Ammonia, often referred to as anhydrous ammonia, is a colorless gas with a bitter taste and a sharp, intensely irritating, characteristic odor. It is one of the highest-volume chemicals produced in the United States and is found in industry, agriculture, and all modes of transportation.


Ammonia is a gas in its natural state and, because of its relatively high boiling point ( – 28°F), is easily liquefiable. Since so much more material can occupy the same space in a liquid form rather than as a gas. ammonia usually is shipped and stored as a liquid. It is colorless as a liquid, but as it vaporizes it may take on a white appearance as it condenses water out of the air. Ammonia is very soluble in water, forming an alkaline solution of ammonium hydroxide.

Ammonia’s specific gravity as a liquid is 0.68. its vapor density as a gas is 0.59, and it freezes at – 1()8°F. A stable compound, ammonia’s molecular formula is NH*, and its molecular weight is 17.0.

Since ammonia is easily liquefiable, it has found use as a refrigerant.


Anhydrous ammonia is classified by the Department of Transportation as a nonflammable gas because its lower flammable limit (16 percent) is above that needed for it to be considered a flammable gas, and its flammable range (16 percent to 25 percent) is not wide enough for it to be considered flammable. However, ammonia will burn as soon as a concentration of 16 percent and its ignition temperature of 1,204°F are reached.

The greatest hazard of ammonia may be its toxicity. It can be detected in a concentration as low as 0.04 ppm (parts per million) and has a short-term exposure limit of 35 ppm. Exposure to 5,000 ppm will be fatal almost immediately. Contact with liquid ammonia will cause frostbite.

Contact with ammonium hydroxide, a very alkaline or caustic base, will cause severe burns to the skin when very high concentrations are contacted. As a vapor, 700 to 1,000 ppm may cause serious eye damage and perhaps blindness.


Ammonia reacts dangerously with many materials. It evolves heat as it dissolves in water. It reacts with acids, aldehydes, amides, isocyanate, organic anhydrides, strong oxidizers, and several metals. It is corrosive to aluminum, copper, lead, tin, zinc, and many alloys. Ammonia may form explosive compounds with calcium hypochlorite, gold, mercury, and silver

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