OCEANOGRAPHY: J. F. McCLENDON 
613 
A half liter of sea water was boiled in an all-glass still and the dis- 
tillate collected in a series of 25 cc. Nessler's tubes. Another series of 
Nessler's tubes were filled with a graded series of concentrations of 
ammonium chloride. One cubic centimeter of Nessler's reagent was 
added to each tube and agitated. After fifteen minutes, the tubes were 
compared colorimetrically and the ammonia recovered from the sea 
water was estimated. After no more ammonia could be distilled from 
the sea water, amalgamated aluminium shavings were introduced into 
the still and the distillation process repeated. The ammonia recovered 
was formed by reduction of nitrates and nitrites. DupKcate analyses 
gave less than 0.01 mgm. of nitrogen per liter as ammonia and less than 
0.01 mgm. nitrogen per liter as nitrates and nitrites. Raben found 
more than ten times these quantities in North Sea water. ^ Evidently, 
Pseudomonas calcis and other organisms have almost completely re- 
moved the fixed nitrogen from Tortugas sea water. The effect of this 
probably explains the scarcity of life in the vicinity of Tortugas as com- 
pared with colder seas (law of minimum). There is, however, a con- 
stant renewal of fixed nitrogen from the atmosphere, from the decay of 
organisms and probably from water rising from the depths of the ocean. 
If Pseudomonas calcis is an important agent in the precipitation of 
CaCOs, its action is evidently more intense in places where calcium 
salts, nitrates and nitrites are carried from the land into the sea. 
That calcium carbonate is withdrawn from surface waters of the 
sea, is shown by chemical analyses. Dittmar^ found an average of 
0.44% less calcium in surface waters than in deeper waters. This is 
true notwithstanding the fact that calcium carbonate is constantly 
being added to the surface waters. The drainage of the land contains 
an excess of calcium carbonate and flows out on the surface of the sea, 
where the water evaporates leaving the excess of CaCOs in the sea 
water. The action of organisms in building calcareous structures may 
account for a large part of the depletion of surface waters, but the pre- 
cipitation of calcareous mud at Tortugas has been observed by Vaughan. 
The analysis of the calcium content of sea water requires double 
precipitation, and filtration for separation from magnesium and hence 
large samples and great care are required for accuracy. Theoretically, 
however, we may detect differences in calcium content by titration. 
Dittmar showed that except for H2O, calcium and gases, sea water is 
remarkably constant in composition. The water content may be 
determined by titration of the chlorides and the gases may be eHmi- 
nated by boiling after the addition of enough acid to decompose the 
carbonates. If we disregard carbonic acid, there is an excess of bases 
