UN/NA Number Reference
DOT Class 8 Corrosive placard

UN 3453: Phosphoric acid, solid

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 3453 is assigned the proper shipping name Phosphoric acid, solid in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 8 Corrosive material, Packing Group III. Required label(s): 8.

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 154)

Hazards: TOXIC. Corrosive. Non-combustible but may decompose producing toxic fumes when heated.

Fire: Use agent appropriate for surrounding fire. Cool containers.

Spill: Do not touch. Avoid inhalation. Use water spray to reduce fumes.

Chemical and Physical Properties

Phosphoric acid appears as a clear colorless liquid or transparent crystalline solid. The pure solid melts at 42.35 °C and has a density of 1.834 g / cm3. Liquid is usually an 85% aqueous solution. Shipped as both a solid and liquid. Corrosive to metals and tissue. Used in making fertilizers and detergents and in food processing.

CAS Number: 7664-38-2
Molecular Formula: H3O4P
Molecular Weight: 97.995 g/mol
Color / Form: Unstable orthorhombic crystals or clear syrupy liquid
Odor: Odorless
Boiling Point: 266 F
Melting Point: 108 °F (NIOSH, 2024)
Autoignition: Not flammable (USCG, 1999)
Specific Gravity: 1.892
Vapor Pressure: 0.03 mmHg
Vapor Density: 1
Water Solubility: Miscible (fully soluble)
Log P: -2.150
pH: pH = 1.5 (0.1 N aqueous solution)

Regulatory Data

CERCLA RQ (40 CFR 302.4)
5000 lb
OSHA PEL
1 1 mg/m 3 (ST) 3 mg/m 3
NIOSH REL
TWA 1 mg/m 3 ST 3 mg/m 3
IDLH
1000 mg/m 3

A release of this material at or above its CERCLA reportable quantity (5000 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: IB8, IP3, T1, TP33. 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 3453 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.