CARBON. The soft black "lead" in our pencils— which is not lead at all but graphite—and the hard diamond, flashing and brilliant, are both pure car bon. The gritty charred mass left after wood is burned, which we call charcoal, and the hard black coal we burn in our furnaces are mostly carbon.
Indeed, the more carbon there is in coal the better it is; if it is more than 90 per cent carbon we call it "hard" coal or "anthracite." Sugar is about 40 per cent carbon, and when a lump of it is heated the charred mass that remains behind is chiefly carbon.
The soot produced when organic matter is burned is almost all carbon.
At ordinary temperatures carbon is an inactive element; graphite or a diamond will lie under water for ages and remain unchanged. Carbon cannot be melted. A thread of carbon inclosed in a glass bulb from which the air has been sucked out, when raised to a very high temperature by an electric current, glows with an extremely bright light, but it neither burns nor melts. This is the principle of the incan descent light. It dissolves to a certain extent in molten iron, and if it is then suddenly cooled under great pressure it sometimes crystallizes into minute diamonds.
Carbon enters into an almost unending number of compounds, and its chemical history is so long and so varied that all chemistry is divided into two great branches, the second of which (called " organic chem istry") is devoted exclusively to carbon compounds.
More than 200,000 carbon compounds are known and thousands are being added every year.
Carbon gives us all our fuel. In coal, kerosene, gas, oil, fat, lard, tallow, suet, blubber, wood, or any form of fuel whatever, carbon is one of the elements which, uniting with the oxygen, gives us heat and light.
Carbon gives us our food and clothing, for carbon is the basis upon which all animal and vegetable tissues are built up. Green grass, hay, honey, and starch all contain carbon. It is present in tea, coffee, bread, vinegar, butter, and almost every other article of food, and cotton and wool are largely made up of this important element.
United with oxygen it forms the gas carbon dioxide. With hydrogen it forms marsh gas and a great number of hydrocarbons, as those of petroleum and numerous coal-tar products. With hydrogen and oxygen it forms acetic acid and other organic acids, alcohols, oils and fats, and the carbohydrates, of which the sugars, starches, and cellulose, important constituents of plants, are the best known.
A great many very complicated compounds occur in plants, and particularly in animals, in which (besides carbon, hydrogen, and oxygen) nitrogen and sometimes sulphur and other elements are present. Carbon also unites with certain metals, and with iron it forms steel and cast-iron. Certain denser forms of carbon, such as retort carbon from gas works and petroleum refining, conduct electricity well and are extensively used in batteries and electric lamps.
Calcium carbide is a compound of calcium and carbon used in generating acetylene gas. (See Charcoal ; Coal ; Diamond; Graphite.)