68 The Estimation of Nitrogen [100 



TO DISTINGUISH BETWEEN 'NITRIC,' 'AMMO- 

 NIACAL' AND 'ORGANIC NITROGEN 



ioo. The value of the nitrogen in manures varies consider- 

 ably according to whether it is in a soluble or an insoluble state. 

 Hence it is often of importance to discover in what state this 

 element occurs. The three most common occurrences are : 



* Nitric,' where it is in direct combination with oxygen, as 



in a nitrate or nitro-compound ; 

 1 Ammoniacal,' where it is in direct combination with 



hydrogen and may be driven off as ammonia by a caustic 



alkaline solution ; 

 4 Organic,' where it is in combination with some organic 



material and is not released as ammonia by caustic 



alkalis. 



A convenient substance for practising on may be prepared 

 by mixing linseed cake with ammonium sulphate and sodium 

 nitrate. 



To obtain an analysis showing the relative quantities of the 

 different forms of nitrogen in this mixture, three operations 

 are necessary. 



Operation I. — Weigh out -5 gram of the mixture. Place it 



in the large flask shown in fig. 29, add 200 c.c. of distilled 



water and 2 grams of calcined magnesia. Attach the absorp- 



N 

 tion flask containing 20 c.c. of — sulphuric acid, and distil 



2 



exactly as described in paragraphs 93-95. Titrate the acid 



with — caustic potash, and calculate the percentage of nitrogen 



which has been liberated by the magnesia. This will give the 

 percentage of ammoniacal nitrogen. 



