Zinc

Zinc,  ₃₀Zn

General properties
Name, symbol	zinc, Zn
Pronunciation	/ˈzɪŋk/ ZINGK
Appearance	silver-gray
Zinc in the periodic table
– ↑ Zn ↓ Cd copper ← zinc → gallium
Atomic number	30
Standard atomic weight (±)	65.38(2)[1]
Element category	transition metal, alternatively considered a post-transition metal
Group, block	group 12, d-block
Period	period 4
Electron configuration	[Ar] 3d10 4s2
per shell	2, 8, 18, 2
Physical properties
Phase	solid
Melting point	692.68 K ​(419.53 °C, ​787.15 °F)
Boiling point	1180 K ​(907 °C, ​1665 °F)
Density near r.t.	7.14 g·cm−3
when liquid, at m.p.	6.57 g·cm−3
Heat of fusion	7.32 kJ·mol−1
Heat of vaporization	115 kJ·mol−1
Molar heat capacity	25.470 J·mol−1·K−1
vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 610 670 750 852 990 1179
Atomic properties
Oxidation states	+2, +1, 0 ​(an amphoteric oxide)
Electronegativity	Pauling scale: 1.65
Ionization energies	1st: 906.4 kJ·mol−1 2nd: 1733.3 kJ·mol−1 3rd: 3833 kJ·mol−1 (more)
Atomic radius	empirical: 134 pm
Covalent radius	122±4 pm
Van der Waals radius	139 pm
Miscellanea
Crystal structure	​hexagonal close-packed (hcp)
Speed of sound thin rod	3850 m·s−1 (at r.t.) (rolled)
Thermal expansion	30.2 µm·m−1·K−1 (at 25 °C)
Thermal conductivity	116 W·m−1·K−1
Electrical resistivity	59.0 nΩ·m (at 20 °C)
Magnetic ordering	diamagnetic
Young's modulus	108 GPa
Shear modulus	43 GPa
Bulk modulus	70 GPa
Poisson ratio	0.25
Mohs hardness	2.5
Brinell hardness	327–412 MPa
CAS Registry Number	7440-66-6
History
Discovery	Indian metallurgists (before 1000 BCE)
First isolation	Andreas Sigismund Marggraf (1746)
Recognized as a unique metal by	Rasaratna Samuccaya (800)
Most stable isotopes
iso NA half-life DM DE (MeV) DP 64Zn 48.6% >2.3×1018 y (β+β+) 1.096 64Ni 65Zn syn 243.8 d ε 1.3519 65Cu γ 1.1155 – 66Zn 27.9% 66Zn is stable with 36 neutrons 67Zn 4.1% 67Zn is stable with 37 neutrons 68Zn 18.8% 68Zn is stable with 38 neutrons 69Zn syn 56 min β− 0.906 69Ga 69mZn syn 13.76 h β− 0.906 69Ga 70Zn 0.6% >1.3×1016 y (β−β−) 0.998 70Ge 71Zn syn 2.4 min β− 2.82 71Ga 71mZn syn 3.97 d β− 2.82 71Ga 72Zn syn 46.5 h β− 0.458 72Ga
Decay modes in parentheses are predicted, but have not yet been observed

Zinc, in commerce also spelter, is a chemical element with symbol Zn and atomic number 30. It is the first element of group 12 of the periodic table. In some respects zinc is chemically similar to magnesium: its ion is of similar size and its only common oxidation state is +2. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest mineable amounts are found in Australia, Asia, and the United States. Zinc production includes froth flotation of the ore, roasting, and final extraction using electricity (electrowinning).

Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC in Judea^[2] and by the 7th century BC in Ancient Greece.^[3] Zinc metal was not produced on a large scale until the 12th century in India and was unknown to Europe until the end of the 16th century. The mines of Rajasthan have given definite evidence of zinc production going back to the 6th century BC.^[4] To date, the oldest evidence of pure zinc comes from Zawar, in Rajasthan, as early as the 9th century AD when a distillation process was employed to make pure zinc.^[5] Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow".

The element was probably named by the alchemist Paracelsus after the German word Zinke. German chemist Andreas Sigismund Marggraf is credited with discovering pure metallic zinc in 1746. Work by Luigi Galvani and Alessandro Volta uncovered the electrochemical properties of zinc by 1800. Corrosion-resistant zinc plating of iron (hot-dip galvanizing) is the major application for zinc. Other applications are in batteries, small non-structural castings, and alloys, such as brass. A variety of zinc compounds are commonly used, such as zinc carbonate and zinc gluconate (as dietary supplements), zinc chloride (in deodorants), zinc pyrithione (anti-dandruff shampoos), zinc sulfide (in luminescent paints), and zinc methyl or zinc diethyl in the organic laboratory.

Zinc is an essential mineral perceived by the public today as being of "exceptional biologic and public health importance", especially increasingly regarding prenatal and postnatal development.^[6] Zinc deficiency affects about two billion people in the developing world and is associated with many diseases.^[7] In children it causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea.^[6] Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans.^[8] Consumption of excess zinc can cause ataxia, lethargy and copper deficiency.

Characteristics

Physical properties

Zinc, also referred to in nonscientific contexts as spelter,^[9] is a bluish-white, lustrous, diamagnetic metal,^[10] though most common commercial grades of the metal have a dull finish.^[11] It is somewhat less dense than iron and has a hexagonal crystal structure, with a distorted form of hexagonal close packing, in which each atom has six nearest neighbors (at 265.9 pm) in its own plane and six others at a greater distance of 290.6 pm.^[12] The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C.^[10][11] Above 210 °C, the metal becomes brittle again and can be pulverized by beating.^[13] Zinc is a fair conductor of electricity.^[10] For a metal, zinc has relatively low melting (419.5 °C, 787.1 F) and boiling points (907 °C).^[14] Its melting point is the lowest of all the transition metals aside from mercury and cadmium.^[14]

Many alloys contain zinc, including brass, an alloy of copper and zinc. Other metals long known to form binary alloys with zinc are aluminium, antimony, bismuth, gold, iron, lead, mercury, silver, tin, magnesium, cobalt, nickel, tellurium and sodium.^[15] Although neither zinc nor zirconium are ferromagnetic, their alloy ZrZn
2 exhibits ferromagnetism below 35 K.^[10]

A bar of zinc generates a characteristic sound when bent, similar to tin cry.

Occurrence

Zinc makes up about 75 ppm (0.0075%) of Earth's crust, making it the 24th most abundant element. Soil contains 5–770 ppm of zinc with an average of 64 ppm. Seawater has only 30 ppb zinc and the atmosphere contains 0.1–4 µg/m³.^[16]

The element is normally found in association with other base metals such as copper and lead in ores.^[17] Zinc is a chalcophile, meaning the element has a low affinity for oxides and prefers to bond with sulfides. Chalcophiles formed as the crust solidified under the reducing conditions of the early Earth's atmosphere.^[18] Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.^[17]

Other minerals from which zinc is extracted include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate).^[19] With the exception of wurtzite, all these other minerals were formed as a result of weathering processes on the primordial zinc sulfides.^[18]

Identified world zinc resources total about 1.9 billion tonnes.^[20] Large deposits are in Australia, Canada and the United States with the largest reserves in Iran.^[18][21][22] At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055.^[23][24] About 346 million tonnes have been extracted throughout history to 2002, and one estimate found that about 109 million tonnes of that remains in use.^[25]

Isotopes

Five isotopes of zinc occur in nature. ⁶⁴Zn is the most abundant isotope (48.63% natural abundance).^[26] This isotope has such a long half-life, at 7018430000000000000♠4.3×10¹⁸ a,^[27] that its radioactivity can be ignored.^[28] Similarly, 70
Zn (0.6%), with a half-life of 7023410248799900000♠1.3×10¹⁶ a is not usually considered to be radioactive. The other isotopes found in nature are 66
Zn (28%), 67
Zn (4%) and 68
Zn (19%).

Several dozen radioisotopes have been characterized. 65
Zn, which has a half-life of 243.66 days, is the most long-lived radioisotope, followed by 72
Zn with a half-life of 46.5 hours.^[26] Zinc has 10 nuclear isomers. ^69mZn has the longest half-life, 13.76 h.^[26] The superscript m indicates a metastable isotope. The nucleus of a metastable isotope is in an excited state and will return to the ground state by emitting a photon in the form of a gamma ray. 61
Zn has three excited states and 73
Zn has two.^[29] The isotopes 65
Zn, 71
Zn, 77
Zn and 78
Zn each have only one excited state.^[26]

The most common decay mode of a radioisotope of zinc with a mass number lower than 66 is electron capture. The decay product resulting from electron capture is an isotope of copper.^[26]

n
30Zn + e− → n
29Cu

The most common decay mode of a radioisotope of zinc with mass number higher than 66 is beta decay (β⁻), which produces an isotope of gallium.^[26]

n
30Zn → n
31Ga + e− + ν
e

Compounds and chemistry

Reactivity

Zinc has an electron configuration of [Ar]3d¹⁰4s² and is a member of the group 12 of the periodic table. It is a moderately reactive metal and strong reducing agent.^[30] The surface of the pure metal tarnishes quickly, eventually forming a protective passivating layer of the basic zinc carbonate, Zn
5(OH)
6(CO₃)
2, by reaction with atmospheric carbon dioxide.^[31] This layer helps prevent further reaction with air and water.

Zinc burns in air with a bright bluish-green flame, giving off fumes of zinc oxide.^[32] Zinc reacts readily with acids, alkalis and other non-metals.^[33] Extremely pure zinc reacts only slowly at room temperature with acids.^[32] Strong acids, such as hydrochloric or sulfuric acid, can remove the passivating layer and subsequent reaction with water releases hydrogen gas.^[32]

The chemistry of zinc is dominated by the +2 oxidation state. When compounds in this oxidation state are formed the outer shell s electrons are lost, which yields a bare zinc ion with the electronic configuration [Ar]3d¹⁰.^[34] In aqueous solution an octahedral complex, [Zn(H
2O)₆]2+
is the predominant species.^[35] The volatilization of zinc in combination with zinc chloride at temperatures above 285 °C indicates the formation of Zn
2Cl
2, a zinc compound with a +1 oxidation state.^[32] No compounds of zinc in oxidation states other than +1 or +2 are known.^[36] Calculations indicate that a zinc compound with the oxidation state of +4 is unlikely to exist.^[37]

Zinc chemistry is similar to the chemistry of the late first-row transition metals nickel and copper, though it has a filled d-shell, so its compounds are diamagnetic and mostly colorless.^[38] The ionic radii of zinc and magnesium happen to be nearly identical. Because of this some of their salts have the same crystal structure^[39] and in circumstances where ionic radius is a determining factor zinc and magnesium chemistries have much in common.^[32] Otherwise there is little similarity. Zinc tends to form bonds with a greater degree of covalency and it forms much more stable complexes with N- and S- donors.^[38] Complexes of zinc are mostly 4- or 6- coordinate although 5-coordinate complexes are known.^[32]

Zinc(I) compounds

Zinc(I) compounds are rare, and requires bulky ligands to stabilize the low oxidation state. Most zinc(I) compounds contains formally the [Zn₂]²⁺ core, which is analogous to the [Hg₂]²⁺ dimeric cation present in mercury(I) compounds. The diamagnetic nature of the ion confirms its dimeric structure. The first zinc(I) compound containing the Zn—Zn bond, (η⁵-C₅Me₅)₂Zn₂, is also the first dimetallocene. The [Zn₂]²⁺ ion rapidly disproportionates into zinc metal and zinc(II), and has only been obtained as a yellow glass formed by cooling a solution of metallic zinc in molten ZnCl₂.^[40]

Zinc (II) compounds

Binary compounds of zinc are known for most of the metalloids and all the nonmetals except the noble gases. The oxide ZnO is a white powder that is nearly insoluble in neutral aqueous solutions, but is amphoteric, dissolving in both strong basic and acidic solutions.^[32] The other chalcogenides (ZnS, ZnSe, and ZnTe) have varied applications in electronics and optics.^[41] Pnictogenides (Zn
3N
2, Zn
3P
2, Zn
3As
2 and Zn
3Sb
2),^[42][43] the peroxide (ZnO
2), the hydride (ZnH
2), and the carbide (ZnC
2) are also known.^[44] Of the four halides, ZnF
2 has the most ionic character, whereas the others (ZnCl
2, ZnBr
2, and ZnI
2) have relatively low melting points and are considered to have more covalent character.^[45]

In weak basic solutions containing Zn2+
ions, the hydroxide Zn(OH)
2 forms as a white precipitate. In stronger alkaline solutions, this hydroxide is dissolved to form zincates ([Zn(OH)₄]2−
).^[32] The nitrate Zn(NO₃)
2, chlorate Zn(ClO₃)
2, sulfate ZnSO
4, phosphate Zn
3(PO₄)
2, molybdate ZnMoO
4, cyanide Zn(CN)
2, arsenite Zn(AsO₂)
2, arsenate Zn(AsO₄)
2·8H
2O and the chromate ZnCrO
4 (one of the few colored zinc compounds) are a few examples of other common inorganic compounds of zinc.^[46][47] One of the simplest examples of an organic compound of zinc is the acetate (Zn(O
2CCH₃)
2).

Organozinc compounds are those that contain zinc–carbon covalent bonds. Diethylzinc ((C
2H₅)
2Zn) is a reagent in synthetic chemistry. It was first reported in 1848 from the reaction of zinc and ethyl iodide, and was the first compound known to contain a metal–carbon sigma bond.^[48]

History

Ancient use

Various isolated examples of the use of impure zinc in ancient times have been discovered. Zinc ores were used to make the zinc–copper alloy brass many centuries prior to the discovery of zinc as a separate element. Judean brass from the 14th to 10th centuries BC contains 23% zinc.^[2]

Knowledge of how to produce brass spread to Ancient Greece by the 7th century BC, but few varieties were made.^[3] Ornaments made of alloys containing 80–90% zinc, with lead, iron, antimony, and other metals making up the remainder, have been found that are 2,500 years old.^[17] A possibly prehistoric statuette containing 87.5% zinc was found in a Dacian archaeological site.^[49]

The oldest known pills were made of the zinc carbonates hydrozincite and smithsonite. The pills were used for sore eyes and were found aboard the Roman ship Relitto del Pozzino, which wrecked in 140 BC.^[50][51]

The manufacture of brass was known to the Romans by about 30 BC.^[52] They made brass by heating powdered calamine (zinc silicate or carbonate), charcoal and copper together in a crucible.^[52] The resulting calamine brass was then either cast or hammered into shape for use in weaponry.^[53] Some coins struck by Romans in the Christian era are made of what is probably calamine brass.^[54]

Strabo writing in the 1st century BC (but quoting a now lost work of the 4th century BC historian Theopompus) mentions "drops of false silver" which when mixed with copper make brass. This may refer to small quantities of zinc that is a by-product of smelting sulfide ores.^[55] Zinc in such remnants in smelting ovens was usually discarded as it was thought to be worthless.^[56]

The Berne zinc tablet is a votive plaque dating to Roman Gaul made of an alloy that is mostly zinc.^[57]

The Charaka Samhita, thought to have been written between 300 and 500 AD,^[58] mentions a metal which, when oxidized, produces pushpanjan, thought to be zinc oxide.^[59] Zinc mines at Zawar, near Udaipur in India, have been active since the Mauryan period. The smelting of metallic zinc here, however, appears to have begun around the 12th century AD.^[60][61] One estimate is that this location produced an estimated million tonnes of metallic zinc and zinc oxide from the 12th to 16th centuries.^[19] Another estimate gives a total production of 60,000 tonnes of metallic zinc over this period.^[60] The Rasaratna Samuccaya, written in approximately the 13th century AD, mentions two types of zinc-containing ores: one used for metal extraction and another used for medicinal purposes.^[61]

Early studies and naming

Zinc was distinctly recognized as a metal under the designation of Yasada or Jasada in the medical Lexicon ascribed to the Hindu king Madanapala and written about the year 1374.^[62] Smelting and extraction of impure zinc by reducing calamine with wool and other organic substances was accomplished in the 13th century in India.^[10][63] The Chinese did not learn of the technique until the 17th century.^[63]

Alchemists burned zinc metal in air and collected the resulting zinc oxide on a condenser. Some alchemists called this zinc oxide lana philosophica, Latin for "philosopher's wool", because it collected in wooly tufts, whereas others thought it looked like white snow and named it nix album.^[64]

The name of the metal was probably first documented by Paracelsus, a Swiss-born German alchemist, who referred to the metal as "zincum" or "zinken" in his book Liber Mineralium II, in the 16th century.^[63][65] The word is probably derived from the German zinke, and supposedly meant "tooth-like, pointed or jagged" (metallic zinc crystals have a needle-like appearance).^[66] Zink could also imply "tin-like" because of its relation to German zinn meaning tin.^[67] Yet another possibility is that the word is derived from the Persian word سنگ seng meaning stone.^[68] The metal was also called Indian tin, tutanego, calamine, and spinter.^[17]

German metallurgist Andreas Libavius received a quantity of what he called "calay" of Malabar from a cargo ship captured from the Portuguese in 1596.^[69] Libavius described the properties of the sample, which may have been zinc. Zinc was regularly imported to Europe from the Orient in the 17th and early 18th centuries,^[63] but was at times very expensive.^{[note 1]}

Isolation

The isolation of metallic zinc was achieved in India by 1300 AD,^[70][71][72] much earlier than in the West. Before it was made in Europe, it was imported from India around 1600 CE.^[73] Postlewayt's Universal Dictionary, a contemporary source giving technological information in Europe, did not mention zinc before 1751 but the element was studied before then.^[61][74]

Flemish metallurgist and alchemist P. M. de Respour reported that he had extracted metallic zinc from zinc oxide in 1668.^[19] By the start of the 18th century, Étienne François Geoffroy described how zinc oxide condenses as yellow crystals on bars of iron placed above zinc ore being smelted.^[19] In Britain, John Lane is said to have carried out experiments to smelt zinc, probably at Landore, prior to his bankruptcy in 1726.^[75]

In 1738 in Great Britain, William Champion patented a process to extract zinc from calamine in a vertical retort style smelter.^[76] His technology was somewhat similar to that used at Zawar zinc mines in Rajasthan, but there is no evidence that he visited the Orient.^[73] Champion's process was used through 1851.^[63]

German chemist Andreas Marggraf normally gets credit for discovering pure metallic zinc even though Swedish chemist Anton von Swab had distilled zinc from calamine four years before.^[63] In his 1746 experiment, Marggraf heated a mixture of calamine and charcoal in a closed vessel without copper to obtain a metal.^[56] This procedure became commercially practical by 1752.^[77]

Later work

William Champion's brother, John, patented a process in 1758 for calcining zinc sulfide into an oxide usable in the retort process.^[17] Prior to this, only calamine could be used to produce zinc. In 1798, Johann Christian Ruberg improved on the smelting process by building the first horizontal retort smelter.^[78] Jean-Jacques Daniel Dony built a different kind of horizontal zinc smelter in Belgium, which processed even more zinc.^[63] Italian doctor Luigi Galvani discovered in 1780 that connecting the spinal cord of a freshly dissected frog to an iron rail attached by a brass hook caused the frog's leg to twitch.^[79] He incorrectly thought he had discovered an ability of nerves and muscles to create electricity and called the effect "animal electricity".^[80] The galvanic cell and the process of galvanization were both named for Luigi Galvani and these discoveries paved the way for electrical batteries, galvanization and cathodic protection.^[80]

Galvani's friend, Alessandro Volta, continued researching this effect and invented the Voltaic pile in 1800.^[79] The basic unit of Volta's pile was a simplified galvanic cell, which is made of a plate of copper and a plate of zinc connected to each other externally and separated by an electrolyte. These were stacked in series to make the Voltaic cell, which in turn produced electricity by directing electrons from the zinc to the copper and allowing the zinc to corrode.^[79]

The non-magnetic character of zinc and its lack of color in solution delayed discovery of its importance to biochemistry and nutrition.^[81] This changed in 1940 when carbonic anhydrase, an enzyme that scrubs carbon dioxide from blood, was shown to have zinc in its active site.^[81] The digestive enzyme carboxypeptidase became the second known zinc-containing enzyme in 1955.^[81]

Production

Mining and processing

Top zinc output countries 2010^[20]

Rank	Country	Tonnes
1	China	3,500,000
2	Peru	1,520,000
3	Australia	1,450,000
4	India	750,000
5	United States	720,000
6	Canada	670,000

Zinc is the fourth most common metal in use, trailing only iron, aluminium, and copper with an annual production of about 12 million tonnes.^[20] The world's largest zinc producer is Nyrstar, a merger of the Australian OZ Minerals and the Belgian Umicore.^[83] About 70% of the world's zinc originates from mining, whereas the remaining 30% comes from recycling secondary zinc.^[84] Commercially pure zinc is known as Special High Grade, often abbreviated SHG, and is 99.995% pure.^[85]

Worldwide, 95% of the zinc is mined from sulfidic ore deposits, in which sphalerite ZnS is nearly always mixed with the sulfides of copper, lead and iron.^[86] There are zinc mines throughout the world, with the main mining areas being China, Australia and Peru. China produced 29% of the global zinc output in 2010.^[20]

Zinc metal is produced using extractive metallurgy.^[87] After grinding the ore, froth flotation, which selectively separates minerals from gangue by taking advantage of differences in their hydrophobicity, is used to get an ore concentrate.^[87] This concentrate consists of about 50% zinc with the rest being sulfur (32%), iron (13%), and SiO
2 (5%).^[87] The composition of this is normally zinc sulfide (80% to 85%), iron sulfide (7.0% to 12%), lead sulfide (3.0% to 5.0%) silica (2.5% to 3.5%), and cadmium sulfide (0.35% to 0.41%).

Roasting converts the zinc sulfide concentrate produced during processing to zinc oxide:^[86]

2 ZnS + 3 O
2 → 2 ZnO + 2 SO
2

The sulfur dioxide is used for the production of sulfuric acid, which is necessary for the leaching process. If deposits of zinc carbonate, zinc silicate or zinc spinel, like the Skorpion Deposit in Namibia are used for zinc production the roasting can be omitted.^[88]

For further processing two basic methods are used: pyrometallurgy or electrowinning. Pyrometallurgy processing reduces zinc oxide with carbon or carbon monoxide at 950 °C (1,740 °F) into the metal, which is distilled as zinc vapor.^[89] The zinc vapor is collected in a condenser.^[86] The below set of equations demonstrate this process:^[86] This allows it to be separated from the other metallic impurities which are involatile.

2 ZnO + C → 2 Zn + CO
2

ZnO + CO → Zn + CO
2

In electrowinning, zinc is leached from the ore concentrate by sulfuric acid:^[90]

ZnO + H
2SO
4 → ZnSO
4 + H
2O

Finally, the zinc is reduced by electrolysis.^[86]

2 ZnSO
4 + 2 H
2O → 2 Zn + 2 H
2SO
4 + O
2

The sulfuric acid regenerated is recycled to the leaching step.

Zinc present in electric arc furnace dusts due to use of galvanised feedstock is recovered by a number of processes, predominately the Waelz process (90% as of 2014).^[91]

Environmental impact

The production for sulfidic zinc ores produces large amounts of sulfur dioxide and cadmium vapor. Smelter slag and other residues of process also contain significant amounts of heavy metals. About 1.1 million tonnes of metallic zinc and 130 thousand tonnes of lead were mined and smelted in the Belgian towns of La Calamine and Plombières between 1806 and 1882.^[92] The dumps of the past mining operations leach significant amounts of zinc and cadmium, and, as a result, the sediments of the Geul River contain significant amounts of heavy metals.^[92] About two thousand years ago emissions of zinc from mining and smelting totaled 10 thousand tonnes a year. After increasing 10-fold from 1850, zinc emissions peaked at 3.4 million tonnes per year in the 1980s and declined to 2.7 million tonnes in the 1990s, although a 2005 study of the Arctic troposphere found that the concentrations there did not reflect the decline. Anthropogenic and natural emissions occur at a ratio of 20 to 1.^[93]

Levels of zinc in rivers flowing through industrial or mining areas can be as high as 20 ppm.^[94] Effective sewage treatment greatly reduces this; treatment along the Rhine, for example, has decreased zinc levels to 50 ppb.^[94] Concentrations of zinc as low as 2 ppm adversely affects the amount of oxygen that fish can carry in their blood.^[95]

Soils contaminated with zinc through the mining of zinc-containing ores, refining, or where zinc-containing sludge is used as fertilizer, can contain several grams of zinc per kilogram of dry soil. Levels of zinc in excess of 500 ppm in soil interfere with the ability of plants to absorb other essential metals, such as iron and manganese. Zinc levels of 2000 ppm to 180,000 ppm (18%) have been recorded in some soil samples.^[94]

Applications

Major applications of zinc include (numbers are given for the US)^[98]

1. Galvanizing (55%)
2. Alloys (21%)
3. Brass and bronze (16%)
4. Miscellaneous (8%)

Anti-corrosion and batteries

The metal is most commonly used as an anti-corrosion agent.^[99] Galvanization, which is the coating of iron or steel to protect the metals against corrosion, is the most familiar form of using zinc in this way. In 2009 in the United States, 55% or 893 thousand tonnes of the zinc metal was used for galvanization.^[98]

Zinc is more reactive than iron or steel and thus will attract almost all local oxidation until it completely corrodes away.^[100] A protective surface layer of oxide and carbonate (Zn
5(OH)
6(CO
3)
2) forms as the zinc corrodes.^[101] This protection lasts even after the zinc layer is scratched but degrades through time as the zinc corrodes away.^[101] The zinc is applied electrochemically or as molten zinc by hot-dip galvanizing or spraying. Galvanization is used on chain-link fencing, guard rails, suspension bridges, lightposts, metal roofs, heat exchangers, and car bodies.^[16]

The relative reactivity of zinc and its ability to attract oxidation to itself makes it an efficient sacrificial anode in cathodic protection (CP). For example, cathodic protection of a buried pipeline can be achieved by connecting anodes made from zinc to the pipe.^[101] Zinc acts as the anode (negative terminus) by slowly corroding away as it passes electric current to the steel pipeline.^{[101][note 2]} Zinc is also used to cathodically protect metals that are exposed to sea water from corrosion.^[102] A zinc disc attached to a ship's iron rudder will slowly corrode, whereas the rudder stays unattacked.^[100] Other similar uses include a plug of zinc attached to a propeller or the metal protective guard for the keel of the ship.

With a standard electrode potential (SEP) of −0.76 volts, zinc is used as an anode material for batteries. (More reactive lithium (SEP −3.04 V) is used for anodes in lithium batteries ). Powdered zinc is used in this way in alkaline batteries and sheets of zinc metal form the cases for and act as anodes in zinc–carbon batteries.^[103][104] Zinc is used as the anode or fuel of the zinc-air battery/fuel cell.^{[105][106][107]} The zinc-cerium redox flow battery also relies on a zinc-based negative half-cell.^[108]

Alloys

A widely used alloy that contains zinc is brass, in which copper is alloyed with anywhere from 3% to 45% zinc, depending upon the type of brass.^[101] Brass is generally more ductile and stronger than copper and has superior corrosion resistance.^[101] These properties make it useful in communication equipment, hardware, musical instruments, and water valves.^[101]

Other widely used alloys that contain zinc include nickel silver, typewriter metal, soft and aluminium solder, and commercial bronze.^[10] Zinc is also used in contemporary pipe organs as a substitute for the traditional lead/tin alloy in pipes.^[109] Alloys of 85–88% zinc, 4–10% copper, and 2–8% aluminium find limited use in certain types of machine bearings. Zinc is the primary metal used in making American one cent coins since 1982.^[110] The zinc core is coated with a thin layer of copper to give the impression of a copper coin. In 1994, 33,200 tonnes (36,600 short tons) of zinc were used to produce 13.6 billion pennies in the United States.^[111]

Alloys of primarily zinc with small amounts of copper, aluminium, and magnesium are useful in die casting as well as spin casting, especially in the automotive, electrical, and hardware industries.^[10] These alloys are marketed under the name Zamak.^[112] An example of this is zinc aluminium. The low melting point together with the low viscosity of the alloy makes the production of small and intricate shapes possible. The low working temperature leads to rapid cooling of the cast products and therefore fast assembly is possible.^[10][113] Another alloy, marketed under the brand name Prestal, contains 78% zinc and 22% aluminium and is reported to be nearly as strong as steel but as malleable as plastic.^[10][114] This superplasticity of the alloy allows it to be molded using die casts made of ceramics and cement.^[10]

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 for which ferrous metal dies would be too expensive.^[115] In building facades, roofs or other applications in which zinc is used as sheet metal and for methods such as deep drawing, roll forming or bending, zinc alloys with titanium and copper are used.^[116] Unalloyed zinc is too brittle for these kinds of manufacturing processes.^[116]

As a dense, inexpensive, easily worked material, zinc is used as a lead replacement. In the wake of lead concerns, zinc appears in weights for various applications ranging from fishing^[117] to tire balances and flywheels.^[118]

Cadmium zinc telluride (CZT) is a semiconductive alloy that can be divided into an array of small sensing devices.^[119] These devices are similar to an integrated circuit and can detect the energy of incoming gamma ray photons.^[119] When placed behind an absorbing mask, the CZT sensor array can also be used to determine the direction of the rays.^[119]

Other industrial uses

Roughly one quarter of all zinc output in the United States (2009), is consumed in the form of zinc compounds;^[98] a variety of which are used industrially. Zinc oxide is widely used as a white pigment in paints, and as a catalyst in the manufacture of rubber. It is also used as a heat disperser for the rubber and acts to protect its polymers from ultraviolet radiation (the same UV protection is conferred to plastics containing zinc oxide).^[16] The semiconductor properties of zinc oxide make it useful in varistors and photocopying products.^[120] The zinc zinc-oxide cycle is a two step thermochemical process based on zinc and zinc oxide for hydrogen production.^[121]

Zinc chloride is often added to lumber as a fire retardant^[122] and can be used as a wood preservative.^[123] It is also used to make other chemicals.^[122] Zinc methyl (Zn(CH₃)
2) is used in a number of organic syntheses.^[124] Zinc sulfide (ZnS) is used in luminescent pigments such as on the hands of clocks, X-ray and television screens, and luminous paints.^[125] Crystals of ZnS are used in lasers that operate in the mid-infrared part of the spectrum.^[126] Zinc sulfate is a chemical in dyes and pigments.^[122] Zinc pyrithione is used in antifouling paints.^[127]

Zinc powder is sometimes used as a propellant in model rockets.^[128] When a compressed mixture of 70% zinc and 30% sulfur powder is ignited there is a violent chemical reaction.^[128] This produces zinc sulfide, together with large amounts of hot gas, heat, and light.^[128] Zinc sheet metal is used to make zinc bars.^[129]

64
Zn, the most abundant isotope of zinc, is very susceptible to neutron activation, being transmuted into the highly radioactive 65
Zn, which has a half-life of 244 days and produces intense gamma radiation. Because of this, Zinc Oxide used in nuclear reactors as an anti-corrosion agent is depleted of 64
Zn before use, this is called depleted zinc oxide. For the same reason, zinc has been proposed as a salting material for nuclear weapons (cobalt is another, better-known salting material).^[130] A jacket of isotopically enriched 64
Zn would be irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, forming a large amount of 65
Zn significantly increasing the radioactivity of the weapon's fallout.^[130] Such a weapon is not known to have ever been built, tested, or used.^[130] 65
Zn is also used as a tracer to study how alloys that contain zinc wear out, or the path and the role of zinc in organisms.^[131]

Zinc dithiocarbamate complexes are used as agricultural fungicides; these include Zineb, Metiram, Propineb and Ziram.^[132] Zinc naphthenate is used as wood preservative.^[133] Zinc, in the form of ZDDP, is also used as an anti-wear additive for metal parts in engine oil.^[134]

Dietary supplement

Zinc is included in most single tablet over-the-counter daily vitamin and mineral supplements.^[135] Preparations include zinc oxide, zinc acetate, and zinc gluconate.^[135] It is believed to possess antioxidant properties, which may protect against accelerated aging of the skin and muscles of the body; studies differ as to its effectiveness.^[136] Zinc also helps speed up the healing process after an injury.^[136] It is also suspected of being beneficial to the body's immune system. Indeed, zinc deficiency may have effects on virtually all parts of the human immune system.^[137]

Zinc deficiency has been associated with major depressive disorder (MDD), and zinc supplements may be an effective treatment.^[138]

Zinc serves as a simple, inexpensive, and critical tool for treating diarrheal episodes among children in the developing world. Zinc becomes depleted in the body during diarrhea, but recent studies suggest that replenishing zinc with a 10- to 14-day course of treatment can reduce the duration and severity of diarrheal episodes and may also prevent future episodes for up to three months.^[139]

The Age-Related Eye Disease Study determined that zinc can be part of an effective treatment for age-related macular degeneration.^[140] Zinc supplementation is an effective treatment for acrodermatitis enteropathica, a genetic disorder affecting zinc absorption that was previously fatal to babies born with it.^[52]

Gastroenteritis is strongly attenuated by ingestion of zinc, and this effect could be due to direct antimicrobial action of the zinc ions in the gastrointestinal tract, or to the absorption of the zinc and re-release from immune cells (all granulocytes secrete zinc), or both.^[141][142] In 2011, researchers at John Jay College of Criminal Justice reported that dietary zinc supplements can mask the presence of drugs in urine. Similar claims have been made in web forums on that topic.^[143]

Although not yet tested as a therapy in humans, a growing body of evidence indicates that zinc may preferentially kill prostate cancer cells. Because zinc naturally homes to the prostate and because the prostate is accessible with relatively non-invasive procedures, its potential as a chemotherapeutic agent in this type of cancer has shown promise.^[144] However, other studies have demonstrated that chronic use of zinc supplements in excess of the recommended dosage may actually increase the chance of developing prostate cancer, also likely due to the natural buildup of this heavy metal in the prostate.^[145]

Zinc lozenges and the common cold

There is some evidence that zinc lozenges may shorten the duration of cold symptoms.^[146] The most positive results have been found in studies in which zinc acetate was used, apparently because acetate does not bind zinc ions.^[147][148]

There is no concern of zinc toxicity in the dosages that were used in the zinc acetate trials with 80–100 mg/day of elemental zinc. The effect of zinc lozenges seems to take place locally in the oropharynx so that it is not a systemic effect, i.e., the effect is not a dietary supplement effect.

Topical use

Topical administration of zinc preparations include ones used on the skin, often in the form of zinc oxide. Zinc preparations can protect against sunburn in the summer and windburn in the winter.^[52] Applied thinly to a baby's diaper area (perineum) with each diaper change, it can protect against diaper rash.^[52]

Chelated zinc is used in toothpastes and mouthwashes to prevent bad breath.^[149] Zinc pyrithione is widely applied in shampoos because of its anti-dandruff function.^[150] Zinc ions are effective antimicrobial agents even at low concentrations.^[151]

Organic chemistry

There are many important organozinc compounds. Organozinc chemistry is the science of organozinc compounds describing their physical properties, synthesis and reactions.^{[152][153][154][155]} Among important applications is the Frankland-Duppa Reaction in which an oxalate ester(ROCOCOOR) reacts with an alkyl halide R'X, zinc and hydrochloric acid to the α-hydroxycarboxylic esters RR'COHCOOR,^[156] the Reformatskii reaction which converts α-halo-esters and aldehydes to β-hydroxy-esters, the Simmons–Smith reaction in which the carbenoid (iodomethyl)zinc iodide reacts with alkene(or alkyne) and converts them to cyclopropane, the Addition reaction of organozinc compounds to carbonyl compounds. The Barbier reaction (1899) is the zinc equivalent of the magnesium Grignard reaction and is better of the two. In presence of just about any water the formation of the organomagnesium halide will fail, whereas the Barbier reaction can even take place in water. On the downside organozincs are much less nucleophilic than Grignards, are expensive and difficult to handle. Commercially available diorganozinc compounds are dimethylzinc, diethylzinc and diphenylzinc. In one study^[157][158] the active organozinc compound is obtained from much cheaper organobromine precursors:

The Negishi coupling is also an important reaction for the formation of new carbon carbon bonds between unsaturated carbon atoms in alkenes, arenes and alkynes. The catalysts are nickel and palladium. A key step in the catalytic cycle is a transmetalation in which a zinc halide exchanges its organic substituent for another halogen with the palladium (nickel) metal center. The Fukuyama coupling is another coupling reaction but this one with a thioester as reactant forming a ketone.

Zinc has found many applications as catalyst in organic synthesis including asymmetric synthesis, being cheap and easily available alternative to precious metal complexes. The results (yield and ee) obtained by using chiral zinc catalysts are comparable to those achieved by palladium, ruthenium, iridium and others and therefore more and more zinc becomes metal of choice for this purpose.^[159]

Biological role

Zinc is an essential trace element for humans^[160] and other animals,^[161] for plants^[93] and for microorganisms.^[162] Zinc is found in nearly 100 specific enzymes^[163] (other sources^[164] say 300), serves as structural ions in transcription factors and is stored and transferred in metallothioneins.^[165] It is "typically the second most abundant transition metal in organisms" after iron and it is the only metal which appears in all enzyme classes.^[93]

In proteins, Zn ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. The theoretical and computational description of this zinc binding in proteins (as well as that of other transition metals) is difficult.^[166]

There are 2-4 grams of zinc^[167] distributed throughout the human body. Most zinc is in the brain, muscle, bones, kidney, and liver, with the highest concentrations in the prostate and parts of the eye.^[168] Semen is particularly rich in zinc, which is a key factor in prostate gland function and reproductive organ growth.^[169]

In humans, zinc plays "ubiquitous biological roles".^[6] It interacts with "a wide range of organic ligands",^[6] and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis. A 2006 study estimated that about 10% of human proteins (2800) potentially bind zinc, in addition to hundreds which transport and traffic zinc; a similar in silico study in the plant Arabidopsis thaliana found 2367 zinc-related proteins.^[93]

In the brain, zinc is stored in specific synaptic vesicles by glutamatergic neurons^[170] and can "modulate brain excitability".^[6] It plays a key role in synaptic plasticity and so in learning.^[171] However, it has been called "the brain's dark horse"^[170] because it also can be a neurotoxin, suggesting zinc homeostasis plays a critical role in normal functioning of the brain and central nervous system.^[170]

Enzymes

Zinc is an efficient Lewis acid, making it a useful catalytic agent in hydroxylation and other enzymatic reactions.^[163] The metal also has a flexible coordination geometry, which allows proteins using it to rapidly shift conformations to perform biological reactions.^[172] Two examples of zinc-containing enzymes are carbonic anhydrase and carboxypeptidase, which are vital to the processes of carbon dioxide (CO
2) regulation and digestion of proteins, respectively.^[173]

In vertebrate blood, carbonic anhydrase converts CO
2 into bicarbonate and the same enzyme transforms the bicarbonate back into CO
2 for exhalation through the lungs.^[174] Without this enzyme, this conversion would occur about one million times slower^[175] at the normal blood pH of 7 or would require a pH of 10 or more.^[176] The non-related β-carbonic anhydrase is required in plants for leaf formation, the synthesis of indole acetic acid (auxin) and alcoholic fermentation.^[177]

Carboxypeptidase cleaves peptide linkages during digestion of proteins. A coordinate covalent bond is formed between the terminal peptide and a C=O group attached to zinc, which gives the carbon a positive charge. This helps to create a hydrophobic pocket on the enzyme near the zinc, which attracts the non-polar part of the protein being digested.^[173]

Other proteins

Zinc serves a purely structural role in zinc fingers, twists and clusters.^[178] Zinc fingers form parts of some transcription factors, which are proteins that recognize DNA base sequences during the replication and transcription of DNA. Each of the nine or ten Zn2+
ions in a zinc finger helps maintain the finger's structure by coordinately binding to four amino acids in the transcription factor.^[175] The transcription factor wraps around the DNA helix and uses its fingers to accurately bind to the DNA sequence.

In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%).^[167] Because transferrin also transports iron, excessive iron reduces zinc absorption, and vice versa. A similar antagonism exists with copper.^[179] The concentration of zinc in blood plasma stays relatively constant regardless of zinc intake.^[180] Cells in the salivary gland, prostate, immune system and intestine use zinc signaling as one way to communicate with other cells.^[181]

Zinc may be held in metallothionein reserves within microorganisms or in the intestines or liver of animals.^[182] Metallothionein in intestinal cells is capable of adjusting absorption of zinc by 15–40%.^[183] However, inadequate or excessive zinc intake can be harmful; excess zinc particularly impairs copper absorption because metallothionein absorbs both metals.^[184]

Dietary intake

In the U.S., the Recommended Dietary Allowance (RDA) is 8 mg/day for women and 11 mg/day for men.^[185] Median intake in the U.S. around 2000 was 9 mg/day for women and 14 mg/day in men.^[186] Oysters, lobster^[187] and red meats, especially beef, lamb and liver have some of the highest concentrations of zinc in food.^[169]

Zinc supplements should only be ingested when there is zinc deficiency or increased zinc necessity (e.g. after surgeries, traumata or burns).^[188][189] Persistent intake of high doses of zinc can cause copper deficiency.^[188]

The concentration of zinc in plants varies based on levels of the element in soil. When there is adequate zinc in the soil, the food plants that contain the most zinc are wheat (germ and bran) and various seeds (sesame, poppy, alfalfa, celery, mustard).^[190] Zinc is also found in beans, nuts, almonds, whole grains, pumpkin seeds, sunflower seeds and blackcurrant.^[191]

Other sources include fortified food and dietary supplements, which come in various forms. A 1998 review concluded that zinc oxide, one of the most common supplements in the United States, and zinc carbonate are nearly insoluble and poorly absorbed in the body.^[192] This review cited studies which found low plasma zinc concentrations after zinc oxide and zinc carbonate were consumed compared with those seen after consumption of zinc acetate and sulfate salts.^[192] However, harmful excessive supplementation is a problem among the relatively affluent, and should probably not exceed 20 mg/day in healthy people,^[193] although the U.S. National Research Council set a Tolerable Upper Intake of 40 mg/day.^[194]

For fortification, however, a 2003 review recommended zinc oxide in cereals as cheap, stable, and as easily absorbed as more expensive forms.^[195] A 2005 study found that various compounds of zinc, including oxide and sulfate, did not show statistically significant differences in absorption when added as fortificants to maize tortillas.^[196] A 1987 study found that zinc picolinate was better absorbed than zinc gluconate or zinc citrate.^[197] However, a study published in 2008 determined that zinc glycinate is the best absorbed of the four dietary supplement types available.^[198]

Deficiency

Zinc deficiency is usually due to insufficient dietary intake, but can be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses.^[7] Groups at risk for zinc deficiency include the elderly, children in developing countries, and those with renal insufficiency.

Symptoms of mild zinc deficiency are diverse.^[186] Clinical outcomes include depressed growth, diarrhea, impotence and delayed sexual maturation, alopecia, eye and skin lesions, impaired appetite, altered cognition, impaired host defense properties, defects in carbohydrate utilization, and reproductive teratogenesis.^[180] Mild zinc deficiency depresses immunity,^[199] although excessive zinc does also.^[167] Animals with a diet deficient in zinc require twice as much food in order to attain the same weight gain as animals given sufficient zinc.^[125]

Despite some concerns,^[200] western vegetarians and vegans have not been found to suffer from overt zinc deficiencies any more than meat-eaters.^[201] Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soyfoods, nuts, peas, and seeds.^[200] However, phytates in many whole-grains and fiber in many foods may interfere with zinc absorption and marginal zinc intake has poorly understood effects. The zinc chelator phytate, found in seeds and cereal bran, can contribute to zinc malabsorption.^[7] There is some evidence to suggest that more than the US RDA (15 mg) of zinc daily may be needed in those whose diet is high in phytates, such as some vegetarians.^[200] These considerations must be balanced against the fact that there is a paucity of adequate zinc biomarkers, and the most widely used indicator, plasma zinc, has poor sensitivity and specificity.^[202] Diagnosing zinc deficiency is a persistent challenge.^[6]

Nearly two billion people in the developing world are deficient in zinc.^[7] In children it causes an increase in infection and diarrhea, contributing to the death of about 800,000 children worldwide per year.^[6] The World Health Organization advocates zinc supplementation for severe malnutrition and diarrhea.^[203] Zinc supplements help prevent disease and reduce mortality, especially among children with low birth weight or stunted growth.^[203] However, zinc supplements should not be administered alone, because many in the developing world have several deficiencies, and zinc interacts with other micronutrients.^[204]

Soil remediation

The Ericoid Mycorrhizal Fungi Calluna, Erica and Vaccinium can grow in zinc metalliferous soils.^[205]

Agriculture

Zinc deficiency is crop plants' most common micronutrient deficiency; it is particularly common in high-pH soils.^[206] Zinc-deficient soil is cultivated in the cropland of about half of Turkey and India, a third of China, and most of Western Australia, and substantial responses to zinc fertilization have been reported in these areas.^[93] Plants that grow in soils that are zinc-deficient are more susceptible to disease. Zinc is primarily added to the soil through the weathering of rocks, but humans have added zinc through fossil fuel combustion, mine waste, phosphate fertilizers, limestone, manure, sewage sludge, and particles from galvanized surfaces. Excess zinc is toxic to plants, although zinc toxicity is far less widespread.^[93]

Precautions

Toxicity

Although zinc is an essential requirement for good health, excess zinc can be harmful. Excessive absorption of zinc suppresses copper and iron absorption.^[184] The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish.^[207] The Free Ion Activity Model is well-established in the literature, and shows that just micromolar amounts of the free ion kills some organisms. A recent example showed 6 micromolar killing 93% of all Daphnia in water.^[208]

The free zinc ion is 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.^[209]

There is evidence of induced copper deficiency in those taking 100–300 mg of zinc daily. A 2007 trial observed that elderly men taking 80 mg daily were hospitalized for urinary complications more often than those taking a placebo.^[210] The USDA RDA is 11 and 8 mg Zn/day for men and women, respectively.^[185] Levels, of 100–300 mg may interfere with the utilization of copper and iron or adversely affect cholesterol.^[184] Levels of zinc in excess of 500 ppm in soil interfere with the ability of plants to absorb other essential metals, such as iron and manganese.^[94] There is also a condition called the zinc shakes or "zinc chills" that can be induced by the inhalation of freshly formed zinc oxide formed during the welding of galvanized materials.^[125] Zinc is a common ingredient of denture cream which may contain between 17 and 38 mg of zinc per gram. There have been claims of disability, and even death, due to excessive use of these products.^[211]

The U.S. Food and Drug Administration (FDA) has stated that zinc damages nerve receptors in the nose, which can cause anosmia. Reports of anosmia were also observed in the 1930s when zinc preparations were used in a failed attempt to prevent polio infections.^[212] On June 16, 2009, the FDA said that consumers should stop using zinc-based intranasal cold products and ordered their removal from store shelves. The FDA said the loss of smell can be life-threatening because people with impaired smell cannot detect leaking gas or smoke and cannot tell if food has spoiled before they eat it.^[213] Recent research suggests that the topical antimicrobial zinc pyrithione is a potent heat shock response inducer that may impair genomic integrity with induction of PARP-dependent energy crisis in cultured human keratinocytes and melanocytes.^[214]

Poisoning

In 1982, the US Mint began minting pennies coated in copper but made primarily of zinc. With the new zinc pennies, there is the potential for zinc toxicosis, which can be fatal. One reported case of chronic ingestion of 425 pennies (over 1 kg of zinc) resulted in death due to gastrointestinal bacterial and fungal sepsis, whereas another patient, who ingested 12 grams of zinc, only showed lethargy and ataxia (gross lack of coordination of muscle movements).^[215] Several other cases have been reported of humans suffering zinc intoxication by the ingestion of zinc coins.^[216][217]

Pennies and other small coins are sometimes ingested by dogs, resulting in the need for medical treatment to remove the foreign body. The zinc content of some coins can cause zinc toxicity, which is commonly fatal in dogs, where it causes a severe hemolytic anemia, and also liver or kidney damage; vomiting and diarrhea are possible symptoms.^[218] Zinc is highly toxic in parrots and poisoning can often be fatal.^[219] The consumption of fruit juices stored in galvanized cans has resulted in mass parrot poisonings with zinc.^[52]

See also

• Zinc alloy electroplating
• Wet storage stain
• List of countries by zinc production

Notes

1. ↑ An East India Company ship carrying a cargo of nearly pure zinc metal from the Orient sank off the coast Sweden in 1745.(Emsley 2001, p. 502)
2. ↑ Electric current will naturally flow between zinc and steel but in some circumstances inert anodes are used with an external DC source.

References

Bibliography

External links

Wikimedia Commons has media related to Zinc.

Look up zinc in Wiktionary, the free dictionary.

• Zinc Fact Sheet from the U.S. National Institutes of Health
• History & Etymology of Zinc
• Statistics and Information from the U.S. Geological Survey
• Reducing Agents > Zinc
• American Zinc Association Information about the uses and properties of zinc.
• Outline safety data for zinc
• ISZB International Society for Zinc Biology, founded in 2008. An international, nonprofit organization bringing together scientists working on the biological actions of zinc.
• Zinc-UK Founded in 2010 to bring together scientists in the United Kingdom working on zinc.
• Zinc at The Periodic Table of Videos (University of Nottingham)

Periodic table (Large cells)
	1	2															3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
1	H																															He
2	Li	Be																									B	C	N	O	F	Ne
3	Na	Mg																									Al	Si	P	S	Cl	Ar
4	K	Ca															Sc	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As	Se	Br	Kr
5	Rb	Sr															Y	Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd	In	Sn	Sb	Te	I	Xe
6	Cs	Ba	La	Ce	Pr	Nd	Pm	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb	Lu	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
7	Fr	Ra	Ac	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	113	Fl	115	Lv	117	118
Alkali metal Alkaline earth metal Lan­thanide Actinide Transition metal Post-​transition metal Metalloid Polyatomic nonmetal Diatomic nonmetal Noble gas Unknown chemical properties

Zinc compounds Zinc(I) Organozinc(I) compounds Zn2(C5(CH3)5)2 Zinc(II) ZnBr2 Zn(CN)2 ZnCl2 Zn(ClO3)2 ZnCrO4 ZnF2 ZnH2 ZnI2 ZnMoO4 Zn(NO3)2 ZnO ZnO2 Zn(OH)2 ZnS ZnSO4 ZnSe ZnTe Zn2P2O7 Zn3Sb2 Zn3As2 Zn3N2 Zn3P2 Zn3(PO4)2 Organozinc(II) compounds Zn(CH3)2 Zn(C2H5)2 Zn(CH(CH3)2)2 Zn(C(CH3)3)2 Zn(C6H5)2 ZnCIH2I

GABAergics Receptor (ligands) GABAA Agonists: (+)-Catechin Bamaluzole Barbiturates (e.g., phenobarbital) DAVA Dihydromuscimol GABA Gabamide GABOB Gaboxadol (THIP) Homotaurine (tramiprosate, 3-APS) Ibotenic acid iso-THAZ iso-THIP Isoguvacine Isomuscimol Isonipecotic acid Kojic amine Lignans (e.g., honokiol) Monastrol Muscimol Neuroactive steroids (e.g., allopregnanolone) Org 20599 Picamilon P4S Progabide Propofol Quisqualamine SL-75102 TACA TAMP Terpenoids (e.g., borneol) Thiomuscimol Tolgabide ZAPA PAMs (abridged; see here for a full list): α-EMTBL Alcohols (e.g., ethanol) Avermectins (e.g., ivermectin) Barbiturates (e.g., phenobarbital) Benzodiazepines (e.g., diazepam) Bromide compounds (e.g., potassium bromide) Carbamates (e.g., meprobamate) Carbamazepine Chloralose Chlormezanone Clomethiazole Dihydroergolines (e.g., ergoloid (dihydroergotoxine)) Etazepine Etifoxine Fenamates (e.g., mefenamic acid) Flavonoids (e.g., apigenin, hispidulin) Fluoxetine Flupirtine Imidazoles (e.g., etomidate) Kava constituents (e.g., kavain) Lanthanum Loreclezole Monastrol Neuroactive steroids (e.g., allopregnanolone, cholesterol) Niacin Nicotinamide (niacinamide) Nonbenzodiazepines (e.g., β-carbolines (e.g., abecarnil), cyclopyrrolones (e.g., zopiclone), imidazopyridines (e.g., zolpidem), pyrazolopyrimidines (e.g., zaleplon)) Norfluoxetine Petrichloral Phenols (e.g., propofol) Phenytoin Piperidinediones (e.g., glutethimide) Propanidid Pyrazolopyridines (e.g., etazolate) Quinazolinones (e.g., methaqualone) Retigabine (ezogabine) ROD-188 Skullcap constituents (e.g., baicalin) Stiripentol Sulfonylalkanes (e.g., sulfonmethane (sulfonal)) Topiramate Valerian constituents (e.g., valerenic acid) Volatiles/gases (e.g., chloral hydrate, chloroform, diethyl ether, paraldehyde, sevoflurane) Antagonists: Bicuculline Coriamyrtin Dihydrosecurinine Gabazine (SR-95531) Hydrastine Hyenachin (mellitoxin) PHP-501 Pitrazepin Securinine Sinomenine SR-42641 SR-95103 Thiocolchicoside Tutin NAMs: 1,3M1B 3M2B 17-Phenylandrostenol α5IA (LS-193,268) β-CCB β-CCE β-CCM β-CCP β-EMGBL Amiloride Anisatin β-Lactams (e.g., penicillins, cephalosporins, carbapenems) Bemegride Bilobalide CHEB Cicutoxin Cloflubicyne Cyclothiazide DHEA DHEA-S Dieldrin (+)-DMBB DMCM DMPC EBOB Etbicyphat FG-7142 (ZK-31906) Fiproles (e.g., fipronil) Flavonoids (e.g., amentoflavone, oroxylin A) Flumazenil Fluoroquinolones (e.g., ciprofloxacin) Flurothyl Furosemide Iomazenil (123I) Isopregnanolone (sepranolone) L-655,708 Laudanosine Leptazol Lindane MaxiPost Morphine Morphine-3-glucuronide MRK-016 Naloxone Naltrexone Nicardipine Oenanthotoxin Pentetrazol (metrazol) Phenylsilatrane Picrotoxin (i.e., picrotin and picrotoxinin) Pregnenolone sulfate Propybicyphat PWZ-029 Radequinil RG-1662 Ro 15-4513 Ro 19-4603 RO4882224 RO4938581 Sarmazenil SCS Suritozole TB-21007 TBOB TBPS TCS-1105 Terbequinil TETS Thujone U-93631 Zinc ZK-93426 GABAA-ρ Agonists: CACA CAMP Homohypotaurine GABA GABOB Ibotenic acid Isoguvacine Muscimol N4-Chloroacetylcytosine arabinoside Picamilon Progabide TACA TAMP Thiomuscimol Tolgabide PAMs: Lanthanides Antagonists: (S)-2-MeGABA (S)-4-ACPBPA (S)-4-ACPCA 2-MeTACA 3-APMPA 4-ACPAM 4-GBA cis-3-ACPBPA CGP-36742 (SGS-742) DAVA Gabazine (SR-95531) Gaboxadol (THIP) I4AA Isonipecotic acid Loreclezole P4MPA P4S SKF-97541 SR-95318 SR-95813 TPMPA trans-3-ACPBPA ZAPA NAMs: Bilobalide Picrotoxin (picrotin, picrotoxinin) ROD-188 Zinc GABAB Agonists: 1,4-Butanediol Aceburic acid Arbaclofen Arbaclofen placarbil Baclofen GABA Gabamide GABOB GBL GHB GHBAL GHV GVL Lesogaberan Phenibut Picamilon Progabide Sodium oxybate SKF-97,541 SL 75102 Tolgabide PAMs: ADX71441 BHF-177 BHFF BSPP CGP-7930 CGP-13501 GS-39783 rac-BHFF Antagonists: 2-Hydroxysaclofen CGP-35348 CGP-46381 CGP-52432 CGP-54626 CGP-55845 CGP-64213 DAVA Homotaurine (tramiprosate, 3-APS) Phaclofen Saclofen SCH-50911 SKF-97541 NAMs: "Compound 14" Transporter (blockers) GAT 4-Aminovaleric acid β-Alanine Arecaidine CI-966 DABA Deramciclane (EGIS-3886, EGYT-3886) EF-1502 Gabaculine Guvacine Ibotenic acid Muscimol Nipecotic acid NNC 05-2090 NO-711 Riluzole SKF-89976A SNAP-5114 TACA Tiagabine VIAAT β-Alanine Bafilomycin A1 Chicago sky blue 6B Evans blue GABA Glycine N-Butyric acid Nigericin Nipecotic acid Valinomycin Vigabatrin Enzyme (inhibitors) GAD 3-Mercaptopropionic acid AAOA L-Allylglycine Semicarbazide GABA-T 3-Hydrazinopropionic acid γ-Acetylenic-GABA AOAA EOS Gabaculine Isoniazid L-Cycloserine Phenelzine PEH Rosmarinic acid (lemon balm) Sodium valproate Valnoctamide Valproate pivoxil Valproate semisodium (divalproex sodium) Valproic acid Valpromide Vigabatrin Others Precursors: 1,4-Butanediol GHB GHBAL Glutamate Glutamine Cofactors: Vitamin B6 Others: GABA-T activators: 3-Methyl-GABA See also: GHBergics • Glutamatergics • Glycinergics

Glutamatergics Receptor (ligands) AMPA Agonists: Glutamate/active site agonists: 5-Fluorowillardiine Acromelic acid (acromelate) AMPA BOAA Domoic acid Glutamate Ibotenic acid Proline Quisqualic acid Willardiine; Positive allosteric modulators: Aniracetam Cyclothiazide CX-516 CX-546 CX-614 Farampator (CX-691, Org 24448) CX-717 CX-1739 CX-1942 Diazoxide Hydrochlorothiazide (HCTZ) IDRA-21 LY-392,098 LY-404,187 LY-451,646 LY-503,430 Mibampator (LY-451,395) Org 26576 Oxiracetam PEPA Piracetam Pramiracetam S-18986 Sunifiram Unifiram Antagonists: ACEA-1011 ATPO Becampanel Caroverine CNQX Dasolampanel DNQX Fanapanel (MPQX) GAMS GYKI-52466 Kynurenic acid Licostinel (ACEA-1021) NBQX PNQX Selurampanel Tezampanel Theanine Topiramate YM90K Zonampanel; Negative allosteric modulators: Barbiturates (e.g., pentobarbital, sodium thiopental) Cyclopropane Enflurane Ethanol Evans blue GYKI-53,655 Halothane Irampanel Isoflurane Perampanel Pregnenolone sulfate Talampanel NMDA Agonists: Glutamate/active site agonists: AMAA Aspartate Glutamate Homocysteic acid (L-HCA) Homoquinolinic acid Ibotenic acid NMDA Proline Quinolinic acid Tetrazolylglycine Theanine; Glycine site agonists: β-Fluoro-D-alanine ACBD ACC (ACPC) ACPD CCG D-Alanine D-Cycloserine D-Serine DHPG Glycine HA-966 L-687,414 L-Alanine L-Serine Milacemide NRX-1074 Rapastinel (GLYX-13) Sarcosine; Polyamine site agonists: Spermidine Spermine Antagonists: Competitive antagonists: AP5 (APV) AP7 CGP-37849 CGP-39551 CGP-39653 CGP-40116 CGS-19755 CPP LY-233,053 LY-235,959 LY-274,614 MDL-100,453 Midafotel (d-CPPene) NPC-12,626 NPC-17,742 PBPD PEAQX Perzinfotel PPDA SDZ-220581 Selfotel; Noncompetitive antagonists: ARR-15,896 Caroverine Dexanabinol FPL-12495 FR-115,427 Hodgkinsine Magnesium MDL-27,266 NPS-1506 Psychotridine Zinc; Uncompetitive pore blockers: 2-MDP 3-MeO-PCP 8A-PDHQ 18-MC α-Endopsychosin Alaproclate Amantadine Aptiganel ARL-12,495 ARL-15,896-AR ARL-16,247 Budipine Conaridine Delucemine Dexoxadrol Dextrallorphan Dieticyclidine Dizocilpine Esketamine Etoxadrol Eticyclidine Gacyclidine Ibogaine Ibogamine Indantadol Ketamine Ketobemidone Lanicemine Loperamide Memantine Methadone (Levomethadone) Methorphan (Dextromethorphan Levomethorphan) Methoxetamine Methoxphenidine Milnacipran Morphanol (Dextrorphan Levorphanol) NEFA Neramexane Nitromemantine Nitrous oxide Noribogaine Orphenadrine PCPr Pethidine (meperidine) Phencyclamine Phencyclidine Propoxyphene Remacemide Rhynchophylline Rimantadine Rolicyclidine Sabeluzole Tabernanthine Tenocyclidine Tiletamine Tramadol Xenon; Glycine site antagonists: 7-CKA ACC ACEA-1011 ACEA-1328 AV-101 Carisoprodol CGP-39653 CNQX DCKA DNQX Felbamate Gavestinel GV-196,771 Kynurenic acid L-689,560 L-701,324 Licostinel (ACEA-1021) LU-73,068 MDL-105,519 Meprobamate MRZ 2/576 PNQX ZD-9379; NR2B subunit antagonists: Besonprodil CERC-301 (MK-0657) CO-101,244 (PD-174,494) Eliprodil Haloperidol Ifenprodil Isoxsuprine Nylidrin Ro8-4304 Ro25-6981 Traxoprodil; Polyamine site antagonists: Arcaine Co 101676 Diaminopropane Diethylenetriamine Huperzine A Putrescine Ro 25-6981; Unclassified/unsorted antagonists: Bumetanide Chloroform Cyclopropane D-αAA Diethyl ether Diphenidine Enflurane Ethanol Flufenamic acid Flupirtine Furosemide Halothane Isoflurane Metaphit Methoxyflurane Niflumic acid Piretanide Toluene Trichloroethane Trichloroethanol Trichloroethylene Xylene Kainate Agonists: Glutamate/active site agonists: 5-Bromowillardiine 5-Iodowillardiine Acromelic acid (acromelate) AMPA ATPA Domoic acid Glutamate Ibotenic acid Kainic acid LY-339,434 Proline Quisqualic acid SYM-2081; Positive allosteric modulators: Cyclothiazide Diazoxide Enflurane Halothane Isoflurane Antagonists: ACEA-1011 CNQX Dasolampanel DNQX GAMS Kynurenic acid Licostinel (ACEA-1021) LY-382,884 NBQX NS102 Selurampanel Tezampanel Theanine Topiramate UBP-302; Negative allosteric modulators: Barbiturates (e.g., pentobarbital, sodium thiopental) Enflurane Ethanol Evans blue NS-3763 Pregnenolone sulfate mGlu1 Agonists: ACPD DHPG Glutamate Ibotenic acid Quisqualic acid Ro01-6128 Ro67-4853 Ro67-7476 VU-71 Antagonists: BAY 36-7620 CPCCOEt LY-367,385 LY-456,236 MCPG NPS-2390 mGlu2 Agonists: BINA CBiPES DCG-IV Eglumegad Glutamate Ibotenic acid LY-379,268 LY-404,039 LY-487,379 LY-566,332 MGS-0028; Positive allosteric modulators: JNJ-40411813 (ADX-71149) Antagonists: APICA CECXG EGLU HYDIA LY-307,452 LY-341,495 MCPG MGS-0039 PCCG-4; Negative allosteric modulators: Decoglurant RO4491533 mGlu3 Agonists: CBiPES DCG-IV Eglumegad Glutamate Ibotenic acid LY-379,268 LY-404,039 LY-487,379 MGS-0028 Antagonists: APICA CECXG EGLU HYDIA LY-307,452 LY-341,495 MCPG MGS-0039; Negative allosteric modulators: Decoglurant RO4491533 mGlu4 Agonists: Glutamate L-AP4 PHCCC VU-001,171 VU-0155,041; Positive allosteric modulators: MPEP Antagonists: CPPG MAP4 MPPG MSOP MTPG UBP-1112 mGlu5 Agonists: ACPD ADX-47273 CDPPB CHPG DFB DHPG Glutamate Ibotenic acid Quisqualic acid VU-1545 Antagonists: CTEP DMeOB LY-344,545 Mavoglurant MCPG NPS-2390 SIB-1757 SIB-1893; Negative allosteric modulators: Basimglurant Dipraglurant Fenobam GRN-529 MPEP MTEP Raseglurant mGlu6 Agonists: Glutamate L-AP4 Antagonists: CPPG MAP4 MPPG MSOP MTPG UBP-1112 mGlu7 Agonists: AMN082 Glutamate L-AP4 Antagonists: CPPG MAP4 MMPIP MPPG MSOP MTPG UBP-1112 mGlu8 Agonists: DCPG Glutamate L-AP4 Antagonists: CPPG MAP4 MPPG MSOP MTPG UBP-1112 Transporter (blockers) EAATs Amphetamine Aspartic acid (aspartate) cis-ACBD DHKA Glutamic acid (glutamate) HIP-A HIP-B Kainic acid L-(-)-threo-3-Hydroxyaspartic acid L-αAA L-CCG-III ((2S,3S,4R)-CCG) L-Serine-O-sulphate (SOS) L-trans-2,4-PDC MPDC SYM-2081 TBOA TFB-TBOA Theanine threo-3-Methylglutamic acid UCPH-101 WAY-213,613 vGluTs 4-Methylene-L-glutamate 6-(4'-Phenylstyryl)-QDC 6-Biphenyl-4-yl-QDC 7-CKA Acid red 114 Amido black 10B (naphthol blue black) Bafilomycin A1 Benzopurpurin 4B Bumetamide Chicago sky blue 6B Aspartic acid (aspartate) DIDS Direct blue 71 Erythro-4-methyl-L-glutamic acid Evans blue Furosemide Glutamic acid (glutamate) Kynurenic acid Nigericin NPPB (N144) Ponceau SS Reactive blue 2 Rose bengal SITS trans-ACDP Trypan blue Valinomycin Xanthurenic acid Enzyme (inhibitors) GAH BPTES CB-839 DON AST 2-Amino-3-butenoic acid AAOA AMB β-DL-Methylene-aspartate Hydrazinosuccinate ALT β-Chloro-L-alanine L-Cycloserine Propargylglycine GDH AAOA Bithionol Chloroquine EGCG GTP GW5074 Hexachlorophene Hydroxylamine Palmitoyl-CoA Pyridoxal phosphate GS 2-Aminoadipic acid JFD01307SC Methionine sulfoximine Phosphinothricin (glufosinate) GAD 3-Mercaptopropionic acid AAOA L-Allylglycine Semicarbazide Others Precursors: GHB L-Glutamine Cofactors: α-Ketoglutaric acid Iron Sulfur Vitamin B2 Vitamin B3 See also: GABAergics • GHBergics • Glycinergics

Glycinergics Receptor (ligands) GlyR Agonists: β-Alanine β-ABA (BABA) β-AIBA Caesium D-Alanine D-Serine GABA Glycine Hypotaurine Ivermectin L-Alanine L-Proline L-Serine L-Threonine MDL-27531 Milacemide Picolinic acid Propofol Quisqualamine Sarcosine Taurine PAMs: Alcohols (e.g., brometone, chlorobutanol (chloretone), ethanol, tert-butanol (2M2P), tribromoethanol, trichloroethanol, trifluoroethanol) Alkylbenzene sulfonate Barbiturates (e.g., pentobarbital, sodium thiopental) Chlormethiazole D12-116 Dihydropyridines (e.g., nicardipine) Etomidate Ginseng constituents (e.g., ginsenosides (e.g., ginsenoside-Rf)) Glutamic acid (glutamate) Ivermectin Ketamine Neuroactive steroids (e.g., alfaxolone, pregnenolone (eltanolone), pregnenolone acetate, minaxolone, Org 20599) Nitrous oxide Penicillin G Propofol Tamoxifen Triclofos Tropeines (e.g., atropine, bemesetron, cocaine, LY-278584, tropisetron, zatosetron) Volatiles/gases (e.g., chloral hydrate, chloroform, desflurane, diethyl ether (ether), enflurane, halothane, isoflurane, methoxyflurane, sevoflurane, toluene, trichloroethane (methyl chloroform), trichloroethylene) Xenon Zinc Antagonists: 2-Aminostrychnine 2-Nitrostrychnine 4-Phenyl-4-formyl-N-methylpiperidine αEMBTL Bicuculline Brucine Cacotheline Caffeine Colchicine Colubrine Cyanotriphenylborate Dendrobine Diaboline Endocannabinoids (e.g., 2-AG, anandamide (AEA)) Gaboxadol (THIP) Gelsemine iso-THAZ Isobutyric acid Isonipecotic acid Isostrychnine Laudanosine N-Methylbicuculline N-Methylstrychnine N,N-Dimethylmuscimol Nipecotic acid Pitrazepin Pseudostrychnine Quinolines (e.g., 4-hydroxyquinoline, 4-hydroxyquinoline-3-carboxylic acid, 5,7-CIQA, 7-CIQ, 7-TFQ, 7-TFQA) RU-5135 Sinomenine Strychnine Thiocolchicoside Tutin NAMs: Amiloride Benzodiazepines (e.g., bromazepam, clonazepam, diazepam, flunitrazepam, flurazepam) Corymine Cyanotriphenylborate Daidzein Dihydropyridines (e.g., nicardipine, nifedipine, nitrendipine) Furosemide Genistein Ginkgo constituents (e.g., bilobalide, ginkgolides (e.g., ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, ginkgolide M)) Imipramine NBQX Neuroactive steroids (e.g., 3α-androsterone sulfate, 3β-androsterone sulfate, deoxycorticosterone, DHEA sulfate, pregnenolone sulfate, progesterone) Opioids (e.g., codeine, dextromethorphan, dextrorphan, levomethadone, levorphanol, morphine, oripavine, pethidine, thebaine) Picrotoxin (i.e., picrotin and picrotoxinin) PMBA Riluzole Tropeines (e.g., bemesetron, LY-278584, tropisetron, zatosetron) Verapamil Zinc Transporter (blockers) GlyT1 ACPPB ALX-1393 ALX-5407 (NFPS) AMG-747 ASP2535 Bitopertin (RG1678/RO4917838) CP-802079 Ethanol Glycyldodecylamide GSK1018921 LY-2365109 Org 24598 Org 25935 (SCH-900435) PF-02545920 PF-03463275 PF-04958242 Sarcosine SSR-103,800 SSR-504,734 GlyT2 Amoxapine Ethanol NAGly Org 25543 Others Precursors: 3-PG GHB L-Serine L-Theonine Cofactors: Vitamin B6 See also: GABAergics • GHBergics • Glutamatergics