HY A. H. S. LUCAS. 



627 



o 



I tried other methods of analysis, but f(juiid that absorption by 

 phosphorus over water was the cleanest, surest, and readiest. 

 Practically in a couple of hours, fresh (;ut phosphorus removed all 

 the oxygen which my simple apparatus could measure. By 

 choosing'' the time of the day for the experiments, the total 

 volume and the volume of the remaining nitrogen could be deter- 

 mined under practically the same conditions of temperature and 

 pressure. I do not claim any extreme accuracy for the 

 experiments. 



First, by way of testing the method, I made several analyses 

 of atmospheric air, of air dissolved in tap- water, and of the gases 

 dissolved in sea-water. The ratio of nitrogen to oxygen given by 

 the apparatus for air, was the orthodox 79 : 21. To collect the 

 gas from water, the water was boiled into a vessel containing 

 water made previously gas-free by prolonged boiling. Thus 

 250 c.c. of tap-water yielded 3-9 c.c. at ordinary temperature and 

 pressure, of which 2-6 c.c. were nitrogen, and 1 -3 c.c. oxygen. The 

 ratio of the nitrogen to the oxygen was then 2 : 1, as it should be 

 if all the gas were dissolved from atmospheric air, inasmuch as 

 oxygen is twice as soluble as nitrogen. There was no carbon 



dioxide. 



The analyses of sea-water gas varied considerably, as might be 

 expected. On referring to the analyses of South Pacific Surface 

 Water collected by the "Challenger," I found that of 16 analyses 

 published in the Report, no two were alike. The carbon dioxide 

 varied from 10-18 to 23-12 per cent, of the total gas. The ratio 

 of nitrogen to oxygen varied from 62-43 : 26-59 to 54-51 : 28-64, 

 evidently varying about a mean of 2 : 1. It would seem that the 

 presence of organisms alters considerably the natural ratio of the 

 gases dissolved from the air. One of the analyses I obtained 



was — 



la 100 vols, of sea-water gas 



Nitrogen 67-1-2 



Oxygen -^ ^^ 



CO, 6-85 



/ 



1 00 00 



55 



