ACIDS, BASES, SALTS, AND NEUTRALIZATION 77 



of the burette to be filled with the solution before beginning the 

 experiment. 



Into a small beaker, measure from the burette exactly 20 

 cc. NH 4 OH, with 10 or 12 drops 

 of cochineal solution, which is 

 changed to a deep purplish color 

 by the alkali ; then slowly add HC1 

 from the other burette, constantly 

 stirring the solution in the beaker 

 until a decided change in color is 

 observed. When all of the NH 4 OH 

 has been neutralized, the solution 

 has a yellowish red color. Note the 

 number of cubic centimeters of 

 HC1 used for neutralizing the 20 cc. 

 of NH 4 OH solution. Add a drop 

 or two from the NH 4 OH burette 

 and note if there is a change of 

 color. When the solution is neu- 

 tralized, one or two drops of HC1 

 or NH 4 OH should give a decided 

 change of color. If too much acid 

 has been used, add a measured 

 amount from the NH 4 OH burette 

 until the solution is neutralized. 

 Finally note the total quantity of 

 HC1 and NH 4 OH used. Repeat this 

 experiment, using 20 cc. of the 

 HC1 solution. 



Questions. ( i ) What was formed 

 when the HC1 neutralized the 

 NH 4 OH solution? (2) Write the 

 reaction. (3) What would be the 

 result if the neutralized solutions Fig> 38.-Burette. 



were evaporated to dryness ? (4) Calculate the amount of HC1 re- 

 quired to neutralize i cc. of NH 4 OH. 



