1897.] COMPOSITIOX OF AMERR'AN i'KTlJOliEUM . 185 



oil applying a vacuum of above 150°. At present eight distillations 

 have been made within 2° limits, up to 300° under 50 mm. Many 

 repetitions within single degree fractions will be necessary to bring 

 together the individual constituents. 



The question is frequently asked whether parafifine is a normal 

 constituent of the crude oil or is it a product of cracking. The 

 answer is easy ; parafifine is not obtained by cracking the crude 

 oil, but it can itself be destroyed by cracking. If paraffine be con- 

 tained in the crude oil it may be separated by distillation, ])rovided 

 cracking be not carried far enough to destroy it entirely. The 

 presence of paraffine seems to be closely connected with the dis- 

 tinction mentioned between the series CnHsn and the series CnH.,n_|.o. 

 Higher distillates in vacuo of crude oils containing the series 

 CnH._,n4_o, so far as I have observed, invariably deposit paraffine. 

 Those oils consisting below 216° of the series CnHgn deposit no 

 paraffine even when the highest distillates that can be collected are 

 cooled to — 20°. It may be interesting to apply this distinction 

 to those oils that have been care fully studied. With reference to the 

 appearance of paraffine in distillates, it should be mentioned that it is 

 observed only in the absence of serious cracking, and that it is easy 

 in vacuum distillation to recognize the point where cracking begins. 

 In distilling 125 liters of Pennsylvania crude oil mentioned above for 

 the purpose of separating the higher constituents, approximately forty 

 liters of residue above 275° under 50 mm. became nearly solid 

 from the amount of paraffine deposited. With the hope that more 

 distillate could be obtained without decomposition, the semi-solid 

 mass was put back into the still and again distilled under 50 mm. 

 Approximately two liters were collected in three distillates, none of 

 which deposited paraffine, and the residue, on cooling, had the con- 

 sistency of a thick tar, with no indication of paraffine. Paraffine 

 separates from the higher distillates of Berea grit petroleum, as well 

 as from all specimens of Ohio and Canadian oils that I have exam- 

 ined ; but none separated from South American petroleum, from 

 Oregon petroleum, nor from Russian Baku oil. 



Since I began the study of petroleum, twelve years ago, I have 

 devoted , considerable time to it, especially during the last seven 

 years. Yet my results barely indicate the enormous field that 

 awaits investigation in the examination of American petroleum. 

 There is no field in industrial chemistry that offers greater induce- 

 ments for fruitful results, both of scientific interest and practical 



