6 FOFONOFF [chap. 1 



Salinity has been defined by Forsch et al. (1902) as the total solid material 

 in grams contained in one kilogram of sea-water when all carbonate has been 

 converted to oxide, the bromine and iodine replaced by chlorine, all organic 

 matter completely oxidized, and the residue heated to constant weight at 

 480°C. Salinity, under this definition, is not equivalent to the total salt content, 

 but for our purposes it is sufficient to assume that a linear relationship exists 

 between them. Estimates of total salt content, made by Lyman and Fleming 

 (1940), are related to the salinity, S, by the formula 



,9totai = 0.043+1.0044*9. 



Salt content can be specified in terms of the ratio of mass of a single ion or 

 group of ions to that of sea-water. Titration of sea-water with silver nitrate 

 precipitates chlorides, bromides and iodides, so that an accurate determination 

 of the quantities of these ions can be made. The chlorine-equivalent of the pre- 

 cipitated halides in grams per kilogram of sea-water is called the chlorinity of 

 sea-water.^ It has been related to the salinity S by the empirical formula 



S = 0.03+1.8050(7^, (5) 



where both salinity S and chlorinity CI are expressed in parts per thousand (%o). 

 If we assume that the ratio of each constituent of sea-water to the salinity is 

 constant, we can introduce a set of multipliers, Aj, giving the mass fraction of 

 the i-th constituent in the form 



Xi = XiS, (6) 



where s is the salinity expressed in grams per gram of sea-water. - 



If we restrict our considerations to processes that do not affect the mass 

 ratios of the constituents, we can introduce a combined chemical potential, 

 /xs, for the dissolved salts. From (2) and (6), we obtain 



i 



Introducing /xw for the specific chemical potential of water in sea-water and 

 fjL for the difference of specific chemical potentials ^lis — /xw, we can express (2), 

 (3) and (4) in the form 



de ^ T d-q-pdv + fjids + dO (7) 



e = Tt] - pv + iJiS + ixv, + (8) 



dfjiv, = —rjdT + vdp — sdiJL. (9) 



By introducing these transformations, we are, in effect, treating the dissolved 

 salts as a single solute. 



1 To avoid variation in the chlorine-equivalent due to refinements in the determination 

 of the atomic weights of the halogens, chlorinity has also been defined in terms of the 

 weight of purified silver (prepared by specified techniques) required to precipitate the 

 halogens. Salinity is then considered to be defined by the empirical formula obtained by 

 Forsch et al. (1902) relating salinity and chlorinity (see equation (5)). 



2 If salinity expressed in parts per thousand is used, (6) becomes Xi = IQ-^XiS. 



