HALLE ZINC-IRON METHOD 435 



of the soil extract to dryness on a steam-bath. Dissolve the 

 soluble portions of the residue in 100 cubic centimeters of 

 ammonia-free distilled water, filtering out any insoluble residue. 

 Place the solution in a flask, add 10 cubic centimeters of sodium 

 amalgam, stopper the flask with a valve which will permit the 

 escape of hydrogen, and allow to stand in a cool room for 24 

 hours. Add 50 cubic centimeters of milk of lime and titrate 

 the ammonia produced by distillation with standard acid and 

 estimate as nitrogen pentoxid. Where the amount of ammonia 

 is small, nesslerizing may be substituted for titration. 



375. Method of the Experiment Station at Mockern. The 

 principle of this reaction is based on the reducing action exercised 

 by nascent hydrogen on a nitrate, the hydrogen being generated 

 by the action of soda-lye on a mixture of zinc dust and finely 

 divided iron. 57 



Ten grams of nitrate are dissolved in 500 cubic centimeters of 

 water. Of this solution 25 cubic centimeters, corresponding 

 to one-half gram, are placed in a distillation flask of about 400 

 cubic centimeters capacity, 120 cubic centimeters of water added, 

 and about five grams of well v. ashed and dried zinc dust and an 

 equal weight of reduced iron. To the solution are added 80 

 cubic centimeters of soda-lye of 32 B. The flask is connected 

 with the condensing apparatus and the distillation carried on 

 synchronously with the reduction, the ammonia being collected 

 in 20 cubic centimeters of titrated sulfuric acid. The distillation 

 is continued from one to two hours, or until 100 cubic centimeters 

 have been distilled, and the remaining sulfuric acid is titrated 

 in the usual way. Soil extracts and sewage waters should be 

 concentrated until they have approximately the proportion of ni- 

 trates given above. 



376. The Halle Zinc-Iron Method. For determining the nitro- 

 gen in Chile saltpeter the foregoing method is conducted at 

 the Halle Station as follows : 58 Ten grams of the nitrate are dis- 

 solved in one liter and 50 cubic centimeters of the solution cor- 



57 Bottcher, Die landwirtschaftlichen Versuchs-Stationen, 1892, 41 : 165. 

 48 Bieler und Schneidewind, Die agricultur-chemische Versuchs- 

 station, Halle a/S., 1892 : 50. 



