|Boiling Point: 630°K, 357°C, 675°F
Melting Point: 234.43°K, -38.72°C, -37.7°F
Electrons Energy Level: 2, 8, 18, 32, 18, 2
Isotopes: 33 + 7 Stable
Heat of Vaporization: 59.229 kJ/mol
Heat of Fusion: 2.295 kJ/mol
Density: 13.546 g/cm3 @ 300°K
Specific Heat: 0.139 J/g°K
Atomic Radius: 1.76Å
Ionic Radius: 1.02Å
Electronegativity: 2 (Pauling); 1.44 (Allrod Rochow)
Vapor Pressure: 0.0002 Pa @ -38.72°C
1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10 6s2
Mercury was known to the ancient Chinese and Hindus and was found in Egyptian tombs that date from 1500 BC. In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health. China's first emperor, Qin Shi Hunag Di said to have been buried in a tomb that contained rivers of flowing mercury, representative of the rivers of China was driven insane and killed by mercury pills intended to give him eternal life. The ancient Greeks used mercury in ointments and the Romans used it in cosmetics. By 500 BC mercury was used to make amalgams with other metals. The Indian word for alchemy is Rasavatam which means the way of mercury. Alchemists often thought of mercury as the First Matter from which all metals were formed. Different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. An ability to transform mercury into any metal resulted from the essentially mercurial quality of all metals. The purest of these was gold, and mercury was required for the transmutation of base (or impure) metals into gold. This was a primary goal of alchemy, either for material or spiritual gain.
|Alchemical Symbol, Mercury|
Hg is the modern chemical symbol for mercury. It comes from hydrargyrum, a Latinized form of the Greek word (hydrargyros), which is a compound word meaning 'water' and 'silver' since it is liquid, like water, and yet has a silvery metallic sheen. The element was named after the Roman god Mercury, known for speed and mobility. It is associated with the planet Mercury. The astrological symbol for the planet is also one of the alchemical symbols for the metal. Mercury is the only metal for which the alchemical planetary name became the common name.
|Additional Representations of Alchemical Symbols for Mercury|
From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution of the mercury compound mercuric nitrate, Hg(NO3)2·2H2O. This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. Its use resulted in widespread cases of mercury poisoning among hatters. Symptoms included tremors, emotional lability, insomnia, dementia and hallucinations. The United States Public Health Service banned the use of mercury in the felt industry in December 1941. The psychological symptoms associated with mercury poisoning may have inspired the phrase "mad as a hatter". Lewis Carrol's "Mad Hatter" in his book Alice's Adventures in Wonderland was based on this fact. Other uses:
Preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), handheld maze games, cleaning, and in-road leveling devices in cars. Mercury compounds have been used in antiseptics, laxatives, antidepressants, and antisyphilitics. It was also allegedly used by allied spies to sabotage German planes. A mercury paste was applied to bare aluminum, causing the metal to rapidly corrode. This would cause mysterious structural failures.
A heavy, silvery transition metal, mercury is one of five elements that are liquid at or near standard room temperature and pressure (the others are the metals cesium, francium, and gallium, plus the nonmetal bromine). Mercury is used in thermometers, barometers and other scientific apparatus, although the use of mercury in thermometers has been largely phased out in clinical and scientific environments (in favor of alcohol-filled, digital or thermistor-based replacements) due to concerns about the element's toxicity. Mercury is still used in dental amalgam. Mercury is mostly obtained by reduction from the mineral cinnabar. Mercury, like lead, is a neurotoxin, and elevated blood mercury levels lead to retardation and deformities in children.
Mercury dissolves to form amalgams with gold, zinc and many metals. Because iron is an exception to this rule, iron flasks have been traditionally used to trade mercury. When heated, mercury also reacts with oxygen in air to form mercury oxide, which then can be decomposed by further heating to higher temperatures. Since it is below hydrogen in the reactivity series of metals, mercury does not react with most acids, such as dilute sulfuric acid, though oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate and nitrate and chloride. Similar to silver, mercury reacts with atmospheric hydrogen sulfide. Mercury even reacts with solid sulfur flakes, which is used in mercury spill kits to absorb mercury vapors (spill kits also use activated charcoal and powdered zinc).
Mercury is an extremely rare element in the earth's crust, having an average crustal abundance by mass of only 0.08 parts per million. However, because it does not blend geochemically with those elements that comprise 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). This makes mercury ore the most easily depleted of all metal ores. Depletion of mercury ores has been a major concern since the 1960s and it is now almost certain that the last mineable deposits were discovered in Algeria in the mid-1970s. Since the early 1970s, total world production of mercury has fallen from 9,000 tons to 1,600 tons due to depletion of reserve.
It is found either as a native metal (rare) or in cinnabar, carderoite, livingtonite and other minerals, with cinnabar (HgS) being the most common ore. Mercury ores usually occur in very young orogenic belts where rock of high density are forced to the crust of the Earth, often in hot springs or other volcanic regions. Most present-day production occurs in Spain, Kyrgzstan, China and Tajikistan. Over 100,000 tons of mercury were mined from the region of Huancavelica, Peru, over the course of three centuries following the discovery of deposits there in 1563. Mercury from Huancavelica was crucial in the production of silver in colonial Spanish America. Many former ores in Italy, Slovenia, the United States and Mexico which once produced a large proportion of the world's supply have now been completely mined out. The metal is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is:
HgS + O2 Hg + SO2
Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures (In the United States, non-prescription sale of mercury fever thermometers is banned by a number of different states and localities). Other uses:
Elemental mercury is the main ingredient in dental amalgams. Controversy over the health effects from the use of mercury amalgams began shortly after its introduction into the western world, nearly 200 years ago. In 1843, The American Society of Dental Surgeons, concerned about mercury poisoning, required its members to sign a pledge that they would not use amalgam. In 1859, The American Dental Association was formed by dentists who believed amalgam was "safe and effective". The ADA "continues to believe that amalgam is a valuable, viable and safe choice for dental patients", as written in their statement on dental amalgam. In 1993, the United States Public Health Service reported that "amalgam fillings release small amounts of mercury vapor", but in such a small amount that it "has not been shown to cause any adverse health effects". This position is not shared by all governments and there is an ongoing dental amalgam controversy. A recent review by an FDA-appointed advisory panel rejected, by a margin of 13-7, the current FDA report on amalgam safety, stating the report's conclusions weren't reasonable, given the quantity and quality of information currently available. Panelists said remaining uncertainties about the risk of so-called silver fillings demanded further research; in particular, on the effects of mercury-laden fillings on children and the fetuses of pregnant women with fillings; and the release of mercury vapor on insertion and removal of mercury fillings.
Mercury and its compounds have been used in medicine for centuries, although they are much less common today than they once were, now that the toxic effects of mercury and its compounds are more widely known and understood.
Mercury (I) chloride (also known as calomel or mercurous chloride) has traditionally been used as a diuretic, topical disinfectant, and laxative. Mercury (II) chloride (also known as mercuric chloride or corrosive sublimate) was once used to treat syphilis (along with other mercury compounds), although it is so toxic that sometimes the symptoms of its toxicity were confused with those of the syphilis it was believed to treat; it was also used as a disinfectant. Blue mass, a pill or syrup in which mercury is the main ingredient, was prescribed throughout the 1800s for numerous conditions including constipation, depression, child-bearing and toothaches. 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 Mercurochrome is still widely used but has been banned in some countries such as the U.S.
Thiomersal, (called Thimerosal in the United States), an organic compound used as a preservative in vaccines, though this use is disappearing.
Some vaccines have contained the preservative Thiomersal (partly ethyl mercury) since the 1930s FDA report. It has been widely speculated that this mercury-based preservative can trigger autism in children who are already genetically predisposed to it; however, medical evidence in recent studies has shown no evidence supporting any such link.
Mercury in the form of one of its common ores, cinnabar, remains an important component of Chinese, Tibetan, and Ayurvedic medicine. As problems may arise when these medicines are exported to countries that prohibit the use of mercury in medicines, in recent times, less toxic substitutes have been devised.
Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries. Thermometers and sphygmomanometers containing mercury were invented in the early 18th and late 19th centuries, respectively. In the early 21st century, their use is declining and has been banned in some countries, states and medical institutions. In 2002, the U.S. Senate passed legislation to phase out the sale of non-prescription mercury thermometers. In 2003, Washington and Maine became the first states to ban mercury blood pressure devices. Mercury compounds are found in some over-the-counter drugs, including topical antiseptics, stimulant laxatives, diaper-rash ointment, eye drops, and nasal sprays. The FDA has inadequate data to establish general recognition of the safety and effectiveness, of the mercury ingredients in these products. Mercury is still used in some diuretics, although substitutes now exist for most therapeutic uses.
In the European Union, RoHS legislation being introduced will ban mercury from certain electrical and electronic products, and limit the amount of mercury in other products to less than 1000 ppm (except for certain exemptions).
The most important salts are:
Laboratory tests have found that an electrical discharge causes the noble gases to combine with mercury vapor. These compounds are held together with Van der Waals forces and result in Hg·Ne, Hg·Ar, Hg·Kr, and Hg·Xe. Organic mercury compounds are also important. Methylmercury is a dangerous compound that is widely found as a pollutant in water bodies and streams.
There are seven stable isotopes of mercury with Hg-202 being the most abundant (29.86%). The longest-lived radioisotopes are 194Hg with a half-life of 444 years, and 203Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. 199Hg and 201Hg are the most often studied NMR-active nuclei, having spins of 1/2 and 3/2 respectively.
|Mercury should be handled with care. Containers of mercury should be securely sealed to avoid spills and evaporation as mercury can be inhaled and absorbed through the skin. Heating of mercury, or compounds of mercury that may decompose when heated, should always be carried out with adequate ventilation in order to avoid exposure to mercury vapor. Mercury should not be displayed in open containers. Most compounds of mercury are toxic, especially its organic compounds.|
Preindustrial deposition rates of mercury from the atmosphere may be in the range of 4 ng/L in the western USA. Although that can be considered a natural level of exposure, regional or global sources have significant effects. Volcanic eruptions can increase the atmospheric source by 46 times.
Mercury enters the environment as a pollutant from various industries:
Mercury also enters into the environment through the disposal (e.g., landfilling, incineration) of certain products. Products containing mercury include: auto parts, batteries, fluorescent bulbs, medical products, thermometers, and thermostats. Due to health concerns, toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, most thermometers now use pigmented alcohol instead of mercury. Mercury thermometers are still occasionally used in the medical field because they are more accurate than alcohol thermometers, though both are being replaced by electronic thermometers. Mercury thermometers are still widely used for certain scientific applications because of their greater accuracy and working range.
One of the worst industrial disasters in history was caused by the dumping of mercury compounds into Minamata Bay, Japan. The Chisso Corporation, a fertilizer and later petrochemical company, was found responsible for polluting the bay from 19321968. It is estimated that over 3,000 people suffered various deformities, severe mercury poisoning symptoms or death from what became known as Minamata disease.
The environmental impact of mercury use in a particular product can sometimes be complicated. For instance compact fluorescent light bulbs, which contain a very small amount of mercury (in 2004 two-thirds of CFL lamps sold contained 5 mg Hg or less per bulb, while 96 percent contained 10 mg or less), are far more efficient than incandescent lamps, and thus may overall emit less mercury to the environment than incandescent lamps, due to mercury content of fly ash from coal power plants.
Historically, one of the largest releases was from the Colex plant, a lithium-isotope separation plant at Oak Ridge. The plant operated in the 1950s and 1960s. Records are incomplete and unclear, but government commissions have estimated that some two million pounds of mercury are unaccounted for.
The primary sources of mercury to the environment are fossil fuel burning (primarily coal) and solid waste incineration (Nriagu & Pacyna, 1988). Power plants in the U.S., according to the EPA, are one of the main sources of mercury pollution48 tons a year.
The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants that need to be controlled to the greatest possible extent. Thus, certain industries that release mercury into the environment must install maximum achievable control technologies (MACT). However, a March 2005 EPA rule took power plants off the list of sources which must reduce mercury to the maximum extent. Instead, a cap and trade rule was issued, with most of the reductions in mercury pollution from power plants beginning in the year 2018. States were also given until November 2006 to impose stricter controls, and several States are doing so. The rule was being subjected to legal challenges from several States in 2005.
Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization, OSHA, and NIOSH all treat mercury as an occupational hazard, and have established specific occupational exposure limits. Environmental releases and disposal of mercury are regulated in the U.S. primarily by the Environmental Protection Agency (EPA).
Mercury in Fish
Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organic compound of mercury. Species of fish that are high on the food chain, such as shark, swardfish, king mackerel, albacore tuna, and tilefish contain higher concentrations of mercury than others. This is because mercury is stored in the muscle tissues of fish, and when a predatory fish eats another fish, it assumes the entire body burden of mercury in the consumed fish. Since fish are less efficient at depurating than accumulating methylmercury, fish-tissue concentrations increase over time. Thus species that are high on the food chain amass body burdens of mercury that can be ten times higher, or more, than the species they consume. This process is called biomagnification.
The complexities associated with mercury fate and transport are relatively succinctly described by USEPA in their 1997 Mercury Study Report to Congress. Because methylmercury and high levels of elemental mercury can be particularly toxic to unborn or young children, organizations such as the EPA and and FDA recommend that women who are pregnant or plan to become pregnant within the next one or two years, as well as young children avoid eating more than 6 ounces (one average meal) of fish per week. In the United States the FDA has an action level for methyl mercury in commercial marine and freshwater fish that is 1.0 parts per million (ppm), and in Canada the limit for the total of mercury content is 0.5 ppm.
Species with characteristically low levels of mercury include shrimp, tilapia, salmon, pollack, and catfish (FDA March 2004). The FDA characterizes shrimp, catfish, pollock, salmon, and canned light tuna as low-mercury seafood, although recent tests have indicated that up to 6 percent of canned light tuna may contain high levels.
Mercury & Aluminum
Mercury readily combines with aluminum to form an amalgam when the two pure metals come into contact. However, when the amalgam is exposed to air, the aluminum oxidizes, leaving behind mercury. The oxide flakes away, exposing more mercury amalgam, which repeats the process. This process continues until the supply of amalgam is exhausted, and since it releases mercury, a small amount of mercury can eat through a large amount of aluminum over time, by progressively forming amalgam and relinquishing the aluminum as oxide.
Aluminum in air is ordinarily protected by a molecule-thin layer of its own oxide (which is not porous to oxygen). Mercury coming into contact with this oxide does no harm. However, if any elemental aluminum is exposed (even by a recent scratch), the mercury may combine with it, starting the process described above, and potentially damaging a large part of the aluminum before it finally ends (Ornitz 1998).
For this reason, restrictions are placed on the use and handling of mercury in proximity with aluminum. In particular, mercury is not allowed aboard aircraft under most circumstances because of the risk of it forming amalgam with exposed aluminum parts in the aircraft.
Due to minimal surface disruption, mercury mines lend themselves to constructive re-use. For example, in 1976 Santa Clara County, California purchased the historic Almaden Quicksilver Mine and proceeded to create a county park on the site, after conducting extensive safety and environmental analysis of the property.
|Ionization Energy (eV): 10.438 eV
Estimated Crustal Abundance: 8.5×10-2 milligrams per kilogram
Estimated Oceanic Abundance: 3×10-5 milligrams per liter