RESEARCHES ON THE VOLATILE HYDROCARBONS. 153 



Determination of Boiling-point. — The quantity of material being quite small, this 

 determination was made in a large test tube, with the usual precautions. It had not 

 a perfectly constant boiling-point, the distillation ranging from 148\4 to 151°.6. 

 Applying the proper corrections to the mean of these observations, gives, for the 

 boiling-point of cumole, 151M, which is doubtless a little too high from the impracti- 

 cability of making a complete separation with the small quantity of material employed. 

 If the boiling-point difference between cumole and cymole, for the difference of C, II 2 

 in their elementary formulaa, is 30°, as there is every reason to believe, then the 

 boiling-point of cumole should be 150°, as I have found the boiling-point of cymole to 

 be but a fraction under 18(T. 



Analysis. — 0.1*700 gramme of cumole gave, by combustion with oxide of 



0.563 of carbonic acid, and 0.1557 of 



Calculated. Pound. 



t « 



Carbon, C 18 108 90.00 90.35 



Hydrogen, H 12 J* 10.00 10-18 



120 100.00 100.53 



Determination of Vapor Density. 



to 



17 

 203 



Temperature of balance, 



Temperature of oil bath, ...••• 



Height of barometer, . . . . • 760.1— • at 15° 



Increment of balloon, 0.44zo 



Capacity of balloon, 232 e. c. 



Density of vapor found, .... 4.2003 

 Theory C 18 H^ = 4 volumes, . . 4.151 



This determination, as well as the results of analysis, confirms, therefore, the formula 

 which Gerhardt and Cahours had assigned to this body. I had anticipated a different 

 result from this, inasmuch as the hydrocarbon from coal-tar naphtha, which I have 

 called iso-cumole, boiling at 170°, or nearly 20° higher than cumole from cuminic acid, 

 had been found, as I have shown above, to have the formula C 18 H 12 . I am forced to 

 the conclusion, therefore, that these two bodies are isomeric, and belong to different 

 series. A preliminary examination of their behavior with reagents indicates that 

 their chemical properties are also different. These will be treated of on a future 



occasion, in Part III. 



vol. ix. 24 



