242 The American Geologist. -^p'"' ^^°^ 
It is apparent that if the distillate consisted of benzene and 
paraffins alone, the gravity of benzene being 0.885, ^"<i of 
a mixture of hexane and heptane, boiling at 80°, being 0.766, 
the greatest possible proportion of benzene in a mixture of 
0.700 (70°) gravity would be 16%. 
There is no reason for supposing that the small pro- 
portion (if any) of aromatic compounds in California petro- 
leum will ever repay the cost of separation, particularly 
as these substances are now very low in price, and readily 
obtainable otherwise. But the presence of the naphthenes 
very seriously affects the quality of some of the products 
of our petroleum, notably the kerosenes. 
It has been pretty well proven by experience that a 
kerosene, to be rated first quality, must consist practically 
of paraffins, as these bodies are the most stable of the 
hydrocarbons, and contain the largest proportion of hydro- 
gen. It is necessar}' that the hydrocarbons should be 
stable, that is, not subject to oxidation or to spontaneous 
decomposition, as otherwise the kerosene will, on standing, 
lose its white color, acquire a foul odor, and be otherwise 
deteriorated. Also, the higher the percentage of hydrogen 
in the kerosene, the smaller will l^e the proportion of air re- 
quired for complete combustion, and the less the tendency 
to smoking when burned. The olefins, which come next to 
the paraffins, contain more carbon and less hydrogen, and 
are more unstable. Consequently, kerosene like the oils 
produced by cracking paraffin petroleums, which consist 
largely of clefins, is of distinctly inferior quality. The 
naphthenes contain a still larger percentage of carbon and 
a smaller percentage of hydrogen than the olefins, but are 
more stable, consequently a kerosene constituted (like that 
produced locally) largely of these bodies, will have more 
tendency to burn with a yellow or smoky flame than either 
of the foregoing, but will be somewhat more stable, when 
purified, than a kerosene produced by cracking. 
The cracking of paraffins produces lighter paraffins 
and olefins, the cracking of olefins ])ro(luces olefins and also 
acetylenes or other highly unsaturated and very unstable 
bodies, while neither the naphthenes nor the benzenes are 
susceptible to cracking, under ordinary conditions. For this 
