96 A TEXTBOOK OF OCEANOGRAPHY 



over before the results could exercise any effect appréciable 

 to analysis. 



Tlie solubility of carbonic acid in water is directly 

 dépendent on the température. 



The following table gives the coefficients of absorption for 

 sea-water of salinity 35" 19 per mille at différent températures, 

 compared with that of pure water : 



0° C. 5° C. 10° C. 15" C. 20° C. 25° C. 30° c. 

 Sait water (after Krogh) ... i*4i l'iy 0*99 o"85 074 o"65 0*57 



Pure water (after Bohr and Bock) 171 1*19 l'ig i"o2 o-88 076 o'ôy 



The différences in the coefficients of absorption of carbonic 

 acid decrease with a higher température, and at 30° C. are 

 about one-third as large as at 0° C. From the above it follows 

 that warm seas contain less carbonic acid than cold. 



The chief source of oceanic carbonic acid is the atmosphère. 

 There must, however, hâve been carbonic acid originally in 

 sea-water. One source of carbonic acid is, according to 

 Dittmar, the océan bottom, especially where through sub- 

 marine éruptions large quantities of gas are discharged. 

 Sources of oceanic origin for carbonic acid hâve not yet been 

 found, a condition probably due to the difficulty of collecting, 

 preserving, and analysing suitable water samples. The bottom 

 layers of waters in the great océans are under a pressure of 

 several hundred atmosphères, and consequently carbonic acid 

 would be tal^en into solution in a liquid condition. Carbonic 

 acid liquéfies at 15° C. under pressure of 52 atmosphères, at 

 10° C. with pressure of 46, at 5° C. with 40, and at 0° C. under 

 pressure of 35 atmosphères, and the critical point for pressure 

 is at 73 atmosphères — that is, at depths of 400 fathoms. Below 

 this depth carbonic acid is not met with in the gaseous 

 condition. 



An increase of carbonic acid due to the respiration of 

 marine organisms is hardly perceptible, except in rare cases, 

 where enclosed areas are responsible. As an example Gullmar 

 Fiord in Bohuslan (Sweden) may be given. The effect of 



