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Hydrogen cyanide

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Synonyms & Trade Names
Formonitrile, Hydrocyanic acid, Prussic acid
CAS No.
74-90-8
RTECS No.
MW6825000
DOT ID & Guide
1051 117(>20% solution)
1051 117(anhydrous)
1613 154(< or =20% solution)
Formula
HCN
Conversion
1 ppm = 1.10 mg/m3
IDLH
50 ppm
See: 74908
Exposure Limits
NIOSH REL
ST 4.7 ppm (5 mg/m3) [skin]
OSHA PEL
TWA 10 ppm (11 mg/m3) [skin] See Appendix G
Measurement Methods
NIOSH 6010 , 6017
See: NMAM or OSHA Methods
Physical Description
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.]
Molecular Weight
27.0
Boiling Point
78°F (96%)
Freezing Point
7°F (96%)
Solubility
Miscible
Vapor Pressure
630 mmHg
Ionization Potential
13.60 eV
Specific Gravity
0.69
Flash Point
0°F (96%)
Upper Explosive Limit
40.0%
Lower Explosive Limit
5.6%
Class IA Flammable Liquid: Fl.P. below 73°F and BP below 100°F. Flammable Gas
Incompatibilities & Reactivities
Amines, oxidizers, acids, sodium hydroxide, calcium hydroxide, sodium carbonate, caustics, ammonia [Note: Can polymerize at 122-140°F.]
Exposure Routes
inhalation, skin absorption, ingestion, skin and/or eye contact
Symptoms
asphyxia; lassitude (weakness, exhaustion), headache, confusion; nausea, vomiting; increased rate and depth of respiration or respiration slow and gasping; thyroid, blood changes
Target Organs
central nervous system, cardiovascular system, thyroid, blood
Personal Protection/Sanitation
(See protection codes)
Skin:Prevent skin contact
Eyes:Prevent eye contact
Wash skin:When contaminated
Remove:When wet (flammable)
Change:No recommendation
Provide:Eyewash, Quick drench
First Aid
(See procedures)
Eye:Irrigate immediately
Skin:Water flush immediately
Breathing:Respiratory support
Swallow:Medical attention immediately
Respirator Recommendations

NIOSH

Up to 47 ppm:
(APF = 10) Any supplied-air respirator

Up to 50 ppm:
(APF = 25) Any supplied-air respirator operated in a continuous-flow mode
(APF = 50) Any self-contained breathing apparatus with a full facepiece
(APF = 50) Any supplied-air respirator with a full facepiece

Emergency or planned entry into unknown concentrations or IDLH conditions:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus

Escape:
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern
Any appropriate escape-type, self-contained breathing apparatus

Important additional information about respirator selection

See also
INTRODUCTION   ICSC CARD: 0492   MEDICAL TESTS: 0117
Page last reviewed: October 30, 2019
Content source: National Institute for Occupational Safety and Health