The importance of these vapours in oil-gas, as contributing to its very high illuminating powers, will be appreciated, when it is considered that with many of them, and those of the denser kind, it is quite saturated. On distilling a portion of liquid, which had condensed in the pipes leading to an oil-gas gasometer, and given to me by Mr. Hennel, of the Apothecaries' Hall, I found it to contain portions of the bicarburet of hydrogen. It was detected by submitting the small quantity of liquid which distilled over before 190° to a cold of 0°, when the substance crystallized from the solution. It is evident, therefore, that the gas from which it was deposited must have been saturated with it. On distilling a portion of recent coal-gas tar,—as was expected, none could be detected in it; but the action of sulphuric acid is sufficient to show the existence of some of these bodies in the coal-gas itself.
With respect to the probable uses of the fluid from compressed oil-gas, it is evident in the first place, that being thus volatile, it will, if introduced into gas, which burns with a pale flame, give such quantity of vapour as to make it brightly illuminating; and even the vapour of those portions which require temperatures of 170°, 180°, or higher, for their ebullition, is so dense as to be fully sufficient for this purpose in small quantities. A taper was burnt out in a jar of common air over water; a portion of fluid boiling at 190° was thrown up into it, and agitated: the mixture then burnt from a large aperture with the bright flame and appearance of oil-gas, though of course many times the quantity that would have been required of oil-gas for the same light was consumed; at the same time there was no mixture of blueness with the flame, whether it were large or small. Mr. Gordon has, I understand, proposed using it in this manner.
The fluid is also an excellent solvent of caoutchouc, surpassing every other substance in this quality. It has already been applied to this purpose.
It will answer all the purposes to which the essential oils are applied as solvents,—as in varnishes, &c.; and in some cases where volatility is required, when rectified it will far surpass them.
It is possible that, at some future time, when we better understand the minute changes which take place during the
