Bicarbonates

BICARBONATES (acid salts), monometallic, acidic salts of carbonic acid H₂CO₃ (e.g., NaHCO₃, sodium bicarbonate). As salts of a very weak acid, bicarbonates are decomposed by all mineral and even most organic acids with the release of free CO₂; they also decompose when heated. Bicarbonates of alkali metals are soluble in water; among alkaline earth metals, the salt of calcium is slightly soluble. The main portion of calcium present in blood is found there precisely in the form of bicarbonates, forming a supersaturated solution. Bicarbonates play an important physiological role, since as salts of a weak acid and a strong base, in the presence of CO₂ they form a buffer system and serve as the main buffer substances regulating the constancy of the blood's active reaction (see Buffer properties). At the same time, the formation and decomposition of bicarbonates determine, mainly, the transport of CO₂ in blood from tissues to the lungs and its elimination during respiration. Practically, all CO₂ present in venous blood is in the form of bicarbonates (see Reserve alkalinity). In addition to regulating the active reaction, bicarbonates also have a certain specific effect on some biological processes. Thus, for example, one of the most important processes of tissue metabolism - anaerobic breakdown of sugar (glycolysis, see) - proceeds only if there is a sufficiently high concentration of bicarbonates.