Mercury Price, Occurrence, Extraction and Uses

Mercury (ancient Greek ὑδράργυρος Hydrargyros, liquid silver ', derived from Latin hydrargyrum (Hg), so named by Dioscurides; Latin argentum vivum and mercurius; English mercury and quicksilver) is a chemical element with the symbol Hg and the atomic number 80. Although it has a closed d-shell, it is often counted among the transition metals. In the periodic table it is in the 2nd subgroup or the 12th IUPAC group, which is also called the zinc group. It is the only metal and, besides bromine, the only element that is liquid under standard conditions. Due to its high surface tension, mercury does not wet its inert base, but rather forms lenticular drops because of its strong cohesion. Like any other metal, it is electrically conductive.

etymologie

Mercury originally means "perky silver", ie fast - see English quick - or moving or living silver (from ahd. Quëcsilabar, quëchsilper, mhd. Quëcsilber, këcsilber to Germanic kwikw, [quick] lively ') as a translation of synonymous Latin argentum vivum, "living silver", e.g. B. Pliny

Sulfur alcohols are called mercaptans ("mercury scavengers") because they can react with mercury to form mercury sulfides.

History

Mercury has been known at least since ancient times. It is already mentioned in the works of Aristotle, Theophrastus of Eresus, Pliny the Elder and other writers of antiquity. From ancient times to the 20th century it was used as a medicinal product (due to its toxicity, which was first reported by the doctor and empiricist Herakleides of Taranto, but with corresponding negative consequences).

In ancient times, mercury was obtained by rubbing cinnabar with vinegar or by heating cinnabar using a sublimation process. Vitruvius was already familiar with the alloy of mercury with gold. This was used for fire gilding objects, whereby the mercury evaporated. In the 5th century AD, the sublimate (mercury (II) chloride) was known as a mercury compound. Paracelsus was the first doctor who made precipitates and basic mercury salts and used them as remedies. From the 16th century onwards, mercury became economically important because it was needed to extract silver from silver ores through amalgam formation.

At the end of the 19th century, mercury was considered a suitable drug for gynecological problems, which is why it was sometimes administered in toxic quantities.

From the end of the 15th to the beginning of the 20th century, mercury preparations such as the gray mercury ointment or asurol were widely used to treat syphilis (most recently also in combination with arsenic compounds such as arsphenamine; see also organic biometallic chemistry). For a mercury cure, the mercury was usually applied to the skin, injected or occasionally even inhaled, which in many cases resulted in symptoms of poisoning. Syphilis was considered a popular disease and allusions to the symptoms of syphilis and the associated mercury poisoning can be found in many literary works of the time.

During the same period, metallic mercury was used to treat obstructions in the intestine. The patient ingested several kilograms of metallic mercury orally in order to overcome the obstacle in the intestine. If he survived treatment, the metal would naturally leave his body with no further symptoms of intoxication.

In the past, mercury (I) chloride was used externally, for example against corneal spots or genital warts, and often internally and until the 1990s as a spermicide in the form of vaginal suppositories for contraception. In the past, almost all Merfen preparations, including lozenges, had the organic mercury compound phenyl mercury borate, which was discovered to be effective around 1951, as an active ingredient, whereas today these are all mercury-free. Merbromin also had an antiseptic effect in Mercurochrome, which was only approved until 2003.

The Dutch physicist Heike Kamerlingh Onnes discovered the phenomenon of superconductivity in mercury for the first time in 1911. The electrical resistance disappears completely below 4,183 Kelvin (−268,967 ° C). The proximity to the boiling point of helium contributed to the discovery, but it is purely coincidental.

In ancient Greece, mercury symbolized both the god Hermes and the planet that belonged to it. This was later adopted by the Romans and alchemists for the equated god Mercurius. Therefore, in Latin mercurius and in English mercury, both the name for mercury and for the planet and god. In English, however, quicksilver is also used as an alternative term for the metal.

Mercury was used in alchemy to refine metals. For example, the addition of mercury should turn copper into silver. The aim was also to solidify the mercury, the fixatio mercurii, for example (described in the 15th century by Hans Kluge) by physico-chemical treatment of a mixture of mercury with vitriol to which other additives such as tartar, saltpeter and glass powder were added.

occurrence

Mercury occurs naturally in its pure form and is the only liquid substance that has traditionally been recognized as a mineral by the IMA. Mercury is also a companion mineral in hard coal.

There are mercury deposits in Serbia, Italy, China, Algeria, Russia and Spain, among others. It is mostly found as a mineral in the form of cinnabar (HgS) in areas with former volcanic activity. Mercury is also less common than normal. The largest cinnabar deposits on earth are located near the Spanish town of Almadén. Production ended in 2003 and the Almadén mine was converted into a visitor mine. Much rarer mercury minerals are montroydite (HgO), paraschachnerite, schachnerite, eugenite, luanheit and moschellandsbergite (all AgHg). Another mineral is Belendorffit (CuHg).

Large amounts of mercury are also bound in the frozen biomass of the permafrost soils of the northern hemisphere. About twice as much mercury is stored in these as in all other soils, the atmosphere and the oceans combined. If the permafrost is thawed more intensely, as is expected from man-made global warming, biological degradation processes would set in, through which the mercury is possibly released into the environment, where it could harm the arctic ecosystems, aquatic life in the oceans and human health, among other things .

Mercury is traditionally traded in metal barrels (English "flask") of 76 pounds (34,473 kg) and quoted on the commodities exchange in the unit "FL" = flask.

Due to the long atmospheric lifespan of elemental mercury of several months to a year, emissions into the air lead to a median air concentration of 1,2 to 1,8 ng / m3 in the northern hemisphere and around 1,0, which is relatively constant over the entire earth's atmosphere .3 ng / mXNUMX in the southern hemisphere.

Extraction and presentation

Pure mercury is obtained by allowing the mercury ore cinnabar (HgS) to react with oxygen (roasting process). The reaction products are elemental mercury and sulfur dioxide:

Around one million tons of metallic mercury has been extracted from cinnabar and other ores worldwide over the past five centuries. About half of this occurred before 1925 (as of 2000).

Features

Mercury is a silver-white, liquid heavy metal. It is sometimes still counted among the precious metals, but is much more reactive than the classic precious metals (for example platinum, gold), which are in the same period. It forms alloys with many metals, the so-called amalgams. Mercury is a poor conductor of electricity compared to other metals. Apart from the noble gases, it is the only element that is monatomic in the gas phase at room temperature.

With a density of 13,5 g / cm3, mercury is around 13,5 times as dense as water, so that, according to Archimedes' principle, its carrying capacity is also 13,5 times as high; thus an iron cube (density 7,9 g / cm3) also floats in mercury. Recently performed Monte Carlo simulations show that the density of mercury is also subject to relativistic effects. Non-relativistic calculations would suggest a density of 16,1 g / cm3.
conductivity

The metal bond in mercury is created by delocalized electrons. These electrons occupy certain, discrete energy levels in bands that are created by the broadening of atomic states through interaction. There is no periodic structure in liquid metals like mercury. Therefore, the quasi-pulse is not a good quantum number and the electronic band configuration cannot be represented in the Brillouin zone, as is usual for solid metals. Due to the Pauli principle, the electrons gradually fill up the energy states, only the conduction band remains incompletely occupied. The electrons in this band are delocalized and form the electron gas. The electrical conductivity can also be explained classically by these electrons.

Physical state

The answer to the question of why mercury is liquid at room temperature can be found in the consideration of the bond between the mercury atoms. First of all, mercury has a very special electron configuration. As an element of the 12th group of the PSE, mercury atoms have completely filled s and d atom orbitals, which means a very stable and energetically favorable constellation. The conduction band is thereby empty. In the case of the lighter homologues zinc and cadmium, which are in the same group of PSE as mercury, but are solid at room temperature, the energetic difference between the valence band and the conduction band is so small that electrons can easily jump from the valence band to the conduction band, creating a metal bond comes about.

The peculiarity of mercury lies in the 14f orbital which is completely filled with 4 electrons. Due to the lanthanide contraction and the relativistic effect, there is an increase in mass and a less efficient shielding of the nuclear charge. Only recently was it possible to demonstrate using a Monte Carlo simulation that the melting point anomaly of mercury is actually due to relativistic effects. Without relativistic effects, a melting point would be expected that would be 105 K higher than that observed experimentally.

Occupied orbitals are thereby drawn closer to the nucleus, as is the valence band of mercury. However, unoccupied orbitals such as the conduction band are not shifted towards the core, which leads to a particularly large energy difference between the valence and conduction band, which is significantly lower for zinc and cadmium. Hardly any electrons can leave the valence band and reach the conduction band, which makes the metal bond unusually weak. This also explains the volatility and the atypical poor conductivity of mercury for metals.

isotope

A total of 34 isotopes and 9 nuclear isomers with mass numbers from 175 to 208 are known of mercury. Seven of these isotopes are stable (with mass numbers 196, 198, 199, 200, 201, 202 and 204). Of the radioactive isotopes, only 194Hg has a relatively long half-life of 444 years (520 years according to more recent data). The other isotopes and core isomers only have half-lives between 1,1 milliseconds and 46,612 days.

Колдонуу

The thermal expansion of mercury is almost an order of magnitude lower compared to other liquids, but shows only about 0 percent linearity errors in the range between 180 ° C and 2 ° C:

In addition, mercury does not wet glass and is easy to detect visually. It is therefore suitable for use in liquid thermometers and contact thermometers. As an outdoor thermometer in very cold regions, however, it can only be used to a limited extent due to its melting point (−38,83 ° C).

Due to its high toxicity, its use is nowadays limited to the scientific field; Depending on the temperature range, mercury can be partially replaced by colored fillings made of alcohol, petroleum, propylene carbonate, pentane, toluene, creosote, isosamyl benzoate, hydrogenated mineral oil or Galinstan as well as electronic thermometers.

The first usable mercury thermometer was developed by Daniel Gabriel Fahrenheit around 1720. A thermometer contains an average of 150 mg of mercury. In a clinical thermometer, the amount can be up to 1 g. This corresponds roughly to a bead with a diameter of 5,2 mm.

Since April 3, 2009, the placing on the market of new mercury-containing clinical thermometers, barometers and blood pressure monitors has been prohibited within the EU; This does not apply to measuring devices for scientific or medical use as well as old and used devices.

High Pure Silver Liquid Mercury 99.999% Mercury For Industrial Usage

Manometer / barometer

The classic design of a manometer (“differential pressure meter”) is a U-tube, the ends of which are connected to the two pressure atmospheres via lines. To this day, mercury is widely used as a pressure gauge liquid. The advantages of mercury are: high density, the non-wetting of glass and the negligible vapor pressure. Mercury is colorless but opaque.

The simplest and oldest design of the barometer is a stable, one-sided closed glass tube with an inner diameter of about 4–6 mm, which is filled to the brim with mercury with the closed end facing down, then closed with the thumb, uprighted upside down and with the thumb under the mercury level in a wide, half-full cup is dipped before the thumb reveals the opening below.

The mercury column in the pipe only sinks until the force of the air pressure outside the pipe and the weight of the mercury in the pipe are in equilibrium. At normal pressure (1 atmosphere) this is 760 mm "mercury column". The old specification in the Torr unit of measurement for air pressure corresponds to the height of the mercury column in millimeters, 1 mm of mercury column corresponds to 133,21 Pascal.

Switch

Due to its electrical conductivity and the very high surface tension (0,476 N / m at 20 ° C), mercury is ideal for use as a contact material in the mercury switches previously used. Because of the problem with the disposal of electronic scrap, the use of mercury in switches has been prohibited in most areas of application in the EU (“RoHS” directive) since 2005. In special applications, contacts wetted with mercury are still used today in order to achieve particularly low contact resistances or to prevent the contacts from bouncing (e.g. Hg relays).

Thanks to gravity, mercury tilt switches work similarly to the spirit level on a spirit level; A movable drop of mercury in a curved or straight glass tube opens and closes the electrical contact between two metal pins melted into the glass, depending on the inclination. Such inclination switches are sometimes found in old staircase light time switches, in thermostats of boilers, in pressure switches of domestic water pumps and as rumble protection in washing machines. In the previously used turbo inverters, a mercury beam was used as a circling "switch finger".

Mercury vapor lamps

Visible part of the mercury spectrum. The purple line is barely visible to the eye. Particularly strong lines are in the (left) subsequent invisible UV.

Hg gas discharge tube

Mercury is used in discharge vessels (mercury vapor lamps) of gas discharge lamps (fluorescent lamps, "energy-saving lamps", cold cathode tubes, high and ultra-high pressure mercury vapor lamps, sunlamps, quartz lamps, so-called "black light lamps").

Amalgam

Mercury spontaneously forms alloys with many other metals called amalgams. Amalgams are z. B. used as a dental filler. A mixture of mercury and powder of metals such as silver can be pressed into a drilled opening in the tooth for a period of time and soon hardens to form amalgam. While tooth material shrinks over the years as a result of bacterial-chemical attack, amalgam has a tendency to expand plastically as a result of high chewing pressure as a metal and has the side effect of inhibiting the growth of bacteria. If a piece of aluminum foil is pressed firmly onto an amalgam filling while chewing - possibly accidentally, as is typical of chocolate packaging - a galvanic element is formed and an electrical direct current flows accordingly, which is perceived as an unpleasant metallic stimulus in the tooth nerve.

In March 2017, a regulation was passed in the European Parliament that significantly restricts the use of amalgam. From July 2018, young people under the age of 15 as well as pregnant and breastfeeding women will no longer be allowed to receive dental fillings made from amalgam. Basically, from then on, premixed mixtures must also be used in order to keep the mercury content optimal. Amalgam separators are then also required in the ordination waste water line. A study should clarify by 2020 whether amalgam should be completely banned from dentistry by 2030. Restrictions have also been imposed on the industrial use of mercury.

Since mercury destroys the protective oxide skin of the aluminum through aluminum amalgam formation, carrying mercury-containing devices (e.g. clinical thermometers) on airplanes is not prohibited, but limited according to the IATA Dangerous Goods Regulations (1 piece / passenger and mandatory in a protective cover - DGR 2.3 ). Mercury is assigned to dangerous goods class 8 - corrosive materials. There is a corrosive effect in connection with almost all metals, including zinc, magnesium and aluminum, which are used in aircraft construction.

Disinfectants and pickling agents

In the wound disinfectant mercurochrome, the active ingredient was an organic mercury salt. The mercuchrome iodine solution available today is a povidone iodine solution. Merfen, another disinfectant, used to contain phenyl mercury borate. HgCl2 (sublimate) was previously used as a disinfectant in hospitals. Thimerosal is an organic mercury compound that is used in very low concentrations as a bactericide to preserve vaccines.

Conventional agriculture uses mercury compounds as a dressing agent for seeds. This has been banned in Germany since 1984. In Iraq there was mass poisoning from 1971–1972 as a result of the consumption of seeds.

Mercury (II) chloride was previously used as a disinfectant and pickling agent as well as for wood preservation and corpse preservation.

electrolysis

In terms of quantity, mercury played a major role in the production of caustic soda and chlorine by chlor-alkali electrolysis using the amalgam process. During the electrolysis, the reduced sodium metal is transferred as an amalgam, a sodium-mercury alloy, into a separate cell, the decomposer, in order to prevent the formation of the explosive chlorine gas and the undesired sodium monooxochlorate (sodium hypochlorite) in the electrolysis cell. Currently, a large part of the German and European facilities working with the amalgam process are being converted to alternative, mercury-free processes (membrane processes) in order to reduce mercury emissions.

Gold washing

One process of gold mining uses mercury to loosen the fine gold dust, creating gold amalgam (see amalgamation). Since mercury becomes liquid at low temperatures, it forms alloys that melt particularly easily. During washing and subsequent annealing to recover pure gold, the mercury is released into the environment. This is the main reason for the high level of environmental pollution caused by this type of gold mining (see also environmental emissions, below). Alternatives to the amalgam process should be promoted. The gold for the German river gold ducats minted between the 17th and 19th centuries was also extracted or purified by amalgamation in order to melt it.

Art

It is said that there were rivers of mercury in the tomb of the first Chinese emperor Qin Shihuangdi. The soil in the area has been scientifically examined and an unnaturally high mercury content has been found. But this alone is no proof of the correctness of the legend.

Mexican archaeologists have found liquid mercury beneath the Mayan temple pyramid of the Quetzalcoatl. The researchers suspect that it is the ritual representation of the Maya underworld river - comparable to the ancient Greek Styx.

The American artist Alexander Calder built a mercury fountain in 1937 to commemorate the victims of mercury mining. Around the year 1000 there were pools filled with mercury in the palaces of the caliphs of Córdoba (Medina az-Zahra), Cairo and Baghdad, which were used to play with the effects of light, as well as mercury ponds set in large porphyry shells (for Cairo, 50 cubits are in Square, i.e. approx. 26 m × 26 m).

Fire gilding was in use for a long time in handicrafts. As in gold mining, the easy amalgam formation and thermal separation of gold and mercury were used here. This method can also be used to gild copper sheets, which was used, for example, for the domes of St. Isaac's Cathedral in St. Petersburg in the 19th century.

Other uses

• The metal is used in button cells and batteries. In the meantime, however, there is only one producer in Taiwan; import into the EU is no longer permitted.
• Mercury vapor rectifier emits light during operation
• In the past it was also used in some electronic tubes such as mercury vapor rectifiers, ignitrons, excitrons, and thyratrons.
• In astronomy, mercury is used to build relatively inexpensive telescopes with a large mirror surface (see liquid mirror): Mercury is filled into a plate-shaped, air-bearing mirror carrier, which is then set in rotation. As a result of the rotation, the mercury is distributed over the entire surface of the mirror support in a thin layer and forms an almost perfect parabolic mirror. A disadvantage of these telescopes is that they can only look vertically upwards (zenith), since only then does a suitable paraboloid of rotation arise as a result of gravity. Without rotation of the mirror, mercury mirrors were used in metrology as a flatness standard.
• The property of mercury to behave like a non-wetting liquid (exceptions: amalgam formers such as copper, silver, gold, aluminum) is the basis for mercury porosimetry. Here, mercury is pressed under pressure (0 to 4000 bar) into pores of different sizes. Statements can be made about the nature, shape, distribution and size of pores and cavities via the pressure applied and the amount of mercury required. This method is used, among other things, in mineralogy, pharmacy and the ceramic sciences.
• In the past, mercury salts were used by hat makers, especially to make castor hats made of beaver fur, which were very fashionable in the 18th century. The English expression "mad as a hatter" ("crazy like a hatter") (see also hat maker syndrome) probably goes back to the application. He was also popularized by the Mad Hatter character in Lewis Carroll's Alice in Wonderland.
• In the past, mercury was used alongside water as a working medium in steam power plants. The vapor of the metal reached a temperature of 500 ° C at a pressure of 10 bar. Despite its thermodynamic advantages, the process did not gain acceptance because of the toxicity of the metal.
• The first nuclear reactors of the fast breeder type were cooled with mercury (e.g. Clementine reactor in Los Alamos / USA 1946–1952 and similar reactors in the Soviet Union). However, due to major corrosion problems and the difficult handling of the poisonous mercury, the company soon switched to liquid sodium. While the Clementine reactor was dismantled by 1970, this is still pending for the Russian mercury-cooled reactors, which were decommissioned more than 50 years ago.
• It has been known for several years that, from around 1955, boiling mercury was used in the military HERMEX project to separate weapons-grade plutonium from spent reactor fuel elements. More than 1000 tons of plutonium-containing mercury from this decommissioned HERMEX project are still stored in the Oak Ridge National Laboratory.
• Also in the Oak Ridge National Laboratory, an extensive project for the extraction of tritium for hydrogen bombs using approx. 1950 tons of mercury was carried out from 1963 to 11.000. About 3% of the mercury was released into the environment.
• Mercury is (or was mainly used in the past) as a working medium in diffusion pumps to generate an oil-free high vacuum.
• Mercury vapor was used to develop the image in the daguerreotype, the first practicable photography process. The resulting photo consisted of a mercury precipitate on a silver-plated copper plate.
• At the end of the 17th century, the physician Anton Nuck introduced the injection of mercury into anatomical specimens.
• Mercury is used in high-power spallation sources as a target for generating neutrons, e.g. B. SNS / USA or JSNS / Japan. Approx. 20 tons of mercury are bombarded with a proton beam with a particle energy of approx. 1 GeV. Mercury atomic nuclei are shattered and around 20 neutrons are released for each irradiated proton. The European Spallation Source ESS planned in Lund (Sweden) is not expected to use any mercury.