370 



H. M. Vernon 



water was not in absolute darkness, as there were oue or two cracks 

 in the woodwork, through wliich minute quantities of light could 

 enter. The analyses were as follow: 



Free NH3 Oigauie NH3 



Original water .227 mgm. .167nigm. 



After 10 days .205 .195 



- 22 - .039 .098 



- 61 - .020 .085 



- 85 - .005 .092 



Here we see that, by the simple process of keeping the water 

 in darkness, no less than 98^ of the free ammonia and 45 to 49 of 

 the organic ammonia, were removed! In another jar of the same water, 

 placed at the same time under conditions of absolute darkness, the 

 change in eomposition was as follows: 



Free NH3 Organic NH3 



After 10 days .201 mgm. .140 mgm. 



- 22 - .(127 .100 



In this case the removal of the ammonia seems to have taken 

 place rather more rapidly. 



In the uext experiment, the jars of water were wrapped up in 

 black paper, and placed in a cupboard, so that by no possibility 

 could a trace of light reach them. One jar coutained ordinary 

 Aquarium water, another contained water which had been filtered 

 through asbestos (in order to determine if there were any diminution 

 in the rate of purification owing to tbe removal of bacteria), and the 

 third also contained Aquarium water, but to it had been added about 

 50 cc. of a water which had previously been kept 31 days in darkness, 

 for it was thought possible that this water might contain numbers 

 of bacteria possessing a special capacity for removing the ammonia 

 from water. The analyses gave the following- results. 



From these figures we see that after 25 days an apparently 

 limiting value for the purification of both the organic and the free 



