152 RESEARCHES ON THE VOLATILE HYDROCARBONS. . 
mark: “The formation of cumene is easily explained. In effect, the cuminic acid 
being represented by Cy H., O,, it appears that C,O,, that is to say, 2 equivalents of 
carbonic acid, are retained by the baryta, while C,, Hy, are set free.” * 
Cn ih, 0, = Cc, + & He 
In another place (p. 88) they remark, that “by suitably managing the heat, and 
employing no more than 6 gr. of cuminic acid at a time, no other products are ever 
obtained than those which we mention.”+ My experiments show that this reaction 
is by no means so simple as thus described. The crude product obtained from the 
mixture of lime and cuminic acid, when subjected to a simple distillation from a tubu- 
lated retort, was found to distil between 155° and 250°, leaving a residue at the latter 
temperature which became semi-fluid on cooling. The distillate thus obtained gave, 
by my process of fractional condensation, an oil boiling at 151°.1, and a residue at 
170°. It is not improbable that the latter may prove to be mostly cymole, Cy Hy; 
but the quantity was too small to admit of pursuing this inquiry with the probability 
of deciding the question. There is evidence, however, that the product obtained by 
Gerhardt and Cahours was not simply pure cumole, as they described it, but a mixture 
of different bodies, which would necessitate a more complicated reaction than that which 
they assigned. Gerhardt and Cahours found the boiling-point of their cumole to be 
constant at 144°. Four years later, Gerhardt,{ having occasion to make a very accu- 
rate determination of the boiling-point of this body, in connection with his research to 
find a law governing the boiling-points of the hydrocarbons, found its boiling-point to 
be 9° higher, viz. 153°, which is but 2° higher than my own determination. The dis- 
agreement between their determinations, it being so considerable, may be more rea- 
sonably accounted for on the supposition that they operated, in the first instance, 
upon a mixture of different bodies; and yet I cannot see how they could have 
obtained the product boiling below 150°. Additional evidence on this point will be 
found in the discrepancy which appears between their determination of the vapor 
density, and that calculated upon theory. 
The specific gravity of my preparation of cumole was found to be 0.8792 at 0°, and 
0.8675 at 15°. 
* “Ta formation du cuméne s’explique aisément. En effet, l'acide cuminique etant représenté par 
Cy Hy O,, on voit que C,O,, c’est-a-dire 2 equivalents d’acide carbonique sont retenus par la baryte, tandis 
que Cz, H,, sont dégage.” — Annales de Chimie et de Physique, 1841, 3° Série, I. 89. 
¢ “En dirigeant la chaleur convenablement, et en n’employant pas plus de 68 d’acide cuminique & la fois, 
on n’obtient jamais d’autre produits que ceux que nous venons de nommer.” 
{ Annales de Chimie et de Physique, 1845 (3), XIV. 107. 
