C. M. Warren on the Volatile Hydrocarbons, 229 
Indeed, leaving out of the calculation the third series from petro- = 
leum (having the general formula C,Hn),—which must remain > 
anomalous,—and also the products from oil of cumin, the aver- es 
: age of all the other boiling-point differences is 29°-75. The few e 
a individual variations from the number 80°, rarely exceeding a 
___ Single degree, may reasonably be attributed to errors of the 
___ thermometer (especially in case of temperatures above 100°), 
____ OF in some instances to a want of purity of one of the compared 
___ substances; which latter cause I doubt not is the case with the 
y from petroleum boiling at 87°, as upon this body I had 
bestowed less labor in fractioning than upon most of the others, 
on account of the extreme volatility and consequent loss of the 
Substance, by which the quantity had become so muc uc 
that I could ill afford further loss. In the case, also, of cymole 
from oil of cumin, and cumole from cuminie acid, in which the = 
boiling-poi - 
ence of 30 = 
mn of mereury. I do not doubt that the true boiling-point 
of this body will be found to be 150°, which would establish the 
difference of 30° between it and cymole. : 
I would here remark that this difference of 80° for the addi- 
oH, was first observed while engaged in fractioning 
ia petroleum, and the oil from Albert coal,—substan- 
fach of two parallel series of constituents, whose boiling-points 
lie so near together. : nee ae 
As no one had preceded me in the investigation of these sub- 
ing-points of the constituents of these mixtures. 
are of the beautiful relation between ele 
