Page:Popular Science Monthly Volume 16.djvu/688

 given to the American method the first decisive success in supplying the public with water-gas.

The oxygen of the steam, as we have seen, on entering the burning coals at the bottom of the furnace, instantly unites in full proportions with the first carbon it encounters, forming carbonic acid. But this carbonic acid, as fast as formed, is driven upward through the fire, and, before it reaches the other gases, its greedy oxygen has gorged itself with a double portion of carbon from the coals, and it is now carbonic oxide—a gas rich with carbon, which is ready to unite in combustion with a further proportion of oxygen wherever it can find it. But it finds no oxygen among the gases to which it is introduced, for the air-blast was shut off when the steam was let on. Consequently, it enters into the compound, and remains as a third combustible.

Meanwhile, the mingled gases are rushing from the furnace, under high pressure, through the flue into the secondary chamber or superheater, and up through the white-hot mass of fire-brick which it contains. Struggling through the hot crevices in attenuated streams, the gases reach a temperature of nearly 2,000°, at which all the elements present are perfectly released and enabled to form such recombinations as their stronger affinities dictate. As the oxygen here finds itself in a hopeless minority, and remains dominated by the superabundant carbon with which it is associated in carbonic oxide, there is no rival to forbid the bans between the king and queen of combustibles—Hydrogen and Carbon.

The charge of coal in the generator makes from five to seven thousand cubic feet of gas: the process of generation taking thirty minutes. The steam is then shut off, and the generation of gas ceases. The lid is raised, the air blast readmitted, and ordinary combustion is resumed. The stoker approaches the fiery pit on a floor level with its mouth and pours in another charge—a barrel of anthracite—fastens down the lid, and for fifteen or twenty minutes the air-blast again urges combustion until the mass in the generator is of a lively red, and the fire-bricks in the superheater are once more white-hot for a second run of gas. At every sixth charge the ashes are raked out, and two barrels of coal, instead of one, are put on.

When the eight sets of apparatus in the Baltimore works are in operation, the actual product per twenty-four hours, with all delays, amounts not unusually to 600,000 cubic feet; and it has been practically demonstrated that 1,000,000 cubic feet could be made by the same apparatus in the same time. Provision is also made for as many more sets of apparatus as may be required by the future extension of the business.

We are now prepared to understand clearly the later and more important process of making pure fuel-gas; which commends itself to us as the next great economic stride of the arts, and therefore as the true "objective point" of this article.