METHOD OF DETERMINING NITROGEN 389 



The nitric acid is estimated by the ferrous iron or other appro- 

 priate method, to be described further on, in another portion of 

 the substance. 



340. Method of French Commission for Determining Nitrogen. 

 Several methods are proposed by this commission for the 

 determination of nitrogen. 34 The old method of combustion with 

 soda-lime which is conducted according to the general principles 

 is described in full. When the nitrogen is to be determined in sub- 

 stances which are not homogeneous and which it is difficult to 

 reduce to a powdered state, a modification of the process, due to 

 Grandeau, is employed. Such substances are, for instance, pieces 

 of cloth, leather, wool, horns and hair. It is almost impossible 

 to obtain a homogeneous mixture of such bodies. Large quan- 

 tities of them are, therefore, according to this method, treated 

 with sulfuric acid and then heated until the decomposition is 

 complete and they are easily reduced to a homogeneous mass. 

 This is best secured by adding some finely powdered gypsum. 

 When the decomposition is completed and a homogeneous mass 

 is secured, the rest of the process is conducted by the usual 

 methods. 



The French commission also recommends the common method 

 already described for the determination of nitrogen in an organic 

 state by the process of Kjeldahl, and of nitrogen in the nitric 

 state and of sulfate of ammonium by the methods usually em- 

 ployed. 



341. Method of Determining Nitrogen Adopted by the Union of 

 German Fertilizer Manufacturers. Nitric Nitrogen. The nitro- 

 gen in the form of nitrates is determined by the method of Ulsch 

 and Devarda. 35 



Ammoniacal Nitrogen. This is determined in the usual way 

 by titration with an alkali. Freshly burned magnesia hydrate is 

 employed as an alkaline reagent, although lime may also be 

 used where little or no organic matter is present, and the am- 

 monia is mostly in the form of ammoniacal salt. Soda-lye should 

 84 Grandeau, Traite" d'Analyse des Matures agricoles, 3d Edition, 1897, 



1 ; 427- 



K Methoden zur Untersuchung der Kunstdiingeniittel, 1903 : 15. 



