Bicarbonate

Bicarbonates, outdated and bicarbonates or acid carbonates, are the salts of carbonic acid, caused by simple neutralization of the acid with a base. Often also the anion of these salts, the bicarbonate ion ( HCO3- ), shortened referred to as bicarbonate. If by further base addition and the second acid function ( carboxy ) neutralized, we obtain carbonates.

As a result, have dissolved bicarbonate ions due to their potential, both a proton to give ( proton donor ) and resume ( proton acceptor ), an important physiological role as part of the carbonic acid -bicarbonate system and thus capacitively largest proportion of blood buffer systems in the regulation the acid- base balance of mammals.

Important are the bicarbonates of sodium bicarbonate (baking soda, salt Bull Rich - NaHCO3), the ammonium ( sal - NH4HCO3 ) and the calcium bicarbonate ( " carbonate hardness " of the water).

Properties of bicarbonates

The aggregate state is fixed as carbonates, because present between the hydrogen ions and cations ionic bonds and thereby transform regular ionic lattice. Bicarbonates are colorless and appear in white powder form, unless the cation introduces a color. Bicarbonates are odorless substances. The most soluble bicarbonates with water form electrically conductive solutions because they form free-moving, hydrated bicarbonate anion addition to the cations. Bicarbonate is amphoteric.

Decomposition: Above a temperature of 50 ° C decomposes hydrogen carbonate; among other things, produce water and carbon dioxide.

The bicarbonates of the alkaline earth metals (calcium, magnesium, barium, strontium ) are highly soluble in water, but are available from the dissociation of carbonic acid in relation to the corresponding carbonates, which are all poorly soluble. In order not to exceed the solubility of the carbonates, the pH must be sufficiently low, which is ensured by the presence of a minimum concentration of free carbonic acid, thus of dissolved carbon dioxide. These are referred to as corresponding carbonic acid. Escapes from the water or is it in lakes consumed by photosynthesis, so the carbonates differ partly in crystalline form from ( scale, marl )

Therefore, it is ( under normal conditions ) is not possible to produce the hydrogen carbonates of alkaline earth metals as a solid. Upon concentration of the solutions, the carbonates are always formed.

Reactions of hydrogen carbonates

Bicarbonate ions react as a weak acid with water to form carbonate ions and oxonium ions. This raises a chemical equilibrium, which lies mainly on the left:

Upon addition of a stronger acid such as hydrochloric acid to this bicarbonates react as a weak base to form carbon dioxide and water:

This reaction is with organic acids for effervescent powder of importance.

With calcium ions, an equilibrium with sparingly soluble calcium carbonate:

This balance shifts strongly on heating to the right side and is responsible for the formation of scale of importance. On passing carbon dioxide into a suspension of calcium carbonate, the equilibrium under dissolving calcium carbonate shifts to the left.

Occurrence and use of sodium bicarbonate

Sodium bicarbonate comes as a mineral ( Nahcolith ) ago in the USA. It takes place in the food industry, for example, as a back- and effervescent powder use. In medicine, it was used for heartburn ( " Bull Salz " ®). Sodium bicarbonate is also a component of fire extinguishing powder.

Producing sodium

This reaction must occur under cooling.

Use of ammonium

Hirschhorn salt is used in the baking of gingerbread and decomposes into ammonia (NH3 ), water and carbon dioxide. The commercial salt usually consists of a mixture of ammonium bicarbonate, ammonium carbonate and ammonium carbamate.

• Substance Group
• Bicarbonate