COMBUSTION AND FUELS 83 



Properties of Fuel Oil. Owing to the great demand for 

 gasoline in all its various grades, the better grades of petroleum, 

 such as those obtained in Pennsylvania, are treated so as to 

 recover the lighter hydrocarbons. Of these, gasoline is among 

 the early distillates, and when the gasoline, naphtha, and kero- 

 sene have been separated, the residue contains the lubricating 

 oils, paraffin, and coke. This residue may be further dis- 

 tilled, so as to obtain the several products named; or, it may be 

 used as a fuel, being then termed fuel oil. In other words, fuel 

 oil is simply the heavier compounds of carbon and hydrogen 

 contained in crude petroleum, the lighter compounds having 

 been driven off by distillation. The analysis of a fuel oil 

 derived from Beaumont crude oil is as follows: 



Constituents Per Cent. 



Carbon 83.26 



Hydrogen 12.41 



Sulphur .50 



Oxygen 3.83 



On comparing this analysis with that of Beaumont crude oil 

 previously given, it will be seen that the relative proportions 

 of hydrogen and carbon have been changed and that a large 

 part of the sulphur has been eliminated by the treatment of 

 the crude oil. 



Calorific Values of Oil Fuels. The combustible elements 

 contained in oil fuels are the same as those in coal, namely, 

 carbon and hydrogen, and possibly a small proportion of sul- 

 phur. The heat of combustion per pound of oil, or the calorific 

 value, may be found approximately from the chemical analysis 

 of the oil by the same formula as that used for rinding the heat 

 value of coal. A more accurate method, however, is to burn a 

 known weight of oil in a calorimeter and to measure the heat 

 generated, from which the heat per pound of the oil may readily 

 be calculated. From the results of available tests it is found 

 that the heat of combustion per pound of oil fuel varies between 

 17,000 and 21,000 B. T. U. The average calorific value of 

 Texas and California crude oils seems to be about 18,600 

 B. T. U. per Ib. 



Atomization of Oil. When coal is used under steam boilers, 

 the furnace contains a considerable amount of fuel; but early 



