A YEAR IN SCIENCE 61 



hydroxide? These substances are called bases. All 

 bases react similarly to these tests. 



Exercise 35. Salts and Neutralization. 



Object: A study of neutralization and its results. 



Apparatus 



Hydrochoric acid (10%) Blue litmus paper 



Sodium hydroxide (10%) Glass rod 



Evaporating dish Bunsen burner 

 Red litmus paper 



Directions: Pour one cubic centimeter of hydro- 

 chloric acid into the evaporating dish. To this add, 

 drop by drop, some sodium hydroxide. Stir constantly 

 to mix the liquids. Test the solution frequently with 

 both kinds of litmus paper. If too much sodium 

 hydroxide is added, the solution will turn the red 

 litmus paper blue ; if too much acid is present, the blue 

 litmus will turn red. Balance the solution by alternately 

 adding a few drops of acid and base until neither 

 litmus paper is affected. When a solution has no effect 

 on either red or blue litmus paper, it is said to be 

 neutral. The process of mixing an acid and base to 

 produce a neutral substance is called neutralization. 



Over a flame evaporate the solution. Examine the 

 residue. What is its appearance? Does it taste like 

 any substance with which you are familiar? This 

 product is called a neutral salt. Dissolve some of it in 

 water. Does the solution have any effect on litmus 

 paper? What was the substance evaporated? What, 

 then, are the products of neutralization? 



