UN/NA Number Reference
DOT Class 8 Corrosive placard

UN 1777: Fluorosulfonic acid

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1777 is assigned the proper shipping name Fluorosulfonic acid in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 8 Corrosive material, Packing Group I. 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 137)

Hazards: Produce flammable gases on contact with water. May ignite on contact with water. Some react violently with water.

Fire: DO NOT use water or foam. Use dry chemical, dry sand, or soda ash.

Spill: Do not touch. Keep material dry. Move containers from water. Dike to prevent water contact.

Chemical and Physical Properties

Fluorosulfonic acid appears as a fuming liquid. Boiling point 163 °C. Density 1.73 g / cm3. Corrosive to metals and to tissue. Both very short contact and the fumes can cause severe painful burns. Used as a catalyst in organic synthesis, in electroplating and as a fluorinating agent.

CAS Number: 7789-21-1
Molecular Formula: FHO3S
Molecular Weight: 100.07 g/mol
Color / Form: COLORLESS LIQUID; REDDISH-BROWN COLOR WITH ACETONE
Boiling Point: 324.9 F
Melting Point: -125.1 °F (USCG, 1999)
Specific Gravity: 1.73 (sinks in water)
Vapor Pressure: 2.5 [mmHg]
Vapor Density: 3.4 (heavier than air)
Water Solubility: SOL IN NITROBENZENE
pH: CONSIDERABLY MORE ACIDIC THAN CONCN H2SO4

Special Provisions

49 CFR 172.102 special provision codes for this entry: A7, A10, B6, B10, N3, N36, T10, TP2. 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 1777 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.