584 Adeney — Dissolved Gases and Fermentative Changes. 



With reference to the quantities of ammonia, nitrous and nitric acids formed 

 during fermentation, we observe that in experiment 3a, the quantity of nitrogen 

 recorded as ammonia is approximately equal to that of the organic nitrogen 

 originally present. The same may be said of the niti-ic nitrogen recorded in 

 experiment 2«, and of the nitrous and nitric nitrogen recorded in experiment 4«. 

 The ammonia determinations recorded in experiments 1 and 2 in Table VIII. are 

 unreliable. They are probably much too high owing to the possibility, which was 

 unfortunately recognised too late, that although the asparagine itself suffered no 

 appreciable decomposition, when the original solution A was distilled in the 

 presence of borax, the compounds formed from it by partial fermentation would, 

 and thus give rise to an evolution of ammonia which did not exist as such in the 

 original solution. 



To avoid this possible source of error as much as possible, it was determined 

 to nesslerize small portions of the solutions diluted with as large volumes of pure 

 water as possible. The ammonia determinations recorded for all experiments 

 after No. 2, both as regards the solution A itself, and with the diluted solutions 

 made from it, were obtained by this means. 



On summing up the results obtained from this series of experiments, we find 

 they afford additional evidence in support of the conclusions which it was possible 

 to draw from those afforded by the three preceding series of experiments with 

 sewage waters, viz. that, when the dissolved oxygen is in excess relatively to the 

 fermentable matter present in a water, the quantities of carbon dioxide and nitric 

 acid formed, and of oxygen absorbed, after complete fermentation^ may be taken as 

 directly proportional to the quantities of the fermentable matters originally 

 present in the water. 



We have also evidence in these results which goes to show that the quantities 

 of carbon dioxide and nitric acid formed on complete fermentation may be taken, 

 for the purpose of water analysis, as quantitative expressions of the fermentable 

 organic carbon, and of the total organic and inorganic nitrogen originally present 

 in the water. This last conclusion is also supported by all the preceding series 

 of experiments. 



We see, however, from the results obtained from these solutions of 

 known strength and composition, that the conditions of experimenting must 

 be strictly laid doAvn, and adhered to if definite conclusions are to be drawn, 

 because : — 



1. We learn that the volume of carbon dioxide evolved during a first stage 

 fermentation, relatively to a given volume of oxygen absorbed, may vary, 

 even under continued aerobic conditions, with the relative quantities of 

 fermentable organic matters, and the dissolved oxygen originally present in the 

 water. 



