§ 97. ESTIMATION OF AMMONIA. 



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§ 97. A'nim€nm.^--rA. portion of the aqueous extract (g 92) is 

 mixed with two relumes of alcohol and filtered. To the filtrate 

 and washings calcined magnesia is added, and the ammonia 

 distilled off into a receiver containing a measured quastity of 

 normal sulphuric or hydrochloric acid, every precaution being 

 taJien to avoid loss of , ammonia and spirting of the magnesia 

 mixture into the receiver. The apparatus I use is represented in 

 Pig. 2. The flask A should not be more than half full of magnesia 



Fig. 2. 



mixture, and a plug of glass wool should be inserted in the neck 

 The small tube e -contains glass beads, which are moistened with 

 part of the acid. The distillation is complete when the vapours 

 that issue on opening the clip h are free from alkaline reaction. 

 The estimation may be completed in either of the two following 

 ways : 



(o) The excess of acid in the receiver is determined volumetri- 

 oally and deducted from the quantity taken. From the differ- 



1 Compare also Morgen, 2eitsclir. f. anal. Chem. xx. 37 (1881), 



6 



