Chemical Classification 311 



of an hour. Put a drop of the weaker acid on another 

 paper and, after putting it aside for a day, examine 

 both papers. The effects in each case may be obtained 

 more readily, if required, by gently heating the papers 

 over a small Bunsen flame. 



Compare the results obtained for the several acids, 

 and, from your observations, prepare a general statement 

 of the properties of acids. 



EXPERIMENT 139. The properties of soluble bases, 

 or alkalis, may be similarly studied. Use solutions of 

 sodium hydroxide, potassium hydroxide, and calcium 

 hydroxide (lime-water) in the performance of each of 

 the following tests : 



(a) Taste very weak solutions of each alkali. 

 (6) Rub a little stronger solution between the 

 fingers. 



(c) Put a drop on a red litmus paper. 



(d) Invert in a trough of alkali a jar of carbon 

 dioxide, obtained as in Experiment 114, or by the 

 method described in Part II. 



(e) Drop strong and weak solutions on filter- 

 paper as in (/) above, and note the action after some 

 time has elapsed. 



Formulate a general statement of the properties of 

 alkalis from the results of your observations. 



EXPERIMENT 140. Study the action of solutions of 

 the following salts sodium chloride (common salt), 

 sodium carbonate (washing-soda), and copper sulphate 

 (blue-stone) when tested as suggested below. 



(a) Taste a very weak solution. 



(6) Drop a little of the solution upon red and 

 upon blue litmus paper. 



(c) Put a crystal of washing-soda in the solution 

 and gently warm. 



