ACIDS 67 



Taste a crystal of tartaric acid; one of citric acid. What 

 taste have they? What is meant by an acid taste? 



b. Acids and Litmus. Test each of the fruit j uices (at home?) 

 and acids of a with blue litmus paper. One piece of litmus 

 paper will do, if, after the color has been changed, you restore 

 the original color. Do this by dipping the paper into dilute 

 ammonia water; then wash off the ammonia water under the 

 faucet. If you wish to dry the litmus paper, lay it on a blotter 

 or a piece of newspaper. Write down all the results. 



Boil some tea leaves with water, and test the solution with 

 blue litmus. Do the same with a piece of an apple; with some 

 dry oak leaves. Give the results. 



c. Acids and Metals. We have already tried the action of 

 zinc with dilute sulphuric acid (cf. Exercise 34). What gas 

 was formed? Try zinc, in a test tube, with dilute hydrochloric 

 acid; also iron filings or small tacks with either dilute sulphuric 

 or hydrochloric acid. Is the same gas formed? 



To a piece of copper wire, or to a cent, add about 5 cu. cm. of 

 dilute nitric acid. Does any reaction take place? Warm the 

 acid if necessary. What kind of a gas is formed this time? 

 What happens to the copper? What is the color of the solution? 

 After a few minutes pour the liquid into another dish, and rinse 

 all the acid from the copper. 



d. Acids and Carbonates. The reactions of acids with 

 carbonates have already been studied (cf. Exercise 40). What 

 happens when soda or marble is treated with a dilute acid? 



Name four ways in which we have tested for an acid. 



EXERCISE 65 

 BASES, OR ALKALIES 



Apparatus and Materials. Glass or porcelain dishes, solid potas- 

 sium hydroxide or sodium hydroxide, red litmus paper, dilute acetic 



