Editing Calcium carbonate (section)

==Preparation==
The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. Pure calcium carbonate (such as for food or pharmaceutical use), can be produced from a pure quarried source (usually [[marble]]).

Alternatively, calcium carbonate is prepared from [[calcium oxide]]. Water is added to give [[calcium hydroxide]] then [[carbon dioxide]] is passed through this solution to [[precipitate]] the desired calcium carbonate, referred to in the industry as precipitated calcium carbonate (PCC). This process is called [[carbonatation]]:<ref name="PCC">{{cite web|title = Precipitated Calcium Carbonate|access-date = 11 January 2014|url = http://www.lime.org/uses_of_lime/other_uses/precip_cc.asp|archive-url = https://web.archive.org/web/20140111165543/http://www.lime.org/uses_of_lime/other_uses/precip_cc.asp|archive-date = 11 January 2014}}</ref>

:{{chem2|CaO + H2O → Ca(OH)2}}
:{{chem2|Ca(OH)2 + CO2 → CaCO3 + H2O}}
In a laboratory, calcium carbonate can easily be crystallized from [[calcium chloride]] ({{chem2|CaCl2}}), by placing an [[aqueous solution]] of {{chem2|CaCl2}} in a [[desiccator]] alongside [[ammonium carbonate]] {{chem2|[NH4]2CO3}}.<ref>{{Cite journal |last1=Kim |first1=Yi-Yeoun |last2=Schenk |first2=Anna S. |last3=Ihli |first3=Johannes |last4=Kulak |first4=Alex N. |last5=Hetherington |first5=Nicola B. J. |last6=Tang |first6=Chiu C. |last7=Schmahl |first7=Wolfgang W. |last8=Griesshaber |first8=Erika |last9=Hyett |first9=Geoffrey |last10=Meldrum |first10=Fiona C. |date=September 2014 |title=A critical analysis of calcium carbonate mesocrystals |journal=Nature Communications |language=en |volume=5 |issue=1 |page=4341 |doi=10.1038/ncomms5341 |issn=2041-1723 |pmc=4104461 |pmid=25014563|bibcode=2014NatCo...5.4341K}}</ref> In the desiccator, ammonium carbonate is exposed to air and decomposes into [[ammonia]], carbon dioxide, and [[water]]. The carbon dioxide then diffuses into the aqueous solution of calcium chloride, reacts with the calcium ions and the water, and forms calcium carbonate.