Carbon is a major component in very large masses of carbonate rock (limestone, dolomite, marble).
Carbon occurs in all known organic life and is the basis of organic chemistry. When united with hydrogen, it forms various hydrocarbons.
When combined with oxygen and hydrogen, carbon can form many groups of important biological compounds, including sugars, lignans, chitins, alcohol, fats and aromatic esters, carotenoids and terpenes. Combined with Nitrogen it forms Alkaloids, and with the addition of sulfur also form anti-biotics, amino acids and rubber products. With the addition of phosphorus to these elements, it forms DNA & RNA, the chemical code carriers of life, Adenosine Triphosphate (ATP), the most important energy-transfer molecules in all living cells.
Coal is the largest commercial source of mineral carbon. Anthracite contains 92-98% carbon.
There are three naturally occurring isotopes, with C-12, and C-13 being stable, while C-14 is radioactive.
Atomic Carbon is a very short-lived species, and therefore, carbon is stabilized in various multi-atomic structures with different molecular configurations called allotropes. The best known allotropes are graphite, diamond, and amorphous carbon.
The largest sources of inorganic carbon are limestone, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil and methane clathrates.
Carbon has the highest sublimation point of all elements. At atmospheric pressure it has no melting point, so it sublimes at about 3,900K.
Solid carbon sublimes in a carbon arc which has a temperature of about 5,530°C. Carbon remains solid at higher temperature than the highest melting point metals such as Tungsten or Rhenium.
Carbon are comparatively unreactive under normal conditions. It does not react with sulfuric Acid, Hydrochloric acid, Chlorine or any alkalis.
At elevated temperatures carbon reacts with oxygen to form carbon oxides, and will reduce such metal oxides as iron oxide to the metal.
Carbon combines with some metals at high temperature to form metallic carbides, such as the iron carbide CEMENTITE in steel, and tungsten carbide, widely used as an abrasive and for making hard tips for cutting tools.
Amorphous Form of carbon is an assortment of carbon atoms in a non-crystalline, irregular, glassy state, which is essentially graphite but not held in a crystalline macrostructure. It is present as a powder. Example of Amorphous Carbon are charcoal, lampblack and activated carbon.
At normal pressure carbon takes the form of graphite. At very high pressure carbon forms the more compact allotrope diamond, having nearly twice the density of graphite.
Graphite deposits are of metamorphic origin, found in association with quartz, mica and feldspars in schists, gneisses and metamorphosed sandstones and limestone as lenses or veins, sometimes of a meter or more in thickness.
Three types of Natural graphite: Amorphous, Flake or Crystalline flake, and vein or lump.
