38 -MABERY—THE COMPOSITION OF PETROLEUM.  [April8, 
350°. Between 300° and 400° cracking begins, and it cannot be 
avoided by straight distillation. The heavy hydrocarbons seem to 
become so inert, by reason of their high molecular weights, they 
cannot retain their atomic composition at their boiling points; they 
simply fall to pieces through the influence of mass. In distillation 
from the crude oil evidently another influence comes into opera- 
tion—the effects of the oxygen, nitrogen and sulphur constituents. 
Since fractional distillation is the only means at present known for 
the separation of the homologous members of these series, the 
problem of their isolation becomes a difficult one. 
Nevertheless I regard this field as offering great attractions, 
provided, as I mentioned some time ago, suitable facilities are pro- 
vided for carrying on the work. A grant of ¢$5000 annually from 
the Carnegie University could be made to yield results commensur- 
ate with the expenditure, for there is no more promising field for 
research of such magnitude awaiting a vigorous hand. As for 
myself, I shall be content with what I have been able to accomplish 
with the aid of the C. M. Warren fund and the facilities of the 
Case School laboratory in defining the series and principal members 
in petroleum from different fields that has come under my obser- 
- vation. 
In presenting a general summary of present knowledge concern- 
ing the composition of petroleum, it may be of interest to refer to 
what was known on this subject twenty years ago when I began the 
work. At that time the only petroleum on the market in America 
was obtained from the Pennsylvania fields and the territory in 
Canada. The composition of Russian petroleum was then under 
investigation by Markownikow. As a result of their elaborate 
investigation on American petroleum Pelouze and Cahours had 
assigned the formula C,H,, 4, as representing the principal series of 
hydrocarbons. But the high specific gravity of their distillates 
could not have been given by hydrocarbons separated from Penn- 
sylvania petroleum, since these bodies give much lower values. 
Since the source of their products was not mentioned, it must be 
assumed that they came from the heavier Canadian oil, although 
the hydrocarbons in this oil have not the composition of the series 
C,H», 42 which Pelouze and Cahours deduced from their analyses, 
but, as we have found by results not yet published, the composition 
of the series C,H,,. Pentane, hexane, heptane and octane had 
been identified by Schorlemmer, and the classic work of C. M. 
