Smelling salts

Smelling salts are chemical compounds used to arouse consciousness. One such compound is ammonium carbonate, a whitish, crystalline solid ((NH4)2CO3.H2O).

Smelling salts release ammonia [NH3] gas, which irritates the mucous membranes of the nose and lungs, and thereby triggers an inhalation reflex (that is, it causes the muscles that control breathing to work faster).

When placed in water, it is called "aromatic spirits of ammonia."

Ammonium carbonate was formerly known as sal volatile. It was also known as spirit or salt of hartshorn, because ammonia was primarily produced from the antlers of male deer (harts).

Smelling salts are often used on athletes and boxers when they are knocked unconscious.