Hydrogen cyanide

Athanor · official

CHN · 27.025 g/mol

IUPAC name: formonitrile

Also called prussic acid, hydrocyanic acid, HCN

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

DangerExtremely flammable liquid and vapor · Fatal if inhaled · Very toxic to aquatic life · Very toxic to aquatic life with long lasting effects

Names and identifiers

IUPAC name: formonitrile
Synonyms: prussic acid, hydrocyanic acid, HCN
+ 36 more
Formonitrile, Prussic acid, Blausaeure, Cyanwasserstoff, Formic anammonide, Cyclon, Evercyn, Zyklon B, Zaclondiscoids, Cyclone B, Aero Liquid HCN, Agent AC, Cyaanwaterstof, Blauwzuur, Cyjanowodor, Acido cianidrico, Acide cyanhydrique, methanenitrile, RCRA waste number P063, Carbon hydride nitride (CHN), Acid, Hydrocyanic, hydridonitridocarbon, hydrogen(nitridocarbonate), EPA Pesticide Chemical Code 045801, 2WTB3V159F, DTXSID9024148, HYDROCYANICUM ACIDUM, CHEBI:18407, Cyanide, Hydrogen, RefChem:6445, DTXCID004148, hydridonitridocarbon;hydrogen(nitridocarbonate);methanenitrile, 200-821-6, Graphitic Carbon Nitride, Hydrogen cyanide [ISO], Blausaeure [German]
Molecular formula: CHN
Empirical formula: CHN
Molecular weight: 27.025 g/mol
Exact mass: 27.01090
CAS number: 74-90-8
PubChem CID: 768
Canonical SMILES: C#N
Isomeric SMILES: C#N
InChI: InChI=1S/CHN/c1-2/h1H
InChIKey: LELOWRISYMNNSU-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Water-white liquid below 26.5 °C[6]
11 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Hydrocyanic acid, aqueous solution, with not more than 20% hydrogen cyanide is a clear colorless aqueous solution of a gas. Has a faint odor of almonds. Can evolve hydrogen cyanide gas, which is (barely) lighter than air. Flame can flash back to the source of a gas leak very easily. Lethal doses of gas may be inhaled. Lethal doses of cyanide can be absorbed from the solution through the skin. [1] CAMEO Chemicals
– Hydrocyanic acid, aqueous solutions, with more than 20% hydrogen cyanide is a clear colorless aqueous solution of a gas. Has an odor of almonds. Can evolve hydrogen cyanide gas, which is (barely) lighter than air. Flame can flash back to the source of a gas leak very easily. Lethal doses of gas may be inhaled. Lethal doses of cyanide can be absorbed from the solution through the skin. [1] CAMEO Chemicals
– Hydrogen cyanide, anhydrous, stabilized appears as a chemical warfare blood agent. A deadly human poison by all routes. Very volatile. Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor. Often used as a 96% solution in water. (NIOSH, 2024) [1] CAMEO Chemicals
– Hydrogen cyanide, anhydrous, stabilized (absorbed) appears as a clear colorless liquid with a faint odor of bitter almonds that is absorbed in a porous inert material. Absorption slows evolution of vapors. Vapors slightly lighter than air. Deadly poison by all routes (absorption through skin of liquid, inhalation of vapors, etc). Prolonged exposure of closed containers to heat may cause violent rupture and rocketing. Rate of onset: Immediate Persistence: Minutes Odor threshold: 1-5 ppm Source/use/other hazard: War gas, pesticide, Herbicide; other industries; Weak acid except in water or m [1] CAMEO Chemicals
– Liquid; Gas Vapor; Liquid; Gas Vapor [2] EPA Chemical Data Reporting (CDR)
– COLOURLESS GAS OR LIQUID WITH CHARACTERISTIC ODOUR. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor. [4] Occupational Safety and Health Administration (OSHA)
– Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor. [Note: Often used as a 96% solution in water.] [5] The National Institute for Occupational Safety and Health (NIOSH)
– Colorless or pale blue liquid below 78°F (25.6°C), colorless gas above 78°F (25.6°C). [5] The National Institute for Occupational Safety and Health (NIOSH)
–shown Water-white liquid below 26.5 °C [6] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 732
– Colorless or pale-blue liquid or gas (above 78 °F) ... [Note: Often used as a 96% solution in water] [6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg
Odor: Bitter almond odor[6]
2 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
–shown Bitter almond odor [6] Hazardous Substances Data Bank (HSDB)cites NOAA; CAMEO Chemicals. Database of Hazardous Materials. Hydrogen cyanide (74-90-8). Natl Ocean Atmos Admin, Off Resp Rest; NOAA Ocean Serv. Available from, as of Dec 20, 2017: https://cameochemicals.noaa.gov/
– ... Bitter, almond-like odor. [6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg
Melting point: -13.29 °C[7]
6 values
5 of 5 sources agree on it (most common value).
Value As written Source
−14 °C 7 °F (96%) (NIOSH, 2024) [1] CAMEO Chemicals
−14 °C 7 °F (96%) (NIOSH, 2024) [1] CAMEO Chemicals
−13 °C -13 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−14 °C 7 °F (96%) [4] Occupational Safety and Health Administration (OSHA)
−13.3 °Cshown -13.29 °C [7] PAC Chemical Database, U.S. Department of Energy
−14 °C 7 °F (96%) [5] The National Institute for Occupational Safety and Health (NIOSH)
Boiling point: 26 °C[3]
6 values
5 of 5 sources agree on it (most common value).
Value As written Source
26 °C 78 °F at 760 mmHg (96%) (NIOSH, 2024) [1] CAMEO Chemicals
26 °C 78 °F at 760 mmHg (96%) (NIOSH, 2024) [1] CAMEO Chemicals
26 °Cshown 26 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
26 °C 78 °F (96%) [4] Occupational Safety and Health Administration (OSHA)
26 °C 26 °C @760 [mm Hg] [7] PAC Chemical Database, U.S. Department of Energy
26 °C 78 °F (96%) [5] The National Institute for Occupational Safety and Health (NIOSH)
Density: 0.6876 @ 20°C[7]
6 values
5 of 5 sources agree on it (most common value).
Value As written Source
– 0.69 (NIOSH, 2024) - Less dense than water [1] CAMEO Chemicals
– 0.69 (NIOSH, 2024) - Less dense than water [1] CAMEO Chemicals
– Relative density (water = 1): 0.69 (liquid) [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– 0.69 [4] Occupational Safety and Health Administration (OSHA)
–shown 0.6876 @ 20°C [7] PAC Chemical Database, U.S. Department of Energy
– 0.69 [5] The National Institute for Occupational Safety and Health (NIOSH)
Solubility in water: Solubility in water: miscible[3]
5 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– Miscible (NIOSH, 2024) [1] CAMEO Chemicals
– Miscible (NIOSH, 2024) [1] CAMEO Chemicals
– Miscible with water [6] Hazardous Substances Data Bank (HSDB)cites Metcalf RL; Insect Control Technology. Kirk-Othmer Encyl Chem Technol 3rd ed. New York NY: John Wiley & Sons V13: 467 (1978)
–shown Solubility in water: miscible [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Miscible [5] The National Institute for Occupational Safety and Health (NIOSH)
log P: -0.25[3]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
– log Kow = -0.25 [6] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 3
–shown -0.25 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
pKa: pKa = 9.2[6]
Vapor pressure: 742 mmHg at 25 °C[6]
3 values
2 of 3 sources agree on it (most common value).
Value As written Source
742 mmHgshown 742 mm Hg at 25 °C [6] Hazardous Substances Data Bank (HSDB)cites Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.
620 mmHg Vapor pressure, kPa at 20 °C: 82.6 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
750 mmHg 750 [mm Hg] @25.4 °C [7] PAC Chemical Database, U.S. Department of Energy
4 more values were reported but failed the checks (unreadable or out of range), so they are not shown.
Flash point: -18 °C c.c.[3]
6 values
5 of 5 sources agree on it (most common value).
Value As written Source
−18 °C 0 °F (96%) (NIOSH, 2024) [1] CAMEO Chemicals
−18 °C 0 °F (96%) (NIOSH, 2024) [1] CAMEO Chemicals
−18 °C 0 °F (-18 °C) (Closed cup) [6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-72
−18 °Cshown -18 °C c.c. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−18 °C 0 °F (96%) [4] Occupational Safety and Health Administration (OSHA)
−18 °C 0 °F (96%) [5] The National Institute for Occupational Safety and Health (NIOSH)
Autoignition temperature: 538 °C (1000 °F)[6]
3 values
2 of 3 sources agree on it (most common value).
Value As written Source
540 °C 1004 °F (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
538 °Cshown 1000 °F (538 °C) [6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-72
538 °C 538 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
–	Hydrocyanic acid, aqueous solution, with not more than 20% hydrogen cyanide is a clear colorless aqueous solution of a gas. Has a faint odor of almonds. Can evolve hydrogen cyanide gas, which is (barely) lighter than air. Flame can flash back to the source of a gas leak very easily. Lethal doses of gas may be inhaled. Lethal doses of cyanide can be absorbed from the solution through the skin.	[1] CAMEO Chemicals
–	Hydrocyanic acid, aqueous solutions, with more than 20% hydrogen cyanide is a clear colorless aqueous solution of a gas. Has an odor of almonds. Can evolve hydrogen cyanide gas, which is (barely) lighter than air. Flame can flash back to the source of a gas leak very easily. Lethal doses of gas may be inhaled. Lethal doses of cyanide can be absorbed from the solution through the skin.	[1] CAMEO Chemicals
–	Hydrogen cyanide, anhydrous, stabilized appears as a chemical warfare blood agent. A deadly human poison by all routes. Very volatile. Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor. Often used as a 96% solution in water. (NIOSH, 2024)	[1] CAMEO Chemicals
–	Hydrogen cyanide, anhydrous, stabilized (absorbed) appears as a clear colorless liquid with a faint odor of bitter almonds that is absorbed in a porous inert material. Absorption slows evolution of vapors. Vapors slightly lighter than air. Deadly poison by all routes (absorption through skin of liquid, inhalation of vapors, etc). Prolonged exposure of closed containers to heat may cause violent rupture and rocketing. Rate of onset: Immediate Persistence: Minutes Odor threshold: 1-5 ppm Source/use/other hazard: War gas, pesticide, Herbicide; other industries; Weak acid except in water or m	[1] CAMEO Chemicals
–	Liquid; Gas Vapor; Liquid; Gas Vapor	[2] EPA Chemical Data Reporting (CDR)
–	COLOURLESS GAS OR LIQUID WITH CHARACTERISTIC ODOUR.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor.	[4] Occupational Safety and Health Administration (OSHA)
–	Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor. [Note: Often used as a 96% solution in water.]	[5] The National Institute for Occupational Safety and Health (NIOSH)
–	Colorless or pale blue liquid below 78°F (25.6°C), colorless gas above 78°F (25.6°C).	[5] The National Institute for Occupational Safety and Health (NIOSH)
–shown	Water-white liquid below 26.5 °C	[6] Hazardous Substances Data Bank (HSDB)cites Larranaga, M.D., Lewis, R.J. Sr., Lewis, R.A.; Hawley's Condensed Chemical Dictionary 16th Edition. John Wiley & Sons, Inc. Hoboken, NJ 2016., p. 732
–	Colorless or pale-blue liquid or gas (above 78 °F) ... [Note: Often used as a 96% solution in water]	[6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg

Value	As written	Source
–shown	Bitter almond odor	[6] Hazardous Substances Data Bank (HSDB)cites NOAA; CAMEO Chemicals. Database of Hazardous Materials. Hydrogen cyanide (74-90-8). Natl Ocean Atmos Admin, Off Resp Rest; NOAA Ocean Serv. Available from, as of Dec 20, 2017: https://cameochemicals.noaa.gov/
–	... Bitter, almond-like odor.	[6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Control & Prevention. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from: https://www.cdc.gov/niosh/npg

Value	As written	Source
−14 °C	7 °F (96%) (NIOSH, 2024)	[1] CAMEO Chemicals
−14 °C	7 °F (96%) (NIOSH, 2024)	[1] CAMEO Chemicals
−13 °C	-13 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−14 °C	7 °F (96%)	[4] Occupational Safety and Health Administration (OSHA)
−13.3 °Cshown	-13.29 °C	[7] PAC Chemical Database, U.S. Department of Energy
−14 °C	7 °F (96%)	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
26 °C	78 °F at 760 mmHg (96%) (NIOSH, 2024)	[1] CAMEO Chemicals
26 °C	78 °F at 760 mmHg (96%) (NIOSH, 2024)	[1] CAMEO Chemicals
26 °Cshown	26 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
26 °C	78 °F (96%)	[4] Occupational Safety and Health Administration (OSHA)
26 °C	26 °C @760 [mm Hg]	[7] PAC Chemical Database, U.S. Department of Energy
26 °C	78 °F (96%)	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	0.69 (NIOSH, 2024) - Less dense than water	[1] CAMEO Chemicals
–	0.69 (NIOSH, 2024) - Less dense than water	[1] CAMEO Chemicals
–	Relative density (water = 1): 0.69 (liquid)	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	0.69	[4] Occupational Safety and Health Administration (OSHA)
–shown	0.6876 @ 20°C	[7] PAC Chemical Database, U.S. Department of Energy
–	0.69	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	Miscible (NIOSH, 2024)	[1] CAMEO Chemicals
–	Miscible (NIOSH, 2024)	[1] CAMEO Chemicals
–	Miscible with water	[6] Hazardous Substances Data Bank (HSDB)cites Metcalf RL; Insect Control Technology. Kirk-Othmer Encyl Chem Technol 3rd ed. New York NY: John Wiley & Sons V13: 467 (1978)
–shown	Solubility in water: miscible	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Miscible	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	log Kow = -0.25	[6] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 3
–shown	-0.25	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
742 mmHgshown	742 mm Hg at 25 °C	[6] Hazardous Substances Data Bank (HSDB)cites Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.
620 mmHg	Vapor pressure, kPa at 20 °C: 82.6	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
750 mmHg	750 [mm Hg] @25.4 °C	[7] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
−18 °C	0 °F (96%) (NIOSH, 2024)	[1] CAMEO Chemicals
−18 °C	0 °F (96%) (NIOSH, 2024)	[1] CAMEO Chemicals
−18 °C	0 °F (-18 °C) (Closed cup)	[6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-72
−18 °Cshown	-18 °C c.c.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−18 °C	0 °F (96%)	[4] Occupational Safety and Health Administration (OSHA)
−18 °C	0 °F (96%)	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
540 °C	1004 °F (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
538 °Cshown	1000 °F (538 °C)	[6] Hazardous Substances Data Bank (HSDB)cites National Fire Protection Association; Fire Protection Guide to Hazardous Materials. 14TH Edition, Quincy, MA 2010, p. 325-72
538 °C	538 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 2
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0
H-bond acceptors: 1
Rotatable bonds: 0
TPSA (Å²): 23.8
Formal charge: 0
XLogP3: 0.1 PubChem
Complexity: 10 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C∞v of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C44.44%
H3.73%
N51.83%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 0.14 Crippen (Wildman and Crippen 1999)
log S (water solubility): -0.1 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 4.03 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 27.03
log P ≤ 5 (Crippen): 0.14
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 1

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Harmonized EU classification (CLP Annex VI). Source [8].

Flammable
Acute toxicity
Environmental hazard

NFPA 704[6]

H224Extremely flammable liquid and vapor
H330Fatal if inhaled
H400Very toxic to aquatic life
H410Very toxic to aquatic life with long lasting effects

Precautionary statements: P210, P233, P240, P241, P242, P243, P260, P271, P273, P280, P284, P303+P361+P353, P304+P340, P316, P320, P370+P378, P391, P403+P233, P403+P235, P405, P501

View all classifications (3)

[8] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH224, H330, H400, H410
[8] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH300, H310, H330, H400, H410
[9] European Chemicals Agency (ECHA) · 344 reports · DangerH224, H300+H310+H330, H300, H310, H330, H372, H400, H410

Exposure limits

PEL-TWA (8-Hour Time Weighted Average): 10 ppm (11 mg/m³)[4]
PEL: TWA 10 ppm (11 mg/m3) [skin] See Appendix G[5]
REL-STEL (Short Term Exposure Limit): 4.7 ppm (5 mg/m³)[4]
REL: ST 4.7 ppm (5 mg/m3) [skin][5]
TLV: (ceiling value): 4.7 ppm as STEL; (skin).[3]
TLV-C (Ceiling): 4.7 ppm [1991][4]

First aid

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]: Refer to the "General First Aid" section. Specific First Aid: For corrosives, in case of contact, immediately flush skin or eyes with running water for at least 30 minutes. Additional flushing may be required. (ERG, 2024)[1]
Excerpt from ERG Guide 117 [Gases - Toxic - Flammable (Extreme Hazard); polymerization hazard]: Refer to the "General First Aid" section. Specific First Aid: In case of contact with liquefied gas, only medical personnel should attempt thawing frosted parts. In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin. (ERG, 2024)[1]
For information on chemical warfare blood agents see the ERG Criminal or Terrorist Use of CBR Agents. (ERG, 2024) Warning: Hydrocyanic acid may be fatal if inhaled, swallowed, or absorbed through skin or mucous membranes. Caution is advised. Signs and Symptoms of Acute Hydrocyanic Acid Exposure: Signs and symptoms of acute exposure to hydrocyanic acid may include hypertension (high blood pressure) and tachycardia (rapid heart rate), followed by hypotension (low blood pressure) and bradycardia (slow heart rate). Cherry red mucous membranes and blood may be noted.[1]
Excerpt from NIOSH Pocket Guide for Hydrogen cyanide: Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Water flush immediately - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water.[1]

Storage

Store only if stabilized. Fireproof. Cool. Separated from food and feedstuffs and incompatible materials. See Chemical Dangers. Store in an area without drain or sewer access.[3]
Keep cylinders of hydrogen cyanide (HCN) cool and away from open flames. Make certain that HCN cylinders are adequately supported and grounded during storage and emptying. Store cylinders in a vertical position. Do not drop cylinders or damage them by impact. Cylinders must be returned to the supplier within 90 days of the filling date marked on the cylinders, regardless of whether or not the contents have been used. This is due to the possibility of HCN becoming unstable over time. If there is any indication that the HCN is becoming unstable, such as a darkening of the product or an increase[6]
Fireproof. Separated from food and feedstuffs. Cool. Store only if stabilized.[6]
Store in a cool, dry, well-ventilated location. Shelf life should not exceed 90 days or as otherwise specified by manufacturer.[6]

Incompatibilities

Preparation of alkyliminoformate chlorides by passing hydrogen chloride rapidly into alcoholic hydrogen cyanide proceeds explosively (probably owing to a sudden exotherm), even with strong cooling.[6]
Cyanogen halides may be prepared by electrolysis of hydrogen cyanide or its salts mixed with halide salts. If ammonium chloride is used as the halide salt, precautions to prevent formation of explosive nitrogen trichloride are necessary.[6]
Avoid addition of such alkaline chemicals as sodium hydroxide, ammonia, calcium hydroxide, and sodium carbonate to hydrogen cyanide since they promote polymerization and induce decomposition, which may cause an explosion. Also, avoid addition of large quantities of acid to hydrogen cyanide, for similar reasons.[6]
Severe explosion hazard when exposed to heat or flame or by chemical reaction with oxidizers.[6]

Always read the supplier’s safety data sheet before working with it.

Spectra

1H NMRHuman Metabolome Database (HMDB) (JEOL · 300 MHz · neat)
13C NMRHazardous Substances Data Bank (HSDB) · SpectraBase (Bruker WM-360)
15N NMRSpectraBase
GC-MSNIST Mass Spectrometry Data Center · SpectraBase
Other MSHazardous Substances Data Bank (HSDB)
IRHazardous Substances Data Bank (HSDB)

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]CAMEO Chemicals · Public domain (NOAA) · via PubChem · retrieved 2026-10-14
[2]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[4]Occupational Safety and Health Administration (OSHA) · Public domain (US DOL) · via PubChem · retrieved 2026-10-14
[5]The National Institute for Occupational Safety and Health (NIOSH) · Public domain (US CDC) · via PubChem · retrieved 2026-10-14
[6]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[7]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[8]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
[9]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[10]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[11]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[12]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[13]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.