AGRICULTURAL ANALYSIS 



lye can not be used for the expulsion of ammonia, but in its place 

 caustic magnesia is applied. 



In all cases where organic matter containing nitrogen is pres- 

 ent, caustic magnesia must be substituted for the soda solution. 

 The magnesia must be added in sufficient excess and the distil- 

 lation continued a little longer than is necessary when soda-lye 

 is used. Otherwise the details of the operation are the same. 



In a mixed fertilizer containing organic nitrogen and ammo- 

 nia salts, the total nitrogen can be determined by the moist com- 

 bustion process, and the ammoniacal nitrogen by distillation with 

 magnesia. The difference between the two results will give the 

 nitrogen due to the organic matter. 



To avoid any danger whatever of decomposing organic nitrog- 

 enous compounds, the ammonia may be determined in the cold 

 by treatment with soda-lye, under a bell- jar containing some set 

 sulfuric acid. The operation must be allowed to continue for 

 many days. Even at the end of a long time it will be found that 

 some ammonia is still escaping. It may, therefore, be finally in- 

 ferred that all the nitrogen as ammonia is not obtained by this 

 process, or that even magnesia may gradually convert other 

 nitrogenous compounds into ammonia. In this connection the 

 methods of determining ammonia in soils in paragraphs 450, 451 

 and 452, Volume I, may be consulted. 



336. Method of Boussingault. The official French method 

 is essentially the original method of Boussingault with slight 

 modifications. It is conducted as follows : 29 In case the sam- 

 ple is ammonium sulfate, about half a gram is placed in a flask 

 of half a liter capacity, together with 300 cubic centimeters of 

 distilled water and two grams of caustic magnesia. The flask 

 is connected with a condenser of glass or metal which ends in a 

 tube drawn out to a point and dipping beneath the set acid in 

 the receiver in the usual way. The acid is colored with litmus 

 or lacmoid tincture. The distillation is continued until about 

 loo cubic centimeters have gone over. The receiver is then re- 

 .moved with the usual precautions and the residual acid titrated. 

 Suppose 20 cubic centimeters of normal acid have been employed" 

 19 Guide pour le Dosage de 1* Azote : 14. 



