36 MABERY—THE COMPOSITION OF PETROLEUM. _ [April3, 
(@) In the case of anhydrous salts the elimination of adsorption — 
is easy, but in order to remove included solvent the cell walls 
enclosing it must be disintegrated. 
(e) Mechanical, thermal and chemical methods of such disinte- 
gration are classified and applied to the preparation of pure 
materials. 
(/) It is pointed out that other impurities besides the solvent 
will usually be enclosed in the cells, and that these other impurities 
must never be forgotten in subsequent processes of purification. 
(g) Finally, it is suggested that these enclosed impurities might 
be used more frequently than they are as a clue to the manner of 
growth of natural minerals, and hence to the mechanism of 
geophysical processes. 
HARVARD UNIVERSITY, CAMBRIDGE, MAss. 
A RESUME OF THE COMPOSITION AND OCCURRENCE 
OF PETROLEUM. 
BY CHARLES F. MABERY. 
(Read April 3, 1903.) 
I have said and written so much about petroleum during the last 
fifteen years, it may seem that I have reached the limit of interest 
and about exhausted the subject. Twenty years ago when I first 
went to Cleveland I began the study of petroleum, and have since 
devoted a considerable portion of my time to the examination of 
the constituents of petroleum from many different fields. But 
instead of exhausting the subject it is evident that only a beginning 
has been made, and the foundation for what is probably the most 
difficult and intricate parts of this interesting field of research. 
The series of hydrocarbons which form the portions of petroleum - 
distilling below 350° zz vacuo, corresponding to 475° atmospheric 
pressure, are now well understood, and the members of the various 
1 The subject matter of this paper is based on the results of work carried on in 
the chemical laboratory of Case School of Applied Science, with aid of grants by 
the American Academy of Arts and Sciences from the C. M. Warren fund for 
chemical research. 
