1825.] obtained by the Decomposition of Oil. 167 



tained in the fluid, inasmuch as even olefiant gas itself is dis- 

 solved 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 elas- 

 ticity, as there seems to be from this body downwards, to com- 

 pounds 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 spiculse in the receiver at 0. A tem- 

 perature 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 atmospheres at common tem- 

 peratures, 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 con- 

 tinue so, yet there is a possibility that processes may be de- 

 vised, 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 tem- 

 perature 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 distilla- 

 tions. Though conscious that these were mixtures, perhaps 

 of unknown bodies, and certainly in unknown proportions, 

 yet experiments were made on their composition by passing 



* Quarterly Journal of Science, xvi. 240, and page 134. 



