H YDP.OGE N AND CARBON. $C$ 



so has examined them at different times, and pu- 

 blished very ingenious dissertations on their com- 

 position. 



From a great many experiments on these gases, 

 at different times, and in different states, I have 

 convinced myself that they usually hold an empy- 

 reumatic oil in solution, and that the differences 

 in their specific gravity, and other properties, de- 

 pend very much upon the proportion of oil pre- 

 sent. Hence no pure gases, fit for examination, 

 and comparable with each other, can be obtained 

 from those vegetable or animal substances which 

 yield an oil when subjected to heat, as is the case 

 with most of them. To this oil is to be ascribed 

 the great» variation in the specific gravity of the 

 gas obtained by distilling pit-coal, as shewn by the 

 experiments of Dr Henry. 



When water and carbon are present together, as 

 is the case in most animal and vegetable substan- 

 ces, they act on each other, and give origin to va- 

 riable quantities of carbonic oxide, which must 

 alsd very much alter the properties of the gas 

 evolved. To these two causes, namely, the oil 

 dissolved, and the carbonic oxide formed, most, if 

 not all the varieties in the combustible gases, ob- 

 tained from animal and vegetable substances, are 

 owing. 



Berthollet, in a dissertation which he lately pu- 

 blished, in the second volume of the Memoir es 

 (PArcueil, has endeavoured to prove that all the 



