[PP 2s0n 
XOXGV): 
ON A SIMPLE FORM OF APPARATUS FOR OBSERVING THE 
RATE OF ABSORPTION OF OXYGEN BY POLLUTED 
WATERS, AND BY OTHER FERMENTING LIQUIDS. 
By W. EH. ADENEY, D.S8c., F.1.C., 
Curator and Examiner in Chemistry in the Royal University, Dublin. 
[Read, January 21; Received for Publication, January 24 ; 
Published, Frpruary 26, 1908. ] 
Tue author has shown in a number of papers, which he has 
communicated to this Society from time to time during the past 
seventeen years, that the true significance of the presence of 
polluting matters in water depends not so much upon their 
quantity, as upon their fermentative properties; that is to say, it 
- depends upon the rate at which they will undergo self-purification 
by fermentation under the influence of the mixed bacteria to be 
found in all polluted waters, except when antiseptics are present, 
and in all river- and sea-water ; and upon the extent and rapidity 
with which the dissolved oxygen of the clean waters, with which 
they become mixed, will be absorbed during the process. 
He has also demonstrated that the process of self-purification 
of waters, under natural conditions, when polluted within limits 
of fouling, takes place in two distinct and progressive steps. 
During the first, the carbon oxidisable substances, that is, the 
fresh polluting organic substances, are oxidised and otherwise 
changed by bacterial fermentation into carbon dioxide, water, 
ammonia, and organic substances of an excretory nature, which 
may be termed nitrifiable organic substances. During the second 
stage these last named substances and ammonium compounds are 
fermented to nitric acid and carbon dioxide. 
The author has furthermore shown that the quantity of 
oxygen absorbed, and of products formed, on the completion of 
each stage of aerobic fermentation, is constant for similar 
