11 



Experiments showed that exposure to white gasoline and to Univis P-38 

 does not measurably alter the electrical conductivity of the aqueous electrolytic 

 solutions under study „ 



B„ TEMPERATURE CONTROL 



The pressure vessel is submerged to within an inch of its upper shoul- 

 der in a 40-gallon thermostatic oil bath which is insulated with 2-5 inches of 

 granular vermiculite . The temperature of the bath is controlled by a resistance 

 heater and Fisher Model 44 thermoregulattng unit with a thermistor probe . The 

 manufacturer claims that this unit responds to temperature changes of + 0.003°C 

 in the temperature range of interest , Initial temperature measurements were 

 made with a National Bureau of Standards calibrated thermometer . A 10- junction, 

 copper -constantan thermocouple was constructed and used in the data runs . 



Deep-ocean temperatures correspond to a few degrees centigrade. A 

 small compressor -type refrigeration unit for the thermostatic bath was designed 

 and constructed by the Harris Manufacturing Co., Inc., to attain the low tempera- 

 tures encountered in deep-ocean waters . This unit, in conjunction with the im- 

 mersion heater, enables the bath to be operated over the range 0-50°C (or a wider 

 range if desired) , This cooling unit and the thermocouple and potentiometer are 

 shown installed in Figure 3 „ 



C. CONDUCTIVITY CELLS 



Two types of conductivity cells were constructed. The first of these 

 was a Jamieson-t3rpe cell(5) (see Figure 7) fabricated of Teflon, with parallel 

 plate platinized platinum electrodes , Its cell constant is about 0.20. In this cell 

 the hydrostatic pressure is transmitted to the electrolytic solution by a movable 

 plug (see Figure 7). The plug is located some distance from the electrodes in 

 order to minimize the effect of its position on the cell constant. 



Since for more concentrated electrolyte solutions a cell with a larger 

 cell constant is required, a special capillary cell (see Figure 8) with a cell con- 

 stant of about 75 was designed, and a glass prototype was constructed. Due to 

 differences in the compressibilities of glass and platinum, glass -platinum seals 

 tend to fracture at high pressures; furthermore, a mercury contact sometimes 

 contaminates the electrolyte.^") In order to avoid these difficulties, the special 

 capillary -type cell (Figure 8) was designed with an electrolyte -hydraulic fluid 

 boundary and with free platinum leads . Tests have shown that the hydraulic 

 fluids used do not alter the resistivity of the electrolyte. The design of this cell 

 was based on the thesis that the electrode snarls would behave as electrical vol- 

 umes as far as ions in the capillary were concerned. Tests on a glass prototype 

 cell do indeed indicate that the measured resistance of an eIectrol3rte -filled cell 



;artl)ur Sl.ltittkJnc. 



S-700 1-0307 



