NITRA 



AMMONIUM NITRATE CHANGED INTO NITRATE. 213 



(3) Formation of nitric acid. 



NH 3 + 4 = HN0 3 + H 2 0. 



Gaseous ammonia, water, and gaseous nitric acid + 81*2. 

 Gaseous ammonia, liquid water, dilute nitric acid + 105' 6. 

 Dissolved ammonia, dilute nitric acid .. +96-8. 



(4) Formation of dissolved ammonium nitrate. 



2NH 3 + 4 = NH 4 N0 3 + H 2 0. 

 Gaseous ammonia, dissolved nitrate ... + 125*3. 

 Or, for KE 3 -f 2 , + 62-6. 



(5) Transformation of dissolved ammonium nitrite into nitrate 

 ly fixation of oxygen. 



This transformation, and more generally that of a dissolved 

 nitrite into a nitrate of the same base, liberates + 21*8 ; a value 

 which is sensibly the same for the various dissolved alkaline 

 nitrites. This value offers the more interest, as the change of 

 the nitrites into nitrate and the inverse transformation take 

 place in nature, as shown by the very curious experiments of 

 Chabrier 1 and the recent researches of Gayon, Deherain, and 

 Maquenne. 



The presence of the nitrites has been remarked in stables, aa 

 co-existing with the nitrates, by Goppelsroder. They also exist 

 in rainstorms. The hyponitrites should also be searched for. 



5. All the foregoing figures are applicable to the oxidation 

 of ammonia by free oxygen, whether this oxidation take place 

 by sudden combustion, or whether it be excited at a lower 

 temperature by spongy platinum, or whether it take place 

 slowly and in the cold state, as in nitrification. 



They show that the formation of the oxygenated compounds 

 of nitrogen by the oxidation of ammonia always takes place 

 with liberation of heat. It can, therefore, always take place 

 without the aid of any foreign energy; the microbes con- 

 fining themselves, as in all cases where their action is exerted, 

 to cause a formation, to which they contribute no energy of 

 their own. 



Conversely, the formation of ammonia by the action of 

 hydrogen on the various oxides of nitrogen liberates more heat 

 than the same formation effected by means of free nitrogen; 

 which accounts for the greater facility of the first reaction. 

 But it is not necessary to go at length into this subject, which 

 is foreign to the question of nitrification, though it plays a 

 certain part in the reduction of the nitrates to the state of 

 ammonia by natural agents. 



6. Various experiments have been made with a view to 

 discovering whether free ammonia could be directly oxidised by 



1 " Oomptes rendus des stances de 1' Academic des Sciences," 1871. 



