568 PROCEEDINGS OP THE AMERICAN ACADEMY. 



In the intervals between these fractions the weights were much 

 smaller. 



After the eighth distillation each fraction was agitated at first with 

 common concentrated sulphuric acid until the acid was not much colored 

 and then several times with fuming sulphuric acid. That the distillates 

 consist almost entirely of the principal hydrocarbon is shown by the 

 slight change in specific gravity by the acid treatment : — 



182°-184° 

 0.8100 Original distillate. 

 0.8093 After treatment with acid. 



There was some loss in weight of the fraction by the acid treatment, 

 but it was doubtless due for the most part to solution of the principal 

 hydrocarbons in the acid. The weights of the fractions before and after 

 treatment were as follows : — 



This solvent action has been observed in other oils with high boiling 

 points in continuous treatment with fuming sulphuric acid, which caused 

 a gradual loss without changing materially the specific gravity. After 

 the purification with the acid, distillation was continued through a 

 Hempel column filled with glass beads or broken glass, under 50 mm. 

 within limits of one degree, until the hydrocarbons collected in consider- 

 able quantities. After the thirtieth distillation, the hydrocarbons came 

 together within the following limits : — 



124°-126°, 142°-143°, 158°-159°, 173°-174°, 189°-190°, 198°-199°. 



Even after nearly continuous distillation of sixteen months, these 

 products showed very little indication of decomposition. Leaks in the 

 apparatus immediately cause decomposition, as shown by a disagreeable 

 odor, and the appearance of the distillates. So long as air is excluded 

 from the hot vapors there is no danger of decomposition. But as we 

 found in attempting to ascertain the boiling points under atmospheric pres- 

 sure, a single distillation in air causes a very rank odor of decomposition.* 



* The difference in stability of the constituents of different petroleums is 

 shown by their behavior when air comes in contact with the hot vapors. In acci- 

 dents that have occurred during distillation, letting in air on the hot vapors, in the 

 case of Pennsylvania petroleum the still becomes filled with dark vapors, but in a 



