Adeney — Dissolved Gases and Fermentative Changes. 565 



The foregoing Table illustrates very clearly the results wliich are obtained by 

 the fermentation of dilutions of the same sewage-water under conditions gradually 

 varying from those in which the atmospheric oxygen is in excess, relatively to 

 the fermentable matters, to those in which the fermentable matters are in 

 excess. 



Solutions 1/100 to 1/80 afford an illustration of the influence of an excess of 

 oxygen. In each of tliese solutions the fermentation has extended to the complete 

 oxidation of the ammonia in the admixed sewage. In solutions 1/70 and 1/60 the 

 conditions were evidently evenly balanced, for both a little free oxygen and a 

 little ammonia were left in each. In solutions 1/50 and 1/40 the influence of 

 gradually increasing quantities of fermentable matters in proportion to atmospheric 

 oxygen is indicated by increasingly small quantities of nitrogen becoming oxidised, 

 and by increasingly large quantities of ammonia left unoxidised. In solutions 

 1/30 and 1/20 we see that no oxidation whatever of nitrogen took place, and we 

 notice for the first time that the volume of carbon dioxide begins to show a slight 

 decrease relatively to the volumes of the gas formed in the more dilute solutions 

 after fei-mentation. This is still more noticeable in the strongest solution 1/10. 

 In this connection it is of interest to note that, simultaneously with the relative 

 decrease in volume of carbon dioxide formed, bodies having offensive odours begin 

 to make their appearance. 



If we examine the contents of the Table a little more closely, we shall find that 

 a number of important conclusions may be drawn as to the quantitative relation- 

 ships existing between the amounts of atmospheric oxygen, and of fermentable 

 matters originally present in the solutions on the one hand, and the products of 

 fermentative changes on the other. These relationships become more apparent 

 when each set of differences between the analytical results given in the Table for 

 each solution are multiplied so as to make them comparable with one another. 

 When so multiplied, the numbers may also be taken to represent the results which 

 would have been obtained by experimenting vsdth undiluted sewage, had that been 

 possible, under the respective conditions represented by each dilution. In the 

 following Table are given the products obtained by multiplying the differences in 

 Table I. as described : — 



[Table II. 



4L2 



