UN 2308 — Nitrosylsulphuric acid, liquid
Placard: Corrosive. ERG Guide 157. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2308 is Nitrosylsulphuric acid, liquid, a toxic corrosive fuming acid assigned to ERG Guide 157. Moisture can release heat and nitrogen oxide/sulfur oxide fumes.
Hazard overview: TOXIC and CORROSIVE nitrosylsulfuric acid liquid; contact may cause severe burns. Reacts with water or moisture, releasing heat and toxic nitrogen oxide/sulfur oxide fumes. Fumes may be highly irritating and corrosive to eyes, skin and respiratory tract.
Response guidance: For a UN 2308 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 157. Establish incident command, isolate the area, stay upwind, control ignition or incompatibility hazards, prevent runoff, dust or vapor spread and base entry/fire-control actions on monitoring and local SOP.
Firefighter training notes: Training for UN 2308 should emphasize corrosive fuming, moisture reaction, runoff control, Level A/B entry decisions, decontamination and incompatible materials. Use ERG 157, SDS and local SOP.
Regulatory context: Nitrosylsulphuric acid, liquid is regulated as a hazardous material for transportation and emergency response purposes. Storage, workplace exposure, emergency planning, spill reporting, waste handling and environmental requirements vary by exact product, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, container markings and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Nitrosylsulphuric acid, liquid should be stored in compatible acid-resistant containers with secondary containment, away from water/moisture, bases, reducing agents, metals, organics, heat and unauthorized access.
UN 2308 Quick Details
Common Hazards of UN 2308
- TOXIC and CORROSIVE nitrosylsulfuric acid liquid; contact may cause severe burns.
- Reacts with water or moisture, releasing heat and toxic nitrogen oxide/sulfur oxide fumes.
- Fumes may be highly irritating and corrosive to eyes, skin and respiratory tract.
- Strong acid may react with metals, bases, reducing agents and organic materials.
- Fire or heating may produce nitrogen oxides, sulfur oxides and other toxic/corrosive gases.
- Runoff may be strongly acidic, toxic and environmentally harmful.
- Containers may rupture or fail when heated or contaminated with water.
Chemical Identity & Physical Properties
Pale yellow to straw-colored oily liquid. Pungent, irritating odor. Fumes in moist air.
| Also known as | Nitrosyl sulfuric acidNitrosylsulfuric acidSulfuric acid nitrosyl esterChamberlain's reagentNOHSO4 |
| CAS Number | 7782-78-7 |
| Appearance | Pale yellow to straw-colored oily liquid. Pungent, irritating odor. Fumes in moist air. |
| Flash Point | Not applicable (non-flammable) |
| Boiling Point | Decomposes before boiling at approximately 73C (163F) |
| Vapor Density | Not applicable (releases corrosive vapors/fumes) |
| Water Reactivity | Reacts violently with water releasing toxic nitrogen oxides and sulfuric acid fumes; generates significant heat |
Fireground Response Guidance — UN 2308
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, aerosol, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing selected from SDS; Level A may be needed for heavy vapor, acid fuming or unknown concentrations.
Isolation & Evacuation
First Actions for a UN 2308 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, dust, mist, smoke or fumes and avoid skin or eye contact.
- Avoid unnecessary water contact with released product unless incident command confirms a compatible control use.
- Do not touch damaged containers or 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 release area and expand the perimeter for fire involvement, vapor spread, dust generation, water reaction or unknown product identity.
- Use ERG Guide 157, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 2308 — Nitrosylsulphuric acid, liquidUse 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.