In chemistry, carbonic acid is the dibasic acid with a chemical formula . The pure compound decomposes at temperatures greater than ca. −80 °C.
In biochemistry and physiology, the gain "carbonic acid" is often applied to aqueous solutions of carbon dioxide, which play an important role in the bicarbonate buffer system, used to retains acid–base homeostasis.
Strictly speaking the term "carbonic acid" talked to the chemical compound with the formula .
Since pKa1 has a return of ca. 6.8 , at equilibrium carbonic acid will be near 50% dissociated in the extracellular fluid cytosol which has a pH of ca.7.2. Note that dissolved carbon dioxide in extracellular fluid is often called as "carbonic acid" in biochemistry literature, for historical reasons. The reaction in which this is the produced
is fast in biological systems. Carbon dioxide can be noted as the anhydride of carbonic acid.
.