☣️ UN 1623 • CLASS 6
UN 1623 — Mercuric arsenate
Placard: Toxic. ERG Guide 151. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ 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.
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UN 1623 Quick Details
UN 1623
Product name: Mercuric arsenate
DOT Class: 6
Placard type: Toxic
ERG Guide: 151 (check current ERG)
Initial isolation: ERG 151: isolate spill 25m all directions; if fire or tank involved, isolate 800m and evacuate 1600m downwind
Common Hazards of UN 1623
- 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.
Chemical Identity & Physical Properties
| Also known as | Mercury arsenateMercuric orthoarsenateArsenic acid mercury(2+) saltMercury(II) arsenate |
| CAS Number | 7784-37-4 |
| Appearance | White to yellowish crystalline powder or solid. Odorless. Stable at room temperature but decomposes upon heating. |
| Flash Point | Not applicable (inorganic solid) |
| Boiling Point | Not applicable (decomposes before boiling) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Slightly soluble in water; no violent reaction but releases toxic ions |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1623
Extinguishing Media
Dry chemical, sand, or CO2 for surrounding fires; avoid dispersing material
PPE Requirements
⚠️ Level A required for large spills; Level B minimum; SCBA mandatory; impervious suit, gloves, boots to prevent any skin contact
Isolation & Evacuation
ERG 151: isolate spill 25m all directions; if fire or tank involved, isolate 800m and evacuate 1600m downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 151).
First Actions for a UN 1623 Incident
- 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
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📋 Copy & Share Field Card
UN 1623 — Mercuric arsenateHAZMAT RADIO NOTE — UN 1623
Product: Mercuric arsenate
Class 6 / Toxic / ERG 151
PPE: Level A required for large spills; Level B minimum; SCBA mandatory; impervious suit, gloves, boots to prevent any skin contact
ISOLATION: ERG 151: isolate spill 25m all directions; if fire or tank involved, isolate 800m and evacuate 1600m 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 1623 — Mercuric arsenate
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: White to yellowish crystalline powder or solid. Odorless. Stable at room temperature but decomposes upon heating.
Water Reactivity: Slightly soluble in water; no violent reaction but releases toxic ions
Extinguishing: Dry chemical, sand, or CO2 for surrounding fires; avoid dispersing material
PPE: Level A required for large spills; Level B minimum; SCBA mandatory; impervious suit, gloves, boots to prevent any skin contact
Isolation: ERG 151: isolate spill 25m all directions; if fire or tank involved, isolate 800m and evacuate 1600m 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/1623 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1623 Mercuric arsenate Cls6 ERG151 | ERG 151: isolate spill 25m all directions; if fire or tank involved, isolate 800 | allfirefighter.com/hazmat/un/1623SMS / 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/1623
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Frequently Asked Questions about UN 1623
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 A required for large spills; Level B minimum; SCBA mandatory; impervious suit, gloves, boots to prevent any skin contact
Water reactivity: Slightly soluble in water; no violent reaction but releases toxic ions. Recommended extinguishing: Dry chemical, sand, or CO2 for surrounding fires; avoid dispersing material.
ERG Guide 151 recommendation: ERG 151: isolate spill 25m all directions; if fire or tank involved, isolate 800m and evacuate 1600m downwind
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.