The Romance of Modern Chemistry

MORE ABOUT FUEL to be used for illuminating purposes, must either be carburetted—that is, provided with hydro-carbons to render its flame luminous, or used with incandescent mantles. In America water gas is frequently used in place of coal gas; in this country it is never supplied alone for lighting purposes, but is often mixed with coal gas. One objection to its use is the excessively poisonous nature of carbon monoxide, referred to in a previous chapter. On this ground it is considered unsafe to dis- tribute to the public coal gas which contains more than about 16 per cent, of carbon monoxide. Has the reader ever realised what an enormous amount of energy is stored up in a pound of coal, or a cubic foot of coal gas ? When the fuel is burned this latent energy becomes manifest in the form of heat, and it is actually found that the heat given out when one pound of coal is burned would be sufficient to raise the temperature of seven tons of water 1° Fahrenheit—say from 60° to 61°. Now heat is convertible into other forms of energy, and may, for example, be transformed into mechanical energy ; thus it has been shown that the quantity of heat which would raise the temperature of one pound of water from 60° to 61° would, if converted into mechanical energy, be able to raise a weight of 772 pounds through 1 foot, or, what is the same thing, a weight of one pound through 772 feet. By means of this mechanical equivalent of heat, as it has been called, some one has calculated that if the energy latent in one pound of coal were converted without loss into mechanical energy, it would do as much as five or six horses working for an hour. But one must admit that this is quite an ideal process. Even in the best engines we can employ to convert the latent energy of fuel into mechanical energy only a 162