136 RESEARCHES ON THE VOLATILE HYDROCARBONS. 



has already been described in detail, in a memoir • On Fractional Condensation," etc. 

 (Memoirs of the American Academy, 1864.) 



This new process was first applied, more especially for the purpose of testing its 

 efficiency, in the separation of benzole from coal-tar naphtha. This mixture was 

 selected for the test on account of the property which benzole possesses, in contradis- 

 tinction from its associates, of being crystallizable at a low temperature, thus affording 

 an additional test of the purity of the product which might be obtained by the 

 process of fractioning. Somewhat to my surprise I found that, after only the fifth 

 series of fractionings, I had obtained benzole so nearly pure that the whole of it 

 would distil from a tubulated retort between 80° and 81° C; and that when congealed, 

 which was effected by placing the containing bottle in pounded ice, not a drop of 

 liquid could be poured from the mass of crystals. From this result, — which, at the 

 least, indicated a near approximation to purity, — taken in connection with other 

 favorable indications, I felt confident that I had accomplished my first object, and had 

 found a process that could, in all probability, be successfully applied in the study of 

 the petroleums, which up to that time (1861) had baffled every attempt to resolve 

 them into their proximate constituents. 



Being naturally anxious to apply the new process in this seemingly more promising 

 field of inquiry, I at once suspended, for the time being, my operations on coal-tar 

 naphtha, and commenced simultaneously the investigation of Pennsylvanian petroleum, 

 and of the oils distilled from Albert coal (from Hillsboro, New Brunswick) in the 

 process of manufacturing illuminating oil. These two substances, neither of which 

 had ever been made the subject of special scientific investigation, were selected as 

 being fair representative types, on the one hand of the native liquid petroleums, and 

 on the other of the artificial coal oils. The comparative study of these two substances 

 seemed to promise additional interest on account of the close analogies which they 

 present, especially when this circumstance is considered in connection with the fact of 

 heir great diversity of origin. This is the limit which at that time was assigned for 

 these researches ; my intention being, so soon as the separations and analyses should 

 be completed, and the boiling-point, and some of the other more important physical 

 characteristics determined, briefly to publish the results, together with the process of 

 fractionmg - preliminary to a complete memoir at a more advanced stage of the 

 work. Before this work had been accomplished, however, it became evident that the 

 bodies contained m these mixtures could not be studied so satisfactorily by themselves 

 as in comparison with other series of hydrocarbons, especially with reference to cer- 

 tain important questions of more general interest ; for example, the question in regard 



