PETROLEUM. 45 



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 

 oiP — and a large number of by-products,^ 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,^ 

 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" 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 River. 



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 which 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 95 of this paper, and Lewis H. Haney, 

 Gasoline prices as affected by interlocking stock ownership and joint cost. Quart. Journ. 

 Econ., vol. 21, pp. 648-65.5. 



' 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. 



