What is the chemical formula Carbit

  Carbides are binary compounds of an element E with carbon C to compounds of type E.xC.y.


The carbides are usually produced from elemental carbon, which is converted at high temperatures with the corresponding element, element oxide or element carbonate in a solid-state reaction.

The production of calcium carbide from coke C and calcium carbonate CaCO3 for example takes place at 2000 ° C in a rotary kiln.

Different types of carbides are formed depending on the electronegativity difference between the element in question and carbon.

Ionic carbides

Ionic carbides have a strong salt character and are typically formed by the strongly electropositive elements of the alkali, alkaline earth and earth elements. There are thus chemical compounds that contain carbon as a more electronegative component.

Typical examples are lithium carbide Li4C, beryllium carbide Be2C, magnesium carbide Mg2C.3, Calcium carbide CaC2 or aluminum carbide Al4C.3.

In their ion lattice they contain the respective metal cation and the carbide ion, which is formally derived from various hydrocarbons. This leads to a further differentiation of the carbides into the methanides (Li4C, Be2C and Al4C.3 contain C4- derived from methane CH4), the acetylides (e.g. CaC2 contains (C22- derived from ethyne (acetylene) C2H2) and allenides (e.g. Mg2C.3 contains C34-, derived from Allen C3H4).

Ionic carbides react with water to form the corresponding metal hydroxide and the corresponding hydrocarbon, which is released through multiple protonation by the water.

The best-known representative is the calcium carbide (CaC) used in the carbide lamp2), often simply called carbide, which releases ethine in the presence of water:

The gray color of the actually white calcium carbide results from impurities in elemental carbon from the manufacturing process (see above). The typical smell of calcium carbide is the monophosphane PH3 attributable to, which is formed in a manner analogous to acetylene by hydrolysis from calcium phosphide. Calcium phosphate occurs in the manufacturing process when the calcium carbonate used contains traces of calcium phosphate as an impurity.

Up until the 1930s, the hydrolysis of calcium carbide was the only way to produce ethyne on an industrial scale and was therefore an important starting material for the development of acetylene chemistry (cf. Reppe chemistry). However, with the advent of the petrochemical industry, this source of ethyne has lost a lot of its importance today.

Covalent carbides

The covalent carbides are formed between carbon and elements with approximately the same electronegativity. The two most important examples are SiC (silicon carbide, "Carborundum®") and B.4C (boron carbide). They consist of covalent bonds between carbon and the respective element. The formation of very strong covalent bonds, combined with a crystal structure that is very similar to hard materials (SiC has a diamond structure) leads to high mechanical stability. Accordingly, these carbides are usually used as hard materials (coatings, grinding tools) and for reinforcing plastics. Silicon carbide is also of interest as a carrier material for catalysts in the chemical industry, since it has a high thermal conductivity and practically no abrasion.

Metal-like carbides

These carbides are derived from the elements of the 4th-7th centuries. Subgroup formed, typical examples are titanium and tungsten. As a rule, they do not have a precisely defined stoichiometry. The reason for this is that individual carbon atoms are embedded in the tetrahedral gaps in the metal lattice (so-called Storage connections or interstitial connections). The resulting substances are in turn characterized by high mechanical and thermal stability and high melting points (3000-4000 ° C) and are used as hard materials and ceramics in chemical apparatus and plant construction as well as cutting and grinding tools.

The ball of a ballpoint pen is made of tungsten carbide, for example.

Carbide shooting

The tradition of carbide shooting is mainly cultivated in Holland and in some parts of northwest Germany and northern Bavaria by young men at weddings, New Year's Eve and New Year's. In Upper Lusatia it is known as Easter shooting. Due to the high risk potential, carbide shooting is forbidden in Germany and only permitted on New Year's Eve and New Year in Holland, but in Germany it is also practiced by young people on New Year's Eve or similar events. Proper carbide shooting celebrations are held in the Netherlands. If you put a few pieces of calcium carbide in a milk can and sprinkle a little water on it, an explosive gas mixture is created in the volume sealed with a lid or a football. The gas mixture is then ignited through a previously drilled hole in the ground. The explosion can throw the lid or soccer ball up to 70m.

Carbide fishing

The same principle was used by some people in the starvation period after the world war, in order to quickly kill and clear away many fish "before the jeep arrives" by exploding a carbide can in fish waters, despite the prohibition by the occupying powers. Carbide was readily available at the time because of its use to make acetylene for welding and because of its use in carbide bicycle lights.

See also

Categories: Fabric Group | Carbide