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Chemical Name: Nitric Acid Hydrochloride (Aqua Regia)
Synonyms: Aqua Regia, Nitrohydrochloric Acid
Recommended Use: Metal refining, laboratory reagent, gold and platinum dissolution
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CAS Number: Nitric Acid: 7697-37-2; Hydrochloric Acid: 7647-01-0
UN Number: 2031 (for nitric acid solution), 1789 (for hydrochloric acid solution)
Concentration: Typically prepared fresh by mixing 1 part concentrated nitric acid with 3 parts concentrated hydrochloric acid
Hazard Classifications: Corrosive to eyes, skin, and respiratory tract; May cause severe burns; Produces toxic gases
Signal Word: Danger
Hazard Statements: Causes severe skin burns and eye damage; May cause respiratory irritation; Very toxic to aquatic life
Pictograms: Corrosive, Toxic, Environmental hazard
Precautionary Statements: Wear protective equipment; Avoid release to environment; Keep container tightly closed; Do not breathe fumes, vapors, or mist
Nitric Acid: 20–30% (by volume in solution)
Hydrochloric Acid: 60–80% (by volume in solution)
Water: Variable, dependent on concentration
Impurities: May include traces of chlorine, nitrogen oxides, and metal ions depending on storage and usage
Note: Mixture produces chlorine and nitrosyl chloride gases on contact with air and metals
Inhalation: Move to fresh air; Seek immediate medical attention; If breathing stops, give artificial respiration
Skin Contact: Remove contaminated clothing; Rinse affected skin with water for 15 minutes; Get medical help
Eye Contact: Flush eyes with running water for at least 15 minutes, keeping eyelids open; Remove contact lenses if safe; Call a physician
Ingestion: Do not induce vomiting; Rinse mouth; Immediately seek medical attention
Most Important Symptoms/Effects: Severe irritation or burns to eyes, skin, mucous membranes and lungs; Delayed lung effects possible
Suitable Extinguishing Media: Use water spray, dry chemical, or appropriate foam for surroundings; Acid itself does not burn but will react with metals producing flammable hydrogen gas
Special Hazards: Reacts violently with reducing agents, organic materials, and most metals; Produces toxic gases including nitrogen oxides, chlorine, and hydrogen chloride
Protective Equipment: Full protective suit and self-contained breathing apparatus
Advice for Firefighters: Move containers from fire area if safe; Cool containers with flooding quantities of water
Other Considerations: Prevent fire-fighting water from contaminating water supplies
Personal Precautions: Wear acid-resistant gloves, face protection, chemical-resistant boots and suit; Evacuate area; Ventilate
Environmental Precautions: Prevent entry into waterways, drains, basements or confined areas
Spill Response: Neutralize with sodium bicarbonate, lime or a suitable neutralizing agent; Absorb with inert, non-combustible material (e.g., sand); Collect and dispose in labeled container
Decontamination: Wash spillage zone with water after removal
Incompatible Materials: Avoid contact with reducing agents, organic materials, metals and bases
Precautions for Safe Handling: Work in a chemical fume hood; Use with proper ventilation and protective equipment; Avoid contact with skin, eyes, and clothing; Do not breathe vapors; Keep away from heat, sparks, and incompatible substances
Storage Conditions: Store in cool, well-ventilated, corrosion-resistant area; Keep container tightly closed; Use glass or specialized plastic containers; Do not store with bases, organic materials or metals
Special Instructions: Always prepare solution fresh; Ensure proper labeling; Avoid prolonged storage as it decomposes and builds pressure
Exposure Limits: Nitric Acid: OSHA PEL 2 ppm (5 mg/m³), Hydrochloric Acid: OSHA PEL 5 ppm (7 mg/m³)
Engineering Controls: Local exhaust, chemical fume hood, closed systems
Personal Protective Equipment: Full-face shield, acid-resistant gloves, impermeable apron, chemical splash goggles, respirator approved for corrosive acids
Hygiene Measures: Wash hands before breaks and after use; Remove contaminated clothing immediately
Monitoring: Use gas detection for nitrogen oxides and chlorine in workplace air
Appearance: Fuming yellow or orange liquid
Odor: Pungent, suffocating
pH: <1 (highly acidic)
Boiling Point: Varies, typically 108–115°C (depends on proportions and concentration)
Melting Point: No distinct value; decomposes and fumes at room temperature
Solubility: Completely miscible with water
Relative Density: 1.1–1.2 (water=1)
Vapor Pressure: Significant, produces corrosive vapors
Other Properties: Releases hazardous fumes on mixing, reacts violently with numerous substances
Chemical Stability: Solution is unstable; decomposes over time
Conditions to Avoid: Heat, sunlight, incompatible materials, confined spaces (pressure buildup)
Incompatible Materials: Bases, metals, organic compounds, oxidizable substances, reducing agents
Hazardous Decomposition Products: Chlorine, nitrogen oxides, hydrogen chloride, nitrosyl chloride
Hazardous reactions: Vigorous exothermic reactions possible with combustible materials and organic compounds
Routes of Exposure: Skin contact, eye contact, inhalation, ingestion
Acute Effects: Severe burns to skin, mucous membranes, and respiratory tract; Potential pulmonary edema; Ingestion can be fatal
Chronic Effects: Prolonged exposure leads to dental erosion, bronchitis, chronic respiratory irritation
Sensitization: Not reported, but repeated contact may increase sensitivity
Carcinogenicity: Not classifiable for mixture; Nitric acid and hydrochloric acid are not listed as carcinogens by IARC
Other Data: Can aggravate pre-existing skin, eye, or respiratory conditions
Ecotoxicity: Very toxic to aquatic organisms, causes long-term damage in aquatic environments
Persistence and Degradability: Readily dissociates in water; Ongoing release of acid and gas can lower pH dangerously
Bioaccumulation Potential: Not expected to bioaccumulate
Mobility: High (soluble and mobile in water environments)
Other Harmful Effects: Acidification of surface waters leads to fish kills and disruption in aquatic food chain
Waste Treatment: Neutralize with suitable alkaline material (lime or soda ash) under controlled conditions
Disposal Method: Dispose in accordance with local, regional, national regulations; Never dispose down drains
Contaminated Packaging: Rinse with neutralizing solution before recycling or disposal
Special Precautions: Handle by trained personnel; Label and store securely until disposal
UN Number: UN2031 or UN1789 (solution form)
Proper Shipping Name: Nitric Acid Mixture, Hydrochloric Acid Mixture, or Aqua Regia, as locally regulated
Transport Hazard Class: 8 (Corrosive)
Packing Group: II or I, depending on concentrations and local guidelines
Environmental Hazards: Marine pollutant; ensure containment
Special Transport Precautions: Use approved, corrosion-resistant containers; Keep upright, avoid shock or impact
OSHA: Listed as hazardous material; requires hazard communication
EPA: Regulated under RCRA as hazardous waste (D002 - corrosive waste)
TSCA Status: Both acids listed
Labeling Requirements: Corrosive, Toxic, Environmental Hazard
International Regulations: Controlled under UN, IMDG, IATA
Workplace Use: Requires training on handling corrosives and emergency procedures
Other Regulatory Details: Some states and countries may have stricter limits or additional controls
