Editing Cyanide (section)

==Applications==

===Mining===
{{Main|Gold cyanidation}}
Cyanide is mainly produced for the [[mining]] of [[silver]] and [[gold]]: It helps dissolve these metals allowing separation from the other solids. In the ''[[cyanide process]]'', finely ground high-grade ore is mixed with the cyanide (at a ratio of about 1:500 parts NaCN to ore); low-grade ores are stacked into heaps and sprayed with a cyanide solution (at a ratio of about 1:1000 parts NaCN to ore). The precious metals are complexed by the cyanide [[anion]]s to form soluble derivatives, e.g., {{chem2|[Ag(CN)2]-}} (dicyanoargentate(I)) and {{chem2|[Au(CN)2]-}} (dicyanoaurate(I)).<ref name=Ullmann>{{cite book|doi=10.1002/14356007.a08_159.pub3 |chapter=Cyano Compounds, Inorganic |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2011 |last1=Gail |first1=Ernst |last2=Gos |first2=Stephen |last3=Kulzer |first3=Rupprecht |last4=Lorösch |first4=Jürgen |last5=Rubo |first5=Andreas |last6=Sauer |first6=Manfred |last7=Kellens |first7=Raf |last8=Reddy |first8=Jay |last9=Steier |first9=Norbert |last10=Hasenpusch |first10=Wolfgang |isbn=978-3-527-30385-4 }}</ref> Silver is less [[Noble metal|"noble"]] than gold and often occurs as the sulfide, in which case redox is not invoked (no {{chem2|O2}} is required). Instead, a displacement reaction occurs:
:{{chem2|Ag2S + 4 NaCN + H2O → 2 Na[Ag(CN)2] + NaSH + NaOH}}
:{{chem2|4 Au + 8 NaCN + O2 + 2 H2O → 4 Na[Au(CN)2] + 4 NaOH}}
The "pregnant liquor" containing these ions is separated from the solids, which are discarded to a [[tailing pond]] or spent heap, the recoverable gold having been removed. The metal is recovered from the "pregnant solution" by reduction with [[zinc]] dust or by [[adsorption]] onto [[activated carbon]]. This process can result in environmental and health problems. A number of [[List of gold mining disasters|environmental disasters]] have followed the overflow of tailing ponds at gold mines. Cyanide contamination of waterways has resulted in numerous cases of human and aquatic species mortality.<ref>{{cite journal |last1=Kumar |first1=Rahul |last2=Saha |first2=Shouvik |last3=Sarita |first3=Dhaka |last4=Mayur B. |first4=Kurade |last5=Kang |first5=Chan Ung |last6=Baek |first6=Seung Han |last7=Jeong |first7=Byong-Hun |title=Remediation of cyanide-contaminated environments through microbes and plants: a review of current knowledge and future perspectives |journal=Geosystem Engineering |date=2016 |volume=70 |issue=1 |pages=28–40 |doi=10.1080/12269328.2016.1218303 |s2cid=132571397 |url=https://www.tandfonline.com/doi/full/10.1080/12269328.2016.1218303 |access-date=24 April 2022}}</ref>

Aqueous cyanide is hydrolyzed rapidly, especially in sunlight. It can mobilize some heavy metals such as mercury if present. Gold can also be associated with arsenopyrite (FeAsS), which is similar to [[iron pyrite]] (fool's gold), wherein half of the sulfur atoms are replaced by [[arsenic]]. Gold-containing arsenopyrite ores are similarly reactive toward inorganic cyanide.<ref>{{Cite journal |last1=Konyratbekova |first1=Saltanat Sabitovna |last2=Baikonurova |first2=Aliya |last3=Akcil |first3=Ata |date=2015-05-04 |title=Non-cyanide Leaching Processes in Gold Hydrometallurgy and Iodine-Iodide Applications: A Review |url=http://www.tandfonline.com/doi/abs/10.1080/08827508.2014.942813 |journal=Mineral Processing and Extractive Metallurgy Review |language=en |volume=36 |issue=3 |pages=198–212 |doi=10.1080/08827508.2014.942813 |bibcode=2015MPEMR..36..198K |issn=0882-7508}}</ref><ref>{{Cite journal |last1=Zhang |first1=Yan |last2=Cui |first2=Mingyao |last3=Wang |first3=Jianguo |last4=Liu |first4=Xiaoliang |last5=Lyu |first5=Xianjun |date=2022 |title=A review of gold extraction using alternatives to cyanide: Focus on current status and future prospects of the novel eco-friendly synthetic gold lixiviants |url=https://linkinghub.elsevier.com/retrieve/pii/S0892687521005653 |journal=Minerals Engineering |language=en |volume=176 |pages=107336 |doi=10.1016/j.mineng.2021.107336|bibcode=2022MiEng.17607336Z}}</ref>

===Industrial organic chemistry===
The second major application of alkali metal cyanides (after mining) is in the production of CN-containing compounds, usually nitriles. [[Acyl cyanide]]s are produced from acyl chlorides and cyanide. [[Cyanogen]], [[cyanogen chloride]], and the trimer [[cyanuric chloride]] are derived from alkali metal cyanides.

===Medical uses===
The cyanide compound [[sodium nitroprusside]] is used mainly in [[clinical chemistry]] to measure [[urine]] [[ketone bodies]] mainly as a follow-up to [[diabetic]] patients. On occasion, it is used in emergency medical situations to produce a rapid decrease in [[blood pressure]] in humans; it is also used as a [[vasodilator]] in vascular research. The cobalt in artificial [[Vitamin B12|vitamin B<sub>12</sub>]] contains a cyanide ligand as an artifact of the purification process; this must be removed by the body before the vitamin molecule can be activated for biochemical use. During [[World War I]], a copper cyanide compound was briefly used by [[Japan]]ese physicians for the treatment of [[tuberculosis]] and [[leprosy]].<ref>{{Cite journal|last=Takano |first=R. |date=August 1916 |title=The treatment of leprosy with cyanocuprol |journal=The Journal of Experimental Medicine |volume=24 |issue= 2|pages=207–211 |url=http://www.jem.org/cgi/content/abstract/24/2/207 |access-date=2008-06-28 |doi=10.1084/jem.24.2.207 |pmc=2125457 |pmid=19868035}}</ref>

===Illegal fishing and poaching===
{{Main|Cyanide fishing}}
Cyanides are illegally used to capture live fish near [[coral reef]]s for the [[aquarium]] and seafood markets. The practice is controversial, dangerous, and damaging but is driven by the lucrative exotic fish market.<ref name="crc">Dzombak, David A; Ghosh, Rajat S; Wong-Chong, George M. ''Cyanide in Water and Soil''. [[CRC Press]], 2006, Chapter 11.2: "Use of Cyanide for Capturing Live Reef Fish".</ref>

Poachers in Africa have been known to use cyanide to poison waterholes, to kill elephants for their ivory.<ref>[http://www.abc.net.au/news/2013-09-25/zimbabwe-poachers-kill-80-elephants-with-cyanide/4981372 Poachers kill 80 elephants with cyanide in Zimbabwe] ''ABC News'', 25 September 2013. Retrieved 30 October 2015.</ref>

===Pest control===
[[M44 (cyanide device)|M44 cyanide devices]] are used in the United States to kill [[coyote]]s and other canids.<ref>{{cite journal|doi=10.1002/wsb.361|title=Animal attendance at M-44 sodium cyanide ejector sites for coyotes|journal=Wildlife Society Bulletin|volume=38|pages=217–220|year=2014|last1=Shivik|first1=John A.|last2=Mastro|first2=Lauren|last3=Young|first3=Julie K. |issue=1 |bibcode=2014WSBu...38..217S |url=http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2419&context=icwdm_usdanwrc}}</ref> Cyanide is also used for pest control in [[New Zealand]], particularly for [[Common Brushtail Possum in New Zealand|possums]], an [[Invasive species in New Zealand|introduced marsupial that threatens the conservation of native species]] and spreads [[tuberculosis]] amongst cattle. Possums can become bait shy but the use of pellets containing the cyanide reduces bait shyness. Cyanide has been known to kill native birds, including the endangered [[Kiwi (bird)|kiwi]].<ref>{{cite web |last = Green| first = Wren |title =The use of 1080 for pest control |publisher = New Zealand Department of Conservation |date = July 2004 |url =http://www.doc.govt.nz/upload/documents/conservation/threats-and-impacts/animal-pests/use-of-1080-04.pdf| access-date = 8 June 2011}}</ref> Cyanide is also effective for controlling the [[dama wallaby]], another introduced marsupial pest in New Zealand.<ref>{{cite journal|last=Shapiro|first=Lee|date=21 March 2011|title=Effectiveness of cyanide pellets for control of dama wallabies (Macropus eugenii)|journal=New Zealand Journal of Ecology |volume=35 |issue=3 |url=http://newzealandecology.org/nzje/new_issues/NZJEcol35_3_287.pdf |archive-url=https://web.archive.org/web/20150203010818/http://newzealandecology.org/nzje/new_issues/NZJEcol35_3_287.pdf |archive-date=2015-02-03 |url-status=live |display-authors=etal}}</ref> A licence is required to store, handle and use cyanide in New Zealand.

Cyanides are used as [[insecticide]]s for fumigating ships.<ref>{{cite web|title=Sodium Cyanide|url=https://pubchem.ncbi.nlm.nih.gov/compound/sodium_cyanide|website=PubChem|publisher=National Center for Biotechnology Information|access-date=2 September 2016|date=2016|quote=Cyanide and hydrogen cyanide are used in electroplating, metallurgy, organic chemicals production, photographic developing, manufacture of plastics, fumigation of ships, and some mining processes.}}</ref> Cyanide salts are used for killing ants,<ref name="EPAReg1994">{{cite web|title=Reregistration Eligibility Decision (RED) Sodium Cyanide|url=https://archive.epa.gov/pesticides/reregistration/web/pdf/3086.pdf |archive-url=https://ghostarchive.org/archive/20221010/https://archive.epa.gov/pesticides/reregistration/web/pdf/3086.pdf |archive-date=2022-10-10 |url-status=live|website=EPA.gov|access-date=2 September 2016|page=7|date=1 September 1994|quote=Sodium cyanide was initially registered as a pesticide on December 23, 1947, to control ants on uncultivated agricultural and non-agricultural areas.}}</ref> and have in some places been used as rat poison<ref name="TariffInfo1921">{{cite web|title=Tariff Information, 1921: Hearings on General Tariff Revision Before the Committee on Ways and Means, House of Representatives|url=http://www.abebooks.com/servlet/SearchResults?tn=Tariff+Information,+1921|website=AbeBooks.com|publisher=US Congress, House Committee on Ways and Means, US Government Printing Office|access-date=2 September 2016|page=3987|date=1921|quote=Another field in which cyanide is used in growing quantity is the eradication of rats and other vermin – especially in the fight against typhus.}}</ref> (the less toxic poison [[arsenic]] is more common).<ref name="PlanetDeadly2013">{{cite web|title=Deadliest Poisons Used by Man|url=http://www.planetdeadly.com/human/deadliest-poisons-man|website=PlanetDeadly.com|access-date=2 September 2016|archive-url=https://web.archive.org/web/20160511033535/http://www.planetdeadly.com/human/deadliest-poisons-man|archive-date=11 May 2016|date=18 November 2013}}</ref>

===Niche uses===
[[Potassium ferrocyanide]] is used to achieve a blue color on cast [[bronze sculpture]]s during the final finishing stage of the sculpture. On its own, it will produce a very dark shade of blue and is often mixed with other chemicals to achieve the desired tint and hue. It is applied using a torch and paint brush while wearing the standard safety equipment used for any patina application: rubber gloves, safety glasses, and a respirator. The actual amount of cyanide in the mixture varies according to the recipes used by each foundry.

Cyanide is also used in [[jewelry]]-making and certain kinds of [[photography]] such as [[sepia toning]].

Although usually thought to be toxic, cyanide and cyanohydrins increase germination in various plant species.<ref>{{Cite journal|doi=10.1104/pp.52.1.23 |last1=Taylorson |first1=R. |last2=Hendricks |year=1973 |first2=SB |title=Promotion of Seed Germination by Cyanide |journal=Plant Physiol. |volume=52 |issue=1 |pages=23–27 |pmid=16658492 |pmc=366431}}</ref><ref>{{Cite journal|last1=Mullick |first1=P. |year=1967 |last2=Chatterji |first2=U. N. |title=Effect of sodium cyanide on germination of two leguminous seeds |journal=Plant Systematics and Evolution |volume=114 |issue=1 |pages=88–91|doi=10.1007/BF01373937|bibcode=1967PSyEv.114...88M |s2cid=2533762}}</ref>

====Human poisoning====
{{main|Cyanide poisoning}}
Deliberate cyanide poisoning of humans has occurred many times throughout history.<ref>{{Cite book
|title=Medical Management of Chemical Casualties Handbook
|edition=4th
|last1=Bernan
|publisher=Government Printing Off
|year=2008
|isbn=978-0-16-081320-7
|page=41
|url=https://books.google.com/books?id=oiw2ZzsBvsoC}}, [https://books.google.com/books?id=oiw2ZzsBvsoC&pg=PA41 Extract p. 41]
</ref>
Common salts such as [[sodium cyanide]] are involatile but water-soluble, so are poisonous by ingestion. [[Hydrogen cyanide]] is a gas, making it more indiscriminately dangerous, however it is lighter than air and rapidly disperses up into the atmosphere, which makes it ineffective as a [[chemical weapon]].

====Food additive====
Because of the high stability of their complexation with [[iron]], ferrocyanides ([[Sodium ferrocyanide]] E535, [[Potassium ferrocyanide]] E536, and Calcium ferrocyanide E538<ref>{{cite book
|title=Benders' dictionary of nutrition and food technology
|edition=7th
|first1=David A.
|last1=Bender
|first2=Arnold Eric
|last2=Bender
|publisher=Woodhead Publishing
|year=1997
|isbn=978-1-85573-475-3
|page=459
|url=https://books.google.com/books?id=IrYfDEl7XPYC}} [https://books.google.com/books?id=IrYfDEl7XPYC&pg=PA459 Extract of page 459]
</ref>) do not decompose to lethal levels in the human body and are used in the food industry as, e.g., an [[anticaking agent]] in [[table salt]].<ref>{{cite book
|title=Geochemical processes in soil and groundwater: measurement – modelling – upscaling
|first1=Horst D.
|last1=Schulz
|first2=Astrid
|last2=Hadeler
|author3=Deutsche Forschungsgemeinschaft
|publisher=Wiley-VCH
|year=2003
|isbn=978-3-527-27766-7
|page=67
|doi=10.1002/9783527609703
|url=http://onlinelibrary.wiley.com/doi/10.1002/9783527609703}}
</ref>