Carbonic acid is an acid with the chemical formula of H2CO3. It is the reaction product of water and carbon dioxide and exists in an equilibrium with water and carbon dioxide whenever the latter is dissolved in the former, for instance in soda water or blood. It is not possible to obtain pure carbonic acid.
Carbonic acid is present in carbonated soft drinks. In such beverages it occurs in approximately 150 times the concentration than in the natural occurrence which aided in the carving of Mammoth Cave.