UN/NA Number Reference
DOT Class 6.1 Toxic Substance placard

UN 1646: Mercury thiocyanate

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 1646 is assigned the proper shipping name Mercury thiocyanate 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 II. Required label(s): 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 151)

Hazards: TOXIC. May be fatal if inhaled, ingested, or absorbed through skin. Contact may cause burns.

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

Spill: Do not touch. Avoid inhalation. Use water spray to reduce dust/vapor. Ventilate.

Chemical and Physical Properties

Mercury thiocyanate appears as an odorless white crystalline powder. Insoluble in water and denser than water. Hence sinks in water. Very toxic by inhalation and ingestion.

CAS Number: 592-85-8
Molecular Formula: C2HgN2S2
Molecular Weight: 316.8 g/mol
Color / Form: White to tan powder
Odor: Odorless
Boiling Point: Decomposes about 329.0 F
Melting Point: 165 °C (decomposes)
Flash Point: greater than 250 F
Specific Gravity: 4 Approximately
Vapor Density: 10.9 (heavier than air)
Water Solubility: Slightly sol in water: 0.069 g/100 ml @ 25 C

Regulatory Data

CERCLA RQ (40 CFR 302.4)
10 lb

A release of this material at or above its CERCLA reportable quantity (10 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, IP2, IP4, T3, 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 1646 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.