Morey (Silliman's Journal, vol. ii, p. 121) observes, that a small quantity of spirit of turpentine being added to a mixture of iron-filings, sulphuric acid, and water, the hydrogen gas produced, will burn with a very pleasant white flame, and without smoke. He also observes, that, if the vapour of spirit of turpentine be made to pass through a tube, covered at the upper end with a fine wire gauze, it burns with much smoke; but, if a quantity of atmospheric air be allowed to mix with it, the smoke ceases, and the flame continues white. If more still be added, the flame lessens, and becomes partly blue. By adding still more and more, it will burn with a very small flame, entirely blue, and with a singular musical sound. If still more be added, the flame, and every ray of light cease; but that the combustion still continues, is certain, from the explosive detonating noise, continuing to be distinctly heard.
Mr. Morey further remarks, that, if tar, containing a considerable proportion of water, is dropped on brick or metal, at a temperature, which will readily evaporate them, the vapours will burn with white shooting streaks, much flame, and without smoke, while the water lasts. Inflamed drops of tar, burn, while falling, with a red flame, and much smoke; but, on reaching boiling water, the smoke instantly disappears, and streaks of a white flame shoot up. He also says, that, if water in one cylinder be made to boil, and the steam be led to the bottom of another, containing rosin, or tar, at a high temperature, after passing up through it, the water, together with the vapourized portion of the rosin or tar, will, when the preparations are properly regulated, burn with an intense white flame, and no smoke; much the greater part of which appears, (by alternately shutting the steam out, or letting it in) to be derived from the water; and also, that if steam be led over the surface of tar in a cylinder, and made to force out a small stream of it through a pipe, into which a quantity of steam is also admitted, and made to mix intimately with it, they burn, with a great body of flame and intense heat, and without smoke, provided the proportions are well regulated. These facts are remarkable, and may probably lead to some useful applications. That water is decomposed, appears more than probable. If water is thrown, in considerable quantities, on oil or tar, in a state of inflammation, as Morey observes, the flame is greatly increased; and if ever so small a drop of water fall into oil at a temperature near boiling, an explosion will take place. He draws the following conclusion, from these circumstances; that we have only to pass the steam of water through oil, heated to the temperature, at which it boils, or takes fire, to produce combustion.
Sec. XI. Of Common Coal, or Pitcoal.
All the variety of coals, belonging to the coal family, are composed principally of charcoal and bitumen, with small quantities of earthy, and metallic matter. Whether we consider the formation of coal, the localities or situation in which it occurs, whether in beds or strata, accompanying other minerals, such as clay-slate, bituminous schistus, sandstone, &c. is of no moment, except so far as the situation in which it is found, indicates or determines its character and qualities. The different kinds of coal owe their variety to the presence or absence of bituminous matter, whether great or small, the quantity of the carbonaceous ingredient, and the presence or absence of anthracite, and other foreign substances. Coal, which is, or ought to be preferred in fire-works, should contain the greatest quantity of bituminous matter; and, while it contains the due proportion of carbon, should be entirely free from anthracite. Coal, and all other inflammable fossils, are characterized by their inflammability, insolubility in water, alcohol, and acids, and by their specific gravity, which scarcely exceeds 2, unless loaded with foreign matter. Coal surcharged with bitumen, burns with a bright flame, and, by distillation, affords more carburetted hydrogen gas, which is used for gas light. Common coal, or pitcoal, burns in cakes, more or less, during combustion. Besides charcoal and bitumen, it contains sometimes pyrites, sulphate of iron, and earth. Slate-coal, however, contains more clay.
The collieries, from which pitcoal is obtained, are more or less extensive in England, and elsewhere. Immense beds of coal are found near Pittsburgh, and Richmond. The Lehigh, and other localities in the United States, produce it also in abundance, but of various qualities. Coal districts, or places in which it is found, may be considered a valuable acquisition to a country; and as coal is so essential in many manufactories, it is a satisfaction to know, that our resources in this particular, are almost inexhaustible;—a fact, which shows, that, while our national industry is the main pillar of national independence, in its true acceptation, the arts, which require a supply of coal, will, for centuries to come, be abundantly furnished with it.
When coal is exposed to the action of heat, in iron retorts or cylinders for the preparation of coal gas, or when it is exposed to heat in coke-ovens, the bitumen, &c. are disengaged, and there remains a coal called coke. Coke, therefore, is nothing more than charred pitcoal.
Mr. Mushet made some valuable experiments on the carbonization and incineration of coals. He found that the Scotch cannel-coal afforded 56.57 volatile matter, 39.43 charcoal, and 4 ashes; while the stone-coal, found under basalt, gave 16.66 volatile matter, 69.74 charcoal, and 13.6 ashes, and oak wood, 80.00 volatile matter, 19.5 charcoal, and 0.5 ashes. The quantity of gas, however, depends entirely on the quality of the coal. A temperature of about 600° to 700° is sufficient to disengage it. A pound of good cannel coal, properly treated in a small apparatus, will yield five cubic feet of gas, equivalent in illuminating power to a mould candle, six in the pound. One pound of coal, on a large scale, affords only 31/2 cubic feet of gas. A gas jet, which consumes half a cubic foot per hour, gives a steady light equal to that of a candle of the above-mentioned size.
The cannel coal, known in Scotland by the name of parrot coal, is very inflammable, takes fire immediately, and produces a brilliant flame. It is used by the poor as a substitute for candles. This coal, we have seen, furnishes an abundance of carburetted hydrogen gas. It has the appearance of jet, and admits of being turned in a lathe.
Stone coal, Kilkenny coal, Welch coal, and glance coal consist almost entirely of charcoal; and hence, when laid on burning coals, they become red-hot, emit a blue lambent flame, in the same manner as charcoal, and at length are wholly consumed, leaving behind a portion of red ashes. They burn without smoke or soot.