In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, CO2−3. The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C(=O)(O–)2. The term is also used as a verb, to describe carbonation: the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages – either by the addition of carbon dioxide gas under pressure, or by dissolving carbonate or bicarbonate salts into the water.