. The Pharmaceutical era. l forms of carbon havebeen known for ages, but the element was not clearlyrecognized as one of the simple substances of nature un-:til near the close of the last century. The proof of theidientJty of the element iu its several natural forms was of until after the Tennant in 1796. and of Mackenzie in 1800. The name is derived from the Latin carbo, coal, orcharcoal. Natural Occurrence.—Carbon occurs free in three allotro-pic forms, diamond and graphite, both crystalline, andin the amorphous condition, as coal. Combined, it existsin vast quantities i
. The Pharmaceutical era. l forms of carbon havebeen known for ages, but the element was not clearlyrecognized as one of the simple substances of nature un-:til near the close of the last century. The proof of theidientJty of the element iu its several natural forms was of until after the Tennant in 1796. and of Mackenzie in 1800. The name is derived from the Latin carbo, coal, orcharcoal. Natural Occurrence.—Carbon occurs free in three allotro-pic forms, diamond and graphite, both crystalline, andin the amorphous condition, as coal. Combined, it existsin vast quantities in the carbon dioxid of the atmosphere,and in the mineral carbonates. Of these the most abun-dant is calcium carbonate, found as chalk, limestone andmarble, and a double carbonate of calcium and mag-nesium known as dolomite. Among other metals zinc,copper, barium and iron also frequently occur as carbon-ates. Carbon is an essential constituent of all organic struc-tures, both animal and vegetable, and is the element left. g. 37.—Natural Forms of the Diamond. behind as charcoal or coke when these substances areheated out of contact with the first of the natural forms of carbon in 948 THE PHARMACEUTICAL EKA. [December 23, 1897. popular eslimntioii is the diamond, wliicU is nearly pureaud colorless crystallized carbon. It crystallizes in theregular system (KIb. 37), is the hardest substance known,capable of abrading all other substances and of beingabraded by none, and is a poor conductor of heat andelectricity. Its brilliancy is due to the numerous inter-nal reflections which take place within it. Its specificgravity is to A dark colored or black variety isknown tiscaiboiiado, and has a specific gravity of It is used for diamond polishing and for pointingrock-cutting tools. Under the name othort. a coarsekind of diamond is used for glass cutting. In the absence of air diamond can be heated to a whiteheat without change, but by the heat of the e
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