264 



GENERAL SCIENCE 



refining of petroleum is essentially a process of distillation 

 in which the crude oil is separated into a number of frac- 

 tions which have different boiling points and compositions. 

 Some of the products obtained are petroleum, ether, gaso- 

 line, naphtha, benzene, kerosene, paraffine, vaseline, and 

 petroleum jelly. Of this list gasoline, naphtha, benzene, 

 and kerosene are quite commonly used as fuels. 



Flash Test. Half fill a 200 cc. beaker with kerosene, 

 and place over water (Figure 229). Stir constantly with 

 an accurate Fahrenheit thermometer 

 and heat slowly until a small flame held 

 over the mouth of the beaker causes a 

 slight explosion and a blue flame. This 

 is the flashing point and should not be 

 lower than 150 Fahrenheit. A lower 

 flashing point indicates the presence of 

 hydrocarbons which have a low boiling 

 point, such as gasoline, and that the 

 kerosene is not safe to use in lamps. 



Alcohols. It is quite probable that 

 alcohol will come into common use as a 

 fuel in the event of a scarcity of petro- 

 leum. It is composed of carbon, hydrogen, and oxygen, 

 and has a high fuel value. Denatured alcohol is simply 

 grain alcohol to which has been added a small quantity 

 of wood alcohol and benzene. 



Sources of Fire. - - The origin of fire furnished the basis 

 of a number of mythological tales. Just when fire was 

 discovered is not known, for it was long before the period 

 of authentic history. Probably friction was the first 

 method used by primitive peoples to raise the temperature 

 of dry wood to the kindling temperature. A hundred 

 years ago a spark of fire was obtained by striking a 



FIG. 229. Method 

 of Obtaining the Flash- 

 ing Point of Kerosene. 



