Hydrogen cyanide

Hydrogen cyanide (HCN), whiles cried prussic acid, is an organic compoond[8] wi the chemical formula HCN. It is a colourless, extremely poisonous an flammable liquid that byls slichtly abuin ruim temperatur, at 25.6 °C (78.1 °F).[9] HCN is produced on an industrial scale an is a heichly valuable precursor tae mony chemical compoonds rangin frae polymers tae pharmaceuticals.

Hydrogen cyanide
Baw an stick model o hydrogen cyanide
Spacefill model of hydrogen cyanide
IUPAC name
  • Formonitrile[1] (substitutive)
  • Hydridonitridocarbon[2] (additive)
Ither names
  • Formic anammonide
  • Hydrocyanic acid
  • Prussic acid
  • Methanenitrile
3D model (JSmol)
3DMet B00275
ECHA InfoCard 100.000.747
EC Nummer 200-821-6
MeSH Hydrogen+Cyanide
RTECS nummer MW6825000
UN nummer 1051
Appearance Very pale, blue, transparent liquid or colourless gas
Odour Ile o bitter almond
Density 0.687 g mL−1
Meltin pynt −14 tae −12 °C; 7 tae 10 °F; 259 tae 261 K
Bylin pynt 25.6 tae 26.6 °C; 78.0 tae 79.8 °F; 298.7 tae 299.7 K
Solubility in ethanol Miscible
Vapour pressur 630 mmHg (20 °C)[3]
kH 75 μmol Pa−1 kg−1
Acidity (pKa) 9.21[4]
Basicity (pKb) 4.79
Refractive index (nD) 1.2675 [5]
Viscosity 201 μPa s
Pynt group C∞v
Molecular shape Linear
2.98 D
Speceefic heat capacity, C 71.00 kJ K−1 mol−1 (at 27 °C)[6]
Staundart molar
113.01 J K−1 mol−1
Std enthalpy o
109.9 kJ mol−1
Std enthalpy o
-426.5 kJ mol−1
GHS pictograms The flame pictogram in the Globally Harmonized Seestem o Classification an Labelling o Chemicals (GHS) The skull-an-crossbones pictogram in the Globally Harmonized Seestem o Classification an Labellin o Chemicals (GHS) The exclamation-mark pictogram in the Globally Harmonized Seestem o Classification an Labellin of Chemicals (GHS)
GHS signal wird DANGER
GHS hazard statements H225, H319, H336
GHS precautionary statements P210, P261, P305+351+338
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressur an temperatur, or is readily dispersed in air an will burn readily. Flash pynt ablo 23 °C (73 °F). E.g., propaneHealth code 4: Very short exposur could cause daith or major residual injury. E.g., VX gasReactivity code 2: Unnergangs violent chemical chynge at elevatit temperatures an pressurs, reacts violently wi water, or mey form explosive mixturs wi watter. E.g., phosphorusSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash pynt −17.8 °C (0.0 °F; 255.3 K)
538 °C (1,000 °F; 811 K)
Explosive leemits 5.6% – 40.0%[3]
Lethal dose or concentration (LD, LC):
501 ppm (rat, 5 min)
323 ppm (moose, 5 min)
275 ppm (rat, 15 min)
170 ppm (rat, 30 min)
160 ppm (rat, 30 min)
323 ppm (rat, 5 min)[7]
200 ppm (mammal, 5 min)
36 ppm (mammal, 2 hr)
107 ppm (human, 10 min)
759 ppm (rabbit, 1 min)
759 ppm (cat, 1 min)
357 ppm (human, 2 min)
179 ppm (human, 1 hr)[7]
US heal exposur leemits (NIOSH):
PEL (Permissible)
TWA 10 ppm (11 mg/m3) [skin][3]
REL (Recommendit)
ST 4.7 ppm (5 mg/m3) [skin][3]
IDLH (Immediate danger)
50 ppm[3]
Relatit compoonds
Relatit alkanenitriles
Except whaur itherwise notit, data are gien for materials in thair staundart state (at 25 °C [77 °F], 100 kPa).
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Infobox references


  1. "Hydrogen Cyanide – Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification. Retrieved 2012-06-04.
  2. "hydrogen cyanide (CHEBI:18407)". Chemical Entities of Biological Interest. UK: European Bioinformatics Institute. 18 October 2009. Main. Retrieved 2012-06-04.
  3. 3.0 3.1 3.2 3.3 3.4 NIOSH Pocket Guide tae Chemical Hazards 0333
  4. Perrin, D. D. (1982). Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution (2nd ed.). Oxford: Pergamon Press.
  5. Patnaik, P. (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8.
  6. "Hydrogen cyanide". NIST Chemistry WebBook.
  7. 7.0 7.1 "Hydrogen cyanide". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
  8. Gail, E.; Gos, S.; Kulzer, R.; Lorösch, J.; Rubo, A.; Sauer, M. (2005), "Cyano Compounds, Inorganic", Ullmann's Encyclopedia o Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a08_159.pub2CS1 maint: multiple names: authors leet (link)
  9. "Wolfram-Alpha: Computational Knowledge Engine".