carbonic

Carbonic is an adjective relating to carbon or to carbonic acid and its derivatives. In chemistry, it most often denotes carbonic acid (H2CO3) and species derived from it, such as bicarbonate (hydrogen carbonate, HCO3−) and carbonate (CO3^2−). Carbonic acid forms when carbon dioxide dissolves in water: CO2 + H2O ⇌ H2CO3, though most dissolved inorganic carbon exists as CO2 and bicarbonate. The carbonic system has two dissociation steps: H2CO3 ⇌ HCO3− + H+, pKa1 ≈ 6.35; HCO3− ⇌ CO3^2− + H+, pKa2 ≈ 10.33 at 25°C. These equilibria govern the buffering of pH in natural waters and many biological fluids.

The enzyme carbonic anhydrase catalyzes the rapid interconversion between CO2 and H2CO3, accelerating gas exchange and metabolic reactions. Carbonates and bicarbonates are major constituents of rocks and soils and contribute to the global carbon cycle through weathering, precipitation, and dissolution processes. In the ocean, the carbonate system helps regulate pH and carbonate ion availability, affecting calcifying organisms.

In practical terms, carbonic compounds are central to beverage carbonation, food processing, and various industrial applications. The concept also underpins physiological and medical topics such as acid–base balance, and geochemical studies of mineral solubility and transport in relation to the carbon cycle.