relative viscosity (Fig 4) whereas if the first hydration sheath is assym- 

 metrical, such as K(H„0)"'" or C1(H 0)~, the ion will be a structure-breaker 

 and will tend to make the surrounding water less ordered as reflected in a 

 decrease in relative viscosity (Fig 4) (Home, 1964). Mg(H 0),"^ SO^(H20) ", 

 it is interesting to note, like many other 2:2 electrolytes is a very power- 

 ful structure -maker (Fig 4). 



THE ELECTRICAL CONDUCTIVITY OF SEA WATER 



Electrical conductivity,/ \ , can be treated as a rate process and its 

 activation energy, E^, calculated from the integrated form the the Arrhenius 

 equation 



^'> £-0.= C/o^ Az -/ofA,) 4'S-76 T2.v//\r 



where the T's are absolute temperatures. E i for sea water exhibits a 

 maximum (Fig 5) and for chlorinities less than about 10 °/oo the maximum 

 occurs at the temperature of maximum density (Home, 1964). The rate-deter- 

 mining step of the "normal" electrical conductivity of aqueous solutions of 

 strong 1:1 electrolytes is "hole" or vacancy formation in the solvent. The 

 process occurs both in the free and clustered water, and the decrease in 

 Eg cond. with decreasing temperatures at temperatures below the maximum 

 reflects the fact that "hole" formation is facilitated by the increasing 

 amount of less dense, more open, clustered water (Home, 1964 and Home and 

 Courant, 1964). 



We have measured the effect of pressure on the electrical conductivity 

 of sea water (Home and Frysinger, 1963). In the range of oceanographic 

 interest, pressure, like temperature, decreases E^ cond indicating that its 

 application tends to disorder liquid water (Home, Myers and Frysinger, 1963). 

 We found that Walden's rule 



« 



/I**;^^ = Constant 



where /y is the viscosity is a good approximation for sea water under the con- 

 dition of varying temperature but not varying pressure (Home and Courant, 1964) 

 However, we found that we were able to curve fit the observed pressure-depen- 

 dence of the electrical conductivity of sea water by simple corrections for 

 (1) the increased dissociation of MgSO^ (Fisher, 1962), (2) the compressi- 

 bility, and (3) the square of the viscosity (Home and Courant, 1964). The 

 apparent dependence on yfl^ is an artifact arising from the reduction of the 

 radii of hydrated ions by pressure (Home, 1963) - a phenomenon first noted 

 by Zisman (1932). The structural effects of pressure differ in one very 

 important respect from those of temperature: temperature breaks up the 

 structure of the bulk water but does not greatly affect. the local water 

 structure near ions, pressure, on the other hand, destroys both the bulk 

 structure and the hydration atmospheres of ions. 



227 



