UN/NA Number Reference
DOT Class 5.1 Oxidizer placard

UN 1463: Chromium trioxide, anhydrous

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1463 is assigned the proper shipping name Chromium trioxide, anhydrous in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 5.1 Oxidizer material, Packing Group II. Required label(s): 5.1, 6.1.

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 141)

Hazards: Oxidizer. TOXIC. May be fatal if inhaled or swallowed. Accelerates combustion.

Fire: Use flooding water. Do not use dry chemical, foam.

Spill: Do not touch. Keep combustibles away. Use water spray.

Chemical and Physical Properties

Chromium trioxide, anhydrous appears as a dark purplish red solid. Under prolonged exposure to fire or heat the containers may explode. Highly toxic. A confirmed human carcinogen.

CAS Number: 10034-81-8
Molecular Formula: CrO3
Molecular Weight: 99.994 g/mol
Color / Form: Dark red, bipyramidal prismatic crystals, flakes or granular powder
Odor: Odorless
Boiling Point: 482 F
Melting Point: 385 °F (NTP, 1992)
Autoignition: May ignite organic materials on contact. (USCG, 1999)
Specific Gravity: 2.7 (sinks in water)
Vapor Pressure: Very low
Water Solubility: Very soluble
pH: Dissolves in water to form a weak acid

Regulatory Data

OSHA PEL
0.005 mg/m³
NIOSH REL
0.0002 mg/m³
IDLH
15 mg/m³

Special Provisions

49 CFR 172.102 special provision codes for this entry: IB8, IP2, IP4, T3, TP33, W31. 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 1463 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.