FORCE AND MOTION" 60 



rated by fractional distillation. That is, if the mixture is 

 heated to a temperature of 150, the substance which boils 

 at that temperature will change into vapor and can be 

 cooled and condensed in a tube through which it passes 

 off. Then if the temperature is raised to 180, the liquid 

 of that boiling point vaporizes. This is called fractional 

 distillation. 



72. Uses of Distillation. It is sometimes necessary at 

 sea to distill sea water in order to have water that contains 



FIG. 28. DISTILLATION 



The glass retort might contain sea water, or a solution of blue vitriol, 

 or molasses and water. 1. On being heated to 212 F., the same vapor 

 would come out in each case. What vapor? 2. Why is water kept run- 

 ning over the neck of the retort? 



no salt, for use in the boilers and for drinking. The distillate 

 is fresh water. 



Alcohol is distilled from liquids prepared from fruits, 

 grains, potatoes, and other plant material. 



Kerosene, benzine, gasolene, and other liquids can be 

 separated from petroleum and from one another, because 

 they have different boiling points. Gasolene has a lower 

 boiling point than benzine; and benzine, a lower one than 

 kerosene. 



