Emulsions 81 



sene and droplets of kerosene mixt with soap 

 solution will exist separately for a long time. 

 There is a second reason why the kerosene 

 will stay emulsified. The droplet is mixt 

 with the soap colloid. The concentration of 

 the colloid is much greater on the surface 

 of the drop than elsewhere. Now when the 

 droplet of kerosene and soap has reacht an 

 equilibrium, that is, the concentration of the 

 soap solution, inside, on the surface, and out- 

 side the droplets have come into adjustment, 

 a coahtion of two droplets of kerosene would 

 cause a readjustment of the concentration 

 of the solution on the surface which would 

 require energy. Consequently the droplet 

 once in equilibrium tends to be stable. 



QUESTIONS 

 (To be answerd in the notebook.) 



5. What three substances are necessary in an 

 emulsion? 



6. Name a colloidal substance. 



7. What is the use of miscible oils? 



8. Which has the greater surface tension soap 

 solution or water? 



9. Define the term surface tension. 



10. T\Tiere about a droplet of liquid does a colloid^ 

 when present, tend to concentrate? 



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