42 MABERY—THE COMPOSITION OF PETROLEUM.  [April3, 
oxidation always proceeding to the formation of ultimate products, 
nitrogen and CO,, and we have found it impossible to check it. 
The same is true of the sulphur compounds, which also appear to 
be methylene derivatives. ‘These bodies oxidize with the greatest 
ease to sulphuric acid, and it is difficult to control the oxidation. 
We have done this, however, and have obtained well-defined sul- 
phones. In general terms, the addition of hydrogen to benzol and 
its homologues weakens the resistive action toward reagents. This 
difference in stability between the series C,H.,4, and the series 
poorer in hydrogen appears in commercial use of the heavier pro- 
ducts. We have recently compared the flashing point and fire test 
to heavy distillates from Pennsylvania crude oil and crude oils from 
California, Texas, etc., and it appears that the products from 
Pennsylvania oil have higher flashing points and fire tests than 
those from other fields. We have an excellent opportunity to 
ascertain the general application of this observation, for we have at 
hand samples in gallon lots of the principal lubricators made from 
Pennsylvania and Ohio oils on the market, and also samples of 
crude oils from the various fields; for example, two barrels of crude 
oil from Baku in the Russian field. 
Products are now being prepared from the crude oils to compare 
with Pennsylvania lubricating oils. The inferior stability of petro- 
leum which the series C,H,, or series poorer in hydrogen pre- 
dominates has appeared in all our work on the various crude oils. 
For instance, the admission of air into hot Pennsylvania distillates 
never causes an explosion ; but explosions are sure to follow the 
contact of air with hot distillates from other fields where the prin- 
cipal series is lower than the series C,H,, 4». 
In combustion it is easy to see the difference in stability, in the 
readier separation of carbon. Then in analysis of a series, say 
from C,,H,, to C,,H,,, in the lower members no carbon separates in 
the boat, but it gradually appears with increasing molecular weight, 
in larger and larger amounts. 
The greater stability of the Hydrocarbbne C,H,, +2 doubtless ex- 
plains the superior quality of burning oils prepared from Pennsyl- 
vania petroleum, together with the fact of a larger proportion of 
hydrogen. The series poorer in hydrogen more readily separates 
carbon as soot and is more difficult to burn. A mixture of the 
two series C,H,,,, and C,H,, forms a good burning oil and prob- 
ably accounts for the excellent quality of Russian burning oil. 
