Adeney — Dissolved Gases and Fermentative Changes. 615 



Here then, with the common condition of similar organism established in 

 each solution, we get, in the absence of peaty matters, nitrous fermentation of 

 ammonia, while in their presence we get a nitric fermentation of either ammonia 

 or of nitrous acid. 



The question therefore suggests itself — do not these peaty matters, when 

 present in a water, exercise a dominating influence on the course of the fermen- 

 tation of ammonia, and determine the nitric fermentation which is so noticeable 

 concurrently with their presence ? 



I would go further and venture to suggest, that the explanation of the 

 observed fact — that the nitrification of ammonia in a mass of aerated soil results 

 normally in the production of nitrates only (Warrington) — is to be referred to the 

 presence of organic substances in the soil, viz. humus, allied in character to the 

 peaty matters of natural waters. 



If this explanation be accepted, the question of nitrification would appear to 

 stand thus : — 



1. The nitrous organisms of soil thrive in inorganic solutions containing 

 ammonia. 



3. The nitric organisms of soil are gradually killed, or lose their vitality, in 

 inorganic solutions containing ammonia. 



3. The nitric organisms of soil thrive in inorganic solutions containing 

 nitrites. 



4. The nitrous organisms cannot oxidize nitrites to nitrates in inorganic 

 solutions. 



5. The presence of peaty or humus matters appears to preserve the vitality of 

 nitric organisms during the fermentation of ammonia, and establishes conditions 

 whereby it is possible for the nitric organisms to thrive simultaneously in the 

 same solution with the nitrous organisms. 



6. Query — Is it possible for either the nitrous, or nitric, or other organisms to 

 separately set up the complete oxidation of ammonia to nitric acid, in the 

 presence of peaty or humus matters ? 



