45 



VI. THE EFFECT OF PRESSURE ON THE ELECTRICAL 

 CONDUCTIVITY OF SEA WATER 



The standard sea water used in the present experiments was P32 (8/1/61), 

 obtained from the I. A. P.O. Standard Sea Water Service of Charlottenlund Slot, 

 Denmark. Its chlorinity, CI, was 19.376 °/oo; its salinity, S, calculated from 

 the definition(26) 



S = 0.03 + (1.805) CI, (13) 



was 35.00°/oo. In addition, sea water solutions of 17.61 0/00 and 9.68°/oo 

 chlorinity (31,81°/oo and 17, 50 0/00 salinity) were prepared by weight dilutions, 

 Inasmuch as de ionized water of specific conductance less than 1 x 10~5 ohm"-*^ 

 cm" was used for these dilutions, the contribution to the conductance from the 

 water used for dilution is negligible (less than 0.05%). 



The experimental results are summarized in Tables IX, X, and XI, 

 and Figures 22, 23, and 24. The specific conductance^ K, is given by 



K = k/R, (14) 



where k is the cell constant and R the resistance. 



The experimental results in Tables IX to XI and Figures 22 to 24 ex- 

 hibit a number of interesting features . In the first place, it is important to 

 notice that the pressure dependence of the specific conductance of sea water over 

 the range of oceanographic interest (15,000 lb/in. 2) is of comparable magnitude 

 to the temperature dependence over the temperature range of interest (5°C). This 

 finding emphasizes the importance of considering both pressure (or depth) and 

 temperature when taking in situ conductivity measurements . 



At a given salinity the plots of specific conductance versus pressure 

 are nearly linear for most of the pressure range of interest (up to 10, 000 lb/in. 2), 

 and, furthermore, the plots at different temperatures appear to have very nearly 

 the same slopes, A K/AP. 



Table XII summarizes the values of these slopes . Inasmuch as these 

 values are ratios of differences, a great deal of the accuracy of the original data 

 has been lost . But, although no temperature dependence of the values of A K/AP is 

 evident from Table XII, there does appear to be an increase in the value of AK/AP 

 with increasing chlorinity. This is shown more clearly in Figure 25. 



artbur B.ILittleJinr. 



S-700 1-0307 



