El '''cianuro de hidrógeno''' [HCN(g)] o '''ácido cianhídrico''' [HCN(ac)], '''ácido prúsico''', '''metanonitrilo''' o '''formonitrilo''' es un [[compuesto químico]] cuya fórmula es: [[Hidrógeno|H]][[Carbono|C]][[Nitrógeno|N]]. La disolución de cianuro de hidrógeno en [[agua]] es llamada ácido cianhídrico. El cianuro de hidrógeno puro es un líquido incoloro, muy [[veneno]]so y altamente volátil, que hierve a los 26°C. Tiene un ligero olor a [[Almendra (fruto)|almendras]] amargas, que algunas personas no pueden detectar debido a un rasgo [[gen]]ético. El cianuro de hidrógeno es ligeramente [[ácido]]. Sus [[sal (química)|sales]] son conocidas como [[cianuro]]s.
== Historia del descubrimiento ==
Hydrogen cyanide was first isolated from a blue dye ([[Prussian blue]]) which had been known from 1704 but had a structure which was unknown. It is now known to be a [[coordination polymer]] with a complex structure and an empirical formula of hydrated ferric ferrocyanide. In 1752, the French chemist [[Pierre Macquer]] made the important step of showing that Prussian blue could be converted to [[iron oxide]] plus a volatile component and that these could be used to reconstitute the dye. The new component was what we now know as hydrogen cyanide. Following Macquer's lead, it was first isolated from Prussian blue in pure form and characterized about 1783 by the Swedish chemist [[Carl Wilhelm Scheele]], and was eventually given the German name ''Blausäure'' (literalmente "ácido azul") because of its acidic nature in water and its derivation from Prussian blue. In English it became known popularly as ''ácido prúsico.''
[[File:HexacyanidoferratIII 2.svg|thumb|center|220px|Anión del [[azul de prusia]]]]
En 1787 el químico francés [[Claude Louis Berthollet]] showed that Prussic acid did not contain oxygen, an important contribution to acid theory, which had hitherto postulated that acids must contain oxygen<ref>{{cite web|url= http://www.allbusiness.com/north-america/canada/370855-1.html |title= Claude Louis Berthollet: A Great Chemist in +he french Tradition. |author= Brian T Newbold |date=1999-11-01 |publisher=Canadian Chemical News |accessdate=2010-03-31}}</ref> (hence the name of [[oxygen]] itself, which is derived from Greek elements that mean "acid-former" and are likewise [[calque]]d into German as ''Sauerstoff''). In 1815 [[Joseph Louis Gay-Lussac]] deduced Prussic acid's chemical formula. The radical cyanide in hydrogen cyanide was given its name from the Greek word for blue, again due to its derivation from Prussian blue.
