130 COMPOSITION OF AMERICAN PETROLEUM. [Feb. 5, 



specific gravity. With reference to the proportion of sulphur con- 

 tents and specific gravity, it seems that all the high sulphur oils 

 have a high specific gravity. 



There is some hope of arriving at a general system of classifica- 

 tion on the basis of the series of hydrocarbons which constitutes 

 the main body of the crude oils. While more must be known con- 

 cerning the composition of the constituents with higher boiling 

 points before such a distinction can be made with desirable precis- 

 ion, I have seen sufficient of the behavior of the higher constituents 

 to believe that such a basis is reasonable. As types of such a classi- 

 fication I should select on the one hand Pennsylvania oil, and on 

 the other, Russian oil from the Baku district. The difference in 

 specific gravity of the crude oils is borne out by the difference in 

 specific gravity of the corresponding distillates, and individual con- 

 stituents with the same boiling points. The typical constituents of 

 Pennsylvania oil, at least below 216°, are members of the series 

 CnHan + a, but the components of the Russian as defined by the 

 researches of Markownikow are the naphthenes of the series C^Han. 

 With reference to the ethylene series CJi,j„ which has seemed to be 

 accepted by some as constituting the main body of American petro- 

 leum, so far as my observation has extended, those hydrocarbons 

 are not contained in any petroleum, at least below 216°, in more 

 than minute quantities. Results which I have yet to publish show 

 that these bodies are contained only in small proportions in lime- 

 stone oils. 



A classification of pretroleum from all known sources evidently 

 demands as its basis conclusive evidence as to the series of hydrocar- 

 bons of which each is chiefly composed. The methods to be pursued 

 in reaching this knowledge have been indicated in my examination of 

 Pennsylvania, Ohio and Canadian oils between 150 and 216 {^Proc. 

 Amer. Acad., xxxii, 121). That the series CnH2n_^2> constitutes the 

 chief body of Pennsylvania crude oil below 150° was well established 

 long ago by independent investigations. Above this point the evi- 

 dence was less satisfactory. To accept the results of Pelouze and 

 Cahours which continued the series C^H^^^a through the entire 

 range of distillates to paraffine, it is necessary to ignore the fact 

 that American petroleum is not composed exclusively of a single 

 homologous series of hydrocarbons, but of a mixture of bodies that 

 require for their separation, not only very prolonged fractional dis- 

 tillation, but searching and vigorous means of purification. 



