26 PROCEEDINGS OF THE AMERICAN ACADEMY. 



—100'^ 100^-150^ 150^-200^ 200^-250° Residue. 



Sulphur 0.054 0.25 0.42 0.61 0.67 



In comparing the percentages of sulphur in the vacuum distillates 

 with those under atmosphei-ic pressure, it is evident that the main 

 body of the sul[)hur compounds collects in the higher portions, leav- 

 ing the fractions below 150° nearly free from sulphur. 



Percentages of sulphur under atmospheric pressure : — 



It is also apparent that distillation in vacuo protects, to a certain 

 extent, the sulphur compounds from decomposition. In ordinary dis- 

 tillation of the crude oil, as has been mentioned, sulphur is invariably 

 observed in the condensing tube. Even in vacuum distillation at high 

 temperatures decomposition cannot be wholly avoided, although the 

 separation of sulphur has never been observed. It is probable that 

 chemical reactions occur within the oil from the action of the various 

 constituents upon one another, such, for example, as the action of the 

 oxygen compounds upon the sulphur compounds. These observations 

 are valuable evidence in favor of vacuum distillation for the sulphur 

 petroleums. 



The percentage of bromine absorbed by the fractions collected in 

 vacuo was also determined : — 



-100° 100°-150^ 150°-200° 200^-350' Residue. Crude Oil. 



Bromine 0.0 4.57 6.60 7.08 24.38 10.19 



It is interesting to compare the bromine absorption in the vacuum 

 distillates with the quantities absorbed in the distillates collected 

 under atmospheric pressure : — 



100^-150° 150°-220° 220^-257° 257^-300'' 300''-330° +330° 



Bromine 0.73 1.74 4.84 5.04 12.10 19.50 



Doubtless the larger absorption of bromine in the vacuum distillates 

 at lower temperatures depends, at least in part, upon the fact that the 

 sulphur compounds are protected from decomposition during distilla- 

 tion, and also upon the extent to which the constituents with higher 

 boiling points are distilled at lower temperatures under the diminished 

 pressure. It would be expected that the residue in the distillation 

 under atmospheric pressure should sliow a liigher absorptive power 

 than that collected in vacuo. The behavior of the higher fractions 



