RESEARCHES ON THE VOLATILE HYDROCARBONS. 149 
sity found and that calculated on the formula Cx H,, is not only more than twice as 
large as the corresponding difference calculated on the formula C,;H,, but that the 
error is reversed ; being with C»H,, a deficiency, while with C,,H,, it is an excess. 
This circumstance has to my mind a good deal of significance, as it goes strongly to 
show that the lower’ formula is the true one. For of the many vapor densities of 
hydrocarbons which I have determined, I have but rarely met with an instance in 
which the density found was not greater than the theoretical density. And I have 
usually observed that the excess of the experimental over the theoretical density is 
‘larger in proportion as the boiling-point of the body is higher, a fact which needs 
explanation. Wurtz* observed a similar difference between the determined and 
calculated vapor densities of bodies of the formule C,H, and C,H,,., which he 
accounted for on the ground that his preparations contained an admixture of bodies 
less volatile, the vapors of which would remain in the balloon, and increase the den- 
sity. But I cannot accept this explanation for the substances here treated of, since 
they invariably distil without residue within a range of one degree of temperature. 
I would rather rely upon the supposition that the high temperature employed causes 
partial decomposition of the substance, which would be the more liable to occur the 
higher the boiling-point of the body. I do not, however, offer this as an explanation, 
but merely make the suggestion. 
PART II. 
HYDROCARBONS FROM OIL OF CUMIN AND CUMINIC ACID. 
Te oil of cumin employed in this research was furnished by Messrs. Reed and 
Cutler, wholesale importers of drugs, etc. of Boston. The package bore the label of 
Eduard Bittner, manufacturer, of Leipzig, and purported to be a genuine preparation, 
answering in all of its obvious physical properties — odor, color, etc. — the description 
given of this oil by Gerhardt and Cahours +} in their original memoir on this substance, 
who, it appears, also employed a commercial preparation. Its behavior in distillation 
left no doubt of its being a genuine article; and this was afterwards confirmed by 
treatment of the cuminole with fused potash, for the production of cuminic acid, its 
comportment with this reagent being in all respects identical with that described by 
Gerhardt and Cahours. Subjected to repeated series of fractionings by my process of 
* Bulletin de la Société Chimique de Paris, 1863, 309. 
+ Annales de Chimie et de Physique, 1841, 3° Série, I. 60. 
