BASES 221 



purposes, the most important characteristic of a base is that 

 it will neutralize an acid and in some measure hinder the 

 damage effected by the former. If, as soon as an acid has 

 been spilled on cloth, a base, such as ammonia, is applied to 

 the affected region, but little harm will be done. In your 

 laboratory experiments you may be unfortunate enough to 

 spill acid on your body or clothing ; if so, quickly apply 

 ammonia. If you delay, the acid does its work, and there is 

 no remedy. If soda (a base) touches black material, it dis- 

 colors it and leaves an ugly brown spot ; but the application 

 of a little acid, such as vinegar or lemon juice, will often 

 restore the original color and counteract the bad effects of 

 the base. Limewater prescribed by physicians in cases of ill- 

 ness is a well-known base. This liquid neutralizes the too 

 abundant acids present in a weak system and so quiets and 

 tones the stomach. 



The interaction of acids and bases may be observed in 

 another way. If blue litmus paper is put into an acid solu- 

 tion, its color changes to red ; if now the red litmus paper is 

 dipped into a base solution, caustic soda, for example, its 

 original color is partially restored. What the acid does, the 

 base undoes, either wholly or in part. Bases always turn red 

 litmus paper blue. 



Bases, like acids, are good or bad according to their use; if 

 they come in contact with cloth, they eat or discolor it, unless 

 neutralized by an acid. But this property of bases, harmful 

 in one way, is put to advantage in the home, where grease is 

 removed from drainpipe and sink by the application of lye, 

 a strong base. If the lye is too concentrated, it will not only 

 eat the grease, but will corrode the metal piping ; it is easy, 

 however, to dilute base solutions to such a degree that they 

 will not affect piping, but will remove grease. Dilute am- 

 monia is used in almost every home and is an indispensable 



