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1825.] in the fluid, inasmuch as even olefiant gas itself is dissolved by it in small proportions, it may be presumed that there is no substance in oil-gas much more volatile than the one requiring a pressure of four atmospheres at 60°, except the well-known compounds; or, in other words, that there is not a series of substances passing upwards from this body to olefiant gas, and possessing every intermediate degree of elasticity, as there seems to be from this body downwards, to compounds requiring 250° or 300° for their ebullition.

In reference to these more volatile products, I may state that I have frequently observed a substance come over in small quantity, rising with the vapour which boils off at 50° or 60°, and crystallizing in spiculæ in the receiver at 0°. A temperature of 8° or 10° causes its fusion and disappearance. It is doubtless a peculiar and definite body, but the quantity is extremely small, or else-it is very soluble in the accompanying fluids. I have not yet been able to separate it, or examine it minutely.

I ventured some time since upon the condensation of various gases, to suggest the possibility of forming a vapour lamp, which containing a brilliantly combustible substance (liquid at a pressure of two, three, or four atmosphere sat common temperatures, but a vapour at less pressure), should furnish a constant light for a length of time, without requiring high or involving inconstant pressure. Such a lamp I have now formed, feeding it with the substance just described; and though at present it is only a matter of curiosity, and perhaps may continue so, yet there is a possibility that processes may be devised, by which the substance may be formed in larger quantity, and render an application of this kind practically useful.

'On the remaining portions of the condensed Oil-gas Liquor.—It has been before mentioned, that by repeated distillations various products were obtained, boiling within limits of temperature which did not vary much, and which when distilled were not resolved into other portions, differing far from each other in volatility, as always happened in the earlier distillations. Though conscious that these were mixtures, perhaps of unknown bodies, and certainly in unknown proportions, yet experiments were made on their composition by passing