138 RESEARCHES ON THE VOLATILE HYDROCARBONS. 
The discovery by Faraday,* in 1825, of benzole (“bicarburetted hydrogen”) in the 
oil compressed from oil-gas, rendered it highly probable, and indeed led this distin- 
guished philosopher to suspect, that this substance might be found in coal-tar naphtha. 
His search for it, however, proved unsuecessful, it having been first detected by Hof- 
mann in 1845.4 This chemist, however, did not attempt to isolate this body, and the 
bare fact of its presence appears to be all that was definitely known of the composi- 
tion of coal-tar naphtha prior to 1849, in which year Mansfield{ published his elabo- 
rate and valuable research, being the first effort at a proximate analysis of this mix- 
ture which appears to have been attended with any considerable measure of success. 
Although a fatal accident, while engaged in his experiments, prevented Mansfield 
from completing the investigation which he had so well begun, yet the work that he 
had already published in an unfinished state must always be regarded as having con- 
tributed much towards.a clear and definite knowledge of the nature of the neutral 
pyrogenous oils contained in coal-tar*naphtha. Indeed, it may be said that little has 
since been added to our knowledge on this subject. Notwithstanding the incomplete- 
ness of his separations of the hydrocarbons, the extent to which he had carried them, 
with the limited means employed, is truly remarkable, and could not have been 
accomplished without an expenditure of labor, and a degree of patient endurance, 
which only those who have experienced the tediousness of such operations can 
appreciate. 
Mansfield claimed to show that the light coal-tar naphtha is composed of a mixture 
of four distinct hydrocarbons, boiling within the range of 80° to 1757, C.; and probably 
having the general formula C, H,_,. The first of these, which he found to boil con- 
stant at 80°, was proved to be identical with benzole, C,,H,. The second, boiling at 
about 113’, was determined, from certain reactions, to be identical with toluole, C,, Hy. 
The special study of this body was deferred, however, with the remark that it had not 
yet been isolated in a state of sufficient purity to claim an analysis. The third body, 
boiling at about 140° to 145’, was said to present all the characteristics of cumole, 
C,s H,,; but this view was not founded on a careful study and comparison of the 
chemical or physical properties of these bodies, but was merely an expression of 
opinion in advance of anticipated results. Of the fourth body, boiling at about 
170° to 175°, Mansfield remarks that it bears so strong a resemblance, in odor and 
other properties, to cymole, CH, as to induce the belief that this substance is 
* Philosophical Transactions of the Royal Society, 1825, CXV. 465. 
J Annalen der Chemie und Pharmacie, 1845, LV. 200. 
} Quarterly Journal of the Chemical Society, 1849, I. 244. 
