Adeney — Dissolved Gases and Fermentative Changes. 613 



Nitric Fermentation in Solution of Urea. 



Turning once more to the results recorded in Table XVII., we notice that 

 those afforded by the more dilute solutions U/20 and 11/40 show that decided 

 quantities of nitric acid were formed, but that apparently the nitrous acid first 

 produced did not siifPer further oxidation. This nitric fermentation may, however, 

 have been brought about by the peaty matters in the tap-water employed for 

 making up the solutions, and it is possible that nitric fermentation would not have 

 set in in their absence. This is a question, however, which I must leave to a 

 further communication. 



Similar Quantities of Carbon Dioxide formed by Fermentation in Solutions 

 containing similar Atomic Proportions of Carbon, as Urea, and as 

 Potassium Sodium Carbonate. 



It is interesting to compare the results with the above two dilute solutions 

 of U, with those obtained from the dilutions IV/40 and IV/80 of the solution of 

 potassium sodium tartrate employed for the experiments recorded in Table XI. 

 These two sets of solutions contained similar quantites of carbon, the one as 

 urea, and the other as tartrate. From the long time during which the solutions 

 were kept, it may be taken that the peaty matter in the tap-water with 

 which they were made up suffered fermentation as well as the added sustances. 

 It is interesting to observe, therefore, that the volumes of carbon dioxide in each 

 set are similar one lo the other. (See also Tables VII. and XII.) 



It will also be noticed that in both sets the conversion into oxidized inorganic 

 products of the fermentable substances originally present in the solutions, must 

 have been nearly quantitatively complete. 



The Theory of Nitrification. 



It seems to have been established from the researches of a number of observers, 

 more especially from those of Mr. Warrington, Professor P. F. Frankland and; 

 Mrs. G. Frankland, Dr. Munro, and M. Winogradsky, that the nitrification 

 effected by soil organisms is brought about by two species, one of which 

 oxidizes ammonia to nitrates, while the other oxidize nitrites to nitrates. 



These observers found that it was easy to obtain a nitrous fermentation in 

 solutions of ammonia containing certain inorganic salts, but practically no organic 

 matter, by means of organisms cultivated from soil. The attempt, however, to 



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