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XXXV. — On the most Volatile Constituents of American Petroleum. By Edmund 



Ronalds, Ph.D. 



(Read loth February 1864.) 



Crude American petroleum evolves, at ordinary temperatures, a quantity of 

 combustible gas, which takes fire on contact with flame, and, when mixed in 

 certain proportions with air, produces an explosive mixture. It is in consequence 

 of this property that it has been thought necessary to pass a very stringent law, 

 known as the Petroleum Bill, with a view of preventing accidents from the 

 incautious storing and handling of the oil. 



The more volatile liquid products obtained by distilling the crude oil are still 

 more highly charged with combustible vapour, which, when these liquids are 

 again distilled, escapes condensation even by the most powerful freezing 

 mixtures. 



The liquid constituents of petroleum have now been carefully studied by 

 Messrs Pelouze and C a hours, and some of them also by Mr Schorlemmer. 

 These eminent chemists have shown that the oil consists essentially of a mixture 

 of the homologues of marsh gas, having the general formula, 



It was during the collection of the more volatile of this series of compounds 

 with a view to their analysis, in which object I have now been forestalled, that my 

 attention was drawn to the large quantities of incondensible gas which escaped at 

 each successive fractionation, and it appeared desirable to ascertain whether the 

 gaseous ingredients of the oil belonged also to the same series, or were accompanied 

 by other hydrocarbons. With this object in view, and still waiting the arrival of 

 some specimens of oil collected and secured in hermetically sealed vessels, direct 

 from the oil wells, I was enabled by the kind permission of Mr Shand of Stirling, 

 ' to collect the gas which floated over the surface of the crude oil in the barrels in 

 which it is imported into this country. I also obtained from the same manufac- 

 I turer some of the very first products of the stills employed in refining the petro- 

 leum on a manufacturing scale. 



The gas floating over the surface of Pennsylvanian oil was collected at a tem- 

 perature of — 1° C, and was observed to contain combustible ingredients. It took 

 ifire instantly on being brought into contact with flame, burning with a very faint, 

 Ibluish light, but without explosion. From Canadian petroleum, which is of much 

 jthicker consistence, no combustible gas was obtained at that temperature. 



The gas was collected over water by simply removing the original wooden 



I VOL. XXIII. PART III. 6 R 



