for an understanding of the physical and chemical properties of the medi- 

 um. These interactions also are important because they affect many of 

 the chemical processes that occur in seawater. For example, short-range 

 interactions in seawater have been shown to affect the pH of the oceans 

 (Weyl, 1961), the solubility of minerals in the oceans (Garrels, Thomp- 

 son, and Siever, 1961), and the ultrasonic absorption of the oceans 

 (Liebermann, 1949; Fisher, 1967). 



Classically the ionic interactions in seawater have been treated by 

 using Bjemim's (1926), ion-pairing model as exemplified by the work 

 of Garrels and Thompson (1962), Kester and Pytkowicz (1968, 1969, 

 1970), Atkinson, Dayhoff, and Ebdon, 1972 and Hawley, 1973. This 

 approach formulates the electrostatic cation-anion interactions in terms 

 of equilibrium constants that can be determined at the temperatures, 

 pressures (Lafon, 1969; Kester and Pytkowicz, 1970; Millero, 1971b; 

 Millero and Berner, 1972), and chemical environments characteristic 

 of the oceans (Kester and Pytkowicz, 1968, 1969, 1970). The results 

 of these methods have been successful in accounting for the activity 

 coefficients of many solutes in the seawater medium (Kester and Py- 

 tkowicz, 1968, 1969, 1970), for the solubility of some minerals in the 

 ocean (Garrels, Thompson, and Siever, 1961), and for the ultrasonic 

 absorption of seawater (Fisher, 1967). Recently, the ion-pairing model 

 has also been useful in explaining the Raman spectra of multicomponent 

 sulfate solutions (Daly et al., 1972). An alternative approach that has 

 been developed recently (Millero, 1971a, 1973a,b) considers ionic inter- 

 actions in more general and less mechanistic terms. The model simply 

 states that any physical property of seawater {Psw) is equal to the 

 property for pure water (Ph^o) plus a contribution from the weighted 

 ion-water interactions of the major components and one from the weight- 

 ed ion-ion interactions of the major components: 



Psw = P//20 + ion-water interactions + ion-ion interactions. (1) 



The first two terms can be estimated from infinite dilution data in 

 single-salt solutions (binary mixtures of salt + H2O). The third term 

 can be divided into a theoretical Debye-Hiickel Limiting Law term and 

 a term arising from deviations from the Limiting Law of the weighted 

 major ionic components. This general approach of examining the physi- 

 cal-chemical properties of seawater serves two purposes. First, it pro- 

 vides the theoretical concentration dependence of the physical-chemical 

 properties and second, it emphasizes the importance of ion-water and 

 ion-ion interactions of major components of seawater. 



Preliminary applications of these methods to the thermodynamic and 

 transport properties of seawater have been successful (Millero et al., 

 1973, and Millero, 1973a,b). All of this preliminary work has been 



14 



