MABERY. — THE COMPOSITION OF PETROLEUM. 581 



The melting point of the solid was found to be 33°-34° corresponding 

 to the melting point, 32°, that Kraflft found for the solid hydrocarbon 

 distilling at, 226°. 5, 50 mm. 



A combustion of the oil filtered from the solid hydrocarbon gave 

 percentages of carbon and hydrogen required for CigHsg. 



0.1495 grm. of the oil gave 0.4715 grm. CO2 and 0.1928 grm. H2O. 



Calculated for Ciglljg. Found. 



85.70 86.00 



14.30 14.33 



A determination of the molecular weight confirmed the formula: — 

 2.5445 grms. of the oil and 24.63 grms. benzol gave a rise of 0°.994. 



Calculated for CioHjg. Found. 



266 267 



The formula was further verified by its index of refraction. 



It gave the index 1.4515, corresponding to the molecular refraction : — 



Calculated for CigHjg. Found. 



87.46 87.51 



With the distillate 212°-214°, 50 mm., the limit is reached of the 

 solid hydrocarbons whose molecular weight can be determined by the 

 freezing point method on account of the crystallization of the hydrocar- 

 bon before the benzol freezes. The molecular weights of solid higher 

 members were determined by the boiling point method. 



The results described in this paper defining the physical properties and 

 formulae of the hydrocarbons separated from Pennsylvania petroleum dif- 

 fer in several essential particulars both from the hydrocarbons obtained 

 by Kraflft by decomposition of the monobasic acids with high molecular 

 weights, and those formerly reported as among the constituents of Penn- 

 sylvania oil. It has been shown that the hydrocarbon at 196° is undecane, 

 CnH24, and not dodecane as found by Pelouze and Cahours. Likewise 

 the hydrocarbon at 216° proved to be dodecane and not tridecane. 

 Since there was no method for ascertaining the molecular weights of 

 these bodies at the time when they were separated by Pelouze and 

 Cahours, and elementary analysis could only determine the series, it was 

 only by analogy that the homologous members of the series could be 

 guessed at. Since 182° was accepted at the boiling point of undecane, 

 naturally dodecane and tridecane should fall into the heaps at 196° and 

 216°. 



