346 AGRICULTURAL ANALYSIS 



22.5 per cent, neutral calcium oxalate, and 67.5 per cent, soda-lime. 

 The combustion tube has a length of 55 centimeters and a diame- 

 ter of 17 millimeters, and is charged as follows: 



Two grams pulverized calcium oxalate. 



Ten grams pulverized soda-lime. 



Ten grams of the reducing compound. 



The nitrate incorporated with 50 grams of the reducing mix- 

 ture: 



Ten grams of the reducing mixture. 



Ten grams pulverized soda-lime. 



The tube is then tightly closed with an asbestos plug and heated 

 gradually from the front backwards, the calcium oxalate fur- 

 nishing finally the gas necessary to drive out the last traces of 

 ammonia. 



The combustion should be terminated in 40 minutes and when 

 completed, the acid, containing the ammonia, is placed in a beaker 

 and .boiled for two or three minutes to drive off the sulfurous 

 and carbonic acids. The titration is then conducted in the usual 

 manner. 



The combustion can be carried on just as well in an iron tube 

 as in a glass one. The reagents employed, especially soda-lime, 

 being hygroscopic, a little water is disengaged in heating, which 

 is condensed at the cold extremity of the tube, and which may 

 absorb a little ammonia unless special precautions are taken to 

 have the materials dry. 



The process is equally applicable to the determination of nitro- 

 gen in all its forms or to mixtures thereof. The method has also 

 been applied to the mixture of ammoniacal and organic nitrogen 

 and to the mixture of ammoniacal, nitric, and organic nitrogen, 

 the combustions having been made both in an iron and a glass 

 tube. The amounts of material to be used vary from one-half 

 gram to a gram, according to its richness in nitrogen. 



THE MOIST COMBUSTION PROCESS 



308. Historical. As long ago as 1868 Wanklyn proposed to 

 conduct the combustion of organic bodies in a wet way, using 

 potassium permanganate as the oxidizing body. 98 About 10 years 

 96 Journal of the Chemical Society, 1868, 21 : 161. 



