UN 1623 — Mercuric arsenate
Placard: Toxic. ERG Guide 151. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1623 is Mercuric arsenate, a toxic arsenic and heavy-metal material assigned to ERG Guide 151. The main responder concern is preventing inhalation of dust and controlling contaminated runoff.
Hazard overview: UN 1623 presents arsenic plus heavy-metal dust, fume and runoff hazards. Dry powder can contaminate clothing and equipment, and heating may produce toxic metal-containing fumes.
Response guidance: For a UN 1623 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 151. Establish incident command, isolate the area, stay upwind, prevent dust or vapor exposure, control runoff and choose entry or cleanup actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1623 should emphasize arsenic/heavy-metal dust exposure, contamination control, SCBA use, runoff containment and decontamination. Common errors include spreading dry powder and treating nonflammable toxic solids as low risk. Use ERG 151, SDS and local SOP.
Regulatory context: Mercuric arsenate is regulated as a toxic arsenic/heavy-metal hazardous material. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by compound, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Mercuric arsenate should be stored in tightly closed compatible containers in a secure, cool, dry, well-ventilated toxic-material area away from food, incompatible chemicals, heat and unauthorized access. Prevent dust release, leaks and contaminated runoff.
UN 1623 Quick Details
Common Hazards of UN 1623
- HIGHLY TOXIC arsenic and heavy-metal material; may be fatal if inhaled, ingested or absorbed through skin.
- Dust or powder can create serious inhalation and contamination hazards.
- Lead or mercury components may add persistent toxic contamination to surfaces, runoff and equipment.
- Avoid skin contact and prevent dust from becoming airborne.
- Fire or heating may produce toxic arsenic, lead or mercury fumes depending on the compound.
- Runoff from fire control or spill control may pollute waterways.
- Specific solubility and toxicity should be verified from SDS and shipping papers.
Chemical Identity & Physical Properties
White to yellowish crystalline powder or solid. Odorless. Stable at room temperature but decomposes upon heating.
| 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 |
Fireground Response Guidance — UN 1623
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for dust, fumes, fire or confined-space exposure. Chemical-resistant gloves, eye/face protection and protective clothing should be selected from SDS; avoid all skin contact and contaminated dust.
Isolation & Evacuation
First Actions for a UN 1623 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing vapors, fumes, dust or mist and avoid all skin or eye contact.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- Avoid creating dust clouds or spreading contaminated powder, solution, runoff or debris.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or leak area and expand the perimeter if dust, vapor, fire involvement or unknown concentration is present.
- Use ERG Guide 151, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1623 — Mercuric arsenateUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.