CHAPTER TWO 



MOLECULAR ATTRACTION 



SECTION 6. How liquids are absorbed: Capillary 

 attraction. 



Why do blotters pull water into themselves when a flat 

 piece of glass will not? 



How does a towel dry your face ? 



Suppose you could turn off nature's laws in the way 

 that you can turn off electric lights. And suppose 

 you stood in front of a switchboard with each switch 

 labeled with the name of the law it would shut off. Of 

 course, there is no such switchboard, but we know pretty 

 well what would happen if we could shut off various 

 laws. One of the least dangerous-looking switches 

 would be one labeled CAPILLARY ATTRACTION. And 

 now, just for fun, suppose that you have turned that 

 switch off in order to see the effect. 



At first you do not notice any change ; but after a 

 while you begin to feel perspiration collecting all over 

 your body as if your clothes were made of rubber sheet- 

 ing. Soon this becomes so uncomfortable that you 

 decide to take a bath. But when you put your wash 

 cloth into the water you find that it will not absorb 

 any water at all ; it gets a little wet on the outside, but 

 remains stiff and is not easy or pleasant to use. You 

 reach for a sponge or a bath brush, but you are no 

 better off. Only the outside of the sponge and brush 

 becomes wet, and they remain for the most part harsh 

 and dry. 



Then perhaps you try to dry yourself with a towel. 

 But that does not work; not a drop of water will the 



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