20 



the pressure vessel, interference pickup still restricts the number of obtainable 

 significant figures, especially when the resistance is high. A filter was added to 

 circumvent this difficulty but was not entirely effective . 



Cell stability, i.e., invariance of resistance with time, is necessary 

 in order to make precision conductivity measurements. Table III summarizes 

 the results of measurements, at a frequency of 1000 cps, of total cell resistance, 

 Rjj^, over extended time intervals . The several cells stabilize within approxi- 

 mately 20 minutes, and subsequent fluctuations are small and random. As men- 

 tioned above, the conductivity of the electrolytic solution is not altered by exposure 

 to the hydraulic fluids . 



TABLE ni 



CELL STABILITY 











Deviation in 









Time 



the Measured 



Temperature 



Solution 



Cell 



Period 



Resistance, R-^ 



('C) 



(M) 





(hr) 



(%) 



25„05± 0,03 



0.020 KCl^ 



TJC-1 



19 



0.062 



25.05± 0.04 



1.00 KCl*^ 



GCC-1 



2.4 



0.012 



25.05± 0.03 



0.20 KCl*^ 



GCC-1 



1.3 



0.007 



27.01+ 0.04 



0.20 KCl^ 



GCC-1 



18 



0.034 



24.91± 0.01 



0.10 KCl^ 



GCC-2 



1 



0.008 



a , In contact with Univis P~38 . 



b . Open to the air . 



Co In contact with white gasoline . 



D. FREQUENCY DEPENDENCE 



Cells for precision conductivity measurements should be so designed 

 that electrical leads and any filling tubes are widely separated. C^) However, 

 since in the present experiments the entire cell must fit into a cavity approxi- 

 mately 9 inches long and 1 inch in diameter, such precautions are unfeasible . 

 Improperly designed conductivity cells may exhibit a Parker effect.C^^) Jones 



artbur Sl.HittlcIlnt. 



S-700 1-0307 



