SALINITY, GASES 49 



" Challenger " Expedition from all parts of 

 the ocean and in all depths are given in the 

 following table : — 



Sea-Salts as Ions. — In the foregoing table 

 the acids and bases are arbitrarily combined, 

 but it is now known that the dissolved sub- 

 stances in sea- water are not accurately repre- 

 sented in this manner, inasmuch as they are 

 present mainly as ions. The aggregate degree 

 of ionic dissociation has been calculated from 

 the freezing and boiling points of sea-water 

 to be about 90 per cent. That is, only one- 

 tenth of the total solids are present as salts 

 pure and simple ; these must comprise 

 not only those named by Dittmar but all 

 the possible combinations of bases with acids, 

 among which calcium and magnesium sul- 

 phates will be relatively in largest proportion. 

 The bulk of the solutes, however, consists of 

 ions, and it would be more rational to write 

 the composition of sea-water thus : — 



