THE PHYSICAL CHEMISTRY OF SEA WATER 571 



Table IV. {Continued) 



Main Dissolved 

 Element —log »soiid —log Goi. Species Solid Phase 



Sc 4.2 9 (OH)? ScP04? 



Ge 4.2 



As 4.4 



Mo 4.0 



Cs 4.5 



La 4.1 8.7 La3+, LaOH + + ? LaPO^? 



Pb 4.3 7.6-8.0 Pb++, PbOH+, PbO^ 



Th 4.5 



Sb 5.3:- 



I 6? 



W 5? 



Hg 5.8 



Tl 5-6 



U 5.0 



Se 6.2 



Ag 6.2 



Cd 6.1 



Bi 6.2 



Au 7.8 



In the literature there are a few accurate studies of the equilibria 

 between aqueous and solid solutions, especially Vaslow and Boyd 

 (1952) on Ag(Cl, Br) and Schmeling (1953) on (Ba, Sr)C03. On 

 the important silicate equilibria so little is known that there is 

 practically no basis for a strict treatment in our present discussion. 



Let us consider a schematic case, without attempting to use 

 any actual values: a solid solution (A,B)L, say (Ca, Sr)C03, 

 which may be described as solid AL, where part of the A ions have 

 been replaced by B. Let the mole fractions be x ^ and Xb so that 

 Xa + Xn = 1. Let us suppose that the solid solution is ideal. 

 Deviations from ideality will not change the following argument. 

 Then the activity of each component is equal to its mole fraction. 

 The conditions for equilibrium with an aqueous solution would be 

 (omitting the charges) : 



{AllLI = .Va^^AL; {BllLj = .VBi^BL 



