1825.] obtained by the Decomposition of Oil. 173 



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 gaso- 

 meter, and given to me by Mr. Hennel, of the Apothecaries' 

 Hall, I found it to contain portions of the bicarburet of hy- 

 drogen. 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 com- 

 pressed 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 illu- 

 minating ; 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, sur- 

 passing 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 un- 

 derstand the minute changes which take place during the 



