UN/NA Number Reference
DOT Class 6.1 Toxic Substance placard

UN 1051: Hydrogen cyanide, stabilized

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1051 is assigned the proper shipping name Hydrogen cyanide, stabilized in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 6.1 Toxic Substance material, Packing Group I. Required label(s): 6.1, 3.

Packing group indicates the degree of danger within a hazard class: PG I is high danger, PG II medium, PG III low. The proper shipping name, hazard class, UN number, and packing group together form the basic shipping description that must appear on shipping papers and, where required, on the package and placard.

Emergency Response (ERG Guide 117)

Hazards: TOXIC. May be fatal if inhaled. Extremely flammable. Vapors heavier than air.

Fire: Do not extinguish unless flow stopped. Water spray to cool containers. Fight from maximum distance.

Spill: Fully encapsulating gas-tight suits required. Do not touch. Stop leak if safe.

Chemical and Physical Properties

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.

CAS Number: 74-90-8
Molecular Formula: CHN
Molecular Weight: 27.03 g/mol
Color / Form: Colorless gas or liquid
Odor: Bitter almond odor
Boiling Point: 79°F (26°C)
Melting Point: 7 °F (96%) (NIOSH, 2024)
Flash Point: 0°F (-18°C)
Autoignition: 1004 °F (USCG, 1999)
Specific Gravity: 0.69 (floats on water)
Vapor Pressure: 630 mmHg (NIOSH, 2024)
Vapor Density: 0.93 (lighter than air)
Water Solubility: Miscible (fully soluble)
Log P: log Kow = -0.25
pH: Very weak acid (does not redden litmus)

Regulatory Data

CERCLA RQ (40 CFR 302.4)
10 lb
EPCRA TPQ (40 CFR 355)
100 lb
OSHA PEL
TWA 10 ppm (11 mg/m 3 ) [skin]
NIOSH REL
ST 4.7 ppm (5 mg/m 3 ) [skin]
IDLH
50 ppm
RCRA Waste Code(s)
[object Object]

A release of this material at or above its CERCLA reportable quantity (10 lb) requires immediate notification to the National Response Center at 800-424-8802.

Special Provisions

49 CFR 172.102 special provision codes for this entry: 1, 387, B35, B61, B65, B77, B82. These codes modify the general requirements (packaging, quantity limits, exceptions) for this specific material. Look up each code in 49 CFR 172.102 for the full text.

Need the full interactive record? Open UN 1051 in the SpillNerd lookup tool for the live database entry with placard graphics, GHS pictograms, full segregation tables, and synonym search. For another material, use the UN number and chemical lookup.

Reference data compiled from the DOT Hazardous Materials Table (49 CFR 172.101), the 2024 Emergency Response Guidebook, and public chemical databases (PubChem, NIOSH, EPA). Always verify the correct shipping description against the current regulation and the manufacturer's SDS Section 14 before shipping.