58 The Estimation of Nitrogen [86, 87 



Part V., but must be thoroughly mastered before attempting the 

 analysis of manures. 



THE SODA LIME PROCESS (WILL AND 

 VARRENTRAP) 



86. Substance used.— Urea, CO(NH 2 ) 2 . 



Method. — The substance is decomposed by contact with 

 red-hot soda lime, and the ammonia thus evolved absorbed in 

 standard sulphuric acid. The amount of acid thus neutralised 

 is determined by titration with standard caustic potash. 



87. This determination may be made in a hard glass tube 

 which has been sealed at one end, but as this is very liable to 

 accidents an iron tube of about J-inch internal diameter which 

 has one end welded up is much preferable. In laboratories 

 where this method is used a supply of these iron tubes, varying 

 in length from 14 to 30 inches, is kept. For this experiment 

 the following apparatus is necessary : 



An 18-inch iron tube (1, fig. 25). 



A copper funnel (2, fig. 25). 



A mortar and pestle. 



A spatula. 



A Will and Varrentrap bulb (fig. 26). 



Corks and cork borers. 



A furnace (fig. 27^. 



Also the following substances : 



Seminormal sulphuric acid. 



/N\ 



Quinquinormal ( — J alkali. 



Granulated soda lime. 



A mixture of 3 parts sugar and 4 parts soda lime. 



Asbestos. 



