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{{About|the metallic element}}
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{{Use mdy dates|date=August 2018}}
{{Infobox zinc}}
'''Zinc''' is a [[chemical element]] with symbol '''Zn''' and atomic number 30. It is the first element in [[group 12 element|group 12]] of the [[periodic table]]. In some respects zinc is chemically similar to [[magnesium]]: both elements exhibit only one normal oxidation state (+2), and the Zn<sup>2+</sup> and Mg<sup>2+</sup> [[ion]]s are of similar size. Zinc is the 24th most abundant [[Abundance of elements in Earth's crust|element in Earth's crust]] and has five stable [[isotope]]s. The most common zinc [[ore]] is [[sphalerite]] (zinc blende), a [[zinc sulfide]] mineral. The largest workable lodes are in Australia, Asia, and the United States. Zinc is refined by [[froth flotation]] of the [[ore]], [[Roasting (metallurgy)|roasting]], and final [[extractive metallurgy|extraction]] using [[electricity]] ([[electrowinning]]).
[[Brass]], an [[alloy]] of [[copper]] and zinc in various proportions, was used as early as the third millennium BC in the [[Aegean Sea|Aegean]], [[Iraq]], the [[United Arab Emirates]], [[Kalmykia]], [[Turkmenistan]] and [[Georgia (country)|Georgia]], and the second millennium BC in [[West India]], [[Uzbekistan]], [[Iran]], [[Syria]], Iraq, and [[Israel]]<ref>{{Cite web|url=http://www.safarmer.com/Indo-Eurasian/Brass2007.pdf|title=Of brass and bronze in prehistoric Southwest Asia|last=Thornton|first=C. P.|date=2007|website=Papers and Lectures Online|publisher=Archetype Publications|isbn=1-904982-19-0|deadurl=no|archiveurl=https://web.archive.org/web/20150924093433/http://www.safarmer.com/Indo-Eurasian/Brass2007.pdf|archivedate=September 24, 2015}}</ref> ([[Judea]]<ref name="Greenwood1997p1201"/>).<ref name=jas5/> Zinc [[metal]] was not produced on a large scale until the 12th century in India, though it was known to the ancient Romans and Greeks.<ref>{{Cite web|url=http://www.rsc.org/periodic-table/element/30/zinc|title=Royal Society Of Chemistry|last=|first=|date=|website=|access-date=|deadurl=no|archiveurl=https://web.archive.org/web/20170711095949/http://www.rsc.org/periodic-table/element/30/zinc|archivedate=July 11, 2017}}</ref> The mines of [[Rajasthan]] have given definite evidence of zinc production going back to the 6th century BC.<ref>{{cite web |url=http://www.infinityfoundation.com/mandala/t_es/t_es_agraw_zinc_frameset.htm |title=India Was the First to Smelt Zinc by Distillation Process |publisher=Infinityfoundation.com |accessdate=April 25, 2014 |deadurl=no |archiveurl=http://arquivo.pt/wayback/20160516192708/http://www.infinityfoundation.com/mandala/t_es/t_es_agraw_zinc_frameset.htm |archivedate=May 16, 2016 }}</ref> 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.<ref>{{cite journal |author=Kharakwal, J. S. |author2=Gurjar, L. K. |last-author-amp=yes |url=http://www.ancient-asia-journal.com/article/view/aa.06112/23 |title=Zinc and Brass in Archaeological Perspective |journal=Ancient Asia |date=December 1, 2006 |volume=1 |pages=139–159 |doi=10.5334/aa.06112 |deadurl=no |archiveurl=https://web.archive.org/web/20131203003250/http://www.ancient-asia-journal.com/article/view/aa.06112/23 |archivedate=December 3, 2013 }}</ref> [[alchemy|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'' (prong, tooth). 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 [[galvanization|zinc plating]] of iron ([[hot-dip galvanizing]]) is the major application for zinc. Other applications are in electrical [[Zinc–carbon battery|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 [[micronutrient|essential mineral]], including to prenatal and postnatal development.<ref name=Hambridge2007>{{Cite journal|author=Hambidge, K. M.|author2=Krebs, N. F.|last-author-amp=yes|title=Zinc deficiency: a special challenge|journal=J. Nutr.|volume=137|date=2007|pmid=17374687|issue=4|pages=1101–5}}</ref> [[Zinc deficiency]] affects about two billion people in the developing world and is associated with many diseases.<ref name=Prasad2003/> In children, deficiency causes growth retardation, delayed sexual maturation, infection susceptibility, and [[diarrhea]].<ref name=Hambridge2007/> [[Enzyme]]s with a zinc atom in the [[prosthetic groups|reactive center]] are widespread in biochemistry, such as [[alcohol dehydrogenase]] in humans.<ref>{{cite book
|first1=Wolfgang|last1=Maret|editor1-first=Lucia |editor1-last=Banci |series=Metal Ions in Life Sciences |volume=12|chapter= Chapter 14 Zinc and the Zinc Proteome
|title=Metallomics and the Cell |date=2013 |publisher=Springer |doi=10.1007/978-94-007-5561-10_14 |isbn=978-94-007-5561-1}}
</ref>
Consumption of excess zinc may cause [[ataxia]], [[lethargy]], and [[copper deficiency]].
==Characteristics==
===Physical properties===
Zinc is a bluish-white, lustrous, [[diamagnetic]] metal,<ref name="CRCp4-41"/> though most common commercial grades of the metal have a dull finish.<ref name="Heiserman1992p123">{{harvnb|Heiserman|1992|p=123}}</ref> It is somewhat less dense than [[iron]] and has a hexagonal [[crystal structure]], with a distorted form of [[Close-packing of equal spheres|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.<ref>Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition p 1277 Oxford Science Publications {{ISBN|0-19-855370-6}}</ref> The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C.<ref name="CRCp4-41"/><ref name="Heiserman1992p123"/> Above 210 °C, the metal becomes brittle again and can be pulverized by beating.<ref>{{Cite book|url=https://books.google.com/?id=SSkKAAAAIAAJ|title=The Useful Metals and Their Alloys|first=John|last=Scoffern|publisher=Houlston and Wright|date=1861|pages=591–603|accessdate=April 6, 2009}}</ref> Zinc is a fair [[electrical conductivity|conductor of electricity]].<ref name="CRCp4-41"/> For a metal, zinc has relatively low melting (419.5 °C) and boiling points (907 °C).<ref name="ZincMetalProps">{{cite web|url=http://www.galvanizeit.org/design-and-fabrication/design-considerations/zinc-metal-properties |title=Zinc Metal Properties |publisher=American Galvanizers Association |date=2008 |accessdate=April 7, 2015 |archiveurl=https://www.webcitation.org/6XcI4VfD2?url=http://www.galvanizeit.org/design-and-fabrication/design-considerations/zinc-metal-properties |archivedate=April 7, 2015 |dead-url=no |df= }}</ref> The melting point is the lowest of all the [[d-block]] metals aside from [[mercury (element)|mercury]] and [[cadmium]]; for this, among other reasons, zinc, cadmium, and mercury are often not considered to be [[transition metal]]s like the rest of the d-block metals are.<ref name=ZincMetalProps/>
Many [[alloy]]s contain zinc, including brass. Other metals long known to form binary alloys with zinc are [[aluminium]], [[antimony]], [[bismuth]], [[gold]], [[iron]], [[lead]], [[mercury (element)|mercury]], [[silver]], [[tin]], [[magnesium]], [[cobalt]], [[nickel]], [[tellurium]], and [[sodium]].<ref>{{Cite book|title=Production and Properties of Zinc: A Treatise on the Occurrence and Distribution of Zinc Ore, the Commercial and Technical Conditions Affecting the Production of the Spelter, Its Chemical and Physical Properties and Uses in the Arts, Together with a Historical and Statistical Review of the Industry|last=Ingalls|first=Walter Renton|publisher=The Engineering and Mining Journal|date=1902|pages=142–6|url=https://books.google.com/?id=RhNDAAAAIAAJ&pg=PA133}}</ref> Although neither zinc nor [[zirconium]] are [[Ferromagnetism|ferromagnetic]], their alloy {{chem|ZrZn|2}} exhibits ferromagnetism below 35 [[Kelvin|K]].<ref name="CRCp4-41"/>
A bar of zinc generates a characteristic sound when bent, similar to [[tin cry]].
===Occurrence===
{{See also|:Category:Zinc minerals|l1=Zinc minerals}}
Zinc makes up about 75 [[Parts per million|ppm]] (0.0075%) of [[Earth's crust]], making it the 24th most abundant element. Soil contains zinc in 5–770 ppm with an average 64 ppm. [[Seawater]] has only 30 [[Parts per billion|ppb]] and the atmosphere, 0.1–4 µg/m<sup>3</sup>.<ref name="Emsley2001p503">{{harvnb|Emsley|2001|p=503}}</ref> The element is normally found in association with other [[base metal]]s such as [[copper]] and [[lead]] in [[ore]]s.<ref name="Lehto1968p822"/> Zinc is a [[Goldschmidt classification#Chalcophile elements|chalcophile]], meaning the element is more likely to be found in minerals together with [[sulfur]] and other heavy [[chalcogen]]s, rather than with the light chalcogen [[oxygen]] or with non-chalcogen electronegative elements such as the [[halogen]]s. [[Sulfide]]s formed as the crust solidified under the [[redox|reducing]] conditions of the early Earth's atmosphere.<ref name="Greenwood1997p1202">{{harvnb|Greenwood|1997|p=1202}}</ref> [[Sphalerite]], which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.<ref name="Lehto1968p822"/>
Other source minerals for zinc include [[smithsonite]] (zinc [[carbonate]]), [[hemimorphite]] (zinc [[silicate]]), [[wurtzite]] (another zinc sulfide), and sometimes [[hydrozincite]] (basic [[zinc carbonate]]).<ref name="Emsley2001p502"/> With the exception of wurtzite, all these other minerals were formed by weathering of the primordial zinc sulfides.<ref name="Greenwood1997p1202"/>
Identified world zinc resources total about 1.9–2.8 billion [[tonne]]s.<ref name=USGSMCS2015>{{cite web|last=Tolcin|first=A. C.|date=2015|url=http://minerals.usgs.gov/minerals/pubs/commodity/zinc/mcs-2015-zinc.pdf|publisher=[[United States Geological Survey]]|accessdate=May 27, 2015|title=Mineral Commodity Summaries 2015: Zinc|deadurl=no|archiveurl=https://web.archive.org/web/20150525183116/http://minerals.usgs.gov/minerals/pubs/commodity/zinc/mcs-2015-zinc.pdf|archivedate=May 25, 2015}}</ref><ref>{{cite journal|last1=Erickson|first1=R. L.|title=Crustal Abundance of Elements, and Mineral Reserves and Resources|journal=U.S. Geological Survey Professional Paper 820|date=1973|pages=21–25}}</ref> Large deposits are in Australia, Canada and the United States, with the largest reserves in [[Iran]].<ref name="Greenwood1997p1202"/><ref>{{cite web|url=http://www.etdb.org/StrategiesAndResearch/Countries/CSPReports/ReportsLibrary/CPS%20Report%20-%20Islamic%20Republic%20of%20Iran.doc |title=Country Partnership Strategy—Iran: 2011–12 |accessdate=June 6, 2011 |publisher=ECO Trade and development bank |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20111026135641/http://www.etdb.org/StrategiesAndResearch/Countries/CSPReports/ReportsLibrary/CPS%20Report%20-%20Islamic%20Republic%20of%20Iran.doc |archivedate=October 26, 2011 |df= }}</ref><ref>{{cite web|url=http://www.iranconmin.de/en/leftnavigation/market|title=IRAN – a growing market with enormous potential|accessdate=March 3, 2010|publisher=IMRG|date=July 5, 2010|deadurl=no|archiveurl=https://web.archive.org/web/20130217181730/http://www.iranconmin.de/en/leftnavigation/market|archivedate=February 17, 2013}}</ref> The most recent estimate of reserve base for zinc (meets specified minimum physical criteria related to current mining and production practices) was made in 2009 and calculated to be roughly 480 Mt.<ref name=USGSMCS2009>{{cite web|last=Tolcin|first=A. C.|date=2009|url=http://minerals.usgs.gov/minerals/pubs/commodity/zinc/mcs-2015-zinc.pdf|publisher=[[United States Geological Survey]]|accessdate=August 4, 2016|title=Mineral Commodity Summaries 2009: Zinc|deadurl=no|archiveurl=https://web.archive.org/web/20160702053035/http://minerals.usgs.gov/minerals/pubs/commodity/zinc/mcs-2015-zinc.pdf|archivedate=July 2, 2016}}</ref> Zinc reserves, on the other hand, are geologically identified ore bodies whose suitability for recovery is economically based (location, grade, quality, and quantity) at the time of determination. Since exploration and mine development is an ongoing process, the amount of zinc reserves is not a fixed number and sustainability of zinc ore supplies cannot be judged by simply extrapolating the combined mine life of today's zinc mines. This concept is well supported by data from the United States Geological Survey (USGS), which illustrates that although refined zinc production increased 80% between 1990 and 2010, the reserve lifetime for zinc has remained unchanged. About 346 million tonnes have been extracted throughout history to 2002, and scholars have estimated that about 109–305 million tonnes are in use.<ref>{{Cite journal|last=Gordon|first=R. B.|author2=Bertram, M. |author3=Graedel, T. E. |title=Metal stocks and sustainability|journal=Proceedings of the National Academy of Sciences|volume=103|date=2006|pmid=16432205|pmc=1360560|doi=10.1073/pnas.0509498103|issue=5|bibcode = 2006PNAS..103.1209G|pages=1209–14 }}</ref><ref>{{cite journal|last1=Gerst|first1=Michael|title=In-Use Stocks of Metals: Status and Implications|journal=Environmental Science and Technology|date=2008|volume=42|issue=19|pages=7038–45|doi=10.1021/es800420p|pmid=18939524|bibcode=2008EnST...42.7038G}}</ref><ref>{{cite journal|last1=Meylan|first1=Gregoire|title=The anthropogenic cycle of zinc: Status quo and perspectives|journal=Resources, Conservation and Recycling|volume=123|date=2016|pages=In press|doi=10.1016/j.resconrec.2016.01.006}}</ref>
[[File:Sphalerite4.jpg|thumb|[[Sphalerite]] (ZnS)|alt=A black shiny lump of solid with uneven surface]]
===Isotopes===
{{Main|Isotopes of zinc}}
Five stable [[isotope]]s of zinc occur in nature, with <sup>64</sup>Zn being the most abundant isotope (49.17% [[natural abundance]]).<ref name="NNDC">{{cite web|url=http://www.nndc.bnl.gov/chart/|author=NNDC contributors|editor=Alejandro A. Sonzogni (Database Manager)|title=Chart of Nuclides|publisher=National Nuclear Data Center, [[Brookhaven National Laboratory]]|accessdate=September 13, 2008|date=2008|location=Upton (NY)|deadurl=no|archiveurl=https://web.archive.org/web/20080522125027/http://www.nndc.bnl.gov/chart|archivedate=May 22, 2008}}</ref><ref name=nubase1>{{NUBASE 2016}}</ref> The other isotopes found in nature are {{chem|66|Zn}} (27.73%), {{chem|67|Zn}} (4.04%), {{chem|68|Zn}} (18.45%), and {{chem|70|Zn}} (0.61%).<ref name=nubase1 /> The most abundant isotope <sup>64</sup>Zn and the rare <sup>70</sup>Zn are theoretically unstable on energetic grounds, though their predicted half-lives exceed {{val|4.3|e=18|u=years}}<ref>{{harvnb|CRC|2006|p='''11'''–70}}</ref> and {{val|1.3|e=16|u=years}},<ref name=nubase1 /> meaning that their radioactivity could be ignored for practical purposes.
Several dozen [[radioisotope]]s have been characterized. {{chem|65|Zn}}, which has a half-life of 243.66 days, is the least active radioisotope, followed by {{chem|72|Zn}} with a half-life of 46.5 hours.<ref name="NNDC"/> Zinc has 10 [[nuclear isomer]]s. <sup>69m</sup>Zn has the longest half-life, 13.76 h.<ref name="NNDC"/> 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]]. {{chem|61|Zn}} has three excited metastable states and {{chem|73|Zn}} has two.<ref>{{Cite journal| last=Audi| first=Georges| title=The NUBASE Evaluation of Nuclear and Decay Properties| journal=Nuclear Physics A| volume=729| issue=1| pages=3–128| publisher=Atomic Mass Data Center| date=2003| doi=10.1016/j.nuclphysa.2003.11.001| bibcode=2003NuPhA.729....3A| last2=Bersillon| first2=O.| last3=Blachot| first3=J.| last4=Wapstra| first4=A. H.| url=http://hal.in2p3.fr/in2p3-00014184| deadurl=no| archiveurl=https://web.archive.org/web/20170103002324/http://hal.in2p3.fr/in2p3-00014184| archivedate=January 3, 2017| df=mdy-all}}</ref> The isotopes {{chem|65|Zn}}, {{chem|71|Zn}}, {{chem|77|Zn}} and {{chem|78|Zn}} each have only one excited metastable state.<ref name="NNDC"/>
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.<ref name="NNDC"/>
:{{nuclide|zinc|n}} + {{SubatomicParticle|link=yes|electron}} → {{nuclide|copper|n}}
The most common decay mode of a radioisotope of zinc with mass number higher than 66 is [[beta decay]] (β<sup>−</sup>), which produces an isotope of [[gallium]].<ref name="NNDC"/>
:{{nuclide|zinc|n}} → {{nuclide|gallium|n}} + {{SubatomicParticle|link=yes|electron}} + {{SubatomicParticle|link=yes|Electron antineutrino}}
<!-- NEEDS CITE
Zinc is too large and heavy to form in stars using the silicon burning process. The stable form of zinc is created in [[supernova]]s via the [[r-process]].-->
==Compounds and chemistry==
{{Main|Compounds of zinc}}
===Reactivity===
{{see also|Clemmensen reduction}}
Zinc has an [[electron configuration]] of [Ar]3d<sup>10</sup>4s<sup>2</sup> and is a member of the [[group 12 element|group 12]] of the [[periodic table]]. It is a moderately reactive metal and strong [[reducing agent]].<ref name=CRC2006p8-29>{{harvnb|CRC|2006|pp='''8'''–29}}</ref> The surface of the pure metal [[tarnish]]es quickly, eventually forming a protective [[Passivation (chemistry)|passivating]] layer of the basic [[Hydrozincite|zinc carbonate]], {{chem|Zn|5|(OH)|6|(CO<sub>3</sub>)|2}}, by reaction with atmospheric [[carbon dioxide]].<ref>{{Cite book|publisher=CRC Press|date=1994|page=121|isbn=0-8247-9213-0|title=Corrosion Resistance of Zinc and Zinc Alloys| first=Frank C.|last=Porter}}</ref> 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]].<ref name="Holl"/> Zinc reacts readily with [[acid]]s, [[alkali]]s and other non-metals.<ref>{{Cite book|last=Hinds|first=John Iredelle Dillard|title=Inorganic Chemistry: With the Elements of Physical and Theoretical Chemistry|publisher=John Wiley & Sons|location=New York|date=1908|edition=2nd|pages=506–508|url=https://books.google.com/?id=xMUMAAAAYAAJ}}</ref> Extremely pure zinc reacts only slowly at [[room temperature]] with acids.<ref name="Holl"/> Strong acids, such as [[hydrochloric acid|hydrochloric]] or [[sulfuric acid]], can remove the passivating layer and subsequent reaction with water releases hydrogen gas.<ref name="Holl"/>
The chemistry of zinc is dominated by the +2 oxidation state. When compounds in this oxidation state are formed, the outer [[electron shell|shell]] ''s'' electrons are lost, yielding a bare zinc ion with the electronic configuration [Ar]3d<sup>10</sup>.<ref>{{Cite book|last=Ritchie|first=Rob|title=Chemistry|publisher=Letts and Lonsdale|date=2004|edition=2nd|page=71|isbn=1-84315-438-2|url=https://books.google.com/?id=idT9j6406gsC}}</ref> In aqueous solution an octahedral complex, {{chem|[Zn(H|2|O)<sub>6</sub>]|2+}} is the predominant species.<ref>{{Cite book|last=Burgess|first=John|title=Metal ions in solution|publisher=Ellis Horwood|location=New York|date=1978|page=147|isbn=0-470-26293-1}}</ref> The [[volatilization]] of zinc in combination with zinc chloride at temperatures above 285 °C indicates the formation of {{chem|Zn|2|Cl|2}}, a zinc compound with a +1 oxidation state.<ref name="Holl"/> No compounds of zinc in oxidation states other than +1 or +2 are known.<ref>{{Cite book|last=Brady|first=James E.|author2=Humiston, Gerard E. |author3=Heikkinen, Henry |title=General Chemistry: Principles and Structure|publisher=John Wiley & Sons|date=1983|edition=3rd|page=671|isbn=0-471-86739-X}}</ref> Calculations indicate that a zinc compound with the oxidation state of +4 is unlikely to exist.<ref>{{Cite journal|journal=Inorganic Chemistry|date=1994|volume=33|issue=10|pages=2122–2131|title=Oxidation state +IV in group 12 chemistry. Ab initio study of zinc(IV), cadmium(IV), and mercury(IV) fluorides|author=Kaupp M.|author2=Dolg M.|author3=Stoll H.|author4=Von Schnering H. G.|doi=10.1021/ic00088a012}}</ref>
Zinc chemistry is similar to the chemistry of the late first-row transition metals, [[nickel]] and copper, though it has a filled d-shell and compounds are [[diamagnetic]] and mostly colorless.<ref name="Greenwood1997p1206"/> The [[ionic radii]] of zinc and magnesium happen to be nearly identical. Because of this some of the equivalent salts have the same [[crystal structure]],<ref>{{harvnb|CRC|2006|pp='''12'''–11–12}}</ref> and in other circumstances where ionic radius is a determining factor, the chemistry of zinc has much in common with that of magnesium.<ref name="Holl">{{Cite book|publisher=Walter de Gruyter|date=1985|edition=91–100| pages=1034–1041|isbn=3-11-007511-3|title=Lehrbuch der Anorganischen Chemie|first1=Arnold F.|last1=Holleman|last2=Wiberg|first2=Egon|last3=Wiberg|first3=Nils|language=German|chapter=Zink}}</ref> In other respects, there is little similarity with the late first-row transition metals. Zinc tends to form bonds with a greater degree of [[covalency]] and much more stable [[Complex (chemistry)|complexes]] with [[nitrogen|N]]- and [[sulfur|S]]- donors.<ref name="Greenwood1997p1206">{{harvnb|Greenwood|1997|p=1206}}</ref> Complexes of zinc are mostly 4- or 6- [[coordinate covalent bond|coordinate]] although 5-coordinate complexes are known.<ref name="Holl"/>
===Zinc(I) compounds===
Zinc(I) compounds are rare and need bulky ligands to stabilize the low oxidation state. Most zinc(I) compounds contain formally the [Zn<sub>2</sub>]<sup>2+</sup> core, which is analogous to the [Hg<sub>2</sub>]<sup>2+</sup> dimeric cation present in [[mercury (element)|mercury]](I) compounds. The [[diamagnetism|diamagnetic]] nature of the ion confirms its dimeric structure. The first zinc(I) compound containing the Zn–Zn bond, [[Decamethyldizincocene|(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Zn<sub>2</sub>]], is also the first [[metallocene|dimetallocene]]. The [Zn<sub>2</sub>]<sup>2+</sup> ion rapidly [[disproportionation|disproportionates]] into zinc metal and zinc(II), and has been obtained only a yellow glass only by cooling a solution of metallic zinc in molten ZnCl<sub>2</sub>.<ref>{{Housecroft3rd|page=739–741, 843}}</ref>
===Zinc(II) compounds===
[[File:Zinc acetate.JPG|thumb|left|Zinc acetate|alt=Sheets of zinc acetate formed by slow evaporation]]
[[File:Zinc chloride.jpg|thumb|Zinc chloride|alt=White lumped powder on a glass plate]]
[[Binary compound]]s of zinc are known for most of the [[metalloid]]s and all the [[nonmetal]]s except the [[noble gas]]es. The oxide [[zinc 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.<ref name="Holl"/> The other [[chalcogen]]ides ([[zinc sulfide|ZnS]], [[zinc selenide|ZnSe]], and [[zinc telluride|ZnTe]]) have varied applications in electronics and optics.<ref>{{cite web|url=http://www.americanelements.com/znsu.html|title=Zinc Sulfide|publisher=[[American Elements]]|accessdate=February 3, 2009|deadurl=no|archiveurl=https://archive.is/20120717190353/http://www.americanelements.com/znsu.html|archivedate=July 17, 2012}}</ref> [[Pnictogenide]]s ([[Zinc nitride|{{chem|Zn|3|N|2}}]], [[zinc phosphide|{{chem|Zn|3|P|2}}]], [[zinc arsenide|{{chem|Zn|3|As|2}}]] and [[zinc antimonide|{{chem|Zn|3|Sb|2}}]]),<ref>{{cite book|author=Grolier contributors|title=Academic American Encyclopedia|url=https://books.google.com/?id=YgI4E7w5JI8C|date=1994|publisher=Grolier Inc.| location=[[Danbury, Connecticut|Danbury]], [[Connecticut]]|isbn=0-7172-2053-2|page=202}}</ref><ref>{{cite web|url=http://www.americanelements.com/znp.html|title=Zinc Phosphide|publisher=[[American Elements]]|accessdate=February 3, 2009|deadurl=no|archiveurl=https://archive.is/20120717120313/http://www.americanelements.com/znp.html|archivedate=July 17, 2012}}</ref> the peroxide ([[zinc peroxide|{{chem|ZnO|2}}]]), the hydride ([[zinc hydride|{{chem|ZnH|2}}]]), and the carbide ({{chem|ZnC|2}}) are also known.<ref>{{Cite journal|journal=Diamond and Related Materials|volume=9|date=2000|title=Peculiarities of interaction in the Zn–C system under high pressures and temperatures|first=A. A.|issue=2|last=Shulzhenko|author2=Ignatyeva, I. Yu. |author3=Osipov, A. S. |author4= Smirnova, T. I. |doi=10.1016/S0925-9635(99)00231-9|pages=129–133|bibcode = 2000DRM.....9..129S }}</ref> Of the four [[halide]]s, [[zinc fluoride|{{chem|ZnF|2}}]] has the most ionic character, while the others ([[zinc chloride|{{chem|ZnCl|2}}]], [[zinc bromide|{{chem|ZnBr|2}}]], and [[zinc iodide|{{chem|ZnI|2}}]]) have relatively low melting points and are considered to have more covalent character.<ref name="Greenwood1997p1211">{{harvnb|Greenwood|1997|p=1211}}</ref>
In weak basic solutions containing {{chem|Zn|2+}} ions, the hydroxide [[Zinc hydroxide|{{chem|Zn(OH)|2}}]] forms as a white [[precipitate]]. In stronger alkaline solutions, this hydroxide is dissolved to form zincates ([[zincate|{{chem|[Zn||(OH)<sub>4</sub>]|2-}}]]).<ref name="Holl"/> The nitrate [[Zinc nitrate|{{chem|Zn(NO<sub>3</sub>)|2}}]], chlorate [[Zinc chlorate|{{chem|Zn(ClO<sub>3</sub>)|2}}]], sulfate [[Zinc sulfate|{{chem|ZnSO|4}}]], phosphate [[Zinc phosphate|{{chem|Zn|3|(PO<sub>4</sub>)|2}}]], molybdate [[Zinc molybdate|{{chem|ZnMoO|4}}]], cyanide [[Zinc cyanide|{{chem|Zn(CN)|2}}]], arsenite {{chem|Zn(AsO<sub>2</sub>)|2}}, arsenate {{chem|Zn(AsO<sub>4</sub>)|2|·8H|2|O}} and the chromate [[Zinc chromate|{{chem|ZnCrO|4}}]] (one of the few colored zinc compounds) are a few examples of other common inorganic compounds of zinc.<ref>{{Cite journal| last=Rasmussen| first=J. K.| author2=Heilmann, S. M.| title=In situ Cyanosilylation of Carbonyl Compounds: O-Trimethylsilyl-4-Methoxymandelonitrile| journal=Organic Syntheses, Collected Volume| volume=7| page=521| date=1990| url=http://www.orgsyn.org/orgsyn/prep.asp?prep=cv7p0521| deadurl=no| archiveurl=https://web.archive.org/web/20070930230236/http://www.orgsyn.org/orgsyn/prep.asp?prep=cv7p0521| archivedate=September 30, 2007| df=mdy-all}}</ref><ref name="perry">{{Cite book|title=Handbook of Inorganic Compounds|last=Perry|first=D. L.|pages=448–458|date=1995|isbn=0-8493-8671-3|publisher=CRC Press}}</ref> One of the simplest examples of an [[organic compound]] of zinc is the acetate ([[Zinc acetate|{{chem|Zn(O|2|CCH<sub>3</sub>)|2}}]]).
[[Organozinc compound]]s are those that contain zinc–carbon covalent bonds. Diethylzinc ([[Diethylzinc|{{chem|(C|2|H<sub>5</sub>)|2|Zn}}]]) 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]].<ref>{{Cite journal|title=On the isolation of the organic radicals|author=Frankland, E.|journal=Quarterly [[Journal of the Chemical Society]]|date=1850|volume=2|issue=3|page=263|doi=10.1039/QJ8500200263|authorlink=Edward Frankland}}</ref>
===Test for zinc===
Cobalticyanide paper (Rinnmann's test for Zn) can be used as a chemical indicator for zinc. 4 g of K<sub>3</sub>Co(CN)<sub>6</sub> and 1 g of KClO<sub>3</sub> is dissolved on 100 ml of water. Paper is dipped in the solution and dried at 100 °C. One drop of the sample is dropped onto the dry paper and heated. A green disc indicates the presence of zinc.<ref>{{Cite book|title=CRC- Handbook of Chemistry and Physics|last=Lide|first=David|publisher=CRC press|year=1998|isbn=0-8493-0479-2|location=|pages=Section 8 Page 1}}</ref>
{{clear}}
==History==
===Ancient use===
[[File:Hemmoorer Eimer.jpg|upright|thumb|Late Roman brass bucket – the [[Hemmoor]]er Eimer from Warstade, Germany, second to third century AD|alt=Large black bowl-shaped bucket on a stand. The bucket has incrustation around its top.]]
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]] thousands of years prior to the discovery of zinc as a separate element. Judean brass from the 14th to 10th centuries BC contains 23% zinc.<ref name="Greenwood1997p1201">{{harvnb|Greenwood|1997|p=1201}}</ref>
Knowledge of how to produce brass spread to [[Ancient Greece]] by the 7th century BC, but few varieties were made.<ref name=jas5>{{cite journal|last=Craddock|first=Paul T.|date=1978|title=The composition of copper alloys used by the Greek, Etruscan and Roman civilizations. The origins and early use of brass|journal=Journal of Archaeological Science|volume=5|issue=1|pages=1–16|doi=10.1016/0305-4403(78)90015-8}}</ref> Ornaments made of [[alloy]]s containing 80–90% zinc, with lead, iron, [[antimony]], and other metals making up the remainder, have been found that are 2,500 years old.<ref name="Lehto1968p822">{{harvnb|Lehto|1968|p=822}}</ref> A possibly prehistoric statuette containing 87.5% zinc was found in a [[Dacia]]n archaeological site.<ref name="Weeks1933p20">{{harvnb|Weeks|1933|p=20}}</ref>
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]], wrecked in 140 BC.<ref>{{cite web |url=https://www.newscientist.com/article/dn23049-worlds-oldest-pills-treated-sore-eyes.html |title=World's oldest pills treated sore eyes |work=New Scientist |date=January 7, 2013 |accessdate=February 5, 2013 |deadurl=no |archiveurl=https://web.archive.org/web/20130122102750/http://www.newscientist.com/article/dn23049-worlds-oldest-pills-treated-sore-eyes.html |archivedate=January 22, 2013 }}</ref><ref>{{citejournal|doi= 10.1073/pnas.1216776110|title=Ingredients of a 2,000-y-old medicine revealed by chemical, mineralogical, and botanical investigations|bibcode=2013PNAS..110.1193G}}</ref>
The manufacture of brass was known to the [[Ancient Rome|Romans]] by about 30 BC.<ref name="Emsley2001p501"/> They made brass by heating powdered [[Calamine (mineral)|calamine]] (zinc [[silicate]] or carbonate), charcoal and copper together in a crucible.<ref name="Emsley2001p501">{{harvnb|Emsley|2001|p=501}}</ref> The resulting [[calamine brass]] was then either cast or hammered into shape for use in weaponry.<ref>{{cite web|title=How is zinc made? |work=How Products are Made |date=2002 |publisher=The Gale Group |url=http://www.answers.com/zinc |accessdate=February 21, 2009 |deadurl=bot: unknown |archiveurl=https://web.archive.org/web/20060411200556/http://www.answers.com/zinc |archivedate=April 11, 2006 |df= }}</ref> Some coins struck by Romans in the Christian era are made of what is probably calamine brass.<ref name="Chambers1901p799">{{harvnb|Chambers|1901|p=799}}</ref>
[[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.<ref>{{Cite book |author=Craddock, P. T. |chapter=Zinc in classical antiquity |editor=Craddock, P.T. |title=2000 years of zinc and brass |publisher=British Museum |location=London |date=1998 |isbn=0-86159-124-0 |pages=3–5 |edition=rev.}}</ref> Zinc in such remnants in smelting ovens was usually discarded as it was thought to be worthless.<ref name="Weeks1933p21">{{harvnb|Weeks|1933|p=21}}</ref>
The [[Berne zinc tablet]] is a votive plaque dating to [[Roman Gaul]] made of an alloy that is mostly zinc.<ref>{{Cite book|last=Rehren|first=Th.|date=1996|title=A Roman zinc tablet from Bern, Switzerland: Reconstruction of the Manufacture|publisher=Archaeometry 94. The Proceedings of the 29th International Symposium on Archaeometry|editor=S. Demirci|display-editors=etal|pages=35–45}}</ref>
The [[Charaka Samhita]], thought to have been written between 300 and 500 AD,<ref>{{cite book|author=Meulenbeld, G. J.|title=A History of Indian Medical Literature|publisher=Forsten|location=Groningen|date=1999|oclc=165833440|volume=IA|pages=130–141}}</ref> mentions a metal which, when oxidized, produces ''pushpanjan'', thought to be zinc oxide.<ref>{{Cite book |author=Craddock, P. T. |display-authors=etal|chapter=Zinc in India |title=2000 years of zinc and brass |publisher=British Museum |location=London |date=1998 |isbn=0-86159-124-0 |page=27 |edition=rev.}}</ref> Zinc mines at Zawar, near [[Udaipur]] in India, have been active since the [[Mauryan period]] ({{circa| 322}} and 187 BCE). The smelting of metallic zinc here, however, appears to have begun around the 12th century AD.<ref name=ammraja>p. 46, Ancient mining and metallurgy in Rajasthan, S. M. Gandhi, chapter 2 in ''Crustal Evolution and Metallogeny in the Northwestern Indian Shield: A Festschrift for Asoke Mookherjee'', M. Deb, ed., Alpha Science Int'l Ltd., 2000, {{ISBN|1-84265-001-7}}.</ref><ref name="Craddock">{{Cite journal
|last=Craddock|first=P. T.|author2=Gurjar L. K. |author3=Hegde K. T. M. |title=Zinc production in medieval India|journal=World Archaeology|volume=15|issue=2|date=1983|publisher=Taylor & Francis|jstor=124653
|pages=211–217
|doi=10.1080/00438243.1983.9979899}}</ref> One estimate is that this location produced an estimated million tonnes of metallic zinc and zinc oxide from the 12th to 16th centuries.<ref name="Emsley2001p502">{{harvnb|Emsley|2001|p=502}}</ref> Another estimate gives a total production of 60,000 tonnes of metallic zinc over this period.<ref name=ammraja /> 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.<ref name="Craddock"/>
===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 (of Taka dynasty) and written about the year 1374.<ref name="Ray1903">{{cite book|last=Ray|first=Prafulla Chandra|title=A History of Hindu Chemistry from the Earliest Times to the Middle of the Sixteenth Century, A.D.: With Sanskrit Texts, Variants, Translation and Illustrations|publisher=The Bengal Chemical & Pharmaceutical Works, Ltd|date=1903|edition=2nd|volume=1|pages=157–158|url=https://books.google.com/?id=DL1HAAAAIAAJ&printsec=titlepage}} (public domain text)</ref> Smelting and extraction of impure zinc by reducing calamine with wool and other organic substances was accomplished in the 13th century in India.<ref name="CRCp4-41">{{harvnb|CRC|2006|p='''4'''–41}}<!-- sic "-" not a range! --></ref><ref name="iza">{{cite web|last=Habashi|first=Fathi|title=Discovering the 8th Metal|publisher=International Zinc Association (IZA)|url=http://www.iza.com/Documents/Communications/Publications/History.pdf|archiveurl=https://web.archive.org/web/20090304154217/http://www.iza.com/Documents/Communications/Publications/History.pdf|archivedate=March 4, 2009|accessdate=December 13, 2008}}</ref> The Chinese did not learn of the technique until the 17th century.<ref name="iza" />
[[File:Zinc-alchemy symbols.png|thumb|left|Various [[alchemical symbol]]s for the element zinc]]
[[Alchemy|Alchemists]] burned zinc metal in air and collected the resulting zinc oxide on a [[Condenser (heat transfer)|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''.<ref>{{Cite book|last=Arny|first=Henry Vinecome|url=https://books.google.com/?id=gRNKAAAAMAAJ|title=Principles of Pharmacy|publisher=W. B. Saunders company|date=1917|edition=2nd|page=483}}</ref>
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.<ref name="iza" /><ref>{{Cite book|title=Georgius Agricola de Re Metallica|first=Herbert Clark|last=Hoover|publisher=Kessinger Publishing|date=2003|page=409|isbn=0-7661-3197-1}}</ref> The word is probably derived from the German {{lang|de|zinke}}, and supposedly meant "tooth-like, pointed or jagged" (metallic zinc crystals have a needle-like appearance).<ref>{{Cite book|title=Ullmann's Encyclopedia of Industrial Chemistry|last=Gerhartz|display-authors=etal |edition=5th|date=1996|isbn=3-527-20100-9|publisher=VHC|page=509|first=Wolfgang}}</ref> ''Zink'' could also imply "tin-like" because of its relation to German ''zinn'' meaning tin.<ref>{{Cite book|author=Skeat, W. W|title=Concise Etymological Dictionary of the English Language|url=https://books.google.com/?id=ls_XijT33IUC&pg=PA622|page=622|publisher=Cosimo, Inc.|date=2005|isbn=1-59605-092-6}}</ref> Yet another possibility is that the word is derived from the [[Persian language|Persian]] word {{lang|fa|سنگ}} ''seng'' meaning stone.<ref>{{Cite book|title=Handbook of Extractive Metallurgy|author=Fathi Habashi|date=1997|isbn=3-527-28792-2|publisher=Wiley-VHC|page=642}}</ref> The metal was also called Indian tin, tutanego, calamine, and spinter.<ref name="Lehto1968p822"/>
German metallurgist [[Andreas Libavius]] received a quantity of what he called "calay" of Malabar from a cargo ship captured from the Portuguese in 1596.<ref>{{Cite book|last=Lach|first=Donald F.|title=Asia in the Making of Europe|chapter=Technology and the Natural Sciences|page=426|url=https://books.google.com/?id=N0xD7BYXv_YC&pg=PA426|date=1994|isbn=0-226-46734-1|publisher=[[University of Chicago Press]]}}</ref> 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,<ref name="iza" /> but was at times very expensive.<ref group=note>An [[East India Company]] ship carrying a cargo of nearly pure zinc metal from the Orient sank off the coast [[Sweden]] in 1745.{{harv|Emsley|2001|p=502}}</ref>
[[File:Andreas Sigismund Marggraf-flip.jpg|thumb|upright|[[Andreas Sigismund Marggraf]] is given credit for first isolating pure zinc|alt=Picture of an old man head (profile). The man has a long face, short hair and tall forehead.]]
===Isolation===
Metallic zinc was isolated in India by 1300 AD,<ref>{{cite book|last=Vaughan|first=L Brent |date=1897 |title=The Junior Encyclopedia Britannica A Reference Library of General Knowledge Volume III P-Z|location=Chicago |publisher=E. G. Melven & Company|article=Zincography}}</ref><ref>{{cite web|url=http://science.marshall.edu/castella/chm448/elements3.pdf|title=Transition Metal Elements|author=Castellani, Michael|accessdate=October 14, 2014|deadurl=no|archiveurl=https://web.archive.org/web/20141010201408/http://science.marshall.edu/castella/chm448/elements3.pdf|archivedate=October 10, 2014}}</ref><ref>{{cite book |last1=Habib |first1=Irfan |editor-last=Chatopadhyaya |editor-first=D. P. |date=2011 |title=Economic History of Medieval India, 1200–1500 |url=https://books.google.com/books?id=K8kO4J3mXUAC&pg=PA86 |location=New Delhi |publisher=Pearson Longman |page=86 |isbn=978-81-317-2791-1 |deadurl=no |archiveurl=https://web.archive.org/web/20160414222551/https://books.google.com/books?id=K8kO4J3mXUAC&pg=PA86 |archivedate=April 14, 2016 }}</ref> much earlier than in the West. Before it was isolated in Europe, it was imported from India in about 1600 CE.<ref name=zinc-eng/> [[Postlewayt|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.<ref name="Craddock"/><ref>{{Cite journal|title=Ancient Lead and Zinc Mining in Rajasthan, India|author1=Willies, Lynn|author2=Craddock, P. T.|author3=Gurjar, L. J.|author4=Hegde, K. T. M. |volume=16|issue=2, Mines and Quarries|date=1984|journal=World Archaeology|jstor=124574|pages=222–233|doi=10.1080/00438243.1984.9979929}}</ref>
Flemish [[metallurgist]] and [[alchemist]] [[P. M. de Respour]] reported that he had extracted metallic zinc from zinc oxide in 1668.<ref name="Emsley2001p502"/> 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 that is being smelted.<ref name="Emsley2001p502"/> In Britain, [[John Lane (metallurgist)|John Lane]] is said to have carried out experiments to smelt zinc, probably at [[Landore]], prior to his bankruptcy in 1726.<ref>{{Cite journal|last=Roberts|first=R. O.|date=1951|title=Dr John Lane and the foundation of the non-ferrous metal industry in the Swansea valley|journal=Gower|publisher=Gower Society|issue=4|page=19}}</ref>
In 1738 in Great Britain, [[William Champion (metallurgist)|William Champion]] patented a process to extract zinc from calamine in a vertical [[retort]] style smelter.<ref>{{Cite book|last=Comyns|first=Alan E.|title=Encyclopedic Dictionary of Named Processes in Chemical Technology|edition=3rd|publisher=CRC Press|isbn=0-8493-9163-6|date=2007|page=71|url=https://books.google.com/?id=Jlq-ckWvQSQC}}</ref> His technique resembled that used at Zawar zinc mines in [[Rajasthan]], but no evidence suggests he visited the Orient.<ref name=zinc-eng>{{Cite journal|first=Rhys|last=Jenkins|title=The Zinc Industry in England: the early years up to 1850|journal=Transactions of the Newcomen Society|volume=25|date=1945|pages=41–52|doi=10.1179/tns.1945.006}}</ref> Champion's process was used through 1851.<ref name="iza" />
German chemist [[Andreas Sigismund Marggraf|Andreas Marggraf]] normally gets credit for discovering pure metallic zinc, even though Swedish chemist Anton von Swab had distilled zinc from calamine four years previously.<ref name="iza" /> In his 1746 experiment, Marggraf heated a mixture of calamine and charcoal in a closed vessel without copper to obtain a metal.<ref name="Weeks1933p21"/> This procedure became commercially practical by 1752.<ref>{{harvnb|Heiserman|1992|p=122}}</ref>
===Later work===
[[File:Luigi Galvani, oil-painting.jpg|thumb|upright|left|[[Galvanization]] was named after [[Luigi Galvani]].|alt=Painting of a middle-aged man sitting by the table, wearing a wig, black jacket, white shirt and white scarf.]]
William Champion's brother, John, patented a process in 1758 for [[calcining]] zinc sulfide into an oxide usable in the retort process.<ref name="Lehto1968p822"/> 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.<ref>{{Cite book|last=Gray|title=Zinc|date=2005|isbn=0-7614-1922-5|publisher=Marshall Cavendish|page=8|first=Leon}}</ref> [[Jean-Jacques Daniel Dony]] built a different kind of horizontal zinc smelter in Belgium that processed even more zinc.<ref name="iza" />
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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.<ref name="ExcelPhysics">{{Cite book|title=Excel Preliminary Physics|last=Warren|first=Neville G.|publisher=Pascal Press|date=2000|page=47|isbn=1-74020-085-3|url=https://books.google.com/?id=eL9Xn6nQ6XQC&printsec=frontcover}}</ref> He incorrectly thought he had discovered an ability of nerves and muscles to create [[electricity]] and called the effect "[[bioelectricity|animal electricity]]".<ref name=IntEncyl>{{Cite book|title=The New International Encyclopaedia|chapter=Galvanic Cell|page=80|date=1903|publisher=Dodd, Mead and Company|url=https://books.google.com/?id=gV1MAAAAMAAJ&pg=PA80}}</ref> The galvanic cell and the process of galvanization were both named for Luigi Galvani, and his discoveries paved the way for [[Battery (electricity)|electrical batteries]], galvanization, and [[cathodic protection]].<ref name=IntEncyl/>
Galvani's friend, [[Alessandro Volta]], continued researching the effect and invented the [[Voltaic pile]] in 1800.<ref name="ExcelPhysics"/> The basic unit of Volta's pile was a simplified [[galvanic cell]], made of plates of copper and zinc separated by an [[electrolyte]] and connected by a conductor externally. The units were stacked in series to make the Voltaic cell, which produced electricity by directing [[electron]]s from the zinc to the copper and allowing the zinc to corrode.<ref name="ExcelPhysics"/>
The non-magnetic character of zinc and its lack of color in solution delayed discovery of its importance to biochemistry and nutrition.<ref name=Cotton1999p626/> This changed in 1940 when [[carbonic anhydrase]], an enzyme that scrubs carbon dioxide from blood, was shown to have zinc in its [[active site]].<ref name=Cotton1999p626/> The digestive enzyme [[carboxypeptidase]] became the second known zinc-containing enzyme in 1955.<ref name=Cotton1999p626>{{harvnb|Cotton|1999|p=626}}</ref>
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