Bicarbonate is an essential component of the bicarbonate buffer system, which plays an important role in maintaining a constant pH value in the body. This means that strong fluctuations can be balanced quickly and easily.

Bicarbonate is responsible for regulating the pH value in the body and thus for balancing acids.

Hydrogen carbonates, also known as acid carbonates or outdated bicarbonates, are salts of carbonic acid that are formed by simple neutralization of this acid with a base. The anion of these salts, the hydrogen carbonate ion (HCO3-), is often referred to as hydrogen carbonate (or bicarbonate) for short. If the second acid function (carboxy group) is also neutralized by further addition of bases, carbonates are obtained.

Dissolved hydrogen carbonate ions therefore have an important physiological significance as a component of the carbonic acid-bicarbonate system and are thus capacitively the largest component of the blood buffer systems in the regulation of the acid-base balance of mammals.

Hydrogen carbonates are salts that are soluble in water and have a basic character. Their name indicates that they contain hydrogen carbonates and cations. The most common hydrogen carbonate is sodium bicarbonate, also known as baking powder.

The structure of a hydrogen carbonate molecule is simple: it consists of a central carbon atom surrounded by four oxygen atoms, to which two hydrogen atoms are bonded. This creates an ion lattice with regular structures. Hydrogen carbonates are odorless substances; they appear white in powder form unless the cation contributes a color.

Hydrogen carbonates are amphoteric compounds: They can act as both acids and bases; depending on the pH value of their solution, they either release or absorb protons (H+ ions).

Alkaline earth metals are usually present in their compounds as hydroxides, carbonates and silicates. Under certain conditions, however, they can also be present in their hydrogen carbonate form. These conditions include a low pH value and the presence of free CO2.

If the pH is low enough to dissociate carbonic acid (which is poorly soluble), a minimum concentration of free CO2 is required to produce hydrogen carbonate solids. This can be avoided by concentrating the solution or removing the CO2 from it (by photosynthesis).

Sodium bicarbonate is a mineral that is found in several places around the world, including the USA. It occurs as a near-colith and is used in food technology, e.g. as baking and sherbet powder. In medicine, it is used to treat heartburn ("Bullrich's salt"®). Sodium hydrogen carbonate is also a component of fire extinguishing powder.