68 LABORATORY EXERCISES 



acid, ammonia water, limewater, washing soda, laundry soap, "Gold 

 Dust," wood ashes, dilute hydrochloric acid. 



a. Examine some solid potassium hydroxide or sodium 

 hydroxide; then dissolve a piece the size of a bean in about 3 

 cu. cm. of water. Rub a little of this solution between your 

 fingers. How does it feel? Dilute the solution with more 

 water, and test it with red litmus paper. You can use the piece 

 of blue litmus of the last exercise, if you will first dip it into 

 dilute acetic acid. Wash off the excess of acid with running 

 water. How does the alkali affect red litmus? 



b. Test the following with red litmus: ammonia water 

 (cf. Exercise 64), limewater, solution of washing soda. Also 

 test a piece of some laundry soap, or its solution, and some wet 

 "Gold Dust." What takes place? 



c. Get some wood ashes (or burn some wood to ashes), treat 

 them with water, and filter the solution. Test the filtrate with 

 red litmus. What is the result? 



d. Put upon a small piece of potassium hydroxide or sodium 

 hydroxide a drop of dilute hydrochloric acid. Is there much 

 effervescence? Let a similar piece stand in the air for a day; 

 then add a drop of acid. What is the result? What has the 

 hydroxide probably taken up from the air? What happens to 

 lime that is exposed to the air? Why does mortar become hard? 

 See 132, text. 



EXERCISE 66 

 NEUTRALIZING A BASE BY AN ACID 



Apparatus and Materials. Glass or porcelain dish, solid sodium 

 hydroxide, litmus paper, dilute and concentrated hydrochloric acid, 

 lemon, limewater, filter paper and funnel, black or blue woolen cloth, 

 ammonia water, baking soda. 



a. In a glass or porcelain dish dissolve a lump of sodium 

 hydroxide the size of a bean in about 10 cu. cm. of water. 



