Car·bon n.  Chem.
 1. An elementary substance, not metallic in its nature, which is present in all organic compounds. Atomic weight 11.97. Symbol C. it is combustible, and forms the base of lampblack and charcoal, and enters largely into mineral coals. In its pure crystallized state it constitutes the diamond, the hardest of known substances, occuring in monometric crystals like the octahedron, etc. Another modification is graphite, or blacklead, and in this it is soft, and occurs in hexagonal prisms or tables. When united with oxygen it forms carbon dioxide, commonly called carbonic acid, or carbonic oxide, according to the proportions of the oxygen; when united with hydrogen, it forms various compounds called hydrocarbons. Compare Diamond, and Graphite.
 2. Elec. A carbon rod or pencil used in an arc lamp; also, a plate or piece of carbon used as one of the elements of a voltaic battery.
 Carbon compounds, Compounds of carbon Chem., those compounds consisting largely of carbon, commonly produced by animals and plants, and hence called organic compounds, though their synthesis may be effected in many cases in the laboratory.
    The formation of the compounds of carbon is not dependent upon the life process.   --I. Remsen
 -- carbon copy, originally, a copy of a document made by use of a carbon paper, but now used generally to refer to any copy of a document made by a mechanical process, such as xerographic copying.
 Carbon dioxide, Carbon monoxide. Chem. See under Carbonic.
 Carbon light Elec., an extremely brilliant electric light produced by passing a galvanic current through two carbon points kept constantly with their apexes neary in contact.
 Carbon point Elec., a small cylinder or bit of gas carbon moved forward by clockwork so that, as it is burned away by the electric current, it shall constantly maintain its proper relation to the opposing point.
 Carbon paper, a thin type of paper coated with a dark-colored waxy substance which can be transferred to another sheet of paper underneath it by pressing on the carbon paper.  It is used by placing a sheet between two sheets of ordinary writing paper, and then writing or typing on the top sheet, by which process a copy of the writing or typing is transferred to the second sheet below, making a copy without the need for writing or typing a second time.  Multiple sheets may be used, with a carbon paper placed above each plain paper to which an impression is to be transferred.  In 1997 such paper was still used, particularly to make multiple copies of filled-in purchase invoice forms, but in most applications this technique has been superseded by the more faithful xerographic reproduction and computerized printing processes.
 Carbon tissue, paper coated with gelatine and pigment, used in the autotype process of photography. --Abney.
 Gas carbon, a compact variety of carbon obtained as an incrustation on the interior of gas retorts, and used for the manufacture of the carbon rods of pencils for the voltaic, arc, and for the plates of voltaic batteries, etc.

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 Gas n.; pl. Gases
 1. An aëriform fluid; -- a term used at first by chemists as synonymous with air, but since restricted to fluids supposed to be permanently elastic, as oxygen, hydrogen, etc., in distinction from vapors, as steam, which become liquid on a reduction of temperature. In present usage, since all of the supposed permanent gases have been liquified by cold and pressure, the term has resumed nearly its original signification, and is applied to any substance in the elastic or aëriform state.
 2. Popular Usage (a) A complex mixture of gases, of which the most important constituents are marsh gas, olefiant gas, and hydrogen, artificially produced by the destructive distillation of gas coal, or sometimes of peat, wood, oil, resin, etc. It gives a brilliant light when burned, and is the common gas used for illuminating purposes. (b) Laughing gas. (c) Any irrespirable aëriform fluid.
 Note: ☞ Gas is often used adjectively or in combination; as, gas fitter or gasfitter; gas meter or gas-meter, etc.
 Air gas Chem., a kind of gas made by forcing air through some volatile hydrocarbon, as the lighter petroleums. The air is so saturated with combustible vapor as to be a convenient illuminating and heating agent.
 Gas battery Elec., a form of voltaic battery, in which gases, especially hydrogen and oxygen, are the active agents.
 Gas carbon, Gas coke, etc. See under Carbon, Coke, etc.
 Gas coal, a bituminous or hydrogenous coal yielding a high percentage of volatile matters, and therefore available for the manufacture of illuminating gas. --R. W. Raymond.
 Gas engine, an engine in which the motion of the piston is produced by the combustion or sudden production or expansion of gas; -- especially, an engine in which an explosive mixture of gas and air is forced into the working cylinder and ignited there by a gas flame or an electric spark.
 Gas fitter, one who lays pipes and puts up fixtures for gas.
 Gas fitting. (a) The occupation of a gas fitter. (b) pl. The appliances needed for the introduction of gas into a building, as meters, pipes, burners, etc.
 Gas fixture, a device for conveying illuminating or combustible gas from the pipe to the gas-burner, consisting of an appendage of cast, wrought, or drawn metal, with tubes upon which the burners, keys, etc., are adjusted.
 Gas generator, an apparatus in which gas is evolved; as: (a) a retort in which volatile hydrocarbons are evolved by heat; (b) a machine in which air is saturated with the vapor of liquid hydrocarbon; a carburetor; (c) a machine for the production of carbonic acid gas, for aërating water, bread, etc. --Knight.
 Gas jet, a flame of illuminating gas.
 Gas machine, an apparatus for carbureting air for use as illuminating gas.
 Gas meter, an instrument for recording the quantity of gas consumed in a given time, at a particular place.
 Gas retort, a retort which contains the coal and other materials, and in which the gas is generated, in the manufacture of gas.
 Gas stove, a stove for cooking or other purposes, heated by gas.
 Gas tar, coal tar.
 Gas trap, a drain trap; a sewer trap. See 4th Trap, 5.
 Gas washer Gas Works, an apparatus within which gas from the condenser is brought in contact with a falling stream of water, to precipitate the tar remaining in it. --Knight.
 Gas water, water through which gas has been passed for purification; -- called also gas liquor and ammoniacal water, and used for the manufacture of sal ammoniac, carbonate of ammonia, and Prussian blue. --Tomlinson.
 Gas well, a deep boring, from which natural gas is discharged. --Raymond.
 Gas works, a manufactory of gas, with all the machinery and appurtenances; a place where gas is generated for lighting cities.
 Laughing gas. See under Laughing.
 Marsh gas Chem., a light, combustible, gaseous hydrocarbon, CH4, produced artificially by the dry distillation of many organic substances, and occurring as a natural product of decomposition in stagnant pools, whence its name. It is an abundant ingredient of ordinary illuminating gas, and is the first member of the paraffin series. Called also methane, and in coal mines, fire damp.
 Natural gas, gas obtained from wells, etc., in Pennsylvania, Ohio, and elsewhere, and largely used for fuel and illuminating purposes. It is chiefly derived from the Coal Measures.
 Olefiant gas Chem.. See Ethylene.
 Water gas Chem., a kind of gas made by forcing steam over glowing coals, whereby there results a mixture of hydrogen and carbon monoxide. This gives a gas of intense heating power, but destitute of light-giving properties, and which is charged by passing through some volatile hydrocarbon, as gasoline.