Ammonium hydroxide

(Aqua ammonia, ammonia)

CAS 1336-21-6



28 to 30% NH3 in H2O


Physical Properties

Colorless liquid

bp: unstable above 27.8 °C, mp - 71.7 °C

Concentrated ammonium hydroxide is a 29% solution of NH3 in H2O.



Strong pungent ammonia odor detectable at 17 ppm

Vapor Density

0.59 for anhydrous NH3 (air = 1.0)


Vapor Pressure

115 mmHg at 20 °C for 29% solution

Autoignition Temperature

690 °C (for ammonia)


Toxicity Data

LD50 oral (rat)

350 mg/kg



35 ppm (27 mg/m3)



25 ppm (17 mg/m3)



35 ppm (27 mg/m3)

Major Hazards

Highly corrosive to the eyes, skin, and mucous membranes.


Ammonia solutions are extremely corrosive and irritating to the skin, eyes, and mucous membranes. Exposure by inhalation can cause irritation of the nose, throat, and mucous membranes. Exposure to high concentrations of ammonia vapor (above approximately 2500 ppm) is life threatening, causing severe damage to the respiratory tract and resulting in bronchitis, chemical pneumonitis, and pulmonary edema, which can be fatal. Eye contact with ammonia vapor is severely irritating, and exposure of the eyes to ammonium hydroxide can result in serious damage and may cause permanent eye injury and blindness. Skin contact can result in severe irritation and burns; contact with the liquid results in cryogenic burns as well. Ingestion of ammonium hydroxide burns the mouth, throat, and gastrointestinal tract and can lead to severe abdominal pain, nausea, vomiting, and collapse.

Ammonium hydroxide has not been found to be carcinogenic or to show reproductive or developmental toxicity in humans. Chronic exposure to ammonia can cause respiratory irritation and damage.

Flammability and Explosibility

Ammonia vapor is slightly flammable (NFPA rating = 1) and ignites only with difficulty. Ammonia forms explosive mixtures with air in the range 16 to 25%. Water, carbon dioxide, or dry chemical extinguishers should be used for ammonia fires.

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