</ref> Modern alternatives to mercury thermometers include resistance thermometers, thermocouples, and thermistor sensors that output to a digital display.<ref>{{cite web|title=Mercury Thermometer Alternatives: Hg Alternatives|publisher=National Institute of Standards and Technology|website=nist.gov|url=https://www.nist.gov/pml/mercury-thermometer-alternatives/mercury-thermometer-alternatives-hg-alternatives|date= 29 November 2021|access-date=22 December 2023}}</ref> <gallery widths="230" heights="160"> File:2023 Rtęciowy termometr lekarski.jpg|Medical mercury thermometer. File:Maximum thermometer close up 2.JPG|The bulb of a mercury-in-glass thermometer. File:Barometer mercury column hg.jpg|Mercury manometer to measure pressure. </gallery>
===Lighting=== Gaseous mercury is used in mercury-vapor lamps, fluorescent lamps, and some neon signs. 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; reflecting a fluorescent ceiling light into a spectrometer is a common calibration practice.<ref>{{cite book |title=A guide to the use and calibration of detector array equipment |last1=Hopkinson |first1=G.R. |last2=Goodman |first2=T.M. |last3=Prince |first3=S.R. |publisher=SPIE Press |date=2004 |page=125 |isbn=978-0-8194-5532-1 |bibcode=2004gucd.book.....H }}</ref> Gaseous mercury is also found in some electron tubes, including ignitrons, thyratrons, and mercury arc rectifiers.<ref>{{cite book|author=Howatson A H|title=An Introduction to Gas Discharges|isbn=978-0-08-020575-5|publisher=Pergamon Press|location= Oxford|date= 1965|chapter=Chapter 8}}</ref> It is also used in specialist medical care lamps for skin tanning and disinfection.<ref>{{cite book|url=https://books.google.com/books?id=-_9lhR_z6j8C&pg=PA104|page=104|title=Transformation of human diploid fibroblasts|author=Milo G E|author2=Casto B C|publisher=CRC Press|date=1990|isbn=978-0-8493-4956-0}}</ref> 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, inconsistent red and blue spots are produced in the light emissions until the initial burning-in process is completed; eventually it will light a consistent dull off-blue color.<ref>{{cite book| page = 363| title= Phosphor handbook| author = Shionoya, S.| publisher = CRC Press| date = 1999| isbn = 978-0-8493-7560-6}}</ref>
<gallery widths="230" heights="160"> File:Germicidal UV discharge tube glow rotate.jpg|The deep violet glow of a mercury vapor discharge in a germicidal lamp, whose spectrum is rich in invisible ultraviolet radiation. File:Mercuryvaporlamp.jpg|Skin tanner containing a low-pressure mercury vapor lamp and two infrared lamps, which act both as light source and electrical ballast File:Leuchtstofflampen-chtaube050409.jpg|Assorted types of fluorescent lamps. File:Mercury discharge tube.jpg|Mercury-discharge spectral calibration lamp. </gallery>
===Electrochemistry=== Liquid mercury is part of a 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.<ref>{{cite book|url=https://books.google.com/books?id=M5pOAAAAIAAJ&pg=PA175|page=175|title=Physiological monitoring and instrument diagnosis in perinatal and neonatal medicine|author=Brans, Y W|author2=Hay W W|publisher=CUP Archive|date= 1995|isbn=978-0-521-41951-2}}</ref> The triple point of mercury, −38.8344 °C, is a fixed point used as a temperature standard for the International Temperature Scale (ITS-90).<ref name="CRC" />
The mercury battery is a non-rechargeable electrochemical battery, a primary cell, that was common in the middle of the 20th century. It was used in a wide variety of applications and was available in various sizes, particularly button sizes. Its constant voltage output and long shelf life gave it a niche use for camera light meters and hearing aids. The mercury cell was effectively banned in most countries in the 1990s due to concerns about the mercury contaminating landfills.<ref>{{cite web |title=IMERC Fact Sheet: Mercury Use in Batteries| url=http://www.newmoa.org/prevention/mercury/imerc/factsheets/batteries.cfm |publisher=Northeast Waste Management Officials' Association |access-date=20 June 2013| date=January 2010 |archive-url=https://web.archive.org/web/20121129031541/http://www.newmoa.org/prevention/mercury/imerc/factsheets/batteries.cfm |archive-date=29 November 2012}}</ref>
===Electromechanical=== As an electrically conductive liquid, it was used in mercury switches (including home mercury light switches installed prior to 1970), tilt switches used in old fire detectors and in some home thermostats.<ref>{{cite book |url=https://books.google.com/books?id=cxPEiSXh44cC&pg=PA260 |page=260 |title=Electrical Installations |author=Shelton, C. |publisher=Nelson Thornes |date=2004 |isbn=978-0-7487-7979-6}}</ref> Owing to its acoustic properties, mercury was used as the propagation medium in delay-line memory devices used in early digital computers of the mid-20th century, such as the UNIVAC I and SEAC.<ref>{{cite journal|journal=Proceedings of the IRE|first=J. P.|last=Eckert|title=A Survey of Digital Computer Memory Systems|date=October 1953|volume=41|issue=10 |pages=1393–1406 |doi=10.1109/JRPROC.1953.274316 |bibcode=1953PIRE...41.1393E }}</ref>
Mercury was a propellant for early ion engines in electric space propulsion systems. Advantages were mercury's high molecular weight, low ionization energy, low dual-ionization energy, high liquid density and liquid storability at room temperature. Disadvantages were concerns regarding environmental impact associated with ground testing and concerns about eventual cooling and condensation of some of the propellant on the spacecraft in long-duration operations. The first spaceflight to use electric propulsion was a mercury-fueled ion thruster developed at NASA Glenn Research Center and flown on the Space Electric Rocket Test "SERT-1" spacecraft launched by NASA at its Wallops Flight Facility in 1964. The SERT-1 flight was followed up by the SERT-2 flight in 1970. Mercury and caesium were preferred propellants for ion engines until Hughes Research Laboratory performed studies finding xenon gas to be a suitable replacement. Xenon is now the preferred propellant for ion engines, as it has a high molecular weight, little or no reactivity due to its noble gas nature, and high liquid density under mild cryogenic storage.<ref>{{cite web |publisher=NASA |access-date=7 July 2009 |url=http://www.nasa.gov/centers/glenn/about/history/ds1.html |title=Glenn Contributions to Deep Space 1 |date=21 May 2008 |url-status=live |archive-url=https://web.archive.org/web/20091001110901/http://www.nasa.gov/centers/glenn/about/history/ds1.html |archive-date=1 October 2009}}</ref><ref>{{cite encyclopedia |encyclopedia=The Internet Encyclopedia of Science |publisher=David Darling |access-date=7 July 2009 |url= http://www.daviddarling.info/encyclopedia/E/electricprop.html |title=Electric space propulsion |url-status=live |archive-url=https://web.archive.org/web/20090530080218/http://www.daviddarling.info/encyclopedia/E/electricprop.html |archive-date=30 May 2009}}</ref>
The Deep Space Atomic Clock (DSAC) under development by the Jet Propulsion Laboratory utilises mercury in a linear ion-trap-based clock. The novel use of mercury permits the creation of compact atomic clocks with low energy requirements ideal for space probes and Mars missions.<ref>{{cite journal |last1=Tjoelker |first1=Robert L. |last2=Prestage |first2=John D. |last3=Burt |first3=Eric A. |last4=Chen |first4=Pin |last5=Chong |first5=Yong J. |last6=Chung |first6=Sang K. |last7=Diener |first7=William |last8=Ely |first8=Todd |last9=Enzer |first9=Daphna G. |last10=Mojaradi |first10=Hadi |last11=Okino |first11=Clay |last12=Pauken |first12=Mike |last13=Robison |first13=David |last14=Swenson |first14=Bradford L. |last15=Tucker |first15=Blake |last16=Wang |first16=Rabi |title=Mercury Ion Clock for a NASA Technology Demonstration Mission |journal=IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control |date=July 2016 |volume=63 |issue=7 |pages=1034–1043 |doi=10.1109/TUFFC.2016.2543738 |pmid=27019481 |bibcode=2016ITUFF..63.1034T }}</ref>
In polarography, both the dropping mercury electrode<ref>{{Cite book | publisher = Elsevier Science | isbn = 978-0-444-51958-0 | last = Zoski | first = Cynthia G. | title = Handbook of Electrochemistry | date = 7 February 2007 }}</ref> and the hanging mercury drop electrode<ref>{{Cite book | edition = 2nd | publisher = CRC | isbn = 978-0-8247-9445-3 | last1 = Kissinger | first1 = Peter | first2 = William R. | last2 = Heineman | title = Laboratory Techniques in Electroanalytical Chemistry, Second Edition, Revised and Expanded | date = 23 January 1996 }}</ref> use elemental mercury. This use allows a new uncontaminated electrode to be available for each measurement or each new experiment.
<gallery widths="230" heights="160"> File:Mercury Switch without housing.jpg|A single-pole, single-throw (SPST) mercury switch. File:Mercury memory.jpg|Mercury memory of UNIVAC I (1951). File:SEACComputer 010.png|Diagram of mercury delay line as used in SEAC computer. File:Deep Space Atomic Clock-DSAC.jpg|The miniaturized Deep Space Atomic Clock is a linear ion-trap-based mercury ion clock, designed for precise and real-time radio navigation in deep space. </gallery>
===Mirrors=== Some transit telescopes use a basin of mercury to form a flat and absolutely horizontal mirror, useful in determining an absolute vertical or perpendicular reference. Concave horizontal parabolic mirrors may be formed by rotating liquid mercury on a disk, the parabolic form of the liquid thus formed reflecting and focusing incident light. Such liquid-mirror 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.<ref>{{cite web|archive-url=https://web.archive.org/web/20030818233315/http://www.govertschilling.nl/artikelen/science/030314_sc.htm|url=http://www.govertschilling.nl/artikelen/science/030314_sc.htm|title=Liquid-mirror telescope set to give stargazing a new spin|date=14 March 2003|archive-date=18 August 2003|publisher=Govert Schilling|access-date=11 October 2008}}</ref><ref>{{cite journal |author=Gibson, B. K. |date=1991 |title=Liquid Mirror Telescopes: History |journal=Journal of the Royal Astronomical Society of Canada |volume=85 |page=158 |bibcode=1991JRASC..85..158G}}</ref><ref>{{cite web|access-date=24 June 2011|url=http://wood.phy.ulaval.ca/index.php/Rotating_Liquid_Mirrors|title=Laval University Liquid mirrors and adaptive optics group|archive-url=https://web.archive.org/web/20110918101521/http://wood.phy.ulaval.ca/index.php/Rotating_Liquid_Mirrors|archive-date=18 September 2011}}</ref> The Fresnel lenses of old lighthouses used to float and rotate in a bath of mercury which acted like a bearing.<ref>{{cite book |url=https://books.google.com/books?id=oY8nG-6B6v0C&pg=PA29 |page=29 |title=Lighthouses |publisher=Osprey Publishing |date=2003 |isbn=978-0-7478-0556-4 |author=Pearson L. F.}}</ref>
===Energy generation=== Experimental mercury vapor turbines were installed to increase the efficiency of fossil-fuel electrical power plants.<ref>{{cite journal |url=https://books.google.com/books?id=9ycDAAAAMBAJ&pg=PA40 |page=40 |title=Popular Science |journal=The Popular Science Monthly |date=1931 |volume=118 |number=3 |issn=0161-7370 |publisher=Bonnier Corporation}}</ref> The South Meadow power plant in Hartford, CT employed mercury as its working fluid, in a binary configuration with a secondary water circuit, for a number of years starting in the late 1920s in a drive to improve plant efficiency. Several other plants were built, including the Schiller Station in Portsmouth, NH, which went online in 1950. The idea did not catch on industry-wide due to the weight and toxicity of mercury, as well as the advent of supercritical steam plants in later years.<ref>{{cite magazine |url=https://books.google.com/books?id=FigDAAAAMBAJ&pg=PA22 |title=Cheaper Power from Quicksilver |author=Mueller, Grover C. |date=September 1929 |magazine=Popular Science}}</ref><ref>{{cite web |url= http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/mercury/mercury.htm |date=13 November 2008 |work=Museum of Retro Technology |title=Mercury as a Working Fluid |archive-url=https://web.archive.org/web/20110221034317/http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/mercury/mercury.htm |archive-date=21 February 2011}}</ref> Similarly, liquid mercury was used as a coolant for some nuclear reactors; however, sodium is proposed for liquid metal cooled reactor, because the high density of mercury requires much more energy to circulate as coolant.<ref>{{cite book |url=https://books.google.com/books?id=2KYVftKE9NUC&pg=PA64 |page=64 |title=Introduction to Nuclear Power |author=James Collier |author2=Geoffrey F. Hewitt |publisher=Taylor & Francis |date=1987 |isbn=978-1-56032-682-3}}</ref>
===Production of chlorine and caustic soda=== Chlorine is produced from sodium chloride (common salt, NaCl) using electrolysis to separate metallic sodium from chlorine gas. Usually salt is dissolved in water to produce a brine. By-products of any such chloralkali process are hydrogen (H<sub>2</sub>) and sodium hydroxide (NaOH), which is commonly called caustic soda or lye. By far the largest use of mercury<ref>{{cite journal|title=The CRB Commodity Yearbook (annual)|journal= The CRB Commodity Yearbook|date= 2000|page=173|issn=1076-2906}}{{vs|date=April 2026}}</ref><ref name="USEPA">{{cite web|url=http://www.epa.gov/nrmrl/pubs/600r02104/600r02104chap3.pdf|author=Leopold, B. R.|date=2002|title=Chapter 3: Manufacturing Processes Involving Mercury. ''Use and Release of Mercury in the United States''|publisher=National Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, Ohio|access-date=1 May 2007 |archive-url = https://web.archive.org/web/20070621093346/http://www.epa.gov/nrmrl/pubs/600r02104/600r02104chap3.pdf |archive-date = 21 June 2007}}</ref> in the late 20th century 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.<ref>{{cite web|url=http://www.eurochlor.org/animations/mercury-cell.asp| title=Chlorine Online Diagram of mercury cell process| publisher=Euro Chlor| access-date=15 September 2006| archive-url=https://web.archive.org/web/20060902010053/http://www.eurochlor.org/animations/mercury-cell.asp <!--Added by H3llBot-->| archive-date=2 September 2006}}</ref> Many of the industrial mercury releases of the 20th century came from this process, although modern plants claim to be safe in this regard.<ref name="USEPA" /> From the 1960s onward, the majority of industrial plants moved away from mercury cell processes towards diaphragm cell technologies to produce chlorine, though 11% of the chlorine made in the United States was still produced with the mercury cell method as of 2005.<ref>{{cite book |last1=O'Brien |first1=Thomas F. |last2=Bommaraju |first2=Tilak V. |last3=Hine |first3=Fumio |title=Handbook of Chlor-Alkali Technology |chapter=History of the Chlor-Alkali Industry |date=2005 |pages=17–36 |doi=10.1007/0-306-48624-5_2 |isbn=978-0-306-48623-4 }}</ref>
===Mining=== Historically, mercury was used extensively in hydraulic gold mining. Large-scale use of mercury stopped in the 1960s. However, mercury is still used in small scale, often illegal, gold prospecting where it can help separate gold particles from a mixture of sand or gravel and water.<ref name=BBC>{{cite news |title=Business Daily: Ghana's illegal gold mines |url=https://www.bbc.co.uk/programmes/w3ct5zjg |agency=BBC |date=Dec 3, 2024}}</ref> Small gold particles may form mercury-gold amalgam and therefore increase the gold recovery rates.<ref name="CRC" /> The use of mercury causes a severe pollution problem in places such as Ghana.<ref name=BBC/> It is estimated that 45,000 metric tons of mercury used in California for placer mining have not been recovered.<ref>{{cite web |url=https://pubs.usgs.gov/fs/2005/3014/ |title=Mercury Contamination from Historical Gold Mining in California |access-date=26 February 2008 |author=Alpers, C. N. |author2=Hunerlach, M. P. |author3=May, J. Y. |author4=Hothem, R. L. |publisher=U.S. Geological Survey |url-status=live |archive-url=https://web.archive.org/web/20080222034946/http://pubs.usgs.gov/fs/2005/3014/ |archive-date=22 February 2008}}</ref> Mercury was also used in silver mining to extract the metal from ore through the patio process.<ref>{{cite web |url=http://corrosion-doctors.org/Elements-Toxic/Mercury-amalgamation.htm |website=Corrosion Doctors |title=Mercury amalgamation |access-date=7 July 2009 |url-status=live| archive-url=https://web.archive.org/web/20090519051437/http://corrosion-doctors.org/Elements-Toxic/Mercury-amalgamation.htm |archive-date=19 May 2009 }}</ref>
===Firearms=== Mercury(II) fulminate is a primary explosive, which has mainly been used as a primer of a cartridge in firearms throughout the 19th and 20th centuries.<ref name=wisniak>{{cite journal |last1=Wisniak |first1=Jaime |title=Edward Charles Howard. Explosives, meteorites, and sugar |journal=Educación Química |date=April 2012 |volume=23 |issue=2 |pages=230–239 |doi=10.1016/s0187-893x(17)30114-3 |doi-access=free }}</ref> Mercury was once used as a gun barrel bore cleaner.<ref>{{cite book |author-link=George William Francis |last=Francis |first=G. W. |title=Chemical Experiments |publisher=D. Francis |date=1849 |page=62 |url=https://archive.org/details/chemicalexperim01frangoog}}</ref><ref>{{cite book |author=Castles, W. T. |author2=Kimball, V. F. |title=Firearms and Their Use |publisher=Kessinger Publishing |date=2005 |page=104 |isbn=978-1-4179-8957-7}}</ref>
===Structural biology=== Mercury-containing compounds are also of use in the field of structural biology. Mercuric compounds such as mercury(II) chloride or potassium tetraiodomercurate(II) can be added to protein crystals in an effort to create heavy atom derivatives that can be used to solve the phase problem in X-ray crystallography via isomorphous replacement or anomalous scattering methods.<ref>{{cite journal |last1=Pike |first1=Ashley C. W. |last2=Garman |first2=Elspeth F. |last3=Krojer |first3=Tobias |last4=von Delft |first4=Frank |last5=Carpenter |first5=Elisabeth P. |title=An overview of heavy-atom derivatization of protein crystals |journal=Acta Crystallographica Section D Structural Biology |date=March 2016 |volume=72 |issue=3 |pages=303–318 |doi=10.1107/S2059798316000401 |pmid=26960118 |pmc=4784662 |bibcode=2016AcCrD..72..303P }}</ref>
==Toxicity and safety== {{See also|Mercury poisoning|Mercury cycle}} {{Chembox
| Name = Mercury | container_only = yes |Section7={{Chembox Hazards | ExternalSDS = | GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|330|360D|372|410}} | PPhrases = {{P-phrases|201|260|273|280|304|340|310|308|313|391|403|233}}<ref>{{Cite web|url=https://www.sigmaaldrich.com/catalog/product/aldrich/294594|title=Mercury 294594|website=Sigma-Aldrich}}</ref> | NFPA-H = 2 | NFPA-F = 0 | NFPA-R = 0 | NFPA-S = | NFPA_ref = }} }} {{Pollution sidebar}} Due to its physical properties and relative chemical inertness, liquid mercury is absorbed very poorly through intact skin and the gastrointestinal tract.<ref name="ATSDR">{{cite web | date=1999| place= Atlanta, GA|publisher=Agency for Toxic Substances and Disease Registry |url=http://www.atsdr.cdc.gov/toxprofiles/tp46.pdf |title=Toxicological Profile for Mercury |access-date=2011-02-22 |url-status=live |archive-url=https://web.archive.org/web/20110721034540/http://www.atsdr.cdc.gov/toxprofiles/tp46.pdf |archive-date=2011-07-21 }}</ref> Mercury vapor is the primary hazard of elemental mercury. As a result, containers of mercury are securely sealed to avoid spills and evaporation. Heating of mercury, or of compounds of mercury that may decompose when heated, should be carried out with adequate ventilation in order to minimize exposure to mercury vapor. The most toxic forms of mercury are its organic compounds, such as dimethylmercury and methylmercury. Mercury can cause both chronic and acute poisoning.<ref name="acutepoisoning">{{cite journal|author=McFarland, RB |author2=Reigel, H|name-list-style=amp|journal=J. Occup. Med. |date=1978 |volume=20|issue=8|pages=532–4 |doi=10.1097/00043764-197808000-00003 |title=Chronic Mercury Poisoning from a Single Brief Exposure|pmid=690736 |bibcode=1978JOEM...20..532M }}</ref><ref name="chronicpoisoning" >{{EHC-ref |id=001 |name=Mercury |date=1976 |isbn=92-4-154061-3}}</ref>
===Releases in the environment=== thumb|right|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 about 4 ng per 1 L of ice deposited{{cn|date=May 2026}}{{clarify|Whats the connection to ice deposition?|date=May 2026}}. Volcanic eruptions and related natural sources are responsible for approximately half of atmospheric mercury emissions.<ref>{{cite web |url=https://toxics.usgs.gov/pubs/FS-051-02/|title=Glacial Ice Cores Reveal A Record of Natural and Anthropogenic Atmospheric Mercury Deposition for the Last 270 Years |publisher=United States Geological Survey (USGS)|access-date=1 May 2007|url-status=live|archive-url=https://web.archive.org/web/20070704010753/http://toxics.usgs.gov/pubs/FS-051-02/|archive-date=4 July 2007}}</ref>
Atmospheric mercury contamination in outdoor urban air at the start of the 21st century was measured at 0.01–0.02 μg/m<sup>3</sup>. A 2001 study measured mercury levels in 12 indoor sites chosen to represent a cross-section of building types, locations and ages in the New York area. This study found mercury concentrations significantly elevated over outdoor concentrations, at a range of 0.0065 – 0.523 μg/m<sup>3</sup>. The average was 0.069 μg/m<sup>3</sup>.<ref>{{cite web |date=May 2003 |publisher=Northeast Waste Management Officials' Association |url=http://www.newmoa.org/prevention/mercury/MercuryIndoor.pdf |access-date=7 July 2009 |title=Indoor Air Mercury|archive-url=https://web.archive.org/web/20090325210734/http://www.newmoa.org/prevention/mercury/MercuryIndoor.pdf|archive-date=25 March 2009}}</ref>
Half of mercury emissions are attributed to mankind. The sources in 2000 can be divided into the following estimated percentages:<ref name="Pacyna"/>{{Update inline|these data are now over 26 years out of date|date=May 2026}} * 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.<ref name="Pacyna" /> * 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.<ref>{{cite journal |doi=10.1021/es048962j |pmid=15819225 |title=Determination of Mercury Evasion in a Contaminated Headwater Stream |date=2005 |last1=Maprani |first1=Antu C. |journal=Environmental Science & Technology |volume=39 |issue=6 |pages=1679–87 |last2=Al |first2=Tom A. |last3=MacQuarrie |first3=Kerry T. |last4=Dalziel |first4=John A. |last5=Shaw |first5=Sean A. |last6=Yeats |first6=Phillip A. |bibcode=2005EnST...39.1679M}}</ref> * 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. * 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, excluding biomass burning, an important source in some regions.<ref name="Pacyna">{{cite journal |journal= Atmos Environ |date=2006 |volume=40 |issue=22 |page=4048|title= Global anthropogenic mercury emission inventory for 2000 |author= Pacyna E G |author2= Pacyna J M |author3= Steenhuisen F |author4= Wilson S |doi=10.1016/j.atmosenv.2006.03.041|bibcode = 2006AtmEn..40.4048P }}</ref> In 2024, aerial mercury emissions from cremation in England were the second-largest source after fuel combustion.<ref name=guardian-20251030>{{cite news |url=https://www.theguardian.com/environment/2025/oct/30/toxin-levels-in-fish-lead-to-calls-for-uk-wide-ban-on-mercury-dental-fillings |title=Toxin levels in fish lead to calls for UK-wide ban on mercury dental fillings |last=Salvidge |first=Rachel |newspaper=The Guardian |date=30 October 2025 |access-date=30 October 2025}}</ref>
A serious industrial disaster was the dumping of waste mercury compounds into Minamata Bay, Japan, between 1932 and 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.<ref name="auto1">{{cite web|url=http://www.env.go.jp/en/chemi/hs/minamata2002/|title=Minamata Disease The History and Measures|publisher=Ministry of the Environment, Government of Japan|access-date=7 July 2009|url-status=live|archive-url=https://web.archive.org/web/20090624205922/http://www.env.go.jp/en/chemi/hs/minamata2002/|archive-date=24 June 2009}}</ref><ref name="auto">{{cite journal |author=Dennis Normile |title=In Minamata, Mercury Still Divides |journal=Science |volume=341 |issue=6153 |pages=1446–7 |date=27 September 2013 |doi=10.1126/science.341.6153.1446 |bibcode=2013Sci...341.1446N |pmid=24072902}}</ref>
China is estimated to produce 50% of mercury emissions, most of which result from production of vinyl chloride.<ref name="Pagliaro 2016">{{cite journal |last1=Ciriminna |first1=Rosaria |last2=Falletta |first2=Ermelinda |last3=Della Pina |first3=Cristina |last4=Teles |first4=Joaquim Henrique |last5=Pagliaro |first5=Mario |title=Industrial Applications of Gold Catalysis |journal=Angewandte Chemie International Edition |date=7 November 2016 |volume=55 |issue=46 |pages=14210–14217 |doi=10.1002/anie.201604656 |pmid=27624999 |bibcode=2016ACIE...5514210C |hdl=2434/463818 |hdl-access=free }}</ref> <!-- Artificial lakes, or reservoirs, may be contaminated with mercury due to the absorption by the water of mercury from submerged trees and soil. For example, Williston Lake in northern British Columbia, created by the damming of the Peace River in 1968, is still sufficiently contaminated with mercury that it is inadvisable to consume fish from the lake.<ref>{{cite web |url=https://www.cbc.ca/news/canada/british-columbia/west-moberly-first-nations-concerned-about-mercury-contamination-in-fish-1.3070702 |title=West Moberly First Nations concerned about mercury contamination in fish |last=Meissner |first=Dirk |agency=The Canadian Press |work=CBC News |date=12 May 2015 |access-date=20 July 2021 }}</ref><ref>{{cite web |url=http://a100.gov.bc.ca/appsdata/acat/documents/r54457/CO94394_FinalReport-FIsh_Mercury_Investigation-Az_1531852633378_1851380586.pdf |title=Williston-Dinosaur Watershed Fish Mercury Investigation: 2017 Report |publisher=Fish and Wildlife Compensation Program, Peace Region |date= June 2018 |access-date=20 July 2021 }}</ref> Permafrost soils have accumulated mercury through atmospheric deposition,<ref>{{cite journal |last1=Schuster |first1=Paul |last2=Schaefer |first2=Kevin |last3=Aiken |first3=George |last4=Antweiler |first4=Ronald |last5=Dewild |first5=John |last6=Gryziec |first6=Joshua |last7=Gusmeroli |first7=Alessio |last8=Hugelius |first8=Gustaf |last9=Jafarov |first9=Elchin |last10=Krabbenhoft |first10=David |last11=Liu |first11=Lin |last12=Herman-Mercer |first12=Nicole |last13=Mu |first13=Cuicui |last14=Roth |first14=David |last15=Schaefer |first15=Tim |last16=Streigl |first16=Robert |last17=Wickland |first17=Kim |last18=Zhang |first18=Tingjun |display-authors=5| title=Permafrost Stores a Globally Significant Amount of Mercury |journal=Geophysical Research Letters |date=2018 |volume=45 |issue=3 |pages=1463–1471 |doi=10.1002/2017GL075571 |bibcode=2018GeoRL..45.1463S |doi-access=free }}</ref> and permafrost thaw in cryospheric regions is also a mechanism of mercury release into lakes, rivers, and wetlands.<ref>{{cite journal |last1=St. Pierre |first1=Kyra A. |last2=Zolkos |first2=Scott |last3=Shakil |first3=Sarah |last4=Tank |first4=Suzanne E. |last5=St. Louis |first5=Vincent L. |last6=Kokelj |first6=Steven V. |title=Unprecedented Increases in Total and Methyl Mercury Concentrations Downstream of Retrogressive Thaw Slumps in the Western Canadian Arctic |journal=Environmental Science & Technology |date=18 December 2018 |volume=52 |issue=24 |pages=14099–14109 |doi=10.1021/acs.est.8b05348 |pmid=30474969 |bibcode=2018EnST...5214099S }}</ref><ref>{{cite journal |last1=Ci |first1=Zhijia |last2=Peng |first2=Fei |last3=Xue |first3=Xian |last4=Zhang |first4=Xiaoshan |title=Permafrost Thaw Dominates Mercury Emission in Tibetan Thermokarst Ponds |journal=Environmental Science & Technology |date=5 May 2020 |volume=54 |issue=9 |pages=5456–5466 |doi=10.1021/acs.est.9b06712 |pmid=32294379 |bibcode=2020EnST...54.5456C }}</ref>
Historically, one of the largest releases was from the Colex plant, a lithium isotope separation plant at Oak Ridge, Tennessee. 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.<ref>{{cite web|publisher = United States Department of Energy|title = Introduction|url = http://www.hss.energy.gov/healthsafety/ohre/new/findingaids/epidemiologic/oakridge1/intro.html|archive-url = https://web.archive.org/web/20070708173535/http://www.hss.energy.gov/healthsafety/ohre/new/findingaids/epidemiologic/oakridge1/intro.html |archive-date = 8 July 2007}}</ref> -->
thumb|upright=0.85|Joss paper burning on the street, a common tradition practiced in Asia, Hong Kong, 2023 Mercury also enters into the environment through the improper disposal of mercury-containing products.<ref>{{cite web |url=http://www.epa.gov/epaoswer/non-hw/reduce/epr/products/mercury.htm|title=Mercury-containing Products|publisher=United States Environmental Protection Agency (EPA)|access-date=1 May 2007|archive-url=https://web.archive.org/web/20070212061414/http://www.epa.gov/epaoswer/non-hw/reduce/epr/products/mercury.htm|archive-date=12 February 2007}}</ref> Due to health concerns, toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, the amount of mercury sold in thermostats in the United States decreased from 14.5 tons in 2004 to 3.9 tons in 2007.<ref>{{cite web |url=http://www.newmoa.org/prevention/mercury/imerc/factsheets/thermostats.pdf |title=IMERC Fact Sheet: Mercury Use in Thermostats |archive-url=https://web.archive.org/web/20120617061326/http://www.newmoa.org/prevention/mercury/imerc/factsheets/thermostats.pdf |archive-date=17 June 2012 |date=January 2010 |publisher=Northeast Waste Management Officials' Association}}</ref>
The tobacco plant readily absorbs and accumulates heavy metals such as mercury from the surrounding soil into its leaves. These are subsequently inhaled during tobacco smoking.<ref>{{cite journal |pmc=3586865 |year=2012 |last1=Pourkhabbaz |first1=A. |title=Investigation of Toxic Metals in the Tobacco of Different Iranian Cigarette Brands and Related Health Issues |journal=Iranian Journal of Basic Medical Sciences |volume=15 |issue=1 |pages=636–644 |last2=Pourkhabbaz |first2=H. |pmid=23493960}}</ref> While mercury is a constituent of tobacco smoke,<ref>{{cite journal |last1=Talhout |first1=Reinskje |last2=Schulz |first2=Thomas |last3=Florek |first3=Ewa |last4=Van Benthem |first4=Jan |last5=Wester |first5=Piet |last6=Opperhuizen |first6=Antoon |title=Hazardous Compounds in Tobacco Smoke |journal=International Journal of Environmental Research and Public Health |volume=8 |issue=12 |year=2011 |pages=613–628 |doi=10.3390/ijerph8020613 |pmid=21556207 |pmc=3084482 |doi-access=free}}</ref> studies have largely failed to discover a significant correlation between smoking and mercury uptake by humans compared to sources such as occupational exposure, fish consumption, and amalgam tooth fillings.<ref>{{cite journal |vauthors=Bernhard D, Rossmann A, Wick G |year=2005| title=Metals in Cigarette Smoke |journal=IUBMB Life |volume=57 |issue=12| pages=805–809 |doi=10.1080/15216540500459667 |pmid=16393783 |doi-access=free }}</ref>
A less well-known source of mercury is the burning of joss paper,<ref>{{cite journal |last1=Shen |first1=Huazhen |last2=Tsai |first2=Cheng-Mou |last3=Yuan |first3=Chung-Shin |last4=Jen |first4=Yi-Hsiu |last5=Ie |first5=Iau-Ren |title=How incense and joss paper burning during the worship activities influences ambient mercury concentrations in indoor and outdoor environments of an Asian temple? |journal=Chemosphere |date=January 2017 |volume=167 |pages=530–540 |doi=10.1016/j.chemosphere.2016.09.159 |pmid=27764746 |bibcode=2017Chmsp.167..530S }}</ref> which is a common tradition practiced in Asia, including China,<ref>{{cite journal |last1=Lin |first1=Chunshui |last2=Huang |first2=Ru-Jin |last3=Duan |first3=Jing |last4=Zhong |first4=Haobin |last5=Xu |first5=Wei |last6=Wu |first6=Yunfei |last7=Zhang |first7=Renjian |title=Large contribution from worship activities to the atmospheric soot particles in northwest China |journal=Environmental Pollution |date=April 2022 |volume=299 |article-number=118907 |doi=10.1016/j.envpol.2022.118907 |pmid=35091017 |bibcode=2022EPoll.29918907L }}</ref> Vietnam, Hong Kong, Thailand, Taiwan and Malaysia.<ref>{{cite journal |last1=Chew |first1=N.K. |last2=Lee |first2=M. K. |last3=Ali |first3=M. |last4=Tan |first4=C. T. |title=Parkinsons disease in occupational exposure to joss paper, a report of two cases |journal=Neurology Asia Journal |date=2003 |volume=8 |url=https://knova.um.edu.my/research_publications_2000_2005/697/ }}</ref>
====Spill cleanup====
Mercury spills pose an immediate threat to people handling the material, in addition to being an environmental hazard if the material is not contained properly. This is of particular concern for visible mercury, or mercury in liquid state, as its unusual appearance and behavior for a metal makes it an attractive nuisance to the uninformed.<ref>{{cite journal |last1=Azziz-Baumgartner |first1=Eduardo |last2=Luber |first2=G. |last3=Schurz-Rogers |first3=H. |last4=Backer |first4=L. |last5=Belson |first5=M. |last6=Kieszak |first6=S. |last7=Caldwell |first7=K. |last8=Lee |first8=B. |last9=Jones |first9=R. |last10=Todd |first10=R. |last11=Rubin |first11=C. |title=Exposure assessment of a mercury spill in a Nevada school—2004 |journal=Clinical Toxicology |date=2007 |volume=45 |issue=4 |pages=391–395 |doi=10.1080/15563650601031569 |pmid=17486480 }}</ref> Procedures have been developed to contain mercury spills, as well as recommendations on appropriate responses based on the conditions of a spill.<ref>{{cite web |title=What to Do If You Spill More Mercury Than the Amount in a Thermometer |url=https://www.epa.gov/mercury/what-do-if-you-spill-more-mercury-amount-thermometer |website=EPA |language=en |date=25 August 2015 }}</ref><ref>{{cite web |title=Action levels for elemental mercury spills |url=https://stacks.cdc.gov/view/cdc/37505 |date=22 March 2012 }}</ref> Tracking liquid mercury away from the site of a spill is a major concern in liquid mercury spills; regulations emphasize containment of the visible mercury as the first course of action, followed by monitoring of mercury vapors and vapor cleanup. Several products are sold as mercury spill adsorbents, ranging from metal salts to polymers and zeolites.<ref>{{cite journal |last1=Yu |first1=Jin-Gang |last2=Yue |first2=Bao-Yu |last3=Wu |first3=Xiong-Wei |last4=Liu |first4=Qi |last5=Jiao |first5=Fei-Peng |last6=Jiang |first6=Xin-Yu |last7=Chen |first7=Xiao-Qing |title=Removal of mercury by adsorption: a review |journal=Environmental Science and Pollution Research |date=March 2016 |volume=23 |issue=6 |pages=5056–5076 |doi=10.1007/s11356-015-5880-x |pmid=26620868 |bibcode=2016ESPR...23.5056Y }}</ref>
===Sediment contamination===
Sediments within large urban-industrial estuaries act as an important sink for point source and diffuse mercury pollution within catchments.<ref name="VaneBeriro2015">{{cite journal |last1=Vane |first1=C.H. |last2=Beriro |first2=D.J. |last3=Turner |first3=G.H. |title=Rise and fall of mercury (Hg) pollution in sediment cores of the Thames Estuary, London, UK |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |volume=105|issue=4|year=2015|pages=285–296 |doi=10.1017/S1755691015000158 |doi-access=free}}</ref> A 2015 study of foreshore sediments from the Thames estuary measured total mercury at 0.01 to 12.07 mg/kg with mean of 2.10 mg/kg and median of 0.85 mg/kg (n = 351).<ref name="VaneBeriro2015" /> The highest mercury concentrations were shown to occur in and around the city of London in association with fine grain muds and high total organic carbon content.<ref name="VaneBeriro2015" /> The strong affinity of mercury for carbon rich sediments has also been observed in salt marsh sediments of the River Mersey, with a mean concentration of 2 mg/kg, up to 5 mg/kg.<ref name="VaneJones2009">{{cite journal |last1=Vane |first1=C.H. |last2=Jones |first2=D.G. |last3=Lister |first3=T.R. |title=Mercury contamination in surface sediments and sediment cores of the Mersey Estuary, UK |journal=Marine Pollution Bulletin |volume=58 |issue=6 |year=2009 |pages=940–946 |doi=10.1016/j.marpolbul.2009.03.006 |pmid=19356771 |bibcode=2009MarPB..58..940V |url=http://nora.nerc.ac.uk/id/eprint/7405/1/Vane_et_al__2009_Mersey_Hg_9_3_09.pdf}}</ref> These concentrations are far higher than those in the salt marsh river creek sediments of New Jersey and mangroves of Southern China, which exhibit low mercury concentrations of about 0.2 mg/kg.<ref name="VaneHarrison2008">{{cite journal |last1=Vane |first1=C.H. |last2=Harrison |first2=I. |last3=Kim |first3=A.W. |last4=Moss-Hayes |first4=V. |last5=Vickers |first5=B.P. |last6=Horton |first6=B.P. |title=Status of organic pollutants in surface sediments of Barnegat Bay-Little Egg Harbor Estuary, New Jersey, USA |journal=Marine Pollution Bulletin |volume=56 |issue=10 |year=2008 |pages=1802–1808 |doi=10.1016/j.marpolbul.2008.07.004 |pmid=18715597 |bibcode=2008MarPB..56.1802V |url=http://nora.nerc.ac.uk/id/eprint/4452/1/Vane_MPB_2008_for_NORA__2_.pdf}}</ref><ref name="VaneHarrison2009">{{cite journal |last1=Vane |first1=C.H. |last2=Harrison |first2=I. |last3=Kim |first3=A.W. |last4=Moss-Hayes |first4=V. |last5=Vickers |first5=B.P. |last6=Hong |first6=K. |title=Organic and metal contamination in surface mangrove sediments of South China |journal=Marine Pollution Bulletin |volume=58 |issue=1 |year=2009 |pages=134–144 |doi=10.1016/j.marpolbul.2008.09.024 |pmid=18990413 |bibcode=2009MarPB..58..134V |url=http://nora.nerc.ac.uk/id/eprint/5547/1/Vane_et_al.%2C_2009.pdf}}</ref>
===Occupational exposure=== thumb|EPA workers clean up residential mercury spill in 2004 Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization,<ref>{{cite web|url=https://www.who.int/news-room/fact-sheets/detail/mercury-and-health|title=Mercury and health|website=World Health Organization|date=31 March 2017|access-date=22 December 2023}}</ref> OSHA, and NIOSH all treat mercury as an occupational hazard; both OSHA and NIOSH, among other regulatory agencies, have established specific occupational exposure limits on the element and its derivative compounds in liquid and vapor form.<ref>{{cite web|url=https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TABLEZ2|publisher=Occupational Safety and Health Administration|title=1910.1000 TABLE Z-2|date=23 June 2006|access-date=22 December 2023}}</ref><ref>{{cite web|url=https://www.cdc.gov/niosh/npg/npgd0383.html|publisher=The National Institute for Occupational Safety and Health|website=Centers for Disease Control and Prevention|title=Mercury compounds [except (organo) alkyls] (as Hg)|date=30 October 2019|access-date=22 December 2023}}</ref> Environmental releases and disposal of mercury are regulated in the U.S. primarily by the United States Environmental Protection Agency.
===Fish=== {{Main|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, bluefin tuna, albacore tuna, and tilefish contain higher concentrations of mercury than others. Because mercury and methylmercury are fat soluble, they primarily accumulate in the viscera, although they are also found throughout the muscle tissue.<ref>{{cite journal |last1=Cocoros |first1=Glenn |last2=Cahn |first2=Phyllis H. |last3=Siler |first3=William |title=Mercury concentrations in fish, plankton and water from three Western Atlantic estuaries |journal=Journal of Fish Biology |date=November 1973 |volume=5 |issue=6 |pages=641–647 |doi=10.1111/j.1095-8649.1973.tb04500.x |bibcode=1973JFBio...5..641C }}</ref> Mercury presence in fish muscles can be studied using non-lethal muscle biopsies.<ref>{{Cite web|date=2015-09-30|title=How We Do Things at IISD-ELA: Collecting a fish muscle biopsy|url=https://www.iisd.org/library/how-we-do-things-iisd-ela-collecting-fish-muscle-biopsy|access-date=2020-07-07|website=IISD|language=en}}</ref> Mercury present in prey fish accumulates in the predator that consumes them. Since fish are less efficient at depurating than accumulating methylmercury, methylmercury concentrations in the fish tissue 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.<ref name="auto1"/><ref name="auto"/>
In the Lower Amazon, mercury contamination in fish is driven by anthropogenic activities such as gold mining and deforestation, which release mercury into aquatic ecosystems.<ref name=":0">{{cite journal |last1=Albuquerque |first1=Fabio Edir Amaral |last2=Minervino |first2=Antonio Humberto Hamad |last3=Miranda |first3=Marta |last4=Herrero-Latorre |first4=Carlos |last5=Barrêto Júnior |first5=Raimundo Alves |last6=Oliveira |first6=Francisco Leonardo Costa |last7=Sucupira |first7=Maria Claudia Araripe |last8=Ortolani |first8=Enrico Lippi |last9=López-Alonso |first9=Marta |title=Toxic and essential trace element concentrations in fish species in the Lower Amazon, Brazil |journal=Science of the Total Environment |date=August 2020 |volume=732 |article-number=138983 |doi=10.1016/j.scitotenv.2020.138983 |pmid=32417551 |bibcode=2020ScTEn.73238983A }}</ref><ref>{{cite journal |last1=Albuquerque |first1=Fabio Edir Amaral |last2=Herrero-Latorre |first2=Carlos |last3=Miranda |first3=Marta |last4=Barrêto Júnior |first4=Raimundo Alves |last5=Oliveira |first5=Francisco Leonardo Costa |last6=Sucupira |first6=Maria Cláudia Araripe |last7=Ortolani |first7=Enrico Lippi |last8=Minervino |first8=Antonio Humberto Hamad |last9=López-Alonso |first9=Marta |title=Fish tissues for biomonitoring toxic and essential trace elements in the Lower Amazon |journal=Environmental Pollution |date=August 2021 |volume=283 |article-number=117024 |doi=10.1016/j.envpol.2021.117024 |pmid=33857879 |bibcode=2021EPoll.28317024A }}</ref> Studies report mercury concentrations in fish muscle tissue ranging from 0.01 to 0.67 μg/g, with carnivorous species like ''Plagioscion squamosissimus'' showing higher levels due to biomagnification, sometimes exceeding the World Health Organization's safety threshold of 0.5 μg/g.<ref name=":0" /> Local communities relying on fish as a dietary staple face potential health risks from mercury exposure. Mercury levels in aquatic species, including fish and shrimp (''Macrobrachium amazonicum''), indicate broader environmental contamination, particularly near mining areas.<ref>{{cite journal |last1=Albuquerque |first1=Fabio Edir Amaral |last2=Minervino |first2=Antonio Humberto Hamad |last3=Miranda |first3=Marta |last4=Herrero-Latorre |first4=Carlos |last5=Barrêto Júnior |first5=Raimundo Alves |last6=Oliveira |first6=Francisco Leonardo Costa |last7=Dias |first7=Salatiel Ribeiro |last8=Ortolani |first8=Enrico Lippi |last9=López-Alonso |first9=Marta |title=Toxic and essential trace element concentrations in the freshwater shrimp Macrobrachium amazonicum in the Lower Amazon, Brazil |journal=Journal of Food Composition and Analysis |date=March 2020 |volume=86 |article-number=103361 |doi=10.1016/j.jfca.2019.103361 |doi-access=free }}</ref> Recent analyses of fish from western Pará further demonstrate elevated concentrations of mercury and other potentially toxic elements in multiple species, with several samples surpassing international food safety guidelines. Risk assessments based on regional consumption patterns suggest that frequent fish consumers may exceed tolerable daily intakes, highlighting ongoing human health concerns linked to mercury release and bioaccumulation in Amazonian aquatic food webs.<ref>{{cite journal |last1=Albuquerque |first1=Fábio Edir Amaral |last2=de Assis |first2=Francisco Flávio Vieira |last3=Miranda |first3=Marta |last4=Sousa |first4=Rejane Santos |last5=Barrêto-Júnior |first5=Raimundo Alves |last6=López Alonso |first6=Marta |last7=Minervino |first7=Antonio Humberto Hamad |title=More Danger Than Meets the Eye: Potentially Toxic Element Contamination in Fish from the Western Pará Poses Significant Hazards to Local Communities |journal=ACS Omega |date=10 February 2026 |volume=11 |issue=7 |article-number=acsomega.5c10676 |doi=10.1021/acsomega.5c10676 |doi-access=free |pmid=41768758 |pmc=12947147 }}</ref>
===Cosmetics=== Some facial creams contain dangerous levels of mercury. Most contain comparatively non-toxic inorganic mercury, but products containing highly toxic organic mercury have been encountered.<ref>{{cite web |url=https://arstechnica.com/science/2019/12/the-horrifying-case-of-organic-mercury-poisoning-from-tainted-skin-cream/ |title=Woman had 524x the normal level of mercury in her blood from skin cream use |last=Mole |first=Beth |website=ArsTechnica |date=20 December 2019 |access-date=20 July 2021}}</ref><ref>{{cite journal |url=https://www.cdc.gov/mmwr/volumes/68/wr/mm6850a4.htm |title=Notes from the Field: Methylmercury Toxicity from a Skin Lightening Cream Obtained from Mexico — California, 2019 |journal=Morbidity and Mortality Weekly Report |vauthors=Mudan, Anita, Copan L, Wang R, et al. |date=20 December 2019 |volume=68 |number=50 |pages=1166–1167 |doi=10.15585/mmwr.mm6850a4|pmid=31856147 |pmc=6936160 }}</ref> New York City residents have been found to be exposed to significant levels of inorganic mercury compounds through the use of skin care products.<ref>{{cite journal|vauthors=McKelvey W, Jeffery N, Clark N, Kass D, Parsons PJ|date= 2010|title=Population-Based Inorganic Mercury Biomonitoring and the Identification of Skin Care Products as a Source of Exposure in New York City| journal=Environ Health Perspect |volume=119|issue=2|publication-date= 2011|doi=10.1289/ehp.1002396|pages=203–9|pmid=20923743|pmc=3040607}}</ref>
===Effects and symptoms of mercury poisoning=== {{Main|Mercury poisoning}}
Toxic effects include damage to the brain, kidneys and lungs. Mercury poisoning can result in several diseases, including acrodynia (pink disease), Hunter-Russell syndrome, and Minamata disease. Symptoms typically include sensory impairment (vision, hearing, speech), disturbed sensation and a lack of coordination. The type and degree of symptoms exhibited depend upon the individual toxin, the dose, and the method and duration of exposure. 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/m<sup>3</sup>.<ref name="ngim">{{cite journal |title=Chronic neurobehavioral effects of elemental mercury in dentists |pmid=1463679 |journal=British Journal of Industrial Medicine|volume=49 |issue=11| date=1992 |author1=Ngim, CH |author2=Foo, SC |author3=Boey, KW |author4=Keyaratnam, J |pmc=1039326 |pages=782–90 |doi=10.1136/oem.49.11.782}}</ref><ref name="liang">{{cite journal |title=Psychological effects of low exposure to mercury vapor: Application of computer-administered neurobehavioral evaluation system |journal=Environmental Research |volume=60 |issue=2| doi=10.1006/enrs.1993.1040 |date=1993 |pmid=8472661 |last1=Liang |first1=Y. X. |last2=Sun |first2=R. K. |last3=Sun |first3=Y. |last4=Chen |first4=Z. Q. |last5=Li |first5=L. H. |bibcode=1993ER.....60..320L |pages=320–7}}</ref>
A study has shown that acute exposure (4–8 hours) to calculated elemental mercury levels of 1.1 to 44 mg/m<sup>3</sup> resulted in chest pain, dyspnea, cough, hemoptysis, impairment of pulmonary function, and evidence of interstitial pneumonitis.<ref name="acutepoisoning" /> 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.<ref name="chronicpoisoning" /><ref>{{EHC-ref |id=118 |name=Inorganic mercury |date=1991 |isbn=92-4-157118-7}}</ref>
===Treatment=== Research on the treatment of mercury poisoning is limited. Currently available drugs for acute mercurial poisoning include chelators ''N''-acetyl-<small>D</small>,<small>L</small>-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.<ref name=Bluhm>{{cite journal |last1=Bluhm |first1=Renata E. |last2=Bobbitt |first2=Robert G. |last3=Welch |first3=Larry W. |last4=Wood |first4=Alastair J.J. |last5=Bonfiglio |first5=J. Frank |last6=Sarzen |first6=Christopher |last7=Heath |first7=Andrew J. |last8=Branch |first8=Robert A. |title=Elemental Mercury Vapour Toxicity, Treatment, and Prognosis After Acute, Intensive Exposure in Chloralkali Plant Workers. Part I: History, Neuropsychological Findings and Chelator effects |journal=Human & Experimental Toxicology |date=May 1992 |volume=11 |issue=3 |pages=201–210 |doi=10.1177/096032719201100308 |pmid=1352115 |bibcode=1992HETox..11..201B }}</ref> 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.<ref name=Bluhm/>
==Regulations==
===International=== 140 countries agreed in the Minamata Convention on Mercury by the United Nations Environment Programme (UNEP) to prevent mercury vapor emissions.<ref>{{cite web |url=http://www.unep.org/newscentre/Default.aspx?DocumentID=2702&ArticleID=9373&l=en |title=Minamata Convention Agreed by Nations |publisher=United Nations Environment Program |access-date=19 January 2013 |url-status=live |archive-url=https://web.archive.org/web/20130130192928/http://www.unep.org/NewsCentre/default.aspx?DocumentID=2702&ArticleID=9373&l=en |archive-date=30 January 2013}}</ref> The convention was signed on 10 October 2013.<ref>{{Cite web|url=https://www.un.org/apps/news/story.asp?NewsID=43963&Cr=mercury&Cr1=#.UPt4ikfdP5M|title=UN News — Governments at UN forum agree on legally-binding treaty to curb mercury pollution|last=Section|first=United Nations News Service|date=19 January 2013|website=UN News Service Section|access-date=22 November 2016|url-status=live|archive-url=https://web.archive.org/web/20161016131029/http://www.un.org/apps/news/story.asp?NewsID=43963&Cr=mercury&Cr1=#.UPt4ikfdP5M|archive-date=16 October 2016}}</ref>
===United States=== 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.<ref name="epa regs">{{cite web |url=http://www.epa.gov/mercury/regs.htm |title=Mercury: Laws and regulations|date=16 April 2008|publisher=United States Environmental Protection Agency|access-date=30 May 2008 |archive-url=https://web.archive.org/web/20080513123415/http://epa.gov/mercury/regs.htm|archive-date=13 May 2008}}</ref> North America contributed approximately 11% of the total global anthropogenic mercury emissions in 1995.<ref>{{cite web |url=http://www.ijc.org/php/publications/html/12br/english/report/chemical/rme.html|title=Reductions in Mercury Emissions|publisher=International Joint Commission on the Great Lakes |archive-url=https://web.archive.org/web/20080828060223/http://www.ijc.org/php/publications/html/12br/english/report/chemical/rme.html|archive-date=28 August 2008|access-date=21 July 2008}}</ref>
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, the EPA promulgated a regulation<ref>{{cite web |url=http://www.epa.gov/air/mercuryrule/|title=Clean Air Mercury Rule|publisher=United States Environmental Protection Agency (EPA)|access-date=1 May 2007|archive-url=https://web.archive.org/web/20070630045554/http://www.epa.gov/air/mercuryrule/|archive-date=30 June 2007}}</ref> that added power plants to the list of sources that should be controlled and instituted a national cap and trade system. States were given until November 2006 to impose stricter controls, but after a legal challenge from several states, the regulations were struck down by a federal appeals court on 8 February 2008. The rule was deemed not sufficient to protect the health of persons living near coal-fired power plants, given the negative effects documented in the EPA Study Report to Congress of 1998.<ref name="nj vs epa">{{cite news|url=http://pacer.cadc.uscourts.gov/docs/common/opinions/200802/05-1097a.pdf|title=State of New Jersey et al., Petitioners vs. Environmental Protection Agency (Case No. 05-1097)|publisher=United States Court of Appeals for the District of Columbia Circuit. Argued 6 December 2007, Decided 8 February 2008|access-date=30 May 2008|url-status=live|archive-url=https://web.archive.org/web/20110203021258/http://pacer.cadc.uscourts.gov/docs/common/opinions/200802/05-1097a.pdf|archive-date=3 February 2011}}</ref> However newer data published in 2015 showed that after introduction of the stricter controls mercury declined sharply, indicating that the Clean Air Act had its intended impact.<ref>{{cite journal |vauthors=Castro MS, Sherwell J |year=2015 |title=Effectiveness of Emission Controls to Reduce the Atmospheric Concentrations of Mercury |journal=Environmental Science & Technology |volume=49 |issue=24| pages=14000–14007 |doi=10.1021/acs.est.5b03576 |pmid=26606506 |bibcode=2015EnST...4914000C}}</ref>
The EPA announced new rules for coal-fired power plants on 22 December 2011.<ref>{{cite news |url=https://www.bostonglobe.com/news/nation/2011/12/22/oldest-dirtiest-power-plants-told-clean/mORfVS1jUOOlXuTPIRQKbL/story.html |title=Oldest, dirtiest power plants told to clean up|date=22 December 2011|newspaper=Boston Globe|access-date=2 January 2012|url-status=live|archive-url=https://web.archive.org/web/20140714151501/http://www.bostonglobe.com/news/nation/2011/12/22/oldest-dirtiest-power-plants-told-clean/mORfVS1jUOOlXuTPIRQKbL/story.html|archive-date=14 July 2014}}</ref> Cement kilns that burn hazardous waste are held to a looser standard than are standard hazardous waste incinerators in the United States, and as a result are a disproportionate source of mercury pollution.<ref>{{cite news|url=https://www.npr.org/2011/11/10/142183546/epa-regulations-give-kilns-permission-to-pollute|title=EPA Regulations Give Kilns Permission To Pollute|author=Howard Berkes|agency=NPR|date=10 November 2011|access-date=2 January 2012|url-status=live|archive-url=https://web.archive.org/web/20111117112612/http://www.npr.org/2011/11/10/142183546/epa-regulations-give-kilns-permission-to-pollute |archive-date=17 November 2011}}</ref>
===European Union=== 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.<ref name="eu regs">{{cite web|url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2003:037:0019:0023:EN:PDF |title=Directive 2002/95/EC on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment|date=27 January 2003}} Article 4 Paragraph 1. e.g. "Member States shall ensure that, from July 1, 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)."</ref> There are restrictions 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).<ref>{{cite web|url=http://www.eiatrack.org/s/1785|title=Mercury compounds in European Union|date=2007|publisher=EIA Track|access-date=30 May 2008|archive-url=https://web.archive.org/web/20080428065154/http://www.eiatrack.org/s/1785|archive-date=28 April 2008}}</ref> 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.<ref name="eu reuters">{{cite news|url=https://www.reuters.com/article/environmentNews/idUSL0988544920070710|title=EU bans mercury in barometers, thermometers|author=Jones H.|date=10 July 2007|publisher=Reuters|access-date=12 September 2017|url-status=live|archive-url=https://web.archive.org/web/20090103193545/http://www.reuters.com/article/environmentNews/idUSL0988544920070710|archive-date=3 January 2009}}</ref>
===Scandinavia=== Norway enacted a total ban on the use of mercury in the manufacturing and import/export of mercury products, effective 1 January 2008.<ref name="norway">{{cite news |url=http://www.eubusiness.com/news-eu/1198237627.85 |title=Norway to ban mercury|date=21 December 2007|publisher=EU Business|access-date=30 May 2008 |archive-url = https://web.archive.org/web/20080121173517/http://www.eubusiness.com/news-eu/1198237627.85 |archive-date = 21 January 2008}}</ref> In 2002, several lakes in Norway were found to have a poor state of mercury pollution, with an excess of 1 μg/g of mercury in their sediment.<ref name="environment norway">{{cite journal |doi=10.1016/j.scitotenv.2005.09.059 |date=2006 |title=Atmospheric mercury in Norway: contributions from different sources |volume=368 |issue=1 |pages=3–9 |pmid=16310836 |journal=The Science of the Total Environment|author1=Berg, T |author2=Fjeld, E |author3=Steinnes, E |bibcode=2006ScTEn.368....3B}}</ref> In 2008, Norway's Minister of Environment Development Erik Solheim said: "Mercury is among the most dangerous environmental toxins. Satisfactory alternatives to Hg in products are available, and it is therefore fitting to induce a ban."<ref>{{cite report |last1=Edlich |first1=Richard F |last2=Rhoads |first2=Samantha K. |last3=Cantrell |first3=Holly S. |last4=Azavedo |first4=Sabrina M. |last5=Newkirk |first5=Anthony T. |title=Banning Mercury Amalgam in the United States |location=USA |publisher=Food and Drug Administration |url=https://www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials/medicaldevices/medicaldevicesadvisorycommittee/dentalproductspanel/ucm236379.pdf |archive-url=https://web.archive.org/web/20131101215237/https://www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials/medicaldevices/medicaldevicesadvisorycommittee/dentalproductspanel/ucm236379.pdf |archive-date=1 November 2013}}</ref> Products containing mercury were banned in Sweden in 2009,<ref>{{Cite web|url=http://www.thelocal.se/20090114/16892 |title=Sweden to ban mercury |work=The Local|date=14 January 2009 |access-date=22 November 2016 |url-status=live |archive-url=https://web.archive.org/web/20160828040807/http://www.thelocal.se/20090114/16892 |archive-date=28 August 2016}}</ref><ref>{{Cite web |url=http://www.thelocal.se/20120421/40396 |title=Sweden may be forced to lift ban on mercury |work=The Local|date=21 April 2012 |access-date=22 November 2016 |url-status=live |archive-url=https://web.archive.org/web/20160828101154/http://www.thelocal.se/20120421/40396 |archive-date=28 August 2016}}</ref> while elemental mercury has been banned from manufacture and use in all but a few applications (such as certain energy-saving light sources and amalgam dental fillings) in Denmark since 2008.<ref>{{cite web|url=https://www2.mst.dk/Udgiv/publications/2014/01/978-87-93026-98-8.pdf|title=Survey of mercury and mercury compounds |website=Miljøstyrelsen |date=2014|access-date=21 December 2023}}</ref>
==See also== {{Portal|Chemistry}} * Mercury (disambiguation) for other uses of the name * COLEX process (isotopic separation) * Mercury pollution in the ocean * Red mercury
== Notes == {{notelist}}
== References ==
{{reflist | colwidth=30em | refs =
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