620 Adeney — Dissolved Gases and Fermentative Changes. 



12. That for similar volumes of oxygen consumed, the quantity of nitrogen 

 oxidized during the fermentation of ammonia is distinctly greater, in the presence 

 of peaty or other fermented organic matters, than in their absence. 



13. That for similar volumes of dissolved atmospheric oxygen consumed, the 

 quantities of carbon dioxide and ammonia "fixed" are also more appreciable in 

 the presence of those organic matters during fermentation, than in their absence. 



14. That from the earliest stages of an aerobic fermentation of a strong 

 solution of pure ui'ea, containing no other easily fermentable organic substances, 

 nitrous nitrogen is formed in addition to ammoniacal nitrogen, in the proportion 

 of about 1:4. It is possible that the chemical changes which here result in the 

 formation of nitrous acid are not analogous to those attending the formation of 

 nitrous acid in the fermentation of ammonia, but rather to those attending the 

 formation of the oxidized organic matter during a first-stage fermentation, the 

 nitrogen,, in the case of urea, taking the place of the carbon in a more highly 

 carbonated organic compound. 



15. That by determining the changes in the dissolved gases, and in the 

 organic and inorganic nitrogenous compounds, which accompany fermentation in 

 natural and polluted waters, it is possible not only to differentiate easily ferment- 

 able from difficultly fermentable substances present, but to approximately estimate 

 their quantity. 



16. That such determinations are of very great value in the case of polluted 

 waters, because in addition to affording very accurate estimations of the total 

 quantities of fermentable matters in them, in terms of the exact volume of 

 atmospheric oxygen necessary for their complete fermentation, it is possible by 

 proper examination to determine what fraction of such volume is required for the 

 first stage of fermentation, and what fraction for the second — distinctions of the 

 utmost importance in considering the technical aspect of the pollution of rivers. 



17. That in the course of the first-stage fermentation of some sewage-waters, 

 there is some evidence to show that appreciable quantities of atmospheric nitro- 

 gen may be fixed. 



Before concluding this portion of my study, it is due to my fi'iend, Mr. James 

 Carson, Assoc. R.CSc.L, to acknowledge the most valuable services which he has 

 rendered me during the whole time I have been engaged upon this investigation. 

 He has not only assisted me throughout in carrj^ing out the very laborious 

 analytical determinations incidental to the work, but has further assisted me by 

 making and perfecting the mechanical arrangements of the beautiful model of my 

 gas-analysis apparatus, which is described in this Paper. 



