Ammonium Hydroxide

OVERVIEW

Ammonium hydroxide (uh-MOH-ni-um hye-DROK-side) is a clear, colorless aqueous solution consisting of ammonia gas dissolved in water. The compound does not exist in any other state. Ammonium hydroxide has a strong pungent, suffocating odor caused by the release of ammonia gas from the solution. Most solutions of ammonium hydroxide range in concentration from less than one percent to about 35 percent ammonia. For most commercial purposes the lowest concentration is about 10 percent ammonia in water.

HOW IT IS MADE

Ammonium hydroxide is prepared by passing ammonia gas (NH₃) into water. Once prepared, ammonium hydroxide solutions tend to be very stable.

KEY FACTS

OTHER NAMES:

Ammonia solution, aqua ammonia, ammonium hydrate, spirits of hartshorn

FORMULA:

NH₄OH

ELEMENTS:

Nitrogen, hydrogen, oxygen

COMPOUND TYPE:

Inorganic base

STATE:

Aqueous solution (exists only in solution)

MOLECULAR WEIGHT:

35.05 g/mol

MELTING POINT:

Not applicable

BOILING POINT:

Not applicable

SOLUBILITY:

Not applicable

COMMON USES AND POTENTIAL HAZARDS

The uses of ammonium hydroxide are closely related to those of ammonia gas from which it is made. The advantage of using ammonium hydroxide over ammonia is that the reactant (the ammonia) may be more easily controlled when dissolved in water than when available as a gas.

Some uses of ammonium hydroxide include:

• As a cleaning agent in a variety of industrial and commercial products, such as household ammonia, where the concentration of the solution is generally in the range of 3 to 10 percent;
• In the manufacture of rayon and other textiles;
• As a refrigerant;
• As a food additive to maintain the proper level of acidity in the food;
• In the production of soaps and detergents, pharmaceuticals, ceramics, explosives, and inks; and
• In the fireproofing of wood.

Health hazards posed by ammonium hydroxide are a consequence of the ammonia present in the solution. When exposed to the air, such solutions tend to release some ammonia gas, which users may breathe in. The gas may then cause irritation of the eyes, nose, and throat that, for weak solutions, is generally unpleasant but not dangerous. Exposure to higher concentrations of ammonia released from ammonium hydroxide may result in more serious health problems, such as severe burning of the eyes, nose, and throat and permanent damage to these parts of the body, including blindness, lung disease, and death. One of the most dangerous hazards posed by ammonium hydroxide occurs when it is mixed with substances containing chlorine, such as bleaching products. That combination may result in large amounts of heat and toxic gases that can cause serious injuries and even death.

Words to Know

AQUEOUS SOLUTION

A solution that consists of some material dissolved in water.

PUNGENT

Intensely sharp or biting.

FOR FURTHER INFORMATION

"Ammonia: Public Health Statement." Agency for Toxic Substances and Disease Registry. http://www.atsdr.cdc.gov/toxprofiles/tp126-c1.pdf (accessed on September 19, 2005).

"Ammonium Hydroxide." Industrial Resources Group, Ltd. http://www.indresgroup.com/aqua.htm (accessed on September 19, 2005).

"Ammonium Hydroxide." Medline Plus Medical Encyclopedia. http://www.nlm.nih.gov/medlineplus/ency/article/002491.htm (accessed on September 19, 2005).

See AlsoAmmonia