124 PROCEEDINGS OF THE AMERICAN ACADEMY. 



one of his private papers, already mentioned in another paper : " The 

 samples analyzed may have contained traces of more highly hydrogeuized 

 substances, and that it would be worth while to treat with HOSOa, and 

 HONOo, and remove these."* It is evidently an error to consider the 

 hydrocarbons C„H2„4_2, especially the lower members, as unstable toward 

 reagents. It has been our experience, in removing aromatic hydrocar- 

 bons from the distillate 160°-216°, that the principal constituents are not 

 affected in the cold by a mixture of nitric and sulphuric acids, nor by 

 fuming sulphuric acid even by warming. After purification, the boiling 

 points do not change in a long course of distillations. No doubt the 

 stability diminishes with a rise in boiling points, but it is sufficient to 

 permit of purification of the members below 21G°. All analyses in this 

 paper point to the general composition C„H2„+2, except for the Cana- 

 dian hydrocarbons 196° and 216°. If continued distillation or treatment 

 with the means of purification we have adopted produces decomposition, 

 the products should scarcely consist at least entirely of lower members 

 of the same series. 



In the comparative examination, the results of which will be described 

 in this paper, two principal objects were kept in view, one of chief im- 

 portance to determine the series of hydrocarbons which form the main 

 body of American petroleum, and the other naturally following, to ascer- 

 tain whether the composition of Pennsylvania, Ohio, and Canadian oils 

 as regards their principal constituents is the same. 



In undertaking a study of the portions of petroleum within the limits 

 of temperature mentioned above, it was at first determined to prepare all 

 distillates from the crude oils, and this has been done in part in the Ohio 

 and Canadian oils. But when it was found that cracking in refinino; did 

 not begin in any considerable extent below 225°, and that distillates from 

 the refinery resembled in all respects, at least in their principal con- 

 stituents, those obtained in vacuum distillation, refinery distillates were 

 more freely employed, especially from Pennsylvania oil. But most of the 

 results on Ohio and Canadian oils were obtained in vacuum distillates, 

 the preparation of which was described in a former paper.f Further assur- 

 ance .igainst decomposition in the Pennsylvania product was gained by 

 selecting during the "run" in the refinery distillation just that por- 

 tion of the distillates that corresponds in gravity to the constituents 

 desired. Experience showed that heavier portions of the crude distil- 

 late should be selected than those corresponding to the constituents 



* Proc. Amer. Acad.. XXXI. 31. t Ibid., XXXI. 1. 



