The Sea-water and its Physical and Chemical Properties 



11 



in the open ocean. It comes within the range where all three factors: HCO3, COg" and 

 free CO2 are present in measurable amounts, although bicarbonate predominates 

 considerably. 



The above values for the apparent dissociation constants are for water at a pressure 

 of one atmosphere. If the pressure is increased the constant also increases since the 

 pressure strengthens the dissociation both of the carbon dioxide and of the neutral 



Fig. 40. Percentage distribution of the three forms of carbon dioxide (free carbon dioxide, 

 bicarbonate, carbonate) in pure water and in sea water as a function of pH (according to 



Buch). 



salts. This dependence implies, as shown in Table 30, that water displaced from the 

 surface downwards to great depths will be more acidic, and inversely that of a sample 

 brought from a definite depth with a collecting bottle will as a consequence of the 

 decrease of pressure show a higher pH (be more alkaline). 



Table 30. Dependence of the concentration constants for carbon dioxide 

 CO2 on the hydrostatic pressure 



Wattenberg gives the example shown in Table 3 1 of this effect. This pressure effect 

 has a practical significance in processes involving the hydrogen-ion concentration such 

 as the life of deep-sea organisms and the solubility of calcium carbonate at the sea 

 bottom. 



Carbon dioxide in the deep layers of the ocean. The work of the "Meteor" Expedition 

 1925-7 gave the first reasonably good information on the distribution of carbon di- 

 oxide in the deep layers of the sea. The essential results have been summarized by 

 Wattenberg (1936). For the most part there is an approximate equilibrium at the 

 surface of the sea between the partial pressures of carbon dioxide in the sea and in the 



