Ammonium Carbonate

Ammonium carbonate (formerly known as sal volatile or salt of hartshorn) is a commercial salt with the chemical formula (NH4)2CO3. It is used when crushed as a smelling salt. It can be crushed when needed in order to revive someone who has fainted. It is also known as baker's ammonia and was a predecessor to the more modern leavening agents baking soda and baking powder.