CARBON, a tetrad, non-metallic ele ment, symbol C. At. wt., 12. Carbon oc curs in three allotropic forms—two crystalline (diamond and graphite), and one amorphous (charcoal). Diamond crystallizes in forms belonging to the regular system. It is transparent, either colorless, or yellow, pink, blue, or green. The hardest substance known, refracts light strongly, is infusible, but is burned into CO2 in oxygen gas at white heat. Sp. gr., 3.5. It is a non-conductor of electricity. It is found in gravel in India, Brazil, etc. Graphite crystallizes in six-sided prisms. Sp. gr., 2.3. It is gray-black, with a metallic luster. It is a good conductor of electricity. Graphite often separates in scales from molten iron; it is used for lead pencils; it is often called black-lead. Amorphous car bon occurs more or less pure in lamp black, wood charcoal, coal, coke, and ani mal charcoal. Sp. gr., from 1.6 to 2. It
is porous, absorbs gases, removes color from organic liquids, is used as a disin fectant, and burns in the air at red heat, forming CO:. When boiled with H,SO4, it is oxidized to CO, and SO2 is also . formed, which escape in gas used as a reducing agent. Carbon forms two oxides with oxygen, CO and CO,, car bonic oxide and carbonic anhydride. The compounds of this element are more numerous than those of all the other ele ments taken together. With hydrogen especially it forms a very large number of compounds, called hydrocarbons, which are possessed of the most diverse properties, chemical and physical. With oxygen, carbon forms only two com pounds, but union between the two ele ments is easily effected. It is one of the regular and most characteristic constitu ents of both animals and plants.