NITROGEN. 177 



In addition, the general manures, e.g., farm-yard manures, 

 sea- weeds, &c., contain all constituents of plant food, together 

 with large quantities of decaying organic matter and water. 



For full descriptions of the methods used in the analysis of 

 manures the reader must refer to some treatise on the suhject 

 only an outline can be given here. 



Determination of Nitrogen. The method to be employed 

 depends upon the possible state of existence of the nitrogen 

 in the manure. 



Organic Nitrogen, such as occurs in farm-yard manure, sea- 

 weed, guano, fish meal, bones, rape-seed "meal and cake, &c. 

 The most satisfactory method is the Kjeldahl process, which 

 may be performed exactly as described under soil analysis, 

 p. 95. The result gives the amount of nitrogen existing as 

 organic compounds and as ammonia, and in most cases a por- 

 tion of that existing as nitrates. As in soil analysis, the nitric 

 nitrogen can be wholly included if salicylic acid be added 

 (v. p. 96). 



Ammoniacal Nitrogen. This can be estimated by distilla- 

 tion with magnesia, MgO, conveniently in a current of steam, 

 and receiving the evolved ammonia in a measured quantity of 

 decinormal sulphuric acid. Potash or soda would also liberate 

 ammonia from ammonium salts, but they would, in addition, 

 decompose a portion of the organic nitrogenous substances, if 

 such were present. 



Nitric Nitrogen. In manures containing a large proportion 

 of this constituent, e.g., sodium nitrate, the determination can 

 conveniently be made by means of Lunge's nitrometer, an in- 

 strument in which the volume of nitric oxide, NO, evolved on 

 shaking up the nitrate with strong sulphuric acid and mercury 

 can be measured. Another satisfactory method of determining 

 nitrate is by Schlosing's method with ferrous chloride and 

 hydrochloric acid. Other methods for the determination of 

 nitric nitrogen are based upon its reduction to ammonia and 

 subsequent distillation with alkali. This reduction may be 



