142 PROCEEDINGS OP THE AMERICAN ACADEMY. 



the main body of this petroleum within these limits, and whatever other 

 bodies may be present, they are to be found only iu comparatively small 

 quantities. As to the proportion of aromatic hydrocarbons in the crude 

 oil, no direct estimation can be based on these observations. 



Fuming sulphuric acid removed 40 per cent of the crude distillate 160°- 

 161°, leaving decane as the remaining GO per cent. Whether the portion 

 removed was mesitylene alone may be questionable, but no doubt it formed 

 the larger part of the body uniting with the fuming acid. Even in such 

 prolonged fractional separations as those described in this paper, it cannot 

 be assumed that nearly all the decane 163°-164° was collected in the 

 fractions which should contain it, neither is it probable that the crude 

 distillate from which was selected the specimen for the separation of these 

 constituents contained all the decane in the corresponding quantity of 

 crude oil. But it is evident that the aromatic hydrocarbons are present 

 in no inconsiderable amounts, and without doubt these bodies have much 

 influence on the illuminating qualities of the oil. As shown by the slight 

 changes in specific gravity after the action of ordinary concentrated sul- 

 phuric acid, the action of this acid in the usual method of refinino- does not 

 include to any considerable extent the removal of the aromatic hydrocar- 

 bons. Its beneficial action seems to concern more especially the decom- 

 position products of distillation and certain constituents present in minute 

 quantities, such as the unsaturated hydrocarbons, the oxygen, and nitroc^en 

 compounds. It scarcely need be mentioned that this applies to the action 

 of sulphuric acid in the cold. When heated, without doubt a part of the 

 aromatic hydrocarbons would be removed, to the detriment of the burnino- 

 qualities. The formation of barium salts from all the distillates treated 

 with fuming sulphuric acid proves the presence in appreciable amounts of 

 a wide range of aromatic hydrocarbons. 



Without reference to the percentages of carbon and hydrogen, the low 

 specific gravity of the hydrocarbons described above is sufficient to show 

 that they are not naphtenes. The following comparison of the unpuri- 

 fied distillates and the purified hydrocarbons as regards their specific 

 gravity with the naphtenes separated by Markownikoff from the Russian 

 oil will perhaps make these differences more clearly understood. 



Baku naphtenes : — 



