40 THE PRODUCTION AND USE OF LIGHT 



all of the distillates of petroleum up to illuminating oil together 

 and selling them as gasoline. While the common grade of 

 gasoline, heavy gasoline, or stove gasoline, as it was called, 

 used to have a density of about 72 to 74B., it now commonly 

 has a density considerably greater, about 62 to 64B. (see 

 Art. 31). This heavier gasoline does not work so well in auto- 

 mobiles during cold weather and manufacturers have been 

 obliged to modify their engines so that they could burn the 

 grade of gasoline obtainable. 



47. Manufacture of Gasoline from Natural Gas. In the 

 vicinity of petroleum wells the atmosphere is charged with the 

 odor of escaping gases. A considerable portion of the flow 

 from an oil well evaporates immediately at the temperature of 

 the atmosphere. This is natural gas. Recently it has been 

 found possible to change this escaping gas into an oil closely 

 resembling gasoline. This is done by placing the gas under 

 very high pressure and at the same time cooling it to a very low 

 temperature. In 1912 there were 250 plants in the United 

 States for changing natural gas from petroleum wells into gaso- 

 line and over 12,000,000 gal. were produced. 



48. Manufacture of Motor Spirit, or Motor Oil. During 

 recent years oil refiners have been constantly searching for 

 some method by which they could profitably produce more 

 gasoline from a barrel of petroleum. In 1911 W. M. Burton, 

 a chemist in the employ of the Standard Oil Company of 

 Indiana, perfected a process of producing a good substitute 

 for gasoline from the residue of petroleum after the illuminating 

 oil has been removed. This new oil is called MOTOR SPIRIT or 

 MOTOR OIL. By a special method of " destructive " distillation 

 a large amount of this motor spirit is obtained. In general, 

 this " destructive " distillation is accomplished by distilling the 

 residue containing the lubricating oils, the paraffin and the tar 

 and coke, under high pressure and therefore at high temperature 

 (see Arts. 154 to 160). 



49. Properties of Motor Spirit. Motor spirit is somewhat 

 lighter than gasoline and has somewhat different properties, 



