Graphite is an allotropic form of carbon, found in large deposits in Mexico, Sri Lanka, Madagascar, and in the United States in Alabama and New York. Graphite is a soft, dark gray, opaque solid with a greasy metallic luster. It crystallizes in hexagonal plates and is volatile only at the temperature of the electric arc. It is a good conductor of heat and electricity, and though it can be burnt to carbon dioxide, is less combustible than diamond. On oxidation with nitric acid and potassium chlorate it yields graphitic acid. Graphite can be obtained artificially by crystallizing any form of carbon from its solution in molten iron and is prepared commercially by heating coke in the electric furnace.
Although graphite is most familiar in lead pencils and stove polish, its most important use is in electrical equipment (electrodes, motor brushes, etc.), electrotyping, and lubricants. It may be mixed with molten babbit or bronze or sintered with these alloys to form self-lubricating bearing metals, called graphited metals. Finely ground (colloidal) graphite will form stable suspensions in water, oils, glycerin, and resins. These are marketed as lubricants under various trade names. Graphite plays an important role in foundries and metal refineries, where it is used for making crucibles and molds, or added to molten metal (steel) to increase the carbon content.
