CHAPTER XIX 

 SOLUTIONS 



108. Solutes and Solvents. When a quantity of a solid, 

 such as salt, is shaken up in water, it soon disappears in the 

 liquid, or as we say, it dissolves or goes into solution. If we test 

 the solution thus made, we find that the solid is evenly dis- 

 tributed through it, for all parts are equally salty. Other 

 soluble substances may now be added to this solution and in 

 every instance they act as the salt did and become evenly 

 distributed through it. The substance that disappears in 

 another in this way is called the solute, and the substance in 

 which it disappears is the solvent. It must not be assumed, 

 however, that because one liquid will dissolve a given solid, 

 that it will dissolve all others. As a matter of fact, there are 

 many exceptions to this rule. Water, for instance, will dis- 

 solve salt, but it will not dissolve camphor. Alcohol, on the 

 other hand, will dissolve camphor but not salt. Water is the 

 best solvent known; that is, it will dissolve the greatest num- 

 ber of substances, but alcohol, ether, and some acids are not 

 far behind it in this respect. Water will not dissolve fats, 

 waxes, gums, or resins, though these readily dissolve in some of 

 the other liquids mentioned. Dry-cleaning processes make 

 use of gasoline instead of water as a solvent for the grease and 

 dirt. When alcohol is used as a solvent, the resultant solu- 

 tion is often called a tincture. In general, crystalline sub- 

 stances dissolve more readily than those which are amorphous, 

 but there are many exceptions to this rule. A substance that 

 will not dissolve in a given liquid is said to be insoluble in it. 

 When in a finely divided state, many insoluble substances will 

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