12 



PRACTICE 5. 

 DETERMINATION OF NITROGEN IN AMMONIUM SULFATE. 



Place 10 cc. of the ammonium sulfate solution in a 500 cc. copper flask, 

 add 240 cc. ammonia-free water and then add carefully, by pouring down 

 the side of the flask, 10 cc. of the concentrated alkali. Connect immedi- 

 ately with the condenser, shake the flask thoroughly, heat slowly, and dis- 

 till into a 300 cc. Erlenmeyer flask containing 10 cc. of the standard hydro- 

 chloric acid and about 15 cc. of ammonia-free water, to a volume of 200 cc. 

 Add lacmoid and titrate the excess acid with standard ammonia. 



Titrations (1) ................................ cc. 



(2) .................................. cc.NH 3 



Average ..................................... cc. NH 3 



Mgs. N in sample ..................................... 



Percent N in dry salt ............................... 



The percentage purity of the dry salt is ................ 



Explain all reactions. 



Does the percentage of nitrogen vary directly or inversely with the ti- 

 tration readings? 



