170 proceedings of the american academy. 



General Conclusions. 



The results described in this paper make it clear that no conclusions 

 can be arrived at concerning the composition of the principal constituents 

 of American petroleum between 151° and 216° without separating from 

 these bodies the various impurities with which they are contaminated in 

 the crude distillates. However far fractional distillation may be carried, 

 it is impossible to effect a separation of those bodies whose boiling points 

 do not differ by more than a few degrees. But fortunately the principal 

 constituents of petroleum are not affected by reagents under conditions 

 which allow the removal of the contaminating bodies. While the state- 

 ment of Pelouze and Cahours that the portions of American petroleum 

 under consideration are not affected by nitric acid nor by fuming sul- 

 phuric acid is not supported by the behavior of distillates used by me in 

 this examination, it is true that the principal constituents are not acted 

 upon by those reagents under conditions that permit of purification. A 

 casual examination of the literature of Pennsylvania petroleum is suffi- 

 cient to reveal the uncertainty and confusion in statements concerning 

 the composition of the portions with higher boiling points. The principal 

 constituents have more commonly been referred to the series C„H2„+2) 

 as suggested by Pelouze and Cahours, who included in this series all 

 the petroleum hydrocarbons, even the least volatile oils and paraffine, 

 although on the basis of Warren's investigations allusions have been 

 made to the unsaturated define hydrocarbons C^H,,, as constituting the 

 main body of Pennsylvania petroleum above 150°, and the belief has 

 been expressed that the naphtene series C^Hj,, should best explain AVar- 

 ren's results. As already stated, above 150° Pelouze and Cahours 

 separated distillates at 162°, 182°, 196°-200°, and 216°-218°, which, 

 with no especial purification, gave analytical data corresponding closely 

 with the theoretical values for the series C„H2„+2. That there are marked 

 differences in the specific gravity of crude and refined distillates appears 

 in the purification of all distillates described in this paper, and it is no 

 easy task to purify the crude distillates so that they shall yield satisfac- 

 tory analytical data. As shown in the following table, the specific gravity 

 determinations by Pelouze and Cahours in the products they analyzed 

 are essentially different from those in Pennsylvania distillates herein 

 presented. The percentages of carbon and hydrogen required for the 

 series C„H2„+2 were obtained in fractions whose specific gravity was even 

 liigher than our crude distillates, which gave values closely agreeing with 

 the series C„H2„. This difference in specific gravity can only be explained 



