Hydrogen Cyanide

Title: Hydrogen Cyanide
CAS Registry Number: 74-90-8
CAS Name: Hydrocyanic acid
Additional Names: prussic acid
Molecular Formula: CHN
Molecular Weight: 27.03
Percent Composition: C 44.43%, H 3.73%, N 51.82%
Line Formula: HCN
Literature References: Prepd on a large scale by the catalytic oxidation of ammonia-methane mixtures (Andrussow Process): see Andrussow, Angew. Chem. 48, 593 (1935); Maffezzoni, Chim. Ind. (Milan) 34, 460 (1952); Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Ed. (Wiley-Interscience, New York, 4th ed., 1975) pp 482-486. Prepd in the lab by acidifying NaCN or K4[Fe(CN)6]: Glemser in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 658-660. Review of toxicology and human exposure: Toxicological Profile for Cyanide (PB98-101207, 1997) 291 pp.
Properties: Colorless gas or liquid; characteristic odor. Burns in air with a blue flame. Flammable. Intensely poisonous even when mixed with air. Must be handled by specially trained experts. mp -13.4°. bp 25.6°. d(gas) 0.941 (air = 1); d(liq) 0.687. Very weakly acid (does not redden litmus). Miscible with water, alc; slightly sol in ether. LC50 in rats, mice, dogs: 544 ppm (5 min), 169 ppm (30 min), 300 ppm (3 min) by inhalation, K. C. Back et al., Reclassification of Materials Listed as Transportation Health Hazards (TSA-20-72-3; PB214-270, 1972).
Melting point: mp -13.4°
Boiling point: bp 25.6°
Density: d(gas) 0.941 (air = 1); d(liq) 0.687
Toxicity data: LC50 in rats, mice, dogs: 544 ppm (5 min), 169 ppm (30 min), 300 ppm (3 min) by inhalation, K. C. Back et al., Reclassification of Materials Listed as Transportation Health Hazards (TSA-20-72-3; PB214-270, 1972)
CAUTION: Potential symptoms of acute overexposure are asphyxia; lassitude, headache, confusion; nausea, vomiting; increased rate and depth of respiration, or slow and gasping respiration. See NIOSH Pocket Guide to Chemical Hazards (PB2003-100121, 2003) p 168; Patty's Industrial Hygiene and Toxicology vol. 2D, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, NewYork, 4th ed., 1994) pp 3119-3127.
Use: Compressed gas as rodenticide, and insect fumigant.
Hydrogen Fluoride Hydrogen Iodide Hydrogen Selenide Hydrogen Sulfide Hydrogen Telluride

Hydrogen cyanide
Hydrogen-cyanide-2D.svg
Ball and stick model of hydrogen cyanide Spacefill model of hydrogen cyanide
Identifiers
CAS number 74-90-8 YesY
PubChem 768
ChemSpider 748 N
UNII 2WTB3V159F YesY
EC number 200-821-6
UN number 1051
KEGG C01326 N
MeSH Hydrogen+Cyanide
ChEBI CHEBI:18407 N
RTECS number MW6825000
3DMet B00275
Jmol-3D images Image 1
Properties
Molecular formula CHN
Molar mass 27.03 g mol−1
Appearance Very pale, blue, transparent liquid or colorless gas
Odor Oil of bitter almond
Density 0.687 g mL−1
Melting point −14 to −12 °C; 7 to 10 °F; 259 to 261 K
Boiling point 25.6 to 26.6 °C; 78.0 to 79.8 °F; 298.7 to 299.7 K
Solubility in water Miscible
Solubility in ethanol Miscible
kH 75 μmol Pa−1 kg−1
Acidity (pKa) 9.21[3]
Basicity (pKb) 4.79
Refractive index (nD) 1.2675 [4]
Viscosity 201 μPa s
Structure
Molecular shape Linear
Dipole moment 2.98 D
Thermochemistry
Specific
heat capacity C
71.00 kJ K−1 mol−1 (at 27 °C)[5]
Std molar
entropy So298
113.01 J K−1 mol−1
Std enthalpy of
formation ΔfHo298
109.9 kJ mol−1
Std enthalpy of
combustion ΔcHo298
-426.5 kJ mol−1
Hazards
EU Index 006-006-00-X
EU classification Flammable F+ Very Toxic T+ Dangerous for the Environment (Nature) N
R-phrases R12, R26/27/28, R50/53
S-phrases (S1/2), S16, S36/37, S38, S45, S53, S59, S61
NFPA 704
NFPA 704.svg
4
4
1
Flash point −17.8 °C; 0.0 °F; 255.3 K
Autoignition temperature 538 °C; 1,000 °F; 811 K
Related compounds
Related alkanenitriles
  • Hydrogen isocyanide
  • Isocyanic acid
  • Thiocyanic acid
  • Cyanogen iodide
  • Cyanogen bromide
  • Cyanogen chloride
  • Cyanogen fluoride
  • Acetonitrile
  • Aminoacetonitrile
  • Glycolonitrile
  • Cyanogen
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Hydrogen cyanide (HCN), sometimes called prussic acid, is an inorganic compound[6] with chemical formula HCN. It is a colorless, extremely poisonous liquid that boils slightly above room temperature, at 25.6 °C (78.1 °F).[7] HCN is produced on an industrial scale and is a highly valuable precursor to many chemical compounds ranging from polymers to pharmaceuticals.