6 



PRACTICE 2. 

 PREPARATION OF A STANDARD AMMONIA SOLUTION. 



Determine, by hydrometer, the specific gravity of concentrated am- 

 monia and calculate, by the use of a specific gravity table, the number of 

 cubic centimeters necessary to make two liters of approximately one-fifth 

 normal ammonia solution. 



Sp. Gr , 



Grams NH 8 per cc 



Grams NH 3 per liter in normal solution 



Grains NH 3 in two liters of 1-5 normal solution 



Cc. of cone. NH 3 equivalent to g. NH 3 



Measure out the required amount of concentrated ammonia, add dis- 

 tilled water to make the total volume up to two liters, and mix thoroughly. 

 Standardize by titrating 10 cc. of the standard hydrochloric acid with the 

 ammonia solution, using lacmoid as an indicator. Make three titrations. 



(1) 10 cc. HC1 is equivalent to cc. NH 3 



(2) 10 cc. HC1 is equivalent to cc. NH 3 



(3) 10 cc. HC1 is equivalent to cc. NH 3 



Average c.c. NH 3 



1 cc. NH 3 is equivalent to Mg N. 



Give reactions in first and second practices, and explain the computa- 

 tions involved in ascertaining the weight of nitrogen in I cc. of the stand- 

 ard ammonia solution. 



