Why is calcium carbonate in organic compounds

Calcium carbonate (technical language), too calcium carbonate or out of date carbonate of lime, is a chemical compound with the chemical formula CaCO3. It is a calcium salt of carbonic acid (carbonate) and consists in the solid state of an ion lattice with Ca2+Ions and CO32-Ions in a ratio of 1: 1.

Calcium carbonate is widespread on earth. It occurs in the form of the minerals calcite and aragonite, but also in bones and teeth as well as in the exoskeleton of crustaceans, corals, mussels, snails and protozoa. Another modification of CaCO3 is the mineral vaterite, which precipitates out in the form of microscopic crystals, especially from oversaturated solutions.

The limestone rock consists of calcium carbonate, but it is seldom pure; it is almost always dolomitised to a varying extent, i.e. H. it is partly a mixed carbonate of calcium and magnesium.

Calcium carbonate itself is hardly soluble in pure water. The limestone is weathered with the formation of the easily soluble calcium hydrogen carbonate Ca (HCO3)2, by absorbing hydrogen ions from acids. Normally it is carbonic acid from the carbon dioxide, as well as nitric acid from the nitrification in the soil, and recently sulfurous acid from the pollution of the air with sulfur dioxide). Most natural occurrences of calcium carbonate owe their creation to the reversal of this dissolution process by removing carbon dioxide.

Natural calcium carbonate

In nature, calcium carbonate forms the minerals calcite and aragonite as well as three different calcium carbonate rocks, which are chemically identical but otherwise differ in some ways:

  • chalk is a fine, microcrystalline sedimentary rock, which was created by the deposition of calcite precipitated by photosynthetic carbonic acid removal as well as the aragonitic shells of small fossil organisms such as coccoliths of the coccolithophores and shells of the chamberlings (Foraminifera). Chalk appears in numerous locations along the European chalk belt, from Great Britain to France to the island of Rügen in northern Germany, and is also extracted in places. Sea chalk at the bottom of lakes or in silted lake basins consists almost entirely of precipitated calcite. (The blackboard chalk used in technology, on the other hand, is mainly made from gypsum (calcium sulfate).)
  • limestone is also biogenic, but more solidified than chalk. It is formed either directly or indirectly from the remains of living things - such as snails, mussels, rock-forming corals and sponges, which secrete calcium carbonate to build external or internal skeletons. It is formed indirectly by the fact that living beings, especially phototrophic, CO2 assimilate and thus alkalize the environment, which leads to the precipitation of calcium carbonate. The size of the carbonate crystals is between that of chalk and marble. There are large limestone deposits in Orgon, France, and in Burgberg in the Allgäu (Germany). Limestone can also be found on the Swabian and Franconian Alb, as well as in the Limestone Alps.
  • Calcite marble is a coarsely crystalline, metamorphic rock that is formed when chalk or limestone is recrystallized under the influence of high temperatures and pressures. Large marble deposits can be found in North America and Europe, for example in Austria, Norway or in Carrara, Italy, the home of the pure white "Statuario" from which Michelangelo created his sculptures. Marbles can also consist of pure dolomite, so a differentiation must be made here.

Although more than five percent of the earth's crust consists of calcium carbonate rocks, only a few deposits are suitable for the extraction of fillers. Purity, whiteness, thickness and homogeneity are just some of the parameters that geologists record when prospecting calcium carbonate deposits around the world.

See also

Calcite, aragonite, limestone alps, lime soap, limestone, lime deposits, boiler stone, carbon cycle, tadelakt, stalactite, water hardness


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Categories: Calcium Compound | Carbonate | Drug