The two chief definite gaseous compounds of those two elements are the light carbureted hydrogen and the heavy carbureted hydrogen, or olefiant gas. The first is easily procured by stirring the bottom of stagnant water on a hot summer’s day, and collecting the bubbles in a bottle filled with water and inverted over the place where the bubbles rise. This gas burns with a yellowish flame, and when mixed with a certain proportion of air, or oxygen gas, explodes with great violence on the application of a flame. It is the much dreaded fire-damp generated so profusely in some coal-mines, and causing such fearful destruction to life and property when accidentally inflamed.
The other compound, the heavy carbureted hydrogen, forms part of the gas used for illumination; and, in fact, whatever substance is employed for artificial light, whether oil, tallow, wax, etc., etc., it is converted into this gas by heat, and then furnishes the light by its own combustion.
This gas has some very curious properties, and may be obtained nearly pure by mixing in a retort, very carefully, one part of spirits of wine and four of sulphuric acid. A lamp must be placed under the retort, when the gas will be speedily disengaged, and come over in great abundance; it may be collected over water.
This gas is transparent, colorless, will not support combustion, but is itself inflammable, burning with a brilliant white light, and being converted into carbonic acid and water. If mixed with three or four times its bulk of oxygen, or with common atmospheric air in much larger proportion, it explodes with great violence.
This gas is sometimes called “olefiant gas,” from the property it has of forming an oily substance when mixed with chlorine.
Experiment.
Into a jar standing over water half full of this gas, pass an equal quantity of chlorine gas. The gases will speedily unite and form an oily-looking liquid, which may be collected from the sides of the jar as it trickles down. By continually supplying the jar with the two gases as they combine, a considerable quantity of this substance may be collected. Care should be taken that the olefiant gas is rather in excess.
The substance produced is insoluble in water, with which it should be washed by shaking them together in a tube, and has a pleasant sweetish taste and aromatic smell, somewhat resembling ether.
Coal Gas.
The gas so universally employed for the purposes of illumination is a mixture of the carbureted and the bi-carbureted hydrogen, with minute portions of other gases scarcely worth mentioning. It is procured by submitting coals to a red heat in iron retorts, having a tube passing from one end, along which passes all the fluid and gaseous matter separated from the coal, namely, gas tar, ammoniacal liquor, and various gases, carbureted hydrogen, carbonic acid, sulphureted hydrogen, etc., etc. The tar and ammoniacal liquor remain in the vessel in which the tubes from the retorts terminate, and the gaseous productions are conveyed through water and lime to separate the impurities; the remaining gas, now fit for use, passes into large iron vessels, called gasometers, inverted over water (like the jars in a pneumatic trough), whence it is sent through pipes and distributed where required. What remains in the retorts is called coke. It consists principally of charcoal mixed with the earthy and metallic particles contained in the coal.