CH. X] 



THE CONDITIONS OF LIFE IN THE SEA 



215 



agent. Nitric acid was finally reduced with sodium amalgam, 

 after precipitation of the mercury salts by magnesium ribbon, and 

 was estimated as ammonia. Raben's results were : 



Amount of nitrogen^ as ammonia, nitrous and nitric acids, 

 in 7nini(j7'amnies, contained in one litre of sea tvater. 



It will be seen that these results shew a distinct seasonal 

 variation. 



Putter's results are of great interest since they shew that 

 nitrogen compounds, other than those that may be recognised by 

 the methods employed by Natterer and Raben, may exist in solu- 

 tion in sea water. Putter's analyses relate to samples which were 

 taken from the surface of the Bay of Naples at a distance of 

 three to four kilometres from the shore and they are hardly 

 comparable with those of Natterer, which were collected from the 

 open sea at some considerable distance from the land. Nitrogen 

 compounds could be recovered from the samples by simple distil- 

 lation in the presence of an alkali, and these were apparently 

 amines and ammonia. In addition to these substances nitrogen 

 was also present as organic matter, which could be estimated by 

 Kjeldahl's method, and it was also present as nitrite and nitrate. 

 Thus a higher nitrogen content was obtained than is indicated 

 by the estimations of Natterer and Raben, but one suspects that 

 some of this excess may be due to the contamination of the sea 

 by discharge from the land, and the insufficient oxidation of the 

 organic nitrogen, through the agency of bacteria. Putter's results 

 are : 



