PETROLEUM. 
17 
usefulness and higher value than the crude oil, and it is upon this 
dominant part that the petroleum-refining industry depends. The 
refinery is merely an ingenious mechanical device whereby the raw 
material, through the agency of physics and chemistry, is fitted into 
the needs of society. As these needs are ever increasing in size and 
diversity, refining practice is in continuous flux, adapting a constant 
substance to a shifting and widening demand. 
At the present time petroleum yields, when completely refined, 
four main products — gasoline, kerosene, fuel oil, and lubricating 
oil 1 — and a large number of by-products , 2 of which benzine, vase- 
line, paraffin, road oil, asphalt, and petroleum coke are well-known 
examples. Most of these products in turn may be broken up into 
other substances, each the starting point of further refinements. 
Under present practice petroleum yields only a few hundred sub- 
stances of commercial value, but the mind can set absolutely no limit 
to the number of useful materials that chemical research may still 
wrest from this raw material. 
While refinery practice is a highly technical matter and varies 
both according to the chemical nature of the oil and the local demand 
for products, we may, for the sake of simplicity, ignore all details , 3 
and note merely that there are three main types of refineries. The 
first of these is called a “ skimming ” or “ topping ” plant, because the 
light oils, gasoline and kerosene, are removed from the rest of the 
products, which are left behind as a residual oil and sold in this 
semicrude condition for fuel purposes. The “ skimming 55 plant, as 
its name implies, makes an incomplete recovery of products, supply- 
ing only those in greatest demand or easiest to make; most of the 
plants of this kind are situated west of the Mississippi Biver. 
The second type of refinery may be termed the straight-run ” 
plant; this produces all four of the main products — gasoline, kero- 
1 These are commercial terms and therefore carry no exact meaning in a chemical 
sense. They are used throughout this paper with their usual rough significance. Since 
the products merge one into the other, there can naturally be between them only an 
arbitrary line of demarcation. As this line has not been precisely fixed, either by com- 
mercial usage or by legal standardization, the terms are merely broad expressions of 
the main fractions into which the crude oil is broken. Gasoline, as here used, covers 
those products of crude oil w'hich are more volatile than kerosene ; the term therefore 
embraces some benzine and naphtha. Kerosene, as here used, is the common type of 
illuminating oil representing the distillate heavier than gasoline, but lighter than fuel 
oil. Fuel oil is used as a broad term, including all distillates heavier than illuminating 
oils and lighter than lubricating oils ; it includes so-called gas oil — a high-grade fuel oil 
used in the manufacture of gas — as well as fuel oil proper, used largely for steam 
raising. The term lubricating oil includes a variety of heavy oils used for lubricating 
purposes. 
2 The term by-product has no exact meaning, though its significance is clear. For an 
economic discussion of this matter, consult page 67 of this paper, and Lewis H. Haney, 
Gasoline prices as affected by interlocking stock ownership and joint cost, Quart. Journ. 
Econ., vol. 21, pp. 648-655. 
3 Such details may be found spread over dozens of pages in standard treatises, such 
as Bacon and Hamor, The American Petroleum Industry, New York, 1916. 
