Editing Caesium (section)

==Production==
Mining and refining pollucite ore is a selective process and is conducted on a smaller scale than for most other metals. The ore is crushed, hand-sorted, but not usually concentrated, and then ground. Caesium is then extracted from pollucite primarily by three methods: acid digestion, alkaline decomposition, and direct reduction.<ref name="USGS"/><ref name="Burt">{{cite book |last=Burt |first=R. O. |date=1993 |chapter=Caesium and cesium compounds |title=Kirk-Othmer encyclopedia of chemical technology |edition=4th |place=New York |publisher=John Wiley & Sons, Inc. |volume=5 |pages=749–764 |isbn=978-0-471-48494-3}}</ref>

In the acid digestion, the [[silicate]] pollucite rock is dissolved with strong acids, such as [[hydrochloric acid|hydrochloric]] (HCl), [[sulfuric acid|sulfuric]] ({{chem|H|2|SO|4}}), [[hydrobromic acid|hydrobromic]] (HBr), or [[hydrofluoric acid|hydrofluoric]] (HF) acids. With hydrochloric acid, a mixture of soluble chlorides is produced, and the insoluble chloride double salts of caesium are precipitated as caesium antimony chloride ({{chem|Cs|4|SbCl|7}}), caesium iodine chloride ({{chem|Cs|2|ICl}}), or caesium hexachlorocerate ({{chem|Cs|2|(CeCl|6|)}}). After separation, the pure precipitated double salt is decomposed, and pure CsCl is precipitated by evaporating the water.

The sulfuric acid method yields the insoluble double salt directly as caesium [[alum]] ({{chem|CsAl(SO|4|)|2|·12H|2|O}}). The [[aluminium sulfate]] component is converted to insoluble [[aluminium oxide]] by roasting the alum with [[carbon]], and the resulting product is [[leaching (metallurgy)|leached]] with water to yield a {{chem|Cs|2|SO|4}} solution.<ref name="USGS"/>

Roasting pollucite with [[calcium carbonate]] and [[calcium chloride]] yields insoluble calcium silicates and soluble caesium chloride. Leaching with water or dilute [[ammonia]] ({{chem|NH|4|OH}}) yields a dilute chloride (CsCl) solution. This solution can be evaporated to produce caesium chloride or transformed into caesium alum or caesium carbonate. Though not commercially feasible, the ore can be directly reduced with potassium, sodium, or calcium in vacuum to produce caesium metal directly.<ref name="USGS"/>

Most of the mined caesium (as salts) is directly converted into [[formate|caesium formate]] (HCOO<sup>−</sup>Cs<sup>+</sup>) for applications such as [[oil drilling]]. To supply the developing market, [[Cabot Corporation]] built a production plant in 1997 at the [[Tanco mine]] near [[Bernic Lake]] in [[Manitoba]], with a capacity of {{convert|12000|oilbbl|m3}} per year of caesium formate solution.<ref>{{cite journal |last1=Benton |first1=William |last2=Turner |first2=Jim |date=2000 |title=Cesium formate fluid succeeds in North Sea HPHT field trials |journal=Drilling Contractor |issue=May/June |pages=38–41 |url=http://www.iadc.org/dcpi/dc-mayjun00/m-cabot.pdf |archive-url=https://web.archive.org/web/20010706223144/http://www.iadc.org/dcpi/dc-mayjun00/m-cabot.pdf |archive-date=2001-07-06 |url-status=live |access-date=26 September 2010}}</ref> The primary smaller-scale commercial compounds of caesium are [[caesium chloride]] and [[caesium nitrate|nitrate]].<ref name="CEC"/>

Alternatively, caesium metal may be obtained from the purified compounds derived from the ore. [[Caesium chloride]] and the other caesium halides can be reduced at {{convert|700|to|800|°C|°F}} with calcium or [[barium]], and caesium metal distilled from the result. In the same way, the aluminate, carbonate, or hydroxide may be reduced by [[magnesium]].<ref name="USGS"/>

The metal can also be isolated by [[electrolysis]] of fused caesium [[cyanide]] (CsCN). Exceptionally pure and gas-free caesium can be produced by {{convert|390|°C}} thermal decomposition of caesium [[azide]] {{chem|CsN|3}}, which can be produced from aqueous [[caesium sulfate]] and [[barium azide]].<ref name="Burt"/> In vacuum applications, caesium [[dichromate]] can be reacted with [[zirconium]] to produce pure caesium metal without other gaseous products.<ref name="CEC">{{cite book |isbn=978-3-11-011451-5 |url=https://books.google.com/books?id=Owuv-c9L_IMC&pg=PA198 |page=198 |others=Eagleson, Mary |editor=Eagleson, Mary |year=1994 |publisher=de Gruyter |location=Berlin |title=Concise encyclopedia chemistry |access-date=8 May 2021 |archive-date=5 March 2024 |archive-url=https://web.archive.org/web/20240305132905/https://books.google.com/books?id=Owuv-c9L_IMC&pg=PA198 |url-status=live }}</ref>
:{{chem|Cs|2|Cr|2|O|7}} + 2 {{chem|Zr}} → 2 {{chem|Cs}} + 2 {{chem|ZrO|2}}+ {{chem|Cr|2|O|3}}

The price of 99.8% pure caesium (metal basis) in 2009 was about {{convert|10|$/g|$/oz|-1}}, but the compounds are significantly cheaper.<ref name="USGS-Cs2"/>