The Hydrogen-ion Concentration, etc., of Sea-Water. 



25 



ature on the obsolete Re"aumur thermometer scale (14 R. = 17.5 C.), 

 which is often unattainable aboard ship or at seaside laboratories. 

 The best practice is to titrate the chlorides of the sea-water with silver- 

 nitrate solution, using potassium chromate as indicator, and, if a 

 constant temperature can not be maintained, to calibrate each new 

 silver solution with standard sea-water. Since the temperature 



1.018 



1.023 



1.024^ 



FIG. 2. Conversion table for finding the density of 

 sea-water, referred to distilled water at 4, from 

 the Cl normality as determined by titration, or 

 the grams of Cl per liter at the titration tem- 

 perature. The density at any other temperature 

 may be determined with the aid of figure 1 by 

 reducing the result to Cl per kilogram and back 

 to Cl per liter at the desired temperature. 



changes affect the volumes of the silver solution and sea- water about 

 equally, they may be ignored. The concentration of sea-water was 

 formerly expressed as the salinity or total salt-content, but it was found 

 that the ratio of the chief salts in sea-water is remarkably constant, 

 and the individual elements may be determined much more accurately 

 than the total salts in one operation. Salinity is no longer deter- 

 mined directly, but is calculated from the chlorine titration according 



