AMMONIUM HYDROXIDE

Ammonium hydroxide
(Aqua ammonia, ammonia)
CAS 1336-21-6

28 to 30% NH₃in H₂ O

Colorless liquid
bp: unstable above 27.8 °C, mp -71.7 °C
Concentrated ammonium hydroxide is a 29% solution of NH₃in H₂ O.

Strong pungent ammonia odor detectable at 17 ppm

0.59 for anhydrous NH₃(air = 1.0)

115 mmHg at 20 °C for 29% solution

690 °C (for ammonia)

LD₅₀ oral (rat) 350 mg/kg

PEL (OSHA) 35 ppm (27 mg/m³)

TLV-TWA (ACGIH) 25 ppm (17 mg/m³)

STEL (ACGIH) 35 ppm (27 mg/m³)

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.

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.

Highly explosive nitrogen halides will form in reactions with halogens, hypohalites, and similar compounds. Reaction with certain gold, mercury, and silver compounds may form explosive products. Violent reactions can occur with oxidizing agents such as chromium trioxide, hydrogen peroxide, nitric acid, chlorite, chlorate, and bromate salts. Exothermic and violent reactions may occur if concentrated ammonium hydroxide solution is mixed with strong acids, acidic metal and nonmetal halides, and oxyhalides.

Ammonium hydroxide should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C. All work with this substance should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact. Containers should be tightly sealed to prevent escape of vapor and should be stored in a cool area separate from halogens, acids, and oxidizers. Containers stored in warm locations may build up dangerous internal pressures of ammonia gas.

In the event of skin contact, immediately wash with soap and water and remove contaminated clothing. In case of eye contact, promptly wash with copious amounts of water for 15 min (lifting upper and lower lids occasionally) and obtain medical attention. If ammonium hydroxide is ingested, obtain medical attention immediately. If large amounts of ammonia are inhaled, move the person to fresh air and seek medical attention at once.

In the event of a spill, soak up ammonium hydroxide with a spill pillow or absorbent material, place in an appropriate container, and dispose of properly. Alternatively, flood the spill with water to dilute the ammonia before cleanup. Boric, citric, and similar powdered acids are good granular neutralizing spill cleanup materials. Respiratory protection may be necessary in the event of a large spill or release in a confined area.

In some localities, ammonium hydroxide may be disposed of down the drain after appropriate neutralization and dilution. In a fume hood, the concentrated solution should be diluted with water to about 4% concentration in a suitably large container, and neutralized with a nonoxidizing strong acid such as HCl. The resulting solution can be discharged to the sanitary sewer. If neutralization and drain disposal are not permitted, excess ammonium hydroxide and waste material containing this substance should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines.

The information in this LCSS has been compiled by a committee of the National Research Council from literature sources and Material Safety Data Sheets and is believed to be accurate as of July 1994. This summary is intended for use by trained laboratory personnel in conjunction with the NRC report Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. This LCSS presents a concise summary of safety information that should be adequate for most laboratory uses of the title substance, but in some cases it may be advisable to consult more comprehensive references. This information should not be used as a guide to the nonlaboratory use of this chemical.

Copyright 1995 National Academy of Sciences. All rights reserved.