Hydrogencarbonat

Hydrogencarbonat (HCO3−), or hydrogen carbonate, is the bicarbonate anion derived from carbonic acid (H2CO3). It is the conjugate base of carbonic acid and the conjugate acid of carbonate (CO3^2−). In aqueous solution it is amphiprotic: it can accept a proton to form H2CO3 or donate a proton to form CO3^2−, a property that underlies its role in buffering systems.

In nature, bicarbonate is abundant in freshwater, seawater and groundwater, produced when carbon dioxide dissolves in water and partially reacts to form HCO3−. The CO2/H2CO3–HCO3−/CO3^2− system acts as a pH buffer around pH 6.1–10.3 (with the two pKa values approximately 6.3 and 10.3), stabilizing pH in biological fluids such as blood where bicarbonate is a major component of the buffering system.

Bicarbonate occurs as salts with various cations, notably sodium bicarbonate NaHCO3, potassium bicarbonate KHCO3 and ammonium bicarbonate NH4HCO3. They are water-soluble and are produced industrially by reacting carbon dioxide with carbonates or by neutralizing carbonic acid.

Common uses include baking and cooking as a leavening agent (baking soda), antacids and urinary alkalinizers, and as a buffering agent in foods and beverages. It is also used in cleaning, cosmetics, and as a pH adjuster in water treatment and chemical processes. In biology and medicine, bicarbonate balance is essential for acid–base homeostasis.

Safety notes: bicarbonates are generally regarded as safe in conventional uses, but excessive intake can cause metabolic alkalosis, electrolyte disturbances, or gas buildup from CO2 release when reacting with acids.