68 Papers from the Department oj Marine Biology. 



variations in excess base near the bottom: South of Iceland and east 

 of the barrier (Rykjanaes Ryg) excess base equals 26, west of the 

 barrier it equals 23.7, and in Davis Strait it equals 23.5, the salinity 

 being about 35 and bearing no relation to excess base. The surface- 

 water of Davis Strait averaged 23.6 excess base and 34 salinity. As an 

 exception due to special conditions, Walter and Schirlitz found that the 

 excess base in bottom-water in depressed parts of the Bay of Naples 

 averaged 24, whereas the surface-water averaged nearly 27. Dole 

 found that the excess base in Tortugas water (near surface) varied 

 from 23.7 to 25.7. Ruppin, on the Poseidon expedition, found that the 

 excess base averaged 25, with 35 salinity. 



Since the excess base or "alkahnity " of sea-water has been expressed 

 in various ways, the following conversion factors are convenient for 

 converting all results to our terminology: 

 Excess base = 0.8933 Xcc. CO2 in normal carbonate. 



= 0.4545 Xmg. CO2 in normal carbonate. 



= 0.588 Xmg. OH equivalent to acid used in titration. 



The total CO2 is often given in milligrams, which may be reduced to 

 cubic centimeters by multiplying by 0.509. 



CARBON-DIOXIDE TENSION OF SEA-WATER. 



We express CO2 tension in parts per 10,000. If sea-water is bottled 

 it undergoes some fermentation with rise in CO2 tension, unless an 

 antiseptic is added. Krogh supposed that the addition of 1 gram 

 HgCl2 per liter caused the CO2 tension to rise 0.35. Krogh found that 

 the CO2 tension of sea-water was low, except where it was diluted with 

 fresh water from the land. Everywhere it increases with depth. In 

 the Baltic he found tensions as high as 16 at a depth of 95 meters and 

 salinity of 1.3. That the CO2 tension of the sea-surface is not in 

 equilibrium with the air is indicated by the fact that Krogh found it 

 to vary from 1.5 to 3 in the North Atlantic. These differences were 

 apparently partly due to change in temperature, since, if the water 

 samples were all tested at 12.5°, the tension varied only from 2.05 

 to 2.95. Perhaps this water came from a uniform source (such as the 

 Gulf Stream) with uniform tension, and the change in temperature on 

 meeting ice and air currents diversified the tension. Since the CO2 

 tension of the sea near the Gulf Stream (at Tortugas) varied from 3.3 to 

 4.7 (calculated from the PJ and Krogh obtained values as low as 1.5 

 in the North Atlantic, we may suppose that the water maintains a 

 relatively constant CO2 content as it flows northward and the lowered 

 temperature decreases the CO2 tension. This supposition is supported 

 by the fact that Palitzsch found that the Ph is relatively constant, and 

 we have shown that the Ph is dependent on the CO2 content and not on 

 the temperature. If sea-water at 30° has 4.5 CO2 tension, simple cooling 

 to 0° will reduce the CO2 tension to about 1.5. 



