Page:International Library of Technology, Volume 93.djvu/109

 302° F. and of kerosene of .820 specific gravity 536° F. Kerosene begins to give off vapor at from 100° to 120° F., and this vapor is mainly nonane, C9H20. Liquid kerosene is a mixture of decane, C10H22, with a little hexadecane, C16H34. The boiling points of these three liquids are as follows: nonane, C9H20, 277° F.; decane, C10H22, 316° F.; hexadecane, C16H32, 536° F. Average kerosene consists chiefly of decane. For the chemical action that takes place when kerosene is burned, that corresponding to the combustion of decane may be taken, without appreciable error.

GASEOUS FUEL

NATURAL GAS

57. Occurrence. — Natural gas is usually found when boring for petroleum, although sometimes it occurs in regions where no petroleum is found. Scarcely any oil wells are bored without finding more or less gas. It consists of the lighter hydrocarbons, usually from 75 to 97 per cent, being marsh gas. The gas is confined under great pressure in the pores of rock or sand, from which it issues at a high velocity as soon as the drill enters the deposit. From the well, the gas is piped to the point at which it is to be used. As the pressure is in many cases too high, a pressure-reducing valve is placed in the supply pipe to reduce the pressure to that desired.

Compared with coal gas, natural gas is a poorer light giver. Its heat-giving power is, however, as good as the best coal gas, and its low price makes it desirable for gas- engine purposes.

58. Composition. — It has been found that natural gas, which is now generally acknowledged to belong to the same class and have the same origin as petroleum, is composed almost entirely of methane, ethane, and propane. The first, or marsh gas, constitutes about three-fourths of all the gas