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MARSH GAS (methane), CH4

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Originally appearing in Volume V17, Page 774 of the 1911 Encyclopedia Britannica.
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MARSH See also:GAS (methane), See also:CH4 , the first member of the See also:series of See also:paraffin See also:hydrocarbons. It occurs as a constituent of the " See also:fire-See also:damp " of See also:coal-mines, in the gases evolved from volcanoes, and in the gases which arise in marshy districts (due to the decomposition of See also:vegetable See also:matter under the See also:surface of See also:water). It is found associated with See also:petroleum and also in human intestinal gases. It is a product of the destructive See also:distillation of complex organic matter (See also:wood, coal, bituminous shale, &c.), forming in this way from 3o to 40% of See also:ordinary See also:illuminating gas. It may be, synthetically obtained by passing a mixture of the vapour of See also:carbon bisulphide with sulphuretted See also:hydrogen over red-hot See also:copper (M. See also:Berthelot, Comptes rendus, 1856, 43, p. 236), CS2 + 2H2S + 8Cu = 4Cu2S + CH4; by passing a mixture of hydrogen and carbon monoxide over reduced See also:nickel at 200—250° C., or hydrogen and carbon dioxide at 230—300° C. (P. See also:Sabatier and J. B. Senderens, Comptes rendus, 1902, 134, pp. 514, 689); by the decomposition of See also:aluminium See also:carbide with water [H.

See also:

Moissan, See also:Bull. See also:Soc. Chim., 1894, (3) II, p. 1012]; and by See also:heating phosphonium iodide with carbon bisulphide in a sealed See also:tube to 120-140 C. (H. See also:Jahn, Ber., 1880, 13, p. 127). It is also obtained by the reduction of many methyl compounds with nascent hydrogen; thus methyl iodide dissolved in methyl See also:alcohol readily yields methane when acted on by the See also:zinc-copper couple (J. H. See also:Gladstone and A. Tribe, Jour. Chem.

Soc., 1884, 45, p. 156) or by the aluminium-See also:

mercury couple. It may be obtained in an indirect manner from methyl iodide by See also:conversion of this See also:compound into zinc methyl, or into See also:magnesium methyl iodide (formed by the See also:action of magnesium on methyl iodide dissolved in anhydrous See also:ether), and decomposing these latter substances with water (E. See also:Frankland, 1856; V. Grignard, 1900), Zn(See also:CH3)2+See also:H2O=2CH4+ZnO; 2CH3MgI +H2O=2CH4+MgI2+ MgO. In the laboratory it is usually prepared by J. B. A. See also:Dumas' method (See also:Ann., 1840, 33, p. 181), which consists in heating an-hydrous See also:sodium acetate with soda See also:lime, CH3CO2Na + NaOH= Na2CO3 + CH4. The product obtained by this method is not pure, containing generally more or less See also:ethylene and hydrogen. Methane is a colourless gas of specific gravity 0.559 (See also:air = I).

It may be condensed to a colourless liquid at -155° to -16o° C. under atmospheric pressure (S. Wroblewsky, Comptes rendus, 1884, 99, p. 136). It boils at -162° C. and freezes at -186°C. Its See also:

critical temperature is -99.5° C. (J. See also:Dewar). The gas is almost insoluble in water, but is slightly soluble in alcohol. It decomposes into its constituents when passed through a red-hot tube, small quantities of other hydrocarbons (ethane, ethylene, See also:acetylene, See also:benzene, &c.) being formed at the same See also:time. It See also:burns with a See also:pale See also:flame, and when mixed with air or See also:oxygen forms a highly explosive mixture. W. A.

See also:

Bone (Jour. Chem. Soc., 1902, 81, p. 535; 1903, 83, p. 1074) has shown that in the oxidation of methane by oxygen at 450—500° C. formaldehyde (or possibly methyl alcohol) is formed as an intermediate product, and is ultimately oxidized to carbon dioxide. Methane is an exceedingly See also:stable gas, being unaffected by the action of chromic See also:acid, nitric acid, or a mixture of nitric and sulphuric acids. See also:Chlorine and See also:bromine, however, react with methane, gradually replacing hydrogen and forming chlor- and brom- substitution products.

End of Article: MARSH GAS (methane), CH4

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