1903.] MABERY—THE COMPOSITION OF PETROLEUM. 37 
series have been identified with respect to their molecular weights. 
But concerning the structure of these hydrocarbons, except those of 
the series C,H,,,, and the lower methylenes nothing whatever is 
known. It is reasonable to assume that the members of the series 
C,H +42, or the so-called paraffine hydrocarbons, have the open- 
chain structure which characterizes the lower members of this 
series. In earlier literature on petroleum it was generally assumed 
that the ethylene hydrocarbons, series C,H,,, formed a considerable 
proportion of the constituents, and even after the discovery of the 
series C,H,,, the naphthenes, according to the earlier nomenclature 
of Markownikow, many writers still insisted on the presence of the 
ethylene hydrocarbons. It is now safe to assert that these bodies 
are present in any petroleum at most in very small amounts. We 
have found them apparently in Canadian petroleum, but in very 
small quantities. 
The series C,H,,, which has been identified in petroleum from 
many sources, is now well known as the methylene series. Ina 
paper published last year on the composition of Pennsylvania 
petroleum, I purposely abstained from naming the hydrocarbons 
with high boiling points of this series which we had separated and 
identified, for although it seemed probable that these bodies were 
methylenes, I preferred not to suggest names for the several mem- 
bers until more is known concerning their structure. The names 
suggested by Dr. Bogert in his summary of the results described in 
that paper for the Journa/ of the American Chemical Society, seems 
to refer those hydrocarbons to the ethylene series ; but any nomen- 
clature for these bodies must await sanction by proof of structure 
when some courageous investigator shall force his way into this 
difficult field. 
Another feature of the petroleum problem is the form of the 
hydrocarbons which form the highest boiling portions—the so- 
called asphaltic hydrocarbons. The main body of these high boil- 
ing oils are no doubt composed of series poorer in hydrogen than the 
methylenes, the series C,H,,_2, CaHmn_4, etc. The hydrocarbons of 
these series already appear in the higher boiling portions of Penn- 
sylvania, Ohio, Canadian, etc., petroleum, as we have shown in 
part, although much of this data has not yet been published. 
It does not at present seem clear how this problem shall be 
attacked. By exclusion of air and depression of boiling points the 
petroleum hydrocarbons can be distilled indefinitely as high as 
