IX. THE ANALYSIS AND VALUATION OF MANUBES 173 



IV. POTASH MANURES. 



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

 weeds, 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 subject only an outline 

 can be given here. 



Determination of Nitrogen. The method to be employed de- 

 pends 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, etc. The most satis- 

 factory method is the Kjeldahl process, which may be performed 

 exactly as described under soil analysis, p. 85. The result gives the 

 amount of nitrogen existing as organic compounds and as ammonia, 

 and in most cases a portion of that existing as nitrates. As in soil 

 analysis, the nitric nitrogen can be wholly included if salicylic acid be 

 added (vide p. 88). 



Ammoniacal Nitrogen. This can be estimated by distillation 

 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 conveni- 

 ently be made by means of Lunge's nitrometer, an instrument 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 brought about by treatment in alkaline solution with zinc and iron 

 (Mocker n's process), or in presence of sulphuric acid by reduced iron 



