The Seo-water and its Physical and Chemical Properties 



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Fig. 39. Distribution of carbon dioxide pressure (given in 10-* atm.) at the surface of the 

 South Atlantic (according to Wattenberg). 



In the open ocean the average value for total free carbon dioxide is usually between 

 45 and 55 ml/1. Ruppin has found for the middle North Sea 45-9 for the Beltsea 36-7 

 and for the southern part of the Baltic 31-9, while Brennecke (1909) found values be- 

 tween 46 and 55 in the Atlantic and in the Indian Ocean and between 45 and 59 in 

 the Antarctic Ocean. In the North Sea Knudsen (1899, "Ingolf" Expedition) found 

 lower values, between 34-1 and 46-6 ml/1. 



Alkalinity. In sea-water the sum of the cations of bases (Na+, K+, Mg2+, Ca2+), is 

 always a little greater than the sum of the anions of strong acids (SO^-, CI", Br-). 

 This excess of base is known as the "alkaline reserve"; it gives sea-water an alkaline 



