A cyanide is essentially any chemical compound that contains monovalent combining group CN (which is also their chemical formula). This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom.
In inorganic cyanides, such as sodium cyanide and potassium cyanide this group is present as the negatively charged polyatomic cyanide ion (CN−); these compounds, which are regarded as salts of hydrocyanic acid, are highly toxic. The cyanide ion is isoelectronic with carbon monoxide and with molecular nitrogen.
Organic cyanides are usually called nitriles; in these, the CN group is linked by a covalent bond to a carbon-containing group, such as methyl (CH3) in methyl cyanide (acetonitrile). Because they do not release cyanide ions, nitriles are generally less toxic, or in the case of insoluble polymers such as acrylic fiber, essentially nontoxic unless burned.
Hydrocyanic acid, also known as hydrogen cyanide, or HCN, is a highly volatile liquid used to produce acrylonitrile, which is used in the production of acrylic fibers, synthetic rubber, and plastics. Cyanides are employed in a number of chemical processes, including fumigation, case hardening of iron and steel, electroplating, and the concentration of ores. In nature, substances yielding cyanide are present in certain seeds, such as the pit of the cherry and apple seeds.
This agent was used during the events of Syphon Filter: Dark Mirror.
During the Red Section assault on KemSynth Petroleum, Malcolm Freeman, the facility foreman, committed suicide with a cyanide overdose rather than submit to interrogation concerning Project Dark Mirror, thus ensuring the absolute security of information about the activities in the petroleum facility, before the Red Section paramilitary members or IPCA personnel could ask him anything.
When he investigated a United Nations attack on the Tuzla Munitions facility, Gabe Logan found a Zivmovic Prijateljstvo thug who also administered a cyanide capsule to himself. Logan reasoned that Zivmovic used extreme standards of discipline and loyalty to have his men stay under his control. They were under explicit orders not to be captured and questioned, but rather to end their lives, should they come under imminent capture. Gabe suspected this had nothing to do whatsoever with information since ZP was a second-rate separatist organisation; as such, this was thought to be more of paranoia than anything else. Gabe, therefore, believed Zivmovic to be a kind of man who 'should never be allowed to come to power'.