FLASHING POINT 



115 



with a low boiling point, then liquids with a higher boil- 

 ing point, and so on. Finally there would remain a black, 

 tarry material. 



The distillation, or refining, of petroleum is carried out on 

 an enormous scale (Fig. 98). 

 The portions ("fractions") 

 having different boiling 

 points are collected sepa- 

 rately, and are known by 

 different commercial names. 

 Some of them are gasoline, 

 naphtha, petroleum ether, 

 kerosene, etc. Some of the 

 hydrocarbons of petroleum 

 have so high a boiling point 

 that they char before they distil, 

 low pressure, " vacuum " 



I I 



I I 1 I 1 I I 



FIG. 98. 



Amount of Petroleum Produced in the 

 United States. 



These are distilled in 

 apparatus (cf. 90), just as the 

 water is distilled off commercially from sugar or salt solu- 

 tion. Vaseline is a high-boiling material obtained from 

 petroleum; paraffin, or "white wax," is another. A 

 residue of coke remains when petroleum is distilled. More 

 than 200 different commercial products are obtained from 

 petroleum. 



122. Flashing Point. Kerosene, which is used in lamps, is composed 

 of hydrocarbons that boil at a moderately high temperature (150 C. to 

 250 C.) If kerosene contains hydrocarbons having too low a boiling 

 point, as is the case with gasoline, its vapor and the air will form an 

 explosive mixture. To prevent kerosene explosions governments 

 insist that a mixture of kerosene vapor and air shall not take fire below 

 a certain temperature; in other words, that the kerosene shall have a 

 certain "flashing point." We find the flashing point (Fig. 99) by put- 



