ACIDS, BASES, AND SALTS 



55 



taste bitter. Litmus paper that has been turned red by 

 acids will be changed back to blue by a base. Some of the 

 most common bases of the household are ammonia water, 

 baking soda, limewater, caustic potash (lye), and caustic 

 soda. Certain strong bases are usually called alkalies. 

 Caustic potash and caustic soda are two of the commonest 

 and strongest alkalies. 



Experiment 17. Into a clean test tube containing pure water 

 put a small piece of blue litmus paper. Pour into the test tube a 

 little hydrochloric acid. What happens to the litmus paper? 

 Now add a solution of caustic soda, drop by drop, until the litmus 

 paper takes on a pale 

 bluish red shade. Taste 

 a drop of the solution in 

 the test tube. The test 

 tube will be found to 

 contain water with com- 

 mon salt dissolved in it. 

 By evaporating the 

 water, crystals of 'salt 

 may be obtained. 



This process of com- 

 bining an acid and a R OCK SALT 

 base in right propor- 

 tions, by which a substance is produced that is neither 

 an acid nor a base, is called neutralization. The result of 

 such a chemical combination is water and a salt. There 

 are many different kinds of salts; but the salt with 

 which we are most familiar is sodium chloride, or 

 common table salt, which resulted from the preceding 

 experiment. 



Strong acids and bases will corrode metals, discolor 

 clothing, or even " eat " holes in it, and cause ugly flesh 



