212 ORIGIN OF THE NITRATES. 



which is partly dissociated, with formation of free ammonia. 

 Now the latter is capable of ulterior oxidation. 



Further, the author has established, by direct and accurate 

 experiments, that dissolved ammonium nitrate in presence of 

 potassium or sodium carbonate is instantly transformed into 

 potassium or sodium nitrate and ammonium carbonate, the 

 strong acid taking by preference the strong base and leaving to 

 the weak acid the weak base. 1 Calcium carbonate produces the 

 same reaction. "We shall return to the consideration of this 

 reaction on account of the part which it plays in natural 

 nitrification. 



If we now consider the thermal phenomena which 

 accompany these various chemical reactions, we shall be able 

 to understand more fully the part played by them in 

 nitrification. 



4. Take first the transformation of ammonia into nitrous 

 acid, nitric acid, and ammonium nitrate 2 



Nitrous acid, NH 3 + 3 = HN0 2 + H 2 0. 



Nitric acid, NH 3 + 4 = HN0 3 + H 2 0. 



Nitrate ammonium, 2NH 3 + 4 = NH 4 N0 3 + H 2 0. 



The formation of gaseous ammonia by its elements 

 N + H 3 = NH 3 



liberates, according to the author's measurements, + 12*2 Cal. ; 

 that of dissolved ammonia liberates + 21 '06 Cal. 

 Lastly, the formation of water, 



H 2 + = H 2 0, 



liberates + 34'5 or + 29'5 according as the water is produced 

 in the liquid or the gaseous state. It follows from the above 

 that the oxidation of ammonia, whether rapid or slow, liberates 

 the following quantities of heat according to the nature and the 

 state of the products to which it gives rise. 



(1) Formation of nitrogen. 



2NH 3 + 3 = N + 3H 2 (X 



Gaseous ammonia and gaseous water + 88-5 - 12-2 = + 76*3. 

 Dissolved ammonia and liquid water + 103-5 - 21-0 = -f- 82-5. 

 Gaseous ammonia and liquid water + 103-5 - 12*2 = + 91-3. 



(2) Formation of nitrous acid. 



-f 3 = HN0 2 + H 2 0. 



Gaseous ammonia, water, and dilute nitrous acid ... + 87'1. 

 Dissolved ammonia, water, and dilute nitrous acid ... 4- 78 - 3. 



1 " Essai de Me*canique Chimique," torn. ii. p. 717, 



2 It would be well, no doubt, also to establish analogous calculations for the 

 hyponitrites (see p. 188). 



