Carbonic acid only exists as an aqueous solution. It is a colourless, odourless, weak acid. When exposed to air for a longer period of time or to heat, it breaks down into carbon dioxide and water. Its salts are called carbonates, while its acid salts are called hydrogen carbonates.
Occurrence and production
In nature, carbonic acid is produced through the dissolution of atmospheric carbon dioxide in water. This plays an important role in weathering processes and in the creation of soil. Its salts are widespread with the most common carbonates being limestone and dolomite. In industry, it is produced by dissolving carbon dioxide in water.
Carbonic acid is added to mineral water and soft drinks.