UN 1798 — Nitrohydrochloric acid
Placard: Corrosive. ERG Guide 157. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1798 is Nitrohydrochloric acid, a Class 8 corrosive acid assigned to ERG Guide 157. It can release irritating acid fumes and cause severe burns to eyes, skin and respiratory tissue.
Hazard overview: UN 1798 presents corrosive liquid, acid fume, heat-on-dilution and acidic-runoff hazards. Contact with some metals may release flammable hydrogen gas, and vapors can accumulate in poorly ventilated areas.
Response guidance: For a UN 1798 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 157. Establish incident command, isolate the area, stay upwind, prevent incompatible contact, control runoff and choose entry or fire-control actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1798 should emphasize corrosive exposure routes, water or oxidizer incompatibility where applicable, air monitoring, PPE selection, decontamination and runoff containment. Use ERG 157, SDS and local SOP.
Regulatory context: Nitrohydrochloric acid is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by concentration, formulation, 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: Nitrohydrochloric acid should be stored in tightly closed compatible containers in a secure, cool, dry, well-ventilated hazardous-material area according to SDS and local procedures.
UN 1798 Quick Details
Common Hazards of UN 1798
- CORROSIVE acid solution; inhalation, ingestion or skin/eye contact may cause severe injury.
- Fumes may contain hydrogen chloride and can injure eyes and respiratory tissue.
- Dilution with water may generate heat and increase fuming.
- Contact with some metals may release flammable hydrogen gas.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff may be strongly acidic and corrosive.
- Vapors may collect in poorly ventilated or low areas depending on concentration and conditions.
Chemical Identity & Physical Properties
Yellow to reddish-brown fuming liquid with a pungent, choking odor. Highly corrosive mixture of concentrated nitric and hydrochloric acids.
| Also known as | Aqua regiaNitro-muriatic acidChloronitrous acidNitromuriatic acidNitro-hydrochloric acid |
| Appearance | Yellow to reddish-brown fuming liquid with a pungent, choking odor. Highly corrosive mixture of concentrated nitric and hydrochloric acids. |
| Flash Point | Not applicable (non-flammable corrosive liquid) |
| Boiling Point | Variable depending on composition, typically 108-121C (226-250F) |
| Vapor Density | Greater than 1 (heavier than air) |
| Water Reactivity | Reacts exothermically with water generating heat and toxic fumes of nitrogen oxides and hydrogen chloride |
Fireground Response Guidance — UN 1798
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, mist, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing selected from SDS for corrosive liquid contact.
Isolation & Evacuation
First Actions for a UN 1798 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, mist or spray and avoid skin or eye contact.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- 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 vapor, dust, fire involvement, water reaction or unknown concentration is present.
- Use ERG Guide 157, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1798 — Nitrohydrochloric acidUse 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.