VIL 
Researches on the Volatile Hydrocarbons. 
By C. M. WARREN. 
Communicated October 11th, 1864. 
Introductory Remarks. — While engaged, a few years since, in attempting to separate 
some of the constituents of coal-tar naphtha by the common process of fractional 
distillation, I was forced to the conviction that that process could not be safely relied 
upon for anything like a complete and accurate analysis of such a complex mixture of 
liquids ; and that, at best, the products thus obtained could not be regarded as any- 
thing better than remote approximations to pure substances; leaving reason to fear 
that there might still be other bodies present, in lesser quantities perhaps, which had 
escaped detection. 
An examination of the results of previous researches on tars, petroleums, etc., served 
in general to confirm the impressions induced by my own less extended experiments ; 
and to increase, rather than lessen, the doubts already existing in my mind as to the 
trustworthiness of the results which had hitherto been published concerning the 
neutral constituents of such mixtures. Influenced by these considerations, and by the 
belief that, if I could succeed in finding a process capable of effecting a more com- 
plete separation of the constituents of such mixtures, it might probably lead to the 
discovery of new bodies, lying between those which had already been described, — I 
was led to undertake the researches, the results of which I am about to record. 
Even if this chief purpose should fail, I was convinced that the expenditure of labor 
in isolating those bodies in a state of greater purity, would be amply compensated by 
the much needed confirmation, or perhaps correction, of the results previously pub- 
lished, in addition to the valuable incidental evidence of the absence of other bodies 
‘which would thus be furnished. The results which I have obtained in the pursuit 
of this object are abundantly sufficient to show that I did not undervalue the work of 
my predecessors, nor over-estimate the importance of the work before me. 
The success which attended my efforts in search of a better process of separation: 
