574 



Adeney — Dissolved Gases and Fermentative Changes. 



nitrous acid to nitric acid, accompanied by a fixation of small quantities of 

 inorganic materials, presumably to form organic matter, as Winogradsky has 

 shown takes place in the nitrous fermentation of ammonia in the absence of 

 organic matter. 



That a number of variations are possible during the fermentation of NH3 and 

 N2O3 in the presence of organic matters that have undergone the first stage of 

 fermentation, I shall show by further experiments. 



Regarding the method of examination, illustrated by these experiments, 

 simply as an analytical probe, it is quite evident that it affords the means of 

 differentiating the character of fermentable matters in waters, and approximately 

 estimating their amount, to a degree quite beyond the power of any other method. 

 Thus, when the samples of raw and filtered sewage water were examined by the 

 methods commonly used, the following results were obtained : — 



Constituents expressed as parts per 1000. 



It is impossible, of course, to draw any conclusion as to the character of the 

 organic matters in either sample from the above results. They do not even give 

 any definite idea of the actual quantities of the organic matter in the samples, 

 neither do they afford the means of estimating the influence which such liquids 

 would exert in river-water when discharged into it. While, on the other hand, the 

 results afforded by the experiments of Series II. and III., above described, give 

 complete answers to each of these points. They show that, on the one hand, the 

 untreated sewage-water underwent a first stage fermentation before true nitrifica- 

 tion, and therefore contained matters which would set up putrefaction if the 

 supply of atmospheric oxygen to all parts were restricted, and that, on the other 

 hand, the filtered sewage-water did not, but nitrification alone, and that therefore 

 putrefaction was impossible in the liquid, even when the supply of dissolved 

 oxygen was restricted. They fm-ther show the exact volumes of atmospheric 

 oxygen required for the complete fermentations in the untreated water, and that 

 required for the complete fermentation in the filtered water, giving at the same 

 time the quantities and character of the products of fermentation. 



