CHAPTER V 

 SOLUTION 



Lemonade is a solution of sugar and lemon-juice in 

 water. Sometimes at the bottom of a glass of lemonade 

 you have found some sugar that has not dissolved. The 

 water had dissolved all the sugar it could. Such a solution 

 is called a saturated solution. Now solutions are of immense 

 importance to life. They are among those things without 

 which life could not possibly continue. We must under- 

 stand them. 



The word solution is a little confusing because it is used 

 in two ways. It is the name of a process. It is also the 

 name of a thing. The process of dissolving is called solu- 

 tion, and a liquid after something has been dissolved in it 

 is also called a solution. The liquid in which something 

 has been dissolved is called the solvent, and the substance 

 dissolved is the solute. In lemonade, water is the solvent, 

 and sugar is a solute. Substances that dissolve are called 

 soluble; if they do not dissolve they are called insoluble. 

 Water dissolves more substances than any other liquid, 

 but there are some substances that are not soluble in 

 water but are soluble in other liquids. We rub off paint 

 with turpentine, because turpentine will dissolve it while 

 water will not, and we take out grass stains with alcohol 

 for the same reason. 



There are many substances, like sugar and salt, that dis- 

 solve in water. This means that when they are put into 

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