What is calcium carbonate?
Calcium carbonate (chemical formula: CaCO3) is the calcium salt of carbonic acid.
Appearance
Calcium carbonate occurs naturally much as the mineral calcite. The sedimentary rock, limestone and metamorphic form thereof, marble, are composed largely of calcite. In nature, calcite is usually partially contaminated with magnesium ions which may be replaced in the crystal lattice of calcite calcium ions. An unstable polymorph of calcite is aragonite. Many sea creatures use aragonite to build their skeletons. When organisms die with aragonite skeletons, sediment their skeleton. Through recrystallization the aragonite is again calcite. The least stable form of calcium carbonate is vaterite. This will naturally almost impossible to find because the transformation from vaterite to calcite is completed within a day.
The shell of the eggs and the shell from slag and shellfish mainly consists of calcium carbonate. It is also a reinforcing mineral in the shells of crustaceans and many insects. Chemically it is calcium carbonate, which occurs in nature, contaminated with all sorts of other substances.
In the household one knows calcium carbonate as one of the components in boiler scale.
Properties of calcium carbonate
Calcium carbonate is a salt and therefore an ionophore. In the pure state, it is a white solid, which is poorly soluble in water. In acids, the substance is soluble.
The low decomposition point (899 ° C) in comparison with the melting point (1339 ° C) has to do with the fact that the equilibrium pressure of CO2 above reaches CaCO3 standard pressure at the decomposition temperature. The compound is then converted to calcium oxide (CaO). By ensuring that the gaseous carbon dioxide may escape can be the melting point of calcium carbonate are not achieved. The molecular weight of calcium carbonate is 100.09 g / mol.
Applications
As a building material
Calcium carbonate is widely used as a building material. It finds applications as a structural element (tooth) and as a decorative element. Limestone often contains easily recognizable fossils. The calcium in limestone indeed generated by the scales of large or small shellfish).
In agriculture
In agriculture is calcium carbonate under the name lime used as soil conditioner. The lime neutralizes the acids with its alkaline carbonate ion and thus increases the pH. For both lime fertilizer with magnesium used (Dolokal and Magkal) as calcium carbonate submitted by Limburg (Limkal and Vitakal). Also a residual product that is released in the production of beet sugar and that calcium carbonate foam (Betacal), in agriculture. Dolokal and Magkal contain about 80% lime (CaCO3) and 19% magnesium carbonate (MgCO3); Dolomite respectively 60% and 8%.
Calcium carbonate is included in the list of pesticides that are allowed by the European Union.
In food and medicine
The mineral has a gray and white pigment and is approved in the European Union as a food coloring agent with the E number E170 (i). For example, it is used as a surface staining for the white "fungus" in various types of dry sausages. It is also used as a solvent for tablets. Calcium carbonate is the primary constituent of, for example, stomach tablets. It is also used in the acidification of wine, and as a stabilizer for canned fruit. Further, it is used as an anti-caking agent for salt, and as a thickening agent. In some types of chewing gum is calcium carbonate used as filler.