CONSTITUENTS OF AMERICAN PETROLEUM. 493 



from the numbers above, it can be shown that the gas analysed must have con- 

 sisted of a mixture of these gases in nearly equal proportions, or of— 



C,Hg, Hydride of Ethyl 794 

 CgHg, Hydride of Propyl 801 



— the correctness of which is confirmed by the amount of oxygen consumed being 

 about the mean of the quantities required for the combustion of these hydrides 

 separately. 



Hydride of ethyl requires 3*5 times its volume of oxygen. 



Hydride of propyl requires 5- times its volume of oxygen. 



The gas floating over the surface of the petroleum is therefore composed of— 



Carbonic acid, . . . . . . . . 127 



Oxygen, ......... 658 



Nitrogen, ........ 54- 



Hydrocarbon, f C^H^ ] ^^'^^ 



In this condition the gas is not explosive, and would only become so on being 

 mixed with a large volume of air. 



The most volatile liquid obtained by collecting the very first runnings from 

 the stills employed in the process of refining petroleum has a specific gravity of 

 0-666. It is not sensibly affected by nitric acid, by oil of vitriol, or by bromine. 

 When distilled, it commences to give off bubbles of gas in abundance at about 

 25^ Cent., but after a few minutes all appearance of boiling ceases, although large 

 quantities of gas and condensible liquid continue to pass over up to 65° or 70° 

 Cent., and the whole liquid is evaporated below 100° Cent. 



This liquid resembles very closely the kerosolene or kerosoform which an 

 American physician of New York has introduced as an ansesthetic agent ; and I 

 am indebted to Dr Simpson for the opportunity of comparing it with a specimen 

 of the latter. The specimen lent me by Dr Simpson was quite indifferent to the 

 above reagents. It had a specific gravity of "6336. It began to boil at 28° Cent., 

 and was nearly completely volatilised at 70° Cent., so that it must have been 

 composed almost exclusively of a mixture of the hydrides of amyl and hexyl, 

 while the crude volatile product from the manufactory contained, in addition to 

 these hydrides, some incondensible gaseous products, and a considerable quantity 

 of the hydride of heptyl. 



The incondensible gases dissolved in this most volatile liquid were expelled 



by gently warming a large quantity (about two gallons) of liquid, and passing 



the gases, before collecting them over water, through a long metallic worm, 



surrounded by a freezing mixture composed of ice and salt ; the whole apparatus 



' having been filled previously with carbonic acid to expel air. 



The first two portions which were collected showed, after separating carbonic 



