8 



PRACTICE 3. 

 BLANK DETERMINATION OF NITROGEN IN REAGENTS USED IN DISTILLING. 



Place 250 cc. of ammonia-free water in a copper flask, add 10 cc. of con- 

 centrated alkali solution (made by dissolving 1000 gm. sodium hydroxid 

 and 25 gm. potassium sulfid in 1000 cc. water), pouring carefully down the 

 side of the flask, connect with the condenser, shake the flask thoroughly, 

 heat up- slowly and distill into a 300 cc. Erlenmeyer flask containing 10 cc. 

 of the standard hydrochloric acid and about 15 cc. ammonia-free water. 

 The end of the delivery tube should dip into the acid solution. Distill to 

 a volume of 200 cc. Add lacmoid and titrate with standard NH.3. 



Titration (1) cc. NH 3 



Titration (2) cc. NH 8 



Average cc. NH 3 



State correction in cc. of standard NH 3 . 



Explain all reactions involved, including the use of the indicator. 



