carried out using data for single-electrolyte solutions. Further refine- 

 ments must await more reliable single-electrolyte data as well as data 

 for the excess thermodynamic and transport functions. 



Measurement and Prediction of the Properties of Solutes in Seawater 



One of the most important problems in examining chemical reactions 

 in seawater is the estimation or prediction of the thermodynamic and 

 kinetic properties of solutes (ionic and non-ionic). The thermodynamic 

 equilibrium of a chemical process A + B — > C can be characterized by 

 an equilibrium constant 



K- ac _ [C] yC 



SLA^B [A][B] 7A7B' ^"-^ 



where a;, [i] and yi are the activity, concentration, and activity coeffi- 

 cients of species i. The effect of pressure on K is given by 



dUn K\ AV 



dP )^ RT' ^^^ 



where 



AV = V(C)-V(A)-V(B). (4) 



V(i) is the partial molal volume of species i. 

 The effect of temperature on K is given by 



Bin K\ AH 



where 



AH = H(C)-H(A)-H(B). (6) 



H(i) is the partial molal enthalpy of species i. 



The determination of the equilibrium constant, its pressure dependence 

 (Millero, 1971b; and Millero and Berner, 1972), and its temperature 

 dependence can be made by (1) direct measurements in seawater (Kester 

 and Pytkowicz, 1968, 1969, 1970), and (2) estimation from known 

 properties of pure water and simple solutions (Millero, 1971a,b). To 

 provide information in the absence of direct measurements, it is impor- 

 tant to develop methods to estimate the activity coefficients, the partial 

 molal volumes, and partial molal enthalpies of solutes in seawater. 



15 



