TRANSFORMATIONS OF CARBON AND NITROGEN. 93 



experimentally to be possible. If nitrogenous material is 

 brought into very intimate contact with oxygen the oxidation 

 may take place. When nitric compounds are mixed intimately 

 with platinum black they are brought into a rather peculiar 

 and very intimate association with oxygen. That platinum 

 black has the power of stimulating oxidation is well known, 

 although the reason is not clear. Under such conditions 

 nitrous bodies are oxidized into nitric acid compounds. This 

 possibility of a purely chemical union between atmospheric 

 oxygen and nitrous bodies led, naturally, to the belief that a 

 similar union of nitrous acid and oxygen occurred in the soil, 

 especially if the soil was porous so as to bring about an inti- 

 mate association of the nitrogen compound and the oxygen, 

 similar to that occurring in platinum black. Experiments 

 were carried out along this line to a considerable extent, de- 

 signed to determine the conditions under which such oxidation 

 most readily occurs. But these experiments led to nothing, 

 for although they were extensively multiplied they did not 

 indicate that the possibility of such oxidation is very great. 

 They were mostly negative in result, simply because they were 

 looking in the wrong direction for the discovery of the chief 

 agents in the process. While it would not be denied to-day 

 that such direct oxidation may occur to a slight extent, it has 

 become evident that the chief agency must be looked for else- 

 where. 



The Nitrification Bacteria. The real explanation of nitrifi- 

 cation has appeared during the last twenty-five years and has 

 proved to be connected with the phenomenon of life. It is very 

 easy to demonstrate that such nitrification actually takes place 

 in ordinary soil. All that is necessary to prove this is to place a 

 quantity of soil in a proper vessel and subject it at intervals to 

 a chemical analysis, when it is found that there is an increase 

 in the amount of nitrates present, after it has remained undis- 

 turbed for a few weeks. The process is slow but practically 



