RESEARCHES ON THE VOLATILE HYDROCARBONS. 151 
Density of vapor found, 4.7281 
Theory Cy Hyg = 4 volumes, 4,7028 
Excess found, 0253 
The calculated density on the formula C, H,, is 4.635; which, compared with the 
density found, would increase the excess to 0.093. Although the determination agrees 
more nearly, indeed almost exactly, with the calculated density on the formula 
Co) Hy, the calculation on the formula C, H,, does not show a greater variation from 
the density found, than we have observed to be quite frequent with hydrocarbons of so 
high boiling-point ; so that it may be questionable which of these formule is the true 
one. I cannot regard the determination of a vapor density as reliable for fixing the 
formula nearer than to within two equivalents of hydrogen. In the absence of oppos- 
ing evidence, it will be wiser, however, to take the formula which agrees best with 
the results of experiment; at least until it shall be shown that the discrepancy 
between the calculated and observed vapor densities of bodies of high boiling-point, 
which appears to be so frequent, is nearly constant, or variable by some fixed law by 
which the amount of the error, in any given case, may be pretty nearly estimated. 
I shall therefore regard this body as having the formula C,, H,,, which is also better 
supported by the results of analysis. On account of its source, and close resemblance 
to oil of turpentine, I think of no better appellation for this body than cumo-oil of 
turpentine ; thus adding another to the long list of isomers of the former substance, 
the chemical relations of which stand in so much need of being further studied. 
2. CUMOLE. 
This body was first obtained by Gerhardt and Cahours,* by the dry distillation of a 
mixture of six parts of crystallized cuminic acid, and twenty-four parts of caustic 
baryta. Abelt obtained the same result by substituting caustic lime for the baryta. 
His product, however, was found to boil 4° above that of Gerhardt and Cahours. 
My preparation was also made by the use of lime. Although the results of my 
experiments confirm the conclusions arrived at by Gerhardt and Cahours as to the 
composition of this body, yet the numerical results differ considerably from theirs. 
I have also observed some new facts regarding the formation of this body. They 
have described the reaction between the baryta and cuminic acid as being much 
more simple than my experiments seem to indicate. On this point they re- 
* Annales de Chimie et de Physique, 1845, 3° Série, IV. 87. 
+ Annalen der Chemie und Pharmacie, 1847, LXIV. 312. 
