E. J. Russell and E. H. Richards 525 



rapidly oxidised to nitrates. On the other hand decarboxylation gives 

 only amines, some at least of which are resistant to further bacterial 

 action, e.g. putrescine and cadaverine, which are among the commonest 

 putrefaction products. It is not known how these would decompose 

 in the soil : we may safely assume that they would ultimately undergo 

 oxidation, but the best results may be anticipated from the deaminisa- 

 tion process. Unfortunately, as already stated, the conditions which 

 determine the two processes are not known. 



The important point for our present investigation is that in the 

 bacterial decompositions of complex nitrogen compounds so far studied 

 the first products are amino-acids, which subsequently give rise to 

 ammonia, and, in anaerobic conditions, to amines as well. 



The decompositions occurring during the purification of sewage. 



These decompositions afford another example of the biochemical 

 decomposition of complex nitrogen compounds, and the investigations 

 bring out three facts of considerable importance for our problem: 



1. The decomposition of complex nitrogen compounds always 

 gives rise to ammonia. 



2. Under anaerobic conditions the conversion is quantitative, 

 the ammonia being exactly equivalent to the amount of complex 

 nitrogen compounds decomposed. 



3. Under aerobic conditions, on the other hand, the ammonia 

 and nitrate formed are not equivalent to the complex compounds 

 decomposed, but there is always a loss. 



The decomposition under anaerobic conditions is well shown in 

 two very careful experiments, each lasting over two years, made by 

 the Royal Commission on Sewage Disposal on the working of septic 

 tanks at Exeter and Ilford^. The conditions obtaining in the tanks 

 are strictly anaerobic. During the two years the amounts of dry 

 matter entering the tanks, and the amounts decomposed were : 



Exeter Ilford 



Suspended solids in sewage (lbs.) ... 126,801 38,824 



Solids in tank sludge .. . ... ... 47,8421 qp 370 11,756) 07 226 



Solids escaping in tank Uquor ... 48,537) ' 15,470) 



SoUds digested 30,422 11,598 



Percentage of solids digested ... 24-0 29-9 



^ McGowan, Houston, Frye and Kershaw, Royal Commission on Sewage Disposal. 

 6th Report, Appendix iv. 1910, pp. 249-51. 



