INTRODUCTORY EXERCISES 25 



stirring with the rod and testing with the litmus until the 

 solution turns neither red litmus blue, nor blue litmus red. 

 If too much acid is added correct it with more basic solu- 

 tion. The acid and the base are now said to be neutralized, 

 and the process is called neutralization. Evaporate this 

 mixture to dryness over the flame. What sort of substance 

 is left in the dish? Taste it. Is it familiar? Does it affect 

 litmus in the solid state or when dissolved in water? 



D. Repeat the above neutralization, using nitric acid 

 instead of hydrochloric. Does the product affect litmus? 



(The products of C and D are called neutral salts. To this 

 class of substances belong most of the minerals of the 

 earth.) This exercise may be continued with other acids 

 and bases at the desire of the experimenter. 



