( 207 ) 



CHAPTEE V. 



ORIGIN OF THE NITRATES. 



1. NATURAL NITRIFICATION. 



1. THE formation of nitre in nature has long been regarded as a 

 most obscure phenomenon. 



It has long been known that the alkalis and the alkaline 

 carbonates, when exposed for some time to the air, yield the 

 reactions of nitric acid. Stahl had already observed this two 

 hundred years ago. At all times and in all places, under the 

 action of natural forces, there are produced small quantities of 

 nitrates. 



2. There also exist certain plants which appear to produce salt- 

 petre, at the expense of the nitrated combinations contained in 

 the soil or in manures. Such are borage, pellitory, beetroot, 

 tobacco, and especially plants of the family of the amarantaceae. 1 

 Nevertheless, the conditions of natural nitrification are still 

 imperfectly known. 



3. It is not proposed to refer here to the sodium nitrate 

 mines in Chili, formed under the influence of geological con- 

 ditions with which we are unacquainted, but only to the 

 nitrification going on every day under our eyes. 



4. In the first place, we know that nitric acid is formed in 

 the atmosphere in small quantities under the influence of 

 storms, simultaneously with a little ammonium nitrate, and 

 introduced into the soil by rain and there united to the bases. 

 This formation is of great interest. But a searching examination 

 has shown that such an origin does not suffice -to account for 

 the production of the nitrates in nature and their concentration 

 in a soil impregnated with animal matter. 



5. As a matter of fact natural nitrification results principally 

 from the slow oxidation of the nitrogenous organic compounds, 

 or even of ammonia, effected by the oxygen of the air, with the 

 aid of water and of an alkaline or earthy carbonate. 



1 Compare note sur Tattraction du salpetre, par Faucher (" Memorial des 

 potidres et salpetres," p. 162. 1883). 



