216 THE CONDITIONS OF LIFE IN THE SEA [PART III 



Amoitnt of nitrogen compounds, in milligr amines, contained 

 in one litre of water from the Bay of Naples. 



Nitrogen obtained by the Kjeldahl reaction 0"56 

 Nitrosfen as nitrite and nitrate 0"18 



Total 0-74 



Carbonic acid and other carbon compounds. These are 

 present in the sea in much larger proportion than are the nitrogen 

 compounds. Carbon dioxide is dissolved from the atmosphere ; 

 is liberated during the decomposition of organic matter; arises 

 from the respiration of animals ; or may be present in combination 

 with bases, as, for instance, in calcium bicarbonate. The amount 

 present per unit volume of water varies greatly geographically, 

 with depth, and with varying salinity of the water; and the 

 whole question of the chemical and physical conditions under 

 which COo may be absorbed by, or liberated from combination in, 

 sea water is much too complex to be discussed here^. Putter, 

 however, made a number of analyses of the amount of carbon 

 dioxide, and other carbon compounds, present in solution in the 

 inshore waters of the Bay of Naples; and his results possess 

 special significance from the point of view of the present enquiry. 

 The methods employed were, apparently, quite sound. The carbon 

 dioxide was liberated from the sample of water by boiling in acid 

 solution in a stream of COo-free air, and was absorbed by soda-lime 

 and sodium hydrate and weighed. The other carbon compounds 

 were estimated by Messinger's method — that is, they were oxidised 

 in the water sample itself by potassium dichromate and sulphuric 

 acid, and the CO formed was oxidised to CO., by passing over 

 glowing copper oxide in a combustion tube, and was absorbed and 

 weighed. The results thus obtained are tabulated on p. 217. 

 Thus three classes of carbon compounds are present. The nature 

 of the volatile acids and other acids and carbohydrates is un- 

 certain, probabty they are substances akin to the humus compounds 

 of the soil, and originate in the mucus, &c., excreted by the algae. 

 Putter's results are of interest since they indicate that a consider- 

 able proportion of carbon compounds may be present in solution 



1 See, however, Kriimmel, Handbuch der Oceanographie, Bd. i. Stuttgart, 1907, 

 pp. 303-317. 



