40 



V, THE EFFECT OF PRESSURE ON THE ELECTRICAL CONDUCTIVITY 

 OF AQUEOUS POTASSIUM CHLORIDE SOLUTIONS 



The molal conductance of an aqueous solution = 010 m in KCl was 

 measured at 25, 35, and 45°C over the pressure range 15 to 100, 000 lb/in o^ 

 in TJC-1 at a frequency of 1000 cps . In each experiment the cell constant at 

 1 atmosphere was calculated on the basis of the measured corrected resistance, 

 and the values of the molal conductance were calculated at the corresponding 

 temperatures (see Figure 20) . The results are summarized in Table VIII and 

 Figure 21 „ 



At 45°C and at pressures below 60,000 Ib/iUo^ the present results 

 are in satisfactory agreement with the results reported earlier by Hamann and 

 Strauss .'^"^^ Discrepancies in the two sets of data appear above 60, 000 Ib/uio^, 

 There are so many uncertainties involved in calculating the constant of the Teflon 

 cell at higher pressures that it remains problematic how much significance can 

 be assigned to these discrepancies „ 



At 25° C the present results and those of Hamann and Strauss are in 

 poor agreement . The causes of this discrepancy are not clear . We place the 

 greater confidence in our own results for the following reasons: 



lo Our 25°C curve more closely parallels the 35°C curve 

 than does their curve , 



2 . The Teflon cell results were in agreement with our glass 

 cell results . 



3 . There appears to be less scatter in our results . 



4 . Our change in the relative molal conductance of KCl with 

 pressure is initially in agreement with the relative change 

 in resistance measured by Adams and Hall .(24) 



With respect to the latter consideration, Adams and Hall, using a glass conduc- 

 tivity cell made very careful measurements of the relative resistance, Rp/Rj, 

 of a fairly concentrated (0,3730 weight %) KCl solution over the pressure range 

 15 to 265 800 lb/tn,2. They did not attempt to estimate cell constants and thereby 

 obtain conductances , It can be shown that Rp/R]^ should vary with pressure in 

 the same way as does the reciprocal of the relative conductance (l/( Ap/ Ai)* 

 Until the variation of the cell constant with pressure becomes significant, the in- 

 itial slopes of Rp/R]^ and Aj/ Ap should be the same. Up to 5000 lb/in „2 a plot 

 of the present values of Ai/ Ap versus P has the same slope as the plot of Adams' 

 and Hall's value of Rp/R, versus P„ However, a plot of Hamann's and Strauss' 



;artliur m.lLittle Jnc-. 



S-700 1-0307 



