Chemical Changes in Mixtures of Sewage and Sea-Water. 3859 
oxygen absorbed, presents interesting features. For the sake cf 
convenience we have tabulated them separately— 
In cubic centimetres per litre. 
Series. Time. 
Oxygen Carbonic Anhydride 
Disappearing. Evolved. 
1 After 6 hours. 0:03 0-24 
” op. DS 9 2°09 e8)7/ 
»” » 48 99 3°21 3°10 
2 9 WD) 95 0-17 0-44 
” oy) 18 99 0°29 0:21 
” OS 50 0-40 0°30 
” 39 90 or) 0:77 0°44 | 
9 9, 028 9p 0°95 0°82 
3 ae 7 days. 0°89 P 1:08 
9 aap la: 39 1:49 1:10 
»” 99 2 99 1-43 0:90 
It is evident that there is a fairly close agreement between the 
two sets of figures which is most striking in the case of the first 
series ; and the conclusion seems warranted that, when sewage decom- 
poses in sea-water, the first chemical change which occurs is chiefly the 
absorption of oxygen and production of almost the equivalent quantity 
of carbonic anhydride. 
The question naturally arises as to the significance of this reac- 
tion. Does it mean that substances of the nature of carbohydrates 
are first attacked, for example, glucose as the simplest type, 
according to the equation :— 
C;H:.0, oF 60, = 6CO, + 6H.O, 
or are the nitrogenous bodies attacked with evolution of 
carbonic anhydride and the formation of more highly oxidized 
substances? This question can only be decided by experi- 
ments on mixtures of substances of definite composition and 
