Editing Calcium (section)

==History==
[[File:Ein Ghazal Venus.jpg|thumb|upright=0.4|One of the [['Ain Ghazal Statues]], made from [[lime plaster]]]]
Calcium, [[Chemical element|like other elements]], was formed through [[nuclear fusion]] in stars, specifically during [[supernova]] explosions. These stellar processes were responsible for creating many of the heavy elements, including calcium, which were then scattered throughout the universe when these stars exploded. Calcium's journey on Earth began with the [[Earth's formation|formation of the planet]], where it became a key part of [[Earth's crust|its crust]].{{cn|date=May 2025}}

Calcium compounds were known for millennia, though their chemical makeup was not understood until the 17th century.{{sfn|Greenwood|Earnshaw|1997|p = 108}} Lime as a [[lime (material)|building material]]<ref name="minerals.usgs">{{cite web | title = Commodity report:Lime | publisher = United States Geological Survey | first = Lori E. | last = Apodaca | date = 2021 | url = http://minerals.usgs.gov/minerals/pubs/commodity/lime/390498.pdf | access-date = 2012-03-06 | archive-date = 2011-11-12 | archive-url = https://web.archive.org/web/20111112224558/http://minerals.usgs.gov/minerals/pubs/commodity/lime/390498.pdf | url-status = dead }}</ref> and as [[lime plaster|plaster for statues]] was used as far back as around 7000&nbsp;BC.<ref>{{Cite journal |title=Burnt Lime Products and Social Implications in the Pre-Pottery Neolithic B Villages of the Near East |journal=Paléorient |first=Yosef |last=Garfinkel |date=1987 | doi = 10.3406/paleo.1987.4417 |jstor=41492234 |volume=13 |issue=1 |pages=69–76}}</ref> The first dated [[lime kiln]] dates back to 2500&nbsp;BC and was found in [[Khafajah]], [[Mesopotamia]].<ref>{{cite book | page =4 | title =Lime Kilns and Lime Burning | isbn =978-0-7478-0596-0 | last1 =Williams | first1 =Richard | date =2004 | publisher =Bloomsbury USA }}</ref><ref>{{cite book | url = https://books.google.com/books?id=vHQsGAKAdYoC | title = Lime and Limestone: Chemistry and Technology, Production and Uses | isbn = 978-3-527-61201-7 | last1 = Oates | first1 = J. A. H | year = 2008| publisher = Wiley }}</ref>

About the same time, dehydrated [[gypsum]] (CaSO{{sub|4}}·2H{{sub|2}}O) was being used in the [[Great Pyramid of Giza]]. This material would later be used for the plaster in the tomb of [[Tutankhamun]]. The [[ancient Roman]]s instead used lime mortars made by heating [[limestone]] (CaCO{{sub|3}}). The name "calcium" itself derives from the Latin word ''calx'' "lime".{{sfn|Greenwood|Earnshaw|1997|p= 108}}

[[Vitruvius]] noted that the lime that resulted was lighter than the original limestone, attributing this to the boiling of the water. In 1755, [[Joseph Black]] proved that this was due to the loss of [[carbon dioxide]], which as a gas had not been recognized by the ancient Romans.<ref name="Weeks" />

In 1789, [[Antoine Lavoisier]] suspected that lime might be an oxide of a fundamental [[chemical element]]. In his table of the elements, Lavoisier listed five "salifiable earths" (i.e., ores that could be made to react with acids to produce salts (''salis'' = salt, in Latin): ''chaux'' (calcium oxide), ''magnésie'' (magnesia, magnesium oxide), ''baryte'' (barium sulfate), ''alumine'' (alumina, aluminium oxide), and ''silice'' (silica, silicon dioxide)). About these "elements", Lavoisier reasoned: {{blockquote|We are probably only acquainted as yet with a part of the metallic substances existing in nature, as all those which have a stronger affinity to oxygen than carbon possesses, are incapable, hitherto, of being reduced to a metallic state, and consequently, being only presented to our observation under the form of oxyds, are confounded with earths. It is extremely probable that barytes, which we have just now arranged with earths, is in this situation; for in many experiments it exhibits properties nearly approaching to those of metallic bodies. It is even possible that all the substances we call earths may be only metallic oxyds, irreducible by any hitherto known process.<ref>Lavoisier, Antoine; Kerr, Robert (translator) (1799) ''Elements of Chemistry'', 4th ed. Edinburgh, Scotland: William Creech. [https://books.google.com/books?id=cbFjAAAAcAAJ&pg=PA218 p. 218]. The original passage appears in: Lavoisier, Antoine (1789) ''[[Traité Élémentaire de Chimie]]''. Paris, France: Cuchet. Vol. 1. [https://books.google.com/books?id=hZch3yOrayUC&pg=PA174 p. 174].</ref>}}

Calcium, along with its congeners magnesium, strontium, and barium, was first isolated by [[Humphry Davy]] in 1808. Following the work of [[Jöns Jakob Berzelius]] and [[Magnus Martin af Pontin]] on [[electrolysis]], Davy isolated calcium and magnesium by putting a mixture of the respective metal oxides with [[mercury(II) oxide]] on a [[platinum]] plate which was used as the anode, the cathode being a platinum wire partially submerged into mercury. Electrolysis then gave calcium–mercury and magnesium–mercury amalgams, and distilling off the mercury gave the metal.{{sfn|Greenwood|Earnshaw|1997|p = 108}}<ref>{{cite journal | last1 = Davy | first1 = H. | date = 1808 | title = Electro-chemical researches on the decomposition of the earths; with observations on the metals obtained from the alkaline earths, and on the amalgam procured from ammonia | url = https://books.google.com/books?id=gpwEAAAAYAAJ&pg=102 | journal = Philosophical Transactions of the Royal Society of London | volume = 98 | pages = 333–70 | doi=10.1098/rstl.1808.0023| doi-access =  | bibcode = 1808RSPT...98..333D | s2cid = 96364168 }}</ref> However, pure calcium cannot be prepared in bulk by this method and a workable commercial process for its production was not found until over a century later.<ref name="Weeks">{{Cite book
|last = Weeks
|first = Mary Elvira
|author-link=Mary Elvira Weeks|author2=Leichester, Henry M.
|year = 1968
|title = Discovery of the Elements
|publisher = Journal of Chemical Education
|pages =505–10
|location = Easton, PA
|lccn = 68-15217
|ref = CITEREFWeeks1968
|isbn = 978-0-7661-3872-8
}}</ref>