☣️ UN 1646 • CLASS 6
Mercury thiocyanate
Placard: Toxic. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
Advertisement
Quick details
UN 1646
Class: 6
Placard type: Toxic
ERG: Guide 151 (check current ERG)
Isolation: ERG 151: isolate spill 25m in all directions. If large spill, isolate 50m and consider evacuation 100m downwind.
Chemical & Response Details
| Also known as | Mercuric thiocyanateMercury(II) thiocyanateMercuric sulfocyanateBis(thiocyanato)mercury |
| CAS Number | 592-85-8 |
| Appearance | White to slightly yellow crystalline powder or solid. Odorless or faint odor. Stable at room temperature. |
| Flash Point | Not applicable (non-flammable solid) |
| Boiling Point | Decomposes before boiling at approximately 165C (329F) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Slightly soluble in water; no violent reaction. Hydrolyzes slowly releasing thiocyanate ions. |
| Extinguishing | Water spray, dry chemical, CO2. Foam not typically required for solid mercury compound. |
| PPE | ⚠️ Level B minimum with full-face respirator; Level A if airborne contamination suspected. Neoprene or nitrile gloves; prevent all skin contact. |
| Isolation | ERG 151: isolate spill 25m in all directions. If large spill, isolate 50m and consider evacuation 100m downwind. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- Highly toxic, may be fatal if inhaled, ingested or absorbed through skin.
- Avoid any skin contact.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive
- Containers may explode when heated.
- Runoff may pollute waterways.
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
Advertisement
📋 Copy & Share
UN 1646 — Mercury thiocyanate HAZMAT RADIO NOTE — UN 1646
Product: Mercury thiocyanate
Class 6 / Toxic / ERG 151
PPE: Level B minimum with full-face respirator; Level A if airborne contamination suspected. Neoprene or nitrile gloves; prevent all skin contact.
ISOLATION: ERG 151: isolate spill 25m in all directions. If large spill, isolate 50m and consider evacuation 100m downwind.
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 1646 — Mercury thiocyanate
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: White to slightly yellow crystalline powder or solid. Odorless or faint odor. Stable at room temperature.
Water Reactivity: Slightly soluble in water; no violent reaction. Hydrolyzes slowly releasing thiocyanate ions.
Extinguishing: Water spray, dry chemical, CO2. Foam not typically required for solid mercury compound.
PPE: Level B minimum with full-face respirator; Level A if airborne contamination suspected. Neoprene or nitrile gloves; prevent all skin contact.
Isolation: ERG 151: isolate spill 25m in all directions. If large spill, isolate 50m and consider evacuation 100m downwind.
— Key Hazards —
• Highly toxic, may be fatal if inhaled, ingested or absorbed through skin.
• Avoid any skin contact.
• Fire may produce irritating, corrosive and/or toxic gases.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
SOURCE: allfirefighter.com/hazmat/un/1646 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1646 Mercury thiocyanate Cls6 ERG151 | ERG 151: isolate spill 25m in all directions. If large spill, isolate 50m and co | allfirefighter.com/hazmat/un/1646SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/1646
Advertisement
FAQ
Highly toxic, may be fatal if inhaled, ingested or absorbed through skin. Avoid any skin contact. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive Containers may explode when heated. Runoff may pollute waterways.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level B minimum with full-face respirator; Level A if airborne contamination suspected. Neoprene or nitrile gloves; prevent all skin contact.
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 151 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.