Sphalerite from Baxter Springs, Kan.
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Metallic chemical element, chemical symbol Zn, atomic number 30. Zinc is a bluish silver metal, ductile when very pure but brittle otherwise. It forms brass (with copper) and many other alloys. Its major use is in galvanizing iron, steel, and other metals. Zinc is an essential trace element, particularly in red blood cells; in snails, it corresponds to iron in the blood of vertebrates. Zinc oxide is used as a pigment, ultraviolet light absorber (to prevent sunburn), dietary supplement and seed treatment, and photoconductor. Zinc's many other compounds (in which it has valence 2 or, rarely, 1) are used in industrial and consumer applications, including as pesticides, pigments, mordants (see dye), fluxes, and wood preservatives.
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Zinc (from Zink) is a metallic chemical element with the symbol Zn and atomic number 30. In nonscientific context it is sometimes called spelter. Zinc plating of steel is the major application for zinc other applications are in batteries and in alloys, for example brass. Sphalerite is the most important zinc ore. Zinc production includes roasting, leaching and at the end electrowinning. Commercially pure zinc is known as Special High Grade, often abbreviated SHG, and is 99.995% pure. Zinc is an essential mineral, necessary for sustaining all life, but at higher concentrations zinc poisoning can occur.
From 100 °C to 210 °C to zinc metal is malleable and can easily be beaten into various shapes. Above , the metal becomes brittle and will be pulverized by beating. Zinc is nonmagnetic.
Zinc has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of isotopically enriched 64Zn, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope Zn-65 with a half-life of 244 days and produce approximately 2.27 MeV of gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several days. Such a weapon is not known to have ever been built, tested, or used.
The name of the metal zinc is unusual and, while vague in origin, was probably first used by Paracelsus, a Swiss-born German chemist, who referred to the metal as "Zincum", in the 16th century. These words in German apparently mean "tooth-like, pointed or jagged part" and, as metallic zinc crystals are needle-like, the derivation appears plausible.
Zinc mines of Zawar, near Udaipur, Rajasthan, India were active during 400 BC. There are references of medicinal uses of zinc in the Charaka Samhita (300 BC). The Rasaratna Samuccaya (800 AD) explains the existence of two types of ores for zinc metal, one of which is ideal for metal extraction while the other is used for medicinal purpose. Because of the low boiling point and high chemical reactivity of this metal (isolated zinc would tend to go up the chimney rather than be captured), the true nature of this metal was not understood in ancient times.
The manufacture of brass was known to the Ebi by about 30 BC, using a technique where calamine and copper were heated together in a crucible. The zinc oxides in calamine were reduced, and the free zinc metal was trapped by the copper, forming an alloy. The resulting calamine brass was either cast or hammered into shape.
Smelting and extraction of impure forms of zinc was accomplished around 1200 AD in India. China did not learn of the technique until 17th Century AD. In the West, impure zinc as a remnant in melting ovens was known since antiquity, but usually discarded as worthless. Strabo mentions it as pseudo-argyros — "mock silver". The Berne zinc tablet is a votive plaque dating to Roman Gaul, probably made from such zinc remnants.
The isolation of metallic zinc in the West may have been achieved independently by several people:
In 1758, William's brother, John, developed a new process for calcining zinc sulfide into an oxide for use in the retort process. Prior to this only calamine could be used to produce zinc. This process was then used into the 20th century. In 1798, Johann Ruberg built the first horizontal retort smelter in Upper Silesia. This was much more fuel efficient and less labor intensive than the vertical retort process. Jean-Jacques Daniel Dony built a different kind of horizontal zinc smelter in Belgium, which processes more.
Zinc is the 23rd most abundant element in the Earth's crust. The most heavily mined ores (sphalerite) tend to contain roughly 10% iron as well as 40–50% zinc. Minerals from which zinc is extracted include sphalerite (zinc sulfide), smithsonite (zinc carbonate), hemimorphite (zinc silicate), and franklinite (a zinc spinel).
The earth has been estimated to have 46 years supply of zinc. A chemist estimated in 2007 that at the current rate of usage, the world's supply of zinc would be exhausted by about the year 2037.
There are zinc mines throughout the world, with the largest producers being China, Australia and Peru. In 2005, China produced almost one-fourth of the global zinc output, reports the British Geological Survey. Zinc mines and refineries in Europe include Tara, Galmoy and Lisheen in Ireland and Zinkgruvan in Sweden.
Zinc metal is produced using extractive metallurgy.
Zinc is the primary metal used in making American one cent coins since 1982. The zinc core is coated with a thin layer of copper to give the impression of a copper coin. In 1994 33,200 tons of zinc were used to produce 13,6 billion pennies.
The most widely used alloy of zinc is brass, in which copper is alloyed with anywhere from 9% to 45% zinc, depending upon the type of brass, along with much smaller amounts of lead and tin. Alloys of 85–88% zinc, 4–10% copper, and 2–8% aluminium find limited use in certain types of machine bearings. Alloys of primarily zinc with small amounts of copper, aluminium, and magnesium are useful in die casting as well as spin casting. An example of this is zinc aluminium. Similar alloys with the addition of a small amount of lead can be cold-rolled into sheets. An alloy of 96% zinc and 4% aluminium is used to make stamping dies for low production run applications where ferrous metal dies would be too expensive.
Zinc is an essential mineral, necessary for sustaining all life. It is a key factor in prostate gland function and reproductive organ growth. It is estimated that 3,000 of the hundreds of thousands of proteins in the human body contain zinc prosthetic groups, one type of which is the so-called zinc finger. In addition, there are over a dozen types of cells in the human body that secrete zinc ions, and the roles of these secreted zinc signals in medicine and health are now being actively studied. Zinc ions are now considered to be neurotransmitters. Cells in the salivary gland, prostate, immune system and intestine use zinc signalling.
Zinc is an activator of certain enzymes, such as carbonic anhydrase. Carbonic anhydrase is important in the transport of carbon dioxide in vertebrate blood. It is also required in plants for leaf formation, the synthesis of indole acetic acid (auxin) and anaerobic respiration (alcoholic fermentation).
Zinc is a good lewis acid, making it a useful catalytic agent in hydroxylation and other enzymatic reactions. Also Zinc has a flexible coordination geometry, allowing enzymes using Zinc to rapidly shift conformations and perform biological reactions .
The US recommended dietary allowance of zinc from puberty on is 11mg for males and 8mg for females, with higher amounts recommended during pregnancy and lactation.
Zinc deficiency occurs where insufficient zinc is available for metabolic needs. It is usually nutritional, but can also be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses.
In clinical trials, both zinc gluconate and zinc gluconate glycine (the formulation used in lozenges) have been shown to shorten the duration of symptoms of the common cold. The amount of glycine can vary from two to twenty moles per mole of zinc gluconate. It should be known that there have been clinical trials that both support the use of zinc for the common cold, and are inconclusive of its effectiveness. All clinical trials have their critics, including the dosage amount used, and the highly subjective format of patient self-reporting the results of their trials.
The free zinc ion is also a powerful Lewis acid up to the point of being corrosive. Stomach acid contains hydrochloric acid, in which metallic zinc dissolves readily to give corrosive zinc chloride. Swallowing a post-1982 American one cent piece (97.5% zinc) can cause damage to the stomach lining due to the high solubility of the zinc ion in the acidic stomach. Zinc toxicity, mostly in the form of the ingestion of US pennies minted after 1982, is commonly fatal in dogs where it causes a severe hemolytic anemia. In pet parrots zinc is highly toxic and poisoning can often be fatal.
There is evidence of induced copper deficiency at low intakes of 100–300 mg Zn/d. The USDA RDA is 15 mg Zn/d. Even lower levels, closer to the RDA, may interfere with the utilization of copper and iron or to adversely affect cholesterol..
There are also cases reported in that humans suffered zinc intoxication by the ingestion of zinc coins.