UN/NA Number Reference
DOT Class 6.1 Toxic Substance placard

UN 2337: Phenyl mercaptan

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 2337 is assigned the proper shipping name Phenyl mercaptan 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 131)

Hazards: HIGHLY FLAMMABLE. TOXIC. May be fatal if inhaled, swallowed, or absorbed through skin. Vapors heavier than air.

Fire: Small: dry chemical, CO2, water spray, alcohol-resistant foam. Large: water spray, fog, alcohol-resistant foam.

Spill: Eliminate ignition sources. Do not touch. Stop leak if safe. Use vapor-suppressing foam. Ventilate area.

Chemical and Physical Properties

Phenyl mercaptan appears as a clear liquid with a repulsive odor. Boiling point 168.3 °C. Insoluble in water and denser than water. Very toxic by ingestion, skin absorption, and by inhalation. Used as a chemical intermediate and in mosquito control.

CAS Number: 108-98-5
Molecular Formula: C6H6S
Molecular Weight: 110.18 g/mol
Color / Form: Water-white liquid
Odor: Repulsive, penetrating, garlic-like odor, especially when impure
Boiling Point: 334.9 F
Melting Point: 5.4 °F (EPA, 1998)
Flash Point: 127 F
Specific Gravity: 1.0728 (sinks in water)
Vapor Pressure: 1 mmHg at 65.48 F
Vapor Density: 3.8 (heavier than air)
Water Solubility: 0.08 % at 77 F
Log P: log Kow = 2.52
pH: Feebly acidic

Regulatory Data

CERCLA RQ (40 CFR 302.4)
100 lb
EPCRA TPQ (40 CFR 355)
500 lb
OSHA PEL
none
NIOSH REL
C 0.1 ppm (0.5 mg/m 3 ) [15-minute]
IDLH
N
RCRA Waste Code(s)
[object Object]

A release of this material at or above its CERCLA reportable quantity (100 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: 2, B9, B14, B32, B77, T20, TP2, TP13, TP38, TP45. 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 2337 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.