measurements. As regards the processes of the second group, the relative changes caused by them 

 are also great, but they affect substances which, for the most part, are in minimum quantities in 

 the sea water and therefore such changes have practically no perceptible effect on the physical 

 properties of sea water. 



This gave rise to the very convenient concept that the salt composition of ocean waters is con- 

 stant, by which we understand the following: the total concentration of the dissolved solid sub- 

 stances in the ocean, depending on local conditions, varies from 0-4 per cent by weight of the dis- 

 solved matter; the amount of gases dissolved in sea water and also the content of the other elements 

 found in insignificant amounts in sea water may also vary considerably, but the ratios between the 

 main ions which determine the physical properties of sea water remain basically constant in both 

 time and space. 



LITERATURE: 62, 153. 



Section 3. Salinity 



The salinity of sea water is characteristic of the concentration of solid matter dissolved in 

 sea water. By salinity we mean the total weight in grams of all salts per 1000 g of sea water. 

 Thus, salinity is the concentration of the solution, expressed in tenths of a per cent (pro mille). 



The study of many samples of sea water (differing considerably in salinity and collected in 

 different parts of the World Ocean) conducted by a number of specialists under the direction of 

 Knudsen, showed quite clearly that the salt composition of ocean waters is constant, at least with 

 regard to the main elements. Thus, we may conclude that the ocean waters of various regions, 

 with the same pressure and temperature, differ only in the total concentration of their dissolved 

 salts. 



After it had been established and verified that the ratios between the main elements of sea 

 water are constant, the total salinity of a given water could be found by simple conversion, once the 

 content of one of the main elements had been determined. 



Chlorine was chosen as this determining element, due to its high percentage content in sea 

 water and the ease with which it can be determined accurately by chemical methods. Knudsen, 

 Forch and Sorensen derived the following empirical formula from their investigations: 



S = 0.030 + 1.8050 CI 



where 5 is salinity in pro milles, i.e. , the total weight of salts in grams per 1000 g of sea water; 

 CI is the chlorine content in pro milles, i.e. , the weight of chlorine in grams per 1000 g of sea 

 water. (By chlorine here, we mean the number of grams of chlorine equivalent to the total amount 

 of halogens, i.e. , of chlorine, bromine and iodine in 1000 g of sea water.) 



Of course, if we consider the salt composition of sea water to be constant we get not only a 

 constant relationship between the chlorine content and salinity, but also constant relationships be- 

 tween the chlorine content and the other main elements of sea water. 



Examining the salinity formula, we see that under the condition that the chlorine content is 

 zero, salinity will still be 0. 03. This is to be explained by the fact that, even though the chlorine 

 content around river mouths may be zero, the total salinity will be determined from the calcium 

 salts contained in the river water. 



