Nitric acid

CAS 7697-37-2





Physical Properties

Colorless, yellowish, or reddish-brown fuming liquid

"Concentrated nitric acid" (68 to 70% HNO3 by wt): bp 122 °C

"White fuming nitric acid" (97.5% HNO3, 2% H2O, <0.5% NOx): bp 83 °C, mp -42 °C

"Red fuming nitric acid" contains 85% HNO3, <5% H2O, and 6 to 15% NOx

Miscible with water in all proportions



Suffocating fumes detectable at <5.0 ppm


Vapor Density

>1 (air = 1.0)


Vapor Pressure

57 mmHg at 25 °C for white fuming nitric acid

49 mmHg at 20 °C for 70% nitric acid


Flash Point

Not flammable


Toxicity Data

LC50 inhal (rat)

2500 ppm (1 h)



2 ppm (5 mg/m3)



2 ppm (5.2 mg/m3)



4 ppm (10 mg/m3)

Major Hazards

Highly corrosive to the eyes, skin, and mucous membranes; powerful oxidizing agent that ignites on contact or reacts explosively with many organic and inorganic substances.



Concentrated nitric acid and its vapors are highly corrosive to the eyes, skin, and mucous membranes. Dilute solutions cause mild skin irritation and hardening of the epidermis. Contact with concentrated nitric acid stains the skin yellow and produces deep painful burns. Eye contact can cause severe burns and permanent damage. Inhalation of high concentrations can lead to severe respiratory irritation and delayed effects, including pulmonary edema, which may be fatal. Ingestion of nitric acid may result in burning and corrosion of the mouth, throat, and stomach. An oral dose of 10 mL can be fatal in humans.

Tests in animals demonstrate no carcinogenic or developmental toxicity for nitric acid. Tests for mutagenic activity or for reproductive hazards have not been performed.


Flammability and

Explosibility Not a combustible substance, but a strong oxidizer. Contact with easily oxidizible materials including many organic substances may result in fires or explosions.


Reactivity and Incompatibility

Nitric acid is a powerful oxidizing agent and ignites on contact or reacts explosively with a variety of organic substances including acetic anhydride, acetone, acetonitrile, many alcohols, thiols, and amines, dichloromethane, DMSO, and certain aromatic compounds


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