UN/NA Number Reference
DOT Class 4.1 Flammable Solid placard

UN 1338: Phosphorus, amorphous

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1338 is assigned the proper shipping name Phosphorus, amorphous in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 4.1 Flammable Solid material, Packing Group III. Required label(s): 4.1.

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 133)

Hazards: Flammable. May be ignited by friction, heat, sparks. May burn rapidly with flare-burning effect.

Fire: Water spray, foam, dry chemical. Some may be extinguished with CO2.

Spill: Eliminate ignition sources. Do not touch. Cover with dry earth, sand, or non-combustible material.

Chemical and Physical Properties

Phosphorus, amorphous (red or violet) appears as red or dark crystals or powder. Not white phosphorus but rather one of the numerous less reactive polymorphic forms of the element. Not soluble in water.

CAS Number: 13967-14-1
Molecular Formula: P
Molecular Weight: 31.9817 g/mol
Color / Form: Exists in three main allotropic forms: white, black, and red. The same liquid is obtained from all forms on melting.
Odor: Garlic-like
Boiling Point: 536 °F at 760 mmHg ; white-yellow ignites at 86 °F in moist air; red ignites at 500 °F. (EPA, 1998)
Melting Point: 111.2 °F white-yellow; 1094 °F violet; 1094 °F red (EPA, 1998)
Autoignition: 500 °F (USCG, 1999)
Specific Gravity: 2.34 red, 2.36 violet; 2.70 black; 1.8 white-yellow (EPA, 1998)
Vapor Pressure: 0.026 mmHg at 68 °F White-yellow (EPA, 1998)
Vapor Density: 4.77 red; 4.42 white-yellow (EPA, 1998) (Relative to Air)
Water Solubility: Black: Insoluble in organic solvents; White: Insoluble in water, slightly soluble in benzene, ethanol, and chloroform, soluble in carbon disulfide; Red: Insoluble in water and organic solvents.

Special Provisions

49 CFR 172.102 special provision codes for this entry: A1, A19, B1, B9, B26, 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 1338 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.