mercury (element)
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Mercury is a
chemical element A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...
; it has
symbol A symbol is a mark, Sign (semiotics), sign, or word that indicates, signifies, or is understood as representing an idea, physical object, object, or wikt:relationship, relationship. Symbols allow people to go beyond what is known or seen by cr ...
Hg and
atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (''n''p) or the number of pro ...
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 Standard temperature and pressure (STP) or standard conditions for temperature and pressure are various standard sets of conditions for experimental measurements used to allow comparisons to be made between different sets of data. The most used ...
; the only other element that is liquid under these conditions is the
halogen The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...
bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
, though metals such as
caesium Caesium (IUPAC spelling; also spelled cesium in American English) is a chemical element; it has Symbol (chemistry), symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only f ...
,
gallium Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
, and
rubidium Rubidium is a chemical element; it has Symbol (chemistry), symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have ...
melt just above
room temperature Room temperature, colloquially, denotes the range of air temperatures most people find comfortable indoors while dressed in typical clothing. Comfortable temperatures can be extended beyond this range depending on humidity, air circulation, and ...
. Mercury occurs in deposits throughout the world mostly as
cinnabar Cinnabar (; ), or cinnabarite (), also known as ''mercurblende'' is the bright scarlet to brick-red form of Mercury sulfide, mercury(II) sulfide (HgS). It is the most common source ore for refining mercury (element), elemental mercury and is t ...
( mercuric sulfide). The red pigment
vermilion Vermilion (sometimes vermillion) is a color family and pigment most often used between antiquity and the 19th century from the powdered mineral cinnabar (a form of mercury sulfide). It is synonymous with red orange, which often takes a moder ...
is obtained by grinding natural cinnabar or synthetic mercuric sulfide. Exposure to mercury and mercury-containing organic compounds is toxic to the
nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...
,
immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...
and
kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...
s of humans and other animals;
mercury poisoning Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashe ...
can result from exposure to water-soluble forms of mercury (such as
mercuric chloride Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. ...
or
methylmercury Methylmercury is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environment ...
) either directly or through mechanisms of
biomagnification Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance, e.g a pesticide, in the tissue (biology), tissues of organisms at successively higher levels in a food chain. This inc ...
. Mercury is used in
thermometer A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
s,
barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...
s,
manometer Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressu ...
s,
sphygmomanometer A sphygmomanometer ( ), also known as a blood pressure monitor, blood pressure machine, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff i ...
s,
float valve A ballcock (also balltap or float valve) is a mechanism or machine for filling water tanks, such as those found in flush toilets, while avoiding overflow and (in the event of low water pressure) backflow. The modern ballcock was invented by J ...
s,
mercury switch A mercury switch is an electricity, electrical switch that opens and closes a electrical circuit, circuit when a small amount of the liquid metal mercury (element), mercury connects metal electrodes to close the circuit. There are several differ ...
es,
mercury relay A mercury relay (mercury displacement relay, mercury contactor) is a relay that uses mercury as the switching element. They are used as high-current switches or contactors, where contact erosion from constant cycling would be a problem for conv ...
s,
fluorescent lamp A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor ...
s and other devices, although concerns about the element's toxicity have led to the phasing out of such mercury-containing instruments. It remains in use in scientific research applications and in amalgam for dental restoration in some locales. It is also used in fluorescent lighting. Electricity passed through mercury vapor in a fluorescent lamp produces short-wave
ultraviolet light Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...
, which then causes the
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...
in the tube to
fluoresce Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...
, making visible light.


Properties


Physical properties

Mercury is a heavy, silvery-white metal that is liquid at room temperature. Compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity. in It has a
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...
of −38.83 °C and a
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...
of 356.73 °C, both the lowest of any stable metal, although preliminary experiments on
copernicium Copernicium is a synthetic chemical element; it has symbol Cn and atomic number 112. Its known isotopes are extremely radioactive, and have only been created in a laboratory. The most stable known isotope, copernicium-285, has a half-life of ap ...
and flerovium have indicated that they have even lower boiling points. This effect is due to
lanthanide contraction The lanthanide contraction is the greater-than-expected decrease in atomic radii and ionic radii of the elements in the lanthanide series, from left to right. It is caused by the poor shielding effect of nuclear charge by the 4f electrons alo ...
and relativistic contraction reducing the orbit radius of the outermost electrons, and thus weakening the metallic bonding in mercury. Upon freezing, the volume of mercury decreases by 3.59% and its density changes from 13.69 g/cm3 when liquid to 14.184 g/cm3 when solid. The coefficient of volume expansion is 181.59 × 10−6 at 0 °C, 181.71 × 10−6 at 20 °C and 182.50 × 10−6 at 100 °C (per °C). Solid mercury is malleable and ductile, and can be cut with a knife. Table of thermal and physical properties of liquid mercury:


Chemical properties

Mercury does not react with most acids, such as dilute
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
, although oxidizing acids such as concentrated sulfuric acid and
nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
or
aqua regia Aqua regia (; from Latin, "regal water" or "royal water") is a mixture of nitric acid and hydrochloric acid, optimally in a molar concentration, molar ratio of 1:3. Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but i ...
dissolve it to give
sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
,
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
, and
chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...
. Like silver, mercury reacts with atmospheric
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
. Mercury reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury (spill kits also use
activated carbon Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that greatly increase the surface ar ...
and powdered zinc).


Amalgams

Mercury dissolves many metals such as
gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
and
silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
to form
amalgams Amalgam most commonly refers to: * Amalgam (chemistry), mercury alloy * Amalgam (dentistry), material of silver tooth fillings ** Bonded amalgam, used in dentistry Amalgam may also refer to: * Amalgam Comics, a publisher * Amalgam Digital, an in ...
.
Iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
is an exception, and iron flasks have traditionally been used to transport the material. Several other first row transition metals with the exception of
manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...
,
copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
and
zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...
are also resistant in forming amalgams. Other elements that do not readily form amalgams with mercury include
platinum Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...
. Sodium amalgam is a common reducing agent in
organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...
, and is also used in high-pressure sodium lamps. Mercury readily combines with
aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
to form a mercury-aluminium amalgam when the two pure metals come into contact. Since the amalgam destroys the
aluminium oxide Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several Aluminium oxide (compounds), aluminium oxides, and specifically identified as alum ...
layer which protects metallic aluminium from oxidizing in-depth (as in iron
rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH) ...
ing), 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. 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.


Isotopes

There are seven stable
isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...
s of mercury, with being the most abundant (29.86%). The longest-lived
radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...
s are with a
half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...
of 444 years, and with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. occurs naturally in tiny traces as an intermediate decay product of . and are the most often studied
NMR Nuclear magnetic resonance (NMR) is a physical phenomenon in which atomic nucleus, nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near and far field, near field) and respond by producing ...
-active nuclei, having spins of and respectively.


Etymology

''Hg'' is the modern
chemical symbol Chemical symbols are the abbreviations used in chemistry, mainly for chemical elements; but also for functional groups, chemical compounds, and other entities. Element symbols for chemical elements, also known as atomic symbols, normally consist ...
for mercury. It is an abbreviation of , a
romanized In linguistics, romanization is the conversion of text from a different writing system to the Roman (Latin) script, or a system for doing so. Methods of romanization include transliteration, for representing written text, and transcription, ...
form of the
ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
name for mercury, (). Hydrargyrum ( ) ''
Random House Webster's Unabridged Dictionary ''Random House Webster's Unabridged Dictionary'' is a large American dictionary, first published in 1966 as ''The Random House Dictionary of the English Language: The Unabridged Edition''. Edited by Editor-in-chief Jess Stein, it contained 315,0 ...
''.
has also been used in English, though the term is now dated. is a Greek compound word meaning , from - (-), the root of () , and () . Like the English name quicksilver (), this name was due to mercury's liquid and shiny properties. The modern English name ''mercury'' comes from the planet Mercury. In medieval
alchemy Alchemy (from the Arabic word , ) is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practised in China, India, the Muslim world, and Europe. In its Western form, alchemy is first ...
, the seven known metals—quicksilver,
gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
,
silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
,
copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
,
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
,
lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
, and tin—were associated with the seven planets. 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 symbol Alchemical symbols were used to denote chemical elements and compounds, as well as alchemy, alchemical apparatus and processes, until the 18th century. Although notation was partly standardized, style and symbol varied between alchemists. Lüdy ...
s 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.


History

Mercury was found in
Egyptian ''Egyptian'' describes something of, from, or related to Egypt. Egyptian or Egyptians may refer to: Nations and ethnic groups * Egyptians, a national group in North Africa ** Egyptian culture, a complex and stable culture with thousands of year ...
tombs that date from 1500 BC;
cinnabar Cinnabar (; ), or cinnabarite (), also known as ''mercurblende'' is the bright scarlet to brick-red form of Mercury sulfide, mercury(II) sulfide (HgS). It is the most common source ore for refining mercury (element), elemental mercury and is t ...
, the most common natural source of mercury, has been in use since the
Neolithic Age The Neolithic or New Stone Age (from Greek 'new' and 'stone') is an archaeological period, the final division of the Stone Age in Mesopotamia, Asia, Europe and Africa (c. 10,000 BCE to c. 2,000 BCE). It saw the Neolithic Revolution, a wid ...
. In
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
and
Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...
, 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. The first emperor of a unified China, Qín Shǐ Huáng Dì—allegedly buried in a
tomb A tomb ( ''tumbos'') or sepulchre () is a repository for the remains of the dead. It is generally any structurally enclosed interment space or burial chamber, of varying sizes. Placing a corpse into a tomb can be called '' immurement'', alth ...
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 Jade is an umbrella term for two different types of decorative rocks used for jewelry or Ornament (art), ornaments. Jade is often referred to by either of two different silicate mineral names: nephrite (a silicate of calcium and magnesium in t ...
mixture formulated by Qin alchemists intended as an elixir of immortality. Khumarawayh ibn Ahmad ibn Tulun, the second
Tulunid The Tulunid State, also known as the Tulunid Emirate or The State of Banu Tulun, and popularly referred to as the Tulunids () was a Mamluk dynasty of Turkic origin who was the first independent dynasty to rule Egypt, as well as much of Syria, s ...
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. In November 2014 "large quantities" of mercury were discovered in a chamber 60 feet below the 1800-year-old pyramid known as the Temple of the Feathered Serpent, the third-largest pyramid of
Teotihuacan Teotihuacan (; Spanish language, Spanish: ''Teotihuacán'', ; ) is an ancient Mesoamerican city located in a sub-valley of the Valley of Mexico, which is located in the State of Mexico, northeast of modern-day Mexico City. Teotihuacan is ...
, Mexico, along with "jade statues, jaguar remains, a box filled with carved shells and rubber balls". In Lamanai, once a major city of the
Maya civilization The Maya civilization () was a Mesoamerican civilization that existed from antiquity to the early modern period. It is known by its ancient temples and glyphs (script). The Maya script is the most sophisticated and highly developed writin ...
, a pool of mercury was found under a marker in a Mesoamerican ballcourt.
Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
recounts that
Daedalus In Greek mythology, Daedalus (, ; Greek language, Greek: Δαίδαλος; Latin language, Latin: ''Daedalus''; Etruscan language, Etruscan: ''Taitale'') was a skillful architect and craftsman, seen as a symbol of wisdom, knowledge and power. H ...
made a wooden statue of
Aphrodite Aphrodite (, ) is an Greek mythology, ancient Greek goddess associated with love, lust, beauty, pleasure, passion, procreation, and as her syncretism, syncretised Roman counterpart , desire, Sexual intercourse, sex, fertility, prosperity, and ...
move by pouring quicksilver in its interior. In
Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...
Daedalus gave the appearance of voice in his statues using quicksilver. The
ancient Greeks Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically re ...
used
cinnabar Cinnabar (; ), or cinnabarite (), also known as ''mercurblende'' is the bright scarlet to brick-red form of Mercury sulfide, mercury(II) sulfide (HgS). It is the most common source ore for refining mercury (element), elemental mercury and is t ...
(mercury sulfide) in ointments; the
ancient Egyptians Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower ...
and the Romans used it in
cosmetics Cosmetics are substances that are intended for application to the body for cleansing, beautifying, promoting attractiveness, or altering appearance. They are mixtures of chemical compounds derived from either Natural product, natural source ...
. By 500 BC mercury was used to make
amalgams Amalgam most commonly refers to: * Amalgam (chemistry), mercury alloy * Amalgam (dentistry), material of silver tooth fillings ** Bonded amalgam, used in dentistry Amalgam may also refer to: * Amalgam Comics, a publisher * Amalgam Digital, an in ...
(Medieval Latin ''amalgama'', "alloy of mercury") with other metals. Alchemists thought of mercury as the First Matter from which all metals were formed. They believed that different
metals A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as against no ...
could be produced by varying the quality and quantity of
sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
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. The mines in
Almadén Almadén () is a town and municipality in the Spanish province of Ciudad Real, within the autonomous community of Castile-La Mancha. The town is located at 4° 49' W and 38° 46' N and is 589 meters (1,932 ft) above sea level. Almadén is approx ...
(Spain), Monte Amiata (Italy), and
Idrija Idrija (, in older sources ''Zgornja Idrija''; , ) is a town in western Slovenia. It is the seat of the Municipality of Idrija. Located in the traditional region of the Slovene Littoral and in the Gorizia Statistical Region, it is notable for it ...
(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. Beginning in 1558, with the invention of the patio process to extract
silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
from
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...
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 New Spain, officially the Viceroyalty of New Spain ( ; Nahuatl: ''Yankwik Kaxtillan Birreiyotl''), originally the Kingdom of New Spain, was an integral territorial entity of the Spanish Empire, established by Habsburg Spain. It was one of several ...
and
Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...
. Initially, the Spanish Crown's mines in Almadén in Southern Spain supplied all the mercury for the colonies. 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. In 1786 the main mine at Huancavelica suffered a sudden collapse that killed over 100 persons and greatly reduced the mine's output. Through the legalization of scavanging known as '' pallaqueo'' mercury production rose again peaking in 1794–1796. The
French Revolutionary Wars The French Revolutionary Wars () were a series of sweeping military conflicts resulting from the French Revolution that lasted from 1792 until 1802. They pitted French First Republic, France against Kingdom of Great Britain, Great Britain, Habsb ...
disrupted European mercury supply to
Spanish America Spanish America refers to the Spanish territories in the Americas during the Spanish colonization of the Americas. The term "Spanish America" was specifically used during the territories' Spanish Empire, imperial era between 15th and 19th centur ...
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. Spain abolished the royal mercury monopoly in 1813.
Mercury poisoning Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashe ...
in the mines left many people disabled through the
early modern period The early modern period is a Periodization, historical period that is defined either as part of or as immediately preceding the modern period, with divisions based primarily on the history of Europe and the broader concept of modernity. There i ...
but mercury itself was not the chief cause of deaths in the mines. The patio process and later
pan amalgamation The pan amalgamation process is a method to extract silver from ore, using salt and copper(II) sulfate in addition to mercury. The process was widely used from 1609 through the 19th century; it is no longer used. The patio process had been used ...
process continued to create great demand for mercury to treat silver ores until the late 19th century.


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) and is the 66th most abundant element in the Earth's crust. 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 A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native element mineral, native deposits singly or in alloys include antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, ma ...
(rare) or in
cinnabar Cinnabar (; ), or cinnabarite (), also known as ''mercurblende'' is the bright scarlet to brick-red form of Mercury sulfide, mercury(II) sulfide (HgS). It is the most common source ore for refining mercury (element), elemental mercury and is t ...
, metacinnabar,
sphalerite Sphalerite is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimentary exhalative, Carbonate-hoste ...
, corderoite, livingstonite and other
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
s, with cinnabar (HgS) being the most common ore. Mercury ores often occur in
hot spring A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...
s or other
volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...
regions. 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 Idrija (, in older sources ''Zgornja Idrija''; , ) is a town in western Slovenia. It is the seat of the Municipality of Idrija. Located in the traditional region of the Slovene Littoral and in the Gorizia Statistical Region, it is notable for it ...
) and Spain (
Almadén Almadén () is a town and municipality in the Spanish province of Ciudad Real, within the autonomous community of Castile-La Mancha. The town is located at 4° 49' W and 38° 46' N and is 589 meters (1,932 ft) above sea level. Almadén is approx ...
), shut down due to the fall of the price of mercury.
Nevada Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...
'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. Mercury is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is: :HgS + O2 → Hg + SO2 In 2020, China was the top producer of mercury, providing 88% of the world output (2200 out of 2500 tonnes), followed by
Tajikistan Tajikistan, officially the Republic of Tajikistan, is a landlocked country in Central Asia. Dushanbe is the capital city, capital and most populous city. Tajikistan borders Afghanistan to the Afghanistan–Tajikistan border, south, Uzbekistan to ...
(178 t), Russia (50 t) and Mexico (32 t). Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning. In China, prison labor was used by a private mining company as recently as the 1950s to develop new cinnabar mines. Thousands of prisoners were used by the Luo Xi mining company to establish new tunnels. Worker health in functioning mines is at high risk. A newspaper claimed that an unidentified
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
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 Foshan (, ; Chinese: 佛山) is a prefecture-level city in central Guangdong Province, China. The entire prefecture covers and had a population of 9,498,863 as of the 2020 census. The city is part of the western side of the Pearl River Delta m ...
and
Guangzhou Guangzhou, Chinese postal romanization, previously romanized as Canton or Kwangchow, is the Capital city, capital and largest city of Guangdong Provinces of China, province in South China, southern China. Located on the Pearl River about nor ...
, and in
Guizhou ) , image_skyline = , image_caption = , image_map = Guizhou in China (+all claims hatched).svg , mapsize = 275px , map_alt = Map showing the location of Guizhou Province , map_caption = Map s ...
province in the southwest. 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 Santa Clara County, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259 as of the 2020 United States census, 2020 census. Santa Clara County and neighboring Sa ...
purchased the historic Almaden Quicksilver Mine and created a county park on the site, after conducting extensive safety and environmental analysis of the property.


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 HgF4 have disputed interpretations and remain difficult (if not impossible) to reproduce.


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 Diamagnetism is the property of materials that are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagn ...
and feature the dimeric cation, Hg. Stable derivatives include the chloride and
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
. In aqueous solution of a mercury(I) salt, slight disproportion of Hg into Hg and results in >0.5% of dissolved mercury existing as . In these solutions, complexation of the with addition of ligands such as
cyanide In chemistry, cyanide () is an inorganic chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom. Ionic cyanides contain the cyanide anion . This a ...
causes disproportionation to go to completion, with all Hg precipitating as elemental mercury and insoluble mercury(II) compounds (e.g.
mercury(II) cyanide Mercury(II) cyanide, also known as mercuric cyanide, is a poisonous compound of mercury and cyanide. It is an odorless, toxic white powder. It is highly soluble in polar solvents such as water, alcohol, and ammonia, slightly soluble in ether ...
if cyanide is used as the ligand). Mercury(I) chloride, a colorless solid also known as calomel, is really the compound with the formula Hg2Cl2, with the connectivity Cl-Hg-Hg-Cl. It reacts with chlorine to give
mercury(II) chloride Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. ...
, 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. Indicative of its tendency to bond to itself, mercury forms
mercury polycations Mercury polycations are polyatomic cations that contain only mercury (element), mercury atoms. The best known example is the ion, found in mercury(I) (mercurous) compounds. The existence of the metal–metal bond in Hg(I) compounds was established ...
, which consist of linear chains of mercury centers, capped with a positive charge. One example is containing the cation.


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 In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are arccos(−) = 109.4712206...° ≈ 109.5° when all four substituents are ...
with other ligands. This behavior is similar to the Ag+ ion. The best known mercury halide is
mercury(II) chloride Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. ...
, an easily sublimating white solid.
Mercury(II) oxide Mercury(II) oxide, also called mercuric oxide or simply mercury oxide, is the inorganic compound with the formula Hg O. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral form montroydite is ...
, the main
oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...
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 Joseph Priestley (; 24 March 1733 – 6 February 1804) was an English chemist, Unitarian, Natural philosophy, natural philosopher, English Separatist, separatist theologian, Linguist, grammarian, multi-subject educator and Classical libera ...
in an early synthesis of pure
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
. Hydroxides of mercury are poorly characterized, as attempted isolation studies of mercury(II) hydroxide have yielded mercury oxide instead. Being a soft metal, mercury forms very stable derivatives with the heavier
chalcogens The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radi ...
. Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore
cinnabar Cinnabar (; ), or cinnabarite (), also known as ''mercurblende'' is the bright scarlet to brick-red form of Mercury sulfide, mercury(II) sulfide (HgS). It is the most common source ore for refining mercury (element), elemental mercury and is t ...
and is the brilliant pigment
vermilion Vermilion (sometimes vermillion) is a color family and pigment most often used between antiquity and the 19th century from the powdered mineral cinnabar (a form of mercury sulfide). It is synonymous with red orange, which often takes a moder ...
. Like ZnS, HgS crystallizes in two forms, the reddish cubic form and the black
zinc blende Sphalerite is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Valley type, and volcanogenic mas ...
form. The latter sometimes occurs naturally as metacinnabar.
Mercury(II) selenide Mercury selenide (HgSe; sometimes mercury(II) selenide) is a chemical compound of mercury and selenium. It is a grey-black crystalline solid semi-metal with a sphalerite structure. The lattice constant is 0.608 nm. HgSe occurs naturally a ...
(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 A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping levels ...
useful as
infrared detector An infrared detector is a detector that reacts to infrared (IR) radiation. The two main types of detectors are thermal and photonic (photodetectors). The thermal effects of the incident IR radiation can be followed through many temperature depe ...
materials. Mercury(II) salts form a variety of complex derivatives with
ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
. These include Millon's base (Hg2N+), the one-dimensional polymer (salts of )), and "fusible white precipitate" or g(NH3)2l2. Known as Nessler's reagent,
potassium tetraiodomercurate(II) Potassium tetraiodomercurate(II) is an inorganic compound with the chemical formula . It consists of potassium cations and tetraiodomercurate(II) anions. It is the active agent in Nessler's reagent, used for detection of ammonia. Preparation The c ...
() is still occasionally used to test for ammonia owing to its tendency to form the deeply colored iodide salt of Millon's base. Mercury fulminate is a
detonator A detonator is a device used to make an explosive or explosive device explode. Detonators come in a variety of types, depending on how they are initiated (chemically, mechanically, or electrically) and details of their inner working, which of ...
widely used in
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...
s.


Organomercury compounds

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 Organocadmium chemistry describes the physical properties, synthesis, reactions, and use of organocadmium compounds, which are organometallic compounds containing a carbon to cadmium chemical bond. Cadmium shares Group 12 element, group 12 with zin ...
and organozinc compounds, organomercury compounds do not react with water. They usually have the formula HgR2, which are often volatile, or HgRX, which are often solids, where R is
aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...
or
alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...
and X is usually halide or acetate.
Methylmercury Methylmercury is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environment ...
, a generic term for compounds with the formula CH3HgX, is a dangerous family of compounds that are often found in polluted water. They arise by a process known as biomethylation.


Applications

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. In some applications, mercury is replaced with less toxic but considerably more expensive
Galinstan Galinstan is a brand name for an alloy composed of gallium, indium, and tin which melts at and is thus liquid at room temperature. In scientific literature, galinstan is also used to denote the eutectic alloy of gallium, indium, and tin, which ...
alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...
.


Medicine


Historical and folk

Mercury and its compounds have been used in medicine, although they are much less common today than they once were, now that the toxic effects of mercury and its compounds are more widely understood. An example of the early therapeutic application of mercury was published in 1787 by
James Lind James Lind (4 October 1716 – 13 July 1794) was a Scottish physician. He was a pioneer of naval hygiene in the Royal Navy. By conducting one of the first ever clinical trials, he developed the theory that citrus fruits cured scurvy. Lind ...
. 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 Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. ...
, among others. Mercury in the form of one of its common ores, cinnabar, is used in various traditional medicines, especially in
traditional Chinese medicine Traditional Chinese medicine (TCM) is an alternative medicine, alternative medical practice drawn from traditional medicine in China. A large share of its claims are pseudoscientific, with the majority of treatments having no robust evidence ...
. Review of its safety has found that cinnabar can lead to significant mercury intoxication when heated, consumed in
overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended. Retrieved on September 20, 2014.
, 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. Mercury(I) chloride (also known as calomel or mercurous chloride) has been used in
traditional medicine Traditional medicine (also known as indigenous medicine or folk medicine) refers to the knowledge, skills, and practices rooted in the cultural beliefs of various societies, especially Indigenous groups, used for maintaining health and treatin ...
as a
diuretic A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics ...
, topical
disinfectant A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
, and
laxative Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation. Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...
.
Mercury(II) chloride Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. ...
(also known as mercuric chloride or corrosive sublimate) was once used to treat
syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms depend on the stage it presents: primary, secondary, latent syphilis, latent or tertiary. The prim ...
(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. It is also used as a disinfectant. 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. 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.


Contemporary

Mercury is an ingredient in dental amalgams.
Thiomersal Thiomersal (International Nonproprietary Name, INN), or thimerosal (United States Adopted Name, USAN, Japanese Accepted Name, JAN), also sold under the name merthiolate, is an organomercury compound. It is a well-established antiseptic and antif ...
(called ''Thimerosal'' in the United States) is an
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
used as a
preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or ...
in
vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifi ...
s, although this use is in decline. Although it was widely speculated that this mercury-based preservative could cause or trigger
autism Autism, also known as autism spectrum disorder (ASD), is a neurodevelopmental disorder characterized by differences or difficulties in social communication and interaction, a preference for predictability and routine, sensory processing d ...
in children, no evidence supports any such link. 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. 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. Mercury is still used in some diuretics, although substitutes such as
thiazide Thiazide () refers to both a class of sulfur-containing organic molecules and a class of diuretics based on the chemical structure of benzothiadiazine. The thiazide drug class was discovered and developed at Merck and Co. in the 1950s. The firs ...
s now exist for most therapeutic uses. In 2003, mercury compounds were found in some
over-the-counter drug Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid pres ...
s, including topical
antiseptics An antiseptic ( and ) is an antimicrobial substance or compound that is applied to living tissue to reduce the possibility of sepsis, infection, or putrefaction. Antiseptics are generally distinguished from ''antibiotics'' by the latter's abili ...
, stimulant laxatives, diaper-rash
ointment A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...
, eye drops, and
nasal spray Nasal sprays are used to deliver medications Route of administration#Local, locally in the nasal cavities or systemic administration, systemically. They are used locally for conditions such as nasal congestion and allergic rhinitis. In some sit ...
s. The FDA has "inadequate data to establish general recognition of the safety and effectiveness" of the mercury ingredients in these products.


Production of chlorine and caustic soda

Chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
is produced from
sodium chloride Sodium chloride , commonly known as Salt#Edible salt, edible salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. It is transparent or translucent, brittle, hygroscopic, and occurs a ...
(common salt, NaCl) using
electrolysis In chemistry and manufacturing, electrolysis is a technique that uses Direct current, direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of c ...
to separate metallic
sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
from chlorine gas. Usually salt is dissolved in water to produce a brine. By-products of any such
chloralkali process The chloralkali process (also chlor-alkali and chlor alkali) is an industrial process for the electrolysis of sodium chloride (NaCl) solutions. It is the technology used to produce chlorine and sodium hydroxide (caustic soda), which are commodi ...
are hydrogen (H2) and
sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly corrosive base (chemistry), ...
(NaOH), which is commonly called caustic soda or
lye Lye is the common name of various alkaline solutions, including soda lye (a solution of sodium hydroxide) and potash lye (a solution of potassium hydroxide). Lyes are used as cleaning products, as ingredients in soapmaking, and in various other c ...
. By far the largest use of mercury 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 A cathode is the electrode from which a conventional current leaves a polarized electrical device such as a lead-acid battery. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. Conventional curren ...
made from mercury; this sodium is then reacted with water to produce sodium hydroxide. Many of the industrial mercury releases of the 20th century came from this process, although modern plants claim to be safe in this regard. 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.


Laboratory uses


Thermometers

Thermometers A thermometer is a device that temperature measurement, measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperatur ...
containing mercury were invented in the early 18th century by
Daniel Gabriel Fahrenheit Daniel Gabriel Fahrenheit FRS (; ; 24 May 1686 – 16 September 1736) was a physicist, inventor, and scientific instrument maker, born in Poland to a family of German extraction. Fahrenheit invented thermometers accurate and consistent enough t ...
, though earlier attempts at making temperature-measuring instruments filled with quicksilver had been described in the 1650s. 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. 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. Modern alternatives to mercury thermometers include
resistance thermometer Resistance thermometers, also called resistance temperature detectors (RTDs), are sensors used to measure temperature. Many RTD elements consist of a length of fine wire wrapped around a heat-resistant ceramic or glass core but other construction ...
s,
thermocouple A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...
s, and
thermistor A thermistor is a semiconductor type of resistor in which the resistance is strongly dependent on temperature. The word ''thermistor'' is a portmanteau of ''thermal'' and ''resistor''. The varying resistance with temperature allows these devices ...
sensors that output to a digital display.


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.


Electrochemistry

Liquid mercury is part of a popular secondary reference
electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...
(called the calomel electrode) in
electrochemistry Electrochemistry is the branch of physical chemistry concerned with the relationship between Electric potential, electrical potential difference and identifiable chemical change. These reactions involve Electron, electrons moving via an electronic ...
as an alternative to the
standard hydrogen electrode In electrochemistry, the standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be at 25 ° ...
. The calomel electrode is used to work out the
electrode potential An electrode is an electrical conductor used to make contact with a nonmetallic part of a Electronic circuit, circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can c ...
of half cells. The
triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three Phase (matter), phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.. It is that temperature and pressure at ...
of mercury, −38.8344 °C, is a fixed point used as a temperature standard for the International Temperature Scale ( ITS-90).


Polarography and crystallography

In
polarography Polarography is a type of voltammetry where the working electrode is a dropping mercury electrode (DME) or a static mercury drop electrode (SMDE), which are useful for their wide cathodic ranges and renewable surfaces. It was invented in 1922 by C ...
, both the dropping mercury electrode and the hanging mercury drop electrode use elemental mercury. This use allows a new uncontaminated electrode to be available for each measurement or each new experiment. Mercury-containing compounds are also of use in the field of
structural biology Structural biology deals with structural analysis of living material (formed, composed of, and/or maintained and refined by living cells) at every level of organization. Early structural biologists throughout the 19th and early 20th centuries we ...
. Mercuric compounds such as
mercury(II) chloride Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. ...
or
potassium tetraiodomercurate(II) Potassium tetraiodomercurate(II) is an inorganic compound with the chemical formula . It consists of potassium cations and tetraiodomercurate(II) anions. It is the active agent in Nessler's reagent, used for detection of ammonia. Preparation The c ...
can be added to protein crystals in an effort to create heavy atom derivatives that can be used to solve the
phase problem In physics, the phase problem is the problem of loss of information concerning the phase that can occur when making a physical measurement. The name comes from the field of X-ray crystallography, where the phase problem has to be solved for the de ...
in
X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...
via isomorphous replacement or anomalous scattering methods.


Niche uses

Gaseous mercury is used in mercury-vapor lamps,
fluorescent lamp A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor ...
s, and some
neon sign In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in Decem ...
s. 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. Gaseous mercury is also found in some Gas filled tube, electron tubes, including ignitrons, thyratrons, and mercury arc rectifiers. It is also used in specialist medical care lamps for skin tanning and disinfection. 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 Neon sign#Bombardment, 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. 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: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. 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.


Skin whitening

Mercury is effective as an active ingredient in skin whitening compounds used to depigment skin. 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.


Firearms

Mercury(II) fulminate is a primary explosive, which has mainly been used as a Primer (firearm)#Internal priming, primer of a Cartridge (firearms), cartridge in firearms throughout the 19th and 20th centuries.


Mining

Mercury is used in illegal gold mining to help separate gold particles from a mixture of sand or gravel and water. Small gold particles may form mercury-gold amalgam and therefore increase the gold recovery rates. The use of mercury causes a severe pollution problem in places such as Ghana.


Historic uses

Many historic applications made use of the peculiar physical properties of mercury, especially as a dense liquid and a liquid metal: * Quantities of liquid mercury ranging from have been recovered from elite Maya civilization, Maya tombs (100–700 AD) or ritual caches at six sites. This mercury may have been used in bowls as Mirrors in Mesoamerican culture, mirrors for Divination, divinatory purposes. Five of these date to the Classic Period of Maya civilization (c. 250–900) but one example predated this. * In Islamic Spain, it was used for filling decorative pools. Later, the American artist Alexander Calder built a mercury fountain for the Spanish Pavilion at the Exposition Internationale des Arts et Techniques dans la Vie Moderne (1937), 1937 World Exhibition in Paris. The fountain is now on display at the Fundació Joan Miró in Barcelona. * The Fresnel lenses of old lighthouses used to float and rotate in a bath of mercury which acted like a bearing. * Mercury
sphygmomanometer A sphygmomanometer ( ), also known as a blood pressure monitor, blood pressure machine, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff i ...
s,
barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...
s, diffusion pumps, Mercury coulometer, coulometers, and many other laboratory instruments took advantage of mercury's properties as a very dense, opaque liquid with a nearly linear thermal expansion. * As an electrically conductive liquid, it was used in
mercury switch A mercury switch is an electricity, electrical switch that opens and closes a electrical circuit, circuit when a small amount of the liquid metal mercury (element), mercury connects metal electrodes to close the circuit. There are several differ ...
es (including Light switch#Mercury switch, home mercury light switches installed prior to 1970), tilt switches used in old fire detectors and in some home thermostats. * Owing to its acoustic properties, mercury was used as the propagation medium in Delay-line memory#Mercury delay lines, delay-line memory devices used in early digital computers of the mid-20th century, such as the SEAC (computer), SEAC computer. * In 1911, Heike Kamerlingh Onnes discovered superconductivity through the cooling of mercury below 4 kelvin shortly after the discovery and production of liquid helium. Its superconductive properties were later determined to be unusual compared to other later-discovered superconductors, such as the more popular niobium alloys. * Experimental mercury vapor turbines were installed to increase the efficiency of fossil-fuel electrical power plants. The South Meadow power plant in Hartford, CT employed mercury as its working fluid, in a Binary cycle power plant, 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 fluid, supercritical steam plants in later years. * Similarly, liquid mercury was used as a coolant for some nuclear reactors; however,
sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
is proposed for reactors cooled with liquid metal, because the high density of mercury requires much more energy to circulate as coolant. * Mercury was a propellant for early ion engines in Electrically powered spacecraft propulsion, 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 Room temperature, colloquially, denotes the range of air temperatures most people find comfortable indoors while dressed in typical clothing. Comfortable temperatures can be extended beyond this range depending on humidity, air circulation, and ...
. 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 Caesium (IUPAC spelling; also spelled cesium in American English) is a chemical element; it has Symbol (chemistry), symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only f ...
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. Other applications made use of the chemical properties of mercury: * The mercury battery is a non-rechargeable Electrochemical cell, 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. * Mercury was used for preserving wood, developing daguerreotypes, Mercury silvering, silvering mirrors, anti-fouling paints, herbicides, interior latex paint, handheld maze games, cleaning, and road leveling devices in cars. Mercury compounds have been used in antiseptics, laxatives, antidepressants, and in syphilis, antisyphilitics. Mercury has been replaced with safer compounds in most, if not all, of these applications. * It was allegedly used by Allies of World War II, allied spies to sabotage Luftwaffe planes: a mercury paste was applied to bare
aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
, causing the metal to rapidly Corrosion, corrode; this would cause structural failures. * Mercury was once used as a gun barrel bore cleaner. * From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution (the term "carroting" arose from this color) of the mercury compound mercuric nitrate, Hg(NO3)2. 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". 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. * Historically, mercury was used extensively in hydraulic mining, hydraulic gold mining (see #Mining. Large-scale use of mercury stopped in the 1960s. However, mercury is still used in small scale, often clandestine, gold prospecting. It is estimated that 45,000 metric tons of mercury used in California for placer mining have not been recovered. Mercury was also used in silver mining to extract the metal from ore through the patio process.


Toxicity and safety

Due to its physical properties and relative chemical inertness, liquid mercury is absorbed very poorly through intact skin and the gastrointestinal tract. 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 Methylmercury is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environment ...
. Mercury can cause both chronic and acute poisoning.


Releases in the environment

Preindustrial deposition rates of mercury from the atmosphere may be about 4 ng per 1 L of ice deposited. Volcanic eruptions and related natural sources are responsible for approximately half of atmospheric mercury emissions. Atmospheric mercury contamination in outdoor urban air at the start of the 21st century was measured at 0.01–0.02 μg/m3. 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/m3. The average was 0.069 μg/m3. Half of mercury emissions are attributed to mankind. The sources can be divided into the following estimated percentages: * 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. * 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. * 6.8% from non-ferrous metal production, typically smelters. * 6.4% from cement production. * 3.0% from waste disposal, including municipal waste, 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 in 2000, excluding biomass burning, an important source in some regions. A serious industrial disasters, 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. China is estimated to produce 50% of mercury emissions, most of which result from production of vinyl chloride. Mercury also enters into the environment through the improper disposal of mercury-containing products. Due to health concerns, waste management, 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. 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. While mercury is a constituent of tobacco smoke, 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. A less well-known source of mercury is the burning of joss paper, which is a common tradition practiced in Asia, including China, Vietnam, Hong Kong, Thailand, Taiwan and Malaysia.


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 doctrine, attractive nuisance to the uninformed. Procedures have been developed to contain mercury spills, as well as recommendations on appropriate responses based on the conditions of a spill. 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 Adsorption, adsorbents, ranging from metal salts to polymers and zeolites.


Sediment contamination

Sediments within large urban-industrial estuaries act as an important sink for Point source pollution, point source and diffuse mercury pollution within Drainage basin, catchments. 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). 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. 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. 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.


Occupational exposure

Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization, Occupational Safety and Health Administration, OSHA, and National Institute for Occupational Safety and Health, 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. Environmental releases and disposal of mercury are regulated in the U.S. primarily by the United States Environmental Protection Agency.


Fish

Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of
methylmercury Methylmercury is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environment ...
, 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. Mercury presence in fish muscles can be studied using non-lethal muscle Biopsy, biopsies. 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 Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance, e.g a pesticide, in the tissue (biology), tissues of organisms at successively higher levels in a food chain. This inc ...
.
Mercury poisoning Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashe ...
happened this way in Minamata, Kumamoto, Minamata, Japan, now called Minamata disease. 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. 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. 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.


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. New York City residents have been found to be exposed to significant levels of inorganic mercury compounds through the use of skin care products.


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


Treatment

Research on the treatment of mercury poisoning is limited. Currently available drugs for acute mercurial poisoning include chelators ''N''-acetyl-D,L-penicillamine (NAP), British Anti-Lewisite (BAL), 2,3-dimercapto-1-propanesulfonic acid (DMPS), and dimercaptosuccinic acid (DMSA). In one small study including 11 construction workers exposed to elemental mercury, patients were treated with DMSA and NAP. 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.


Regulations


International

140 countries agreed in the Minamata Convention on Mercury by the United Nations Environment Programme (UNEP) to prevent mercury vapor emissions. The convention was signed on 10 October 2013.


United States

In the United States, the United States Environmental Protection Agency, Environmental Protection Agency is charged with regulating and managing mercury contamination. Several laws give the EPA this authority, including the Clean Air Act (United States), 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. North America contributed approximately 11% of the total global anthropogenic mercury emissions in 1995. The United States Clean Air Act (1990), 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 that added power plants to the list of sources that should be controlled and instituted a national emissions trading, 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. 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. The EPA announced new rules for coal-fired power plants on 22 December 2011. 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.


European Union

In the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
, the directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (see Restriction of Hazardous Substances Directive, RoHS) bans mercury from certain electrical and electronic products, and limits the amount of mercury in other products to less than 1000 Parts per million, ppm. 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)." There are restrictions for mercury concentration in packaging (the limit is 100 ppm for sum of mercury,
lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
, hexavalent chromium and cadmium) and batteries (the limit is 5 ppm). In July 2007, the European Union also banned mercury in non-electrical measuring devices, such as
thermometer A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
s and
barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...
s. 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.


Scandinavia

Norway enacted a total ban on the use of mercury in the manufacturing and import/export of mercury products, effective 1 January 2008. 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. 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." Products containing mercury were banned in Sweden in 2009, 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.


See also

* COLEX process (isotopic separation) * Mercury pollution in the ocean * Red mercury


Notes


References


Further reading

*


External links


Chemistry in its element podcast
(MP3) from the Royal Society of Chemistry's Chemistry World
Mercury


at ''The Periodic Table of Videos'' (University of Nottingham)
Centers for Disease Control and Prevention – Mercury Topic







Stopping Pollution: Mercury
– Oceana
Natural Resources Defense Council (NRDC): Mercury Contamination in Fish guide
– Natural Resources Defense Council, NRDC
NLM Hazardous Substances Databank – Mercury

BBC – Earth News – Mercury "turns" wetland birds such as ibises homosexual

Changing Patterns in the Use, Recycling, and Material Substitution of Mercury in the United States
United States Geological Survey
Thermodynamical data on liquid mercury.
* {{DEFAULTSORT:Mercury Mercury (element), Chemical elements Coolants Endocrine disruptors Native element minerals Neurotoxins Nuclear reactor coolants Occupational safety and health Transition metals Chemical elements with rhombohedral structure Mercury compounds Mercury minerals Mercury poisoning