610 Adeney — Dissolved Gases and Fermentative Changes. 



Nitrification of Pure Urea : An Exception. 



As I have shown in the earlier part of this Paper, easily fermentable nitro- 

 genous organic matter, when attacked by water-organisms under continued aerobic 

 conditions, suffer two distinct stages of change, first, the organic carbon is nearly 

 completely oxidized to carbon dioxide, and the organic nitrogen converted into 

 ammonia ; second, the ammonia thus formed is oxidized to nitrous or nitric acid. 



Tliat urea, when mixed with other organic substances, sliows no exception to 

 this rule has been proved by the researches of Warrington and of Munro, and also 

 of other observers ; the last-named observer has shown, indeed, that when this 

 substance is mixed only with such a simple body as potassium oxalate,* tlie course 

 of fermentation proceeds as above described. 



The experiments which I have to describe were, however, made with simple 

 solutions of urea in tap-water, containing in addition only a little sodium 

 carbonate and potassium phosphate. 



These experiments were commenced with two objects in view — (1) to ascertain 

 whether nitrogen is evolved during the carbon stage of fermentation of urea, 

 (2) to determine the nature of the nitrogen fermentation, which, it was antici- 

 pated, would follow the carbon fermentation. 



The experiments were commenced in Januaiy, 1893, but the solutions were 

 not examined again until nearly two years afterwards, and I was then surprised 

 to find that even in a comparatively strong solution, containing as much as 0'05 

 grammes of urea per litre, a quantity of nitrous nitrogen, equal to 0*0016 grammes, 

 had been formed, although it was apparently evident from the volume of carbon 

 dioxide formed produced, at the same time, that not more than half the organic 

 carbon originally present in the solution had been converted into that gas. It 

 was feared, at first, that this was due to some leakage which might have occurred 

 between the stopper and neck of the bottle in which the solution was preserved. 



Accordingly, another set of experiments with urea was started, but this time 

 with stronger solutions. A similar quantity of nitrous nitrogen was, however, 

 again found, after fermentation, in a solution containing ten times the quantity 

 of urea. 



It accordingly seemed evident that urea, when unmixed with other organic 

 substances, does undergo a change from the very commencement of fermentation, 

 which apparently differs essentially in character from that of other easily ferment- 

 able organic substances so far as they are known. In the annexed Table will be 

 found the particulars and results of the experiments above referred to. 



* Loc. cit., p. 640. 



