21 



and Bollinger(ll) have pointed out that this phenomenon is equivalent to a capaci- 

 tor and a resistance in parallel with the resistance across the conductivity cell. 

 The Parker effect becomes more pronounced with increasing frequency. A series 

 of preliminary studies was conducted to detect any dependence of Rm on the fre- 

 quency used for the measurement. The results, summarized in Table IV and in 

 Figures 12 and 13, show that the measured resistance is not dependent upon the 

 frequency of the measurement. Sodium bicarbonate was used in these studies, 

 because the conductivity of solutions of this electrolyte is less likely to alter due 

 to pickup of carbon dioxide from the air . A frequency of 1000 ops was chosen 

 for all subsequent experiments . 



E. WALL EFFECT 



Although no frequency dependence was observed, the results in Table 

 IV indicate that the measured resistance is somewhat less when the conductivity 

 cell is inside of the pressure vessel than when it is outside immersed in the 

 thermostatic bath. Table V presents further experiments designed to examine 

 this effect. We performed all these experiments on cell TJC-T. The observed 

 decreases in measured resistance when the cells are in the pressure vessel are 

 summarized in Table VI . Although this effect is very small (less than 1%), we 

 nevertheless applied a correction for it. The observed depression of measured 

 resistance when the conductivity cells are within the pressure vessel was attrib- 

 uted to a resistance in parallel with that of the cell . The actual resistance of the 

 conductivity cell, Rcj was calculated from the relation 



J_ _ _1_ J_ 



R ~ R ' " R 



(2) 



where R^,' is the measured resistance corrected by equation (1) for the resistance 

 of the leads and closure, and Rg is spurious resistance in parallel with the cell. 

 The resistivity of the hydraulic fluid is very large compared with that of the aqueous 

 solutions in the cells; however, because one electrical lead is grounded to the pres- 

 sure vessel, the cell is literally surrounded by a very large electrode. Although 

 the scatter is large. Table VI shows that, roughly speaking, the percent reduction 

 in measured resistance is independent of the value of the resistance being measured, 

 that is to say 



R ;::=^ CR ' (3) . 



s c 



where C is a constant whose value, on the basis of the average reduction given in 

 Table VI is about 240 . The observation that C is roughly constant indicates that 

 the spurious electrical path, at least in part, involves the electrolytic solution in 

 the cell. 



:artbur Sl.lLittkJnt. 



S-700 1-0307 



