682 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The boiling point of tridecane has been variously stated at 219°, 216° 

 and 212°-2I5°. But neither of these temperatures can be accepted as 

 the boiling point of tridecane since its molecular weight is found to be 

 that of the hydrocarbon boiling at 225°-226°. 



The hydrocarbon tetradecane boils at 236°-238°, the same boiling 

 point as was assigned to the tridecane separated by Pelouze and 

 Cahours, but the specific gravity of tetradecane, 0.7812 at 20° is es- 

 sentially lower than that found by Pelouze and Cahours, 0.809. 



Pentadecane, boiling point 156°-157°, is nearly the same in boiling 

 point as the hydrocarbon separated by Pelouze and Cahours, boiling 

 point 260°, although its specific gravity, 0.7896 at 20°, is much lower 

 than they found, — 0.825 at 19°. 



The boiling point of hexadecane is not very different from that given 

 by Pelouze and Cahoux's, but its specific gravity is considerably lower. 

 It does not differ in boiling point materially from hexadecane which 

 Krafft obtained by heating palmitic acid, nor from that of hexadecane, 

 boiling point 278°, obtained by Zincke from normal octyl iodide.* Since, 

 however, the oils obtained by freezing out the solid hydrocarbons have 

 specific gravities considerably higher than those of the original distillates, 

 and apparently belong to another series, as shown by analysis and refrac- 

 tion indices, it is possible that the solid hydrocarbons held in solution in 

 the oils have their boiling points depressed in the fractional distillation 

 by which they were separated from the main body of the crude oil. Still, 

 the molecular weights of the solid hydrocarbons correspond to definite 

 formulas; for instance, from the distillate 300°-301°, atmospheric pres- 

 sure, octodecane was separated, in a practically pure form. 



The less volatile portions of Pennsylvania petroleum consist of several 

 series of hydrocarbons. The series CnHj,, is liquid even at low tem- 

 peratures, of higher specific gravity, and another is composed of solid 

 hydrocarbons, of the series CnH2„+2- 



In a former paper f it was shown that the high values assigned by 

 Pelouze and Cahours as the specific gravity of the distillates separated 

 by them from petroleum, indicated that their hydrocarbons were sep- 

 arated from Canadian petroleum. The same inference is supported by 

 the high specific gravity of the hydrocarbons separated by Pelouze and 

 Cahours boiling above 216°, as compared with the specific gravity of 

 the hydrocarbons separated from Pennsylvania petroleum described in 

 this paper. 



* Ann. Chem. u. Pharm. 152, 15. 

 t These Proceedings, XXXII. 171. 



