578 Adeney — Dissolved Gases and Fermentative Changes. 



Continuing the train of thought suggested by the three preceding series of 

 experiments, we may note in the first instance that the experiments recorded in 

 the Tables VII. and VIII. afford further evidence that the fermentation, which 

 may take jjlace in a natural water containing unfermented matters in solution, 

 under aerobic conditions, does so in two distinct stages. 



That ammonia, and not nitrous or nitric acid, is formed during the first stage 

 of fermentation of nitrogenous organic matters, even in the continued presence of 

 an excess of dissolved oxygen, is clearly proved by experiments 1, 2, and 3, in 

 Table VII., and by la and 3a in Table VIII. 



We may note also that experiment 6, recorded in Table VII., affords another, 

 but more definite, illustration of that phase of nitrification, which had apparently 

 been set up in solution 1/4 of Series III., and which, as I stated above, might 

 afford an explanation of the exceptional results afforded by this solution. From 

 the results recorded of this experiment 6, we see that an oxidation of ammonia, 

 and possibly also of nitrous acid, took place, and that at the same time small 

 quantities of carbon dioxide, and also of ammonia, or of nitrous acid, or both, 

 were fixed, no doubt, from Winogradsky's experiments, to form organic matter. 

 It is interesting to observe that in each exj^eriment here quoted, the quantity of 

 nitric acid formed is practically exactly equivalent to that of ammonia lost, and 

 that the difference between total inorganic nitrogen before and after fermentation 

 corresj^onds witli the loss of nitrous nitrogen during fermentation. It is just 

 possible from this, that, in nitric fermentation, nitrous acid may enter into the 

 reaction by which organic matters are formed from inorganic materials. But this 

 requires further experimental investigation. 



Another point to be noted in reference to these two experiments is, that in one 

 (solution 1/4, Series III.) the volume of dissolved oxygen absorbed is decidedly 

 in excess of that theoretically required for the oxidation of ammonia to nitric acid, 

 while it is a little less in the other experiment (6). This difference may have been 

 due to a difference in character of the organic matter present in the two solutions, 

 since there can be no doubt, from experiments I have yet to describe, that 

 organic matters which have themselves undergone change during a previous first 

 stage fermentation, exercise a marked influence on the subsequent stage of fer- 

 mentation, or true nitrification, and that these fermented organic matters vary 

 very much in chemical character, so far as nitrification is concerned, I hope to 

 illustrate by further experiments. 



The quantities of carbon dioxide, and inorganic nitrogen fixed in experiment 

 6 are small, so small, in fact, that the errors attending their determination are 

 unfortunately much too appreciable to warrant an attempt to draw definite 

 conclusions as to any quantitative relationship which may exist between them. 



The modification in the method of experimenting employed for the Series IV., 



