CHAPTER NINE 



MINGLING OF MOLECULES 



SECTION 41. Solutions and emulsions. 



How does soap make your hands clean ? 



Why will gasoline take a grease spot out of your clothes? 



If we were to go back to our convenient imaginary 

 switchboard to turn off another law, we should find near 

 the heat switches, and not far from the chemistry ones, 

 a switch labeled SOLUTION. Suppose we turned it off : 



The fishes in the sea are among the first creatures 

 to be surprised by our action. For instantly all the 

 salt in the ocean drops to the bottom like so much sand, 

 and most salt-water fishes soon perish in the fresh 

 water. 



If some one is about to drink a cup of tea and has 

 sweetened it just to his taste, you can imagine his amaze- 

 ment when, bringing it to his lips, he finds himself drink- 

 ing tasteless, white, milky water. Down in the bottom 

 of the cup is a sediment of sugar, like so much fine gravel, 

 with a brownish dust of tea covering it. 



To see whether or not the trouble is with the sugar 

 itself, he may take some sugar out of the bowl and taste 

 it, it is just like white sand. Wondering what has 

 happened, and whether he or the sugar is at fault, he 

 reaches for the vinegar cruet. The vinegar is no longer 

 clear, but is a colorless liquid with tiny specks of brown 

 floating about in it. Tasting it, he thinks it must be 

 dusty water. Salt, pepper, mustard, onions, or any- 

 thing he eats, is absolutely tasteless, although some of 

 the things smell as strong as ever. 



To tell the truth, I doubt if the man has a chance to 



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