METHANE, CH4, also known• in the im pure state as Marsh Gas, or Firedamp, is found in large quantities in the gases evolved from petroleum wells, oil springs and mud volcanoes. It is present in stagnant pools (hence the name marsh gas) and in certain localities where or ganic matter is allowed to decay in a limited supply of air. The firedamp of coal mines is methane mixed with a small percentage of car bon dioxide, nitrogen and oxygen. Enormous quantities of methane are present in the burn ing gases that constitute the ((Holy at Baku in the neighborhood of the Caspian Sea. Methane is formed in the fermentation of com pounds like cellulose, milk sugar or calcium butyrate, in the thermal decomposition of al cohol, ethane, ethylene or acetylene and in the dry distillation of vegetable matter. Illumi nating gas, produced by the destructive distil lation of coal, may contain as much as 40 per cent of methane by volume.
The compound may be prepared in a fairly pure state, (1) by treating commercial alumi num carbide with water; (2) by the interaction of hydrogen and an oxide of carbon at 250° C., in the presence of finely-divided catalyzers like cobalt, nickel or iron; (3) by heating a mix ture of fused sodium acetate and dry soda-lime; (4) by the interaction of carbon bisulphide, me tallic copper and hydrogen sulphide at an ele vated temperature; (5) by maintaining charcoal from sugar in a stream of pure, dry hydrogen at 1.150° C. Chemically pure methane has been prepared by the reduction of methyl iodide. In this process the iodine is mixed with equal vol ume' of alcohol and treated with the "zinc-cop per* couple.
Methane is a colorless inodorous gas with a density =0.559 (air-1). It burns with a faintly luminous flame and with the evolution of much heat. Mixed with air or oxygen in
certain proportions and then ignited it explodes violently, one volume of methane forming with 9.5 volumes of air an extremely explosive mix ture. On account of its low boiling point meth ane was for a long time known as one of the permanent gases. It was liquefied by Cailletet in 1877. The liquid is colorless, boils at — 164° C. and solidifies at —185.5° C. when the pres sure is diminished to 80 millimeters.
Methane is a saturated compound and is ex tremely stable. Reagents like fuming nitric acid, strong sulphuric acid or phosphoric anhy dride have practically no action upon it even at elevated temperatures. In the presence of chlorine, bromine or fluorine, methane under goes a chemical change by substitution, i.e., by the replacement of one or more' hydrogen atoms by equivalent atoms of the halogen. Long contact with chlorine, for example, even in dif fused daylight and at ordinary temperatures, will convert methane into CH.CI (methyl chlor ide), CI-LC1, (methylene chloride), ClICIB (chloroform) and CC14 (carbon tetrachlor ide), a molecule of hydrochloric acid being evolved with the introduction of each atom of halogen. At temperatures not lower than 1.300° C. methane has been completely decom posed into carbon and hydrogen. With a mix ture of nitrogen and 'hydrogen in the electric arc it has been successfully converted into hy drocyanic acid. Patents have also been taken for the oxidation of methane (under the cata lytic action of tan bark) into formic acid, meth_ i alcohol • and formaldehyde. See GASES