ON THE OXIDATION OF AMMONIA IN SEA WATER. 305 
This rapid reduction of ammonia is probably due to the oxygen given 
off by the Ulva. To check this conclusion, water containing ‘008 
grm. NH, per 100 litres was placed in a bell-jar in the dark and 
a quantity of Ulva placed in it. 
After twenty hours it contained . +008 grm. NH, per 100 litres. 
After forty es a 2 , 008 
Thus when assimilation was not proceeding the quantity of 
ammonia remained stationary. Decomposition then commenced, 
for— 
3) bP) 
After standing in the dark sixty-four 
hours it contained. : . ‘012 grm. NH, per 100 litres. 
After standing in the dark eighty- 
eight hours it contained . . °030 5 $5 
The jar was now placedinthe window, andafter standing there forty- 
eight hours it contained ‘007 grm. NH, per 100 litres. That the reduc- 
tion of ammonia in sea water by Ulva depends upon the assimilation 
of the latter is further shown by the following experiments. Water, 
into which some Ulva had been put, had stood seven days in a 
position moderately illuminated. 
It contained ; : : . °037 grm. NH, per 100 litres. 
After standing in the window twenty- 
four hours it contained . 5 Oe i ne 
After standing in the window forty- 
eight hours it contained SOLO A Fs 
After standing in the window 
seventy-two hours it contained . ‘015 3 3 
The available carbon dioxide had apparently been used up after 
the first twenty-four hours, and the plant was unable then to keep 
down the ammonia. A small quantity of carbon dioxide was now 
blown through the water, and after twelve hours it contained *009 
germ. NH, per 100 litres. A further quantity of carbon dioxide 
was blown through overnight, and after standing seven hours in 
daylight the water contained ‘006 grm. NH, per 100 litres. That 
the reduction in the amount of ammonia was not due to the 
agitation of the water is shown by the following experiment. 
Water containing much ammonia was placed with Ulva in bright 
sunshine. 
It contained at the commencement ‘009 grm. NH, per 100 litres ; 
after five hours 003 bs a 
after forty-one hours 006 a = 
PP) 
PP) 
showing the same series of changes as in the previous experiment. 
Carbonic acid gas was now blown through it, and it was still found 
