i8 



PROPERTIES OF SOLUTIONS 



Table 4 gives the pH values for solutions of some common acids and bases. 



TABLE 4 pH VALUES OF SOME COMMON ACIDS AND BASES 



Buffer Action. — Suppose that i cc. of a normal hydrochloric acid solu- 

 tion be added to 10 cc. of a normal solution of sodium chloride. The initial 

 pH value of this latter solution will not be sensibly different from that of 

 the water with which it is made. * It will be found that the pH of the solu- 

 tion will drop abruptly to a value of about one. If, on the other hand, a 



8 7 6 

 ML. I N HCl 



e 7 a 9 10 H 



ML. I N NaOH 



Fig. I. Curves illustrating buffer action. 



normal hydrochloric acid solution be added, i cc. at a time, to 10 cc. of a 

 normal solution of sodium acetate it will be found that change in the pH of 

 this solution takes place much more slowly. These facts, as well as the others 

 discussed in this section, are illustrated graphically in Fig. i. It is evident 



4 The pH of distilled water when in equilibrium with the carbon dioxide of 

 the atmosphere is about 5.7. 



