CHAPTER IX. 

 NITRIFICATION. 



Nitrification. When substances such as dung, urine, 

 blood, flesh, or other debris of plants, containing organic 

 nitrogen compounds, are incorporated with the soil putre- 

 faction and decay (p. 100) break them down little by 

 little, the nitrogen sooner or later becoming oxidized and 

 a nitrate is formed. It was by taking advantage of this 

 oxidizing process that nitre or saltpetre (potassium 

 nitrate) was formerly obtained in considerable quantities 

 from so-called " nitre-beds," which were carefully con- 

 structed heaps of animal and vegetable refuse, kept moist 

 with urine and other liquids ; the nitrogen was oxidized 

 and the potassium nitrate formed was subsequently 

 dissolved out and purified. 



This natural production of nitrate, which occurs in 

 varying degrees in most soils, is termed nitrification. It 

 was formerly considered a purely chemical process, but 

 in 1877 Schloesing and Miintz, while investigating the 

 chemical changes in sewage, discovered that the oxida- 

 tion of ammonium compounds into nitrates was the 

 result of the vital activity of living organisms. The 

 process was readily checked by applications of chloroform 

 vapour to the soil, and by heating the latter to a 

 temperature of 100 C. They were not able to isolate 

 the special nitric " ferments," but they determined the 

 134 



