“REPORT NUMBER 1270862 PROJECT TRIDENT TECHNICAL REPORT THE EFFECT OF PRESSURE ON THE ELECTRICAL CONDUCTIVITY OF SEA WATER ARTHUR D. LITTLE, INC. 35 ACORN PARK CAMBRIDGE, MASSACHUSETTS DEPARTMENT OF THE NAVY BUREAU OF SHIPS NObsr-81564 $-7001-0307 AUGUST 1962 ec ¢¢O9€00 TOEO Oo MAA IOHM/18lNi REPORT NUMBER 1270862 | ooo wo PROJECT TRIDENT TECHNICAL REPORT THE EFFECT OF PRESSURE ON THE ELECTRICAL CONDUCTIVITY OF SEA WATER BY R. A. HORNE G. R. FRYSINGER ARTHUR D. LITTLE, INC. 35 ACORN PARK CAMBRIDGE, MASSACHUSETTS DEPARTMENT OF THE NAVY BUREAU OF SHIPS NObsr-81564 $-7001-0307 AUGUST 1962 Vmagiar rhe TIONAA ree s ic D anue2and 10 Daa yiTouano> ANAS mata Aaz 2 is | USA Os i We eRe a & - yy si At, at a RT aR awa) an, Aue i . ine . : alt his . ble aut 3 a0 TIMI HATS eaiMe a0) DaAgaua New ae Lee Spi rin’ ill TABLE OF CONTENTS Page List of Figures Vv List of Tables vil I, SUMMARY 1 Il, INTRODUCTION 2 Il. DESCRIPTION OF APPARATUS 3 A. HIGH-PRESSURE EQUIPMENT 3 B. TEMPERATURE CONTROL iil C,. CONDUCTIVITY CELLS 11 D. CONDUCTIVITY BRIDGE 14 IV. EQUIPMENT CALIBRATION 18 A, TEMPERATURE MEASUREMENT 18 B. LEAD CORRECTIONS 19 C. CELL STABILITY 19 D, FREQUENCY DEPENDENCE 20 E. WALL EFFECT 21 F, PLUG POSITION AND LIQUID LEVEL EFFECTS 27 G. DETERMINATION OF CELL CONSTANTS 28 H. PRESSURE DEPENDENCE OF CELL CONSTANTS 31 I. EQUILIBRATION 33 V. THE EFFECT OF PRESSURE ON THE ELECTRICAL CON- DUCTIVITY OF AQUEOUS POTASSIUM CHLORIDE SOLUTIONS 40 VI. THE EFFECT OF PRESSURE ON THE ELECTRICAL CON- DUCTIVITY OF SEA WATER 45 REFERENCES 64 Arthur D Little, Inc. $-7001-0307 rs yeu ¥ TY. i \ rh tsi ote LIST OF FIGURES Figure _No. Page i High-Pressure Apparatus (Front View) 4 2 High-Pressure Apparatus (Rear View) 5) 3 Thermostatic Bath 6 4 Schematic Diagram of 200, 000 psi Pressure-Producing Equipment 7 5 Pressure Vessel 9 6 Details of Pressure Vessel Closure 10 d Parallel-Plate-Type Conductivity Cell 12 8 Capillary-Type Conductivity Cell (GCC-2) 13 9 Capillary-Type Conductivity Cell (GCC-2) tS 10 Conductivity Bridge 16 11 Conductivity Bridge, Shieided Ratio Box 17 12 Frequency Dependence of the Tefion Jamieson-Type Cell (TJC-1) 23 13 Frequency Dependence of the Glass Capillary~-Type Cell (GCC-1) 24 14 Jamieson Cell, Cross Section 32 15 Proposed Phase Diagram of Teflon 35 16 Relative Volume Changes for Teflon 36 17 Hysteresis Due to Failure of System to Thermally Equilibrate 37 18 Equilibration Time at Pressure ~ Pressure Approached from Above 38 Arthur D Little, Inc. S-7001-0307 vi LIST OF FIGURES (Continued) Figure meNorm Page 19 Equilibration Time at Pressure ~- Pressure Approached from Below 39 20 Molal Conductance of Aqueous 0.010 m KCl Solutions 42 21 Molal Conductance of 0.010 m KCi Solutions 44 aD Specific Conductance of 19.376°/o0 Chiorinity Sea Water 53 23 Specific Conductance of 17.6°/oo Chlorinity Sea Water 54 24 Specific Conductance of 9.6°/oo Chiorinity Sea Water 55 25 Variation of Slope With Chlorinity of Sea Water 57 26 Observed and Calculated Specific Conductances of 35 97/00 Salinity Sea Water at 0°C 59 27 Specific Conductance of 0.50 m NaCl 62 28 Relative Resistance of NaCl Solutions 63 Arthur D Little, Inc. S-7001-0307 vii LIST OF TABLES Table I Comparison of Temperature in Cavity and Bath 18 II Lead Corrections (25°C) 19 Ill Cell Stability 20 IV Frequency Dependence Over the Range 200 to 20, 000 cps 22 V Resistance Inside and Outside the Bomb AS) VI Reduction of Measured Resistance 26 VII Cell Constant Determinations 29 Vill Molal Conductance of 0.010 m KCl! Solutions 43 Ix Specific Conductance of 19.376 °/oo Chiorinity Sea Water 46 X Specific Conductance of 17.61°/o0o0 Chlorinity Sea Water 49 XI Specific Conductance of 9.68°/oo Chlorinity Sea Water 51 XII Slopes of Specific Conductance versus Pressure Curves 56 XII Comparison of Calculated and Observed Specific Conductances 58 XIV Composition of Sea Water 60 Arthur DLittle Inc. S-7001-0307 ik ws I. SUMMARY This report describes measurements made in the laboratories of Arthur D. Little, Inc., of the effect of pressure on the electrical conductivity of sea water of different salinities (and chlorinities) and at various tempera- tures. The first part of this report describes the design, construction, and calibration of the equipment, while the experimental data and the conclusions are presented in the second part. Over the range 0 to 25°C, 15 to 10,000 Ib/ in.~, and 9.68 to 19.38 9/00 chlorinity the specific conductance at pressure P (in lb/ in.) can be approximated from the value at one atmosphere, Kj T, Cl using the simple empirical relation ~ -8 Kp. T,Cl iy Ki rc oF oi ox 10 Ci P where Cl is the chlorinity in parts per thousand. If P is expressed in bars this relation becomes -7 J Ko cl = Kirc + 70x IO Gl Arthur D Little Ine. S$-7001-0307 Il, INTRODUCTION In the past, studies of the variation of physical and chemical proc~- esses with environmental conditions have concentrated on that parameter which varies most widely in commonplace experience, namely, temperature. As our explorations move into the ocean depths, knowledge of additional environmental factors will have to increase. In underwater operations the temperature range of interest covers only a few degrees centigrade, whereas the pressure range covers 10,000 atmospheres. For undersea operations, our knowledge of the pressure dependence of physical and chemical processes should be ideally as complete as our present knowledge of the temperature dependence of these proc- esses. Relatively little experimental research has been conducted in the areas of moderately high and high pressure physics and chemistry. Much of the earlier work, it is worthy of note, was prompted by oceanographical and geological inter- ests. The importance of detailed knowledge concerning the electrical conduc- tivity of the sea and of the variation of this parameter with concentration, tem- perature, and pressure is widely recognized. As a consequence of The Conference on Physical and Chemical Properties of Sea Water, held at Easton, Maryland, in September, 1958, (1) sponsored by the Office of Naval Research and the Committee on Oceanography of the National Academy of Sciences, the Committee on Chemi- cal Properties recommended "that electrical conductivity be used as a sea~water characteristic, '' and the Committee on Physical Properties reported that knowledge of ''the effect of pressure on the conductivity of sea water would be useful." Ina paper given at this same conference, D. W. Pritchard of the Chesapeake Bay Insti- tute of Johns Hopkins University noted that the "lack of certain basic information restricts the use of in situ conductivity measurements in deep water for the de- termination of salinity. There appears to have been no investigation of the effect of pressure on the conductivity of sea water. Thus it would seem very desirable to include a study of the pressure effect of conductivity in any program developed to improve our knowledge of the physical and chemical properties of sea water ."(2, 3) Arthur D Uittle Ine. $-7001-0307 Ill. DESCRIPTION OF APPARATUS A. HIGH-PRESSURE EQUIPMENT 1. Operation The high-pressure equipment was designed and constructed by Harwood Engineering Company, Inc., Walpole, Massachusetts. The assembied equipment is shown in Figures 1, 2, and 3, and a schematic representation of it is given in Figure 4. We can best describe this equipment by describing its operation, which is as follows. Close drain valve 4 (see Figure 4) and the valve on handpump 3. Open needle valve 5 and the valves on handpumps 1 and 2, and pump with handpump 3 until the hydraulic fluid begins to escape from release valve 7. This operation brings the piston of the intensifier to the bottom of its stroke and brings the pres- sure on the high-pressure side of the intensifier to 10,000 psi. Next, close the valves on handpumps | and 2, and open the valve on handpump 3. Raise the piston of the intensifier by pumping first handpump 1 until the desired pressure is ob- tained. (Release valve 6 releases at 10,000 psi.) If pressures higher than 10, 000 psi are desired, handpump 2 is used. Handpump 1 was inciuded in the system be- cause of its greater effectiveness in the lower pressure range. Hydraulic fluid escapes from release valve 6 when the Bourdon-type gauge (10, Figure 4) on the low-pressure side of the intensifier reads approximately 10,000 psi. The pres- sure multiplication factor of the intensifier is 16. The pressure on the high- pressure side of the intensifier is measured by a manganin cell* and recorded on a Foxboro Dynalog recorder (11, Figure 4). When the intensifier piston reaches the top of its stroke, the pressure on the high-pressure side will cease to increase as the pressure on the low-pres- sure side increases. In order to continue to increase the pressure on the high- pressure side of the intensifier, a second piston stroke is required. This stroke is accomplished by slowly opening the valve on handpump 2, opening the needle *Manganin is a Cu-Mn-Ni alloy whose electrical resistivity is pressure-sensitive. The manganin element was calibrated by Harwood Engineering Company by a dead weight testing technique, and the pressure reading is accurate to within 0.5 to 1% (at full scale deflection). A novel feature of the present apparatus is the location of the manganin element in a fitting rather than in its own separate pressure vessel. This arrangement, while making the manganin element more vulnerable to damage, simplifies construction and appreciably reduces the ex- pense of the equipment. Arthur A ALittle, Inc. $-7001-0307 FIGURE 1 HIGH PRESSURE APPARATUS (FRONT VIEW) The conductivity bridge is on the left with the bath thermoregulator beneath. The man- ganin cell recorder is set on top of the cabinet of the high pressure producing equipment. The three hand pumps are in the foreground. FIGURE 2 HIGH PRESSURE APPARATUS (REAR VIEW) The shielding has been moved aside to show the bath and the pressure produc- ing equipment. The release valve 7 is just visible in the lower left corner. To the right is the intensifier and the high pressure check valve. The connec- tion containing the manganin cell is partially hidden by the left hand support of the steel plate shielding on the bath. The top of the pressure vessel with its closure in and electrical leads attached is visible over the walls of the bath. Arthur A Little Pre. S-7001--0307 FIGURE 3 THERMOSTATIC BATH Showing cooling unit and thermocouple potentiometer. LNAWNdINOE ONIONGOUd-FUNSSAUd ISd 000 ‘00Z AO WYYOVIC OILLVINAHOS v AYN dWAdGNVH !sd000'0r Eee 8 a 7 dWNdONVH '!s¢ 00001 oO _ iE dWNdGNVH '!sd0000! 22 OIE) ee Esl Ce eee Nee © SNIVA 3SV3135yY JANIVA NOSHO ve JANIWA 3SV313uy {ii se __— NIVYO TASSSA SYNSSAYd OL —S=—_ 4 1739 NINVONVW SNIVA MOSHO @ #3040934 @ 39NVS fy SISISNSLN! SNIWA 310343N func. 4 Arthur DHittle, S-7001--0307 valve 5, closing the valve on handpump 3, and then pumping on handpump 3 until the intensifier piston is returned to the bottom of its stroke, indicated by the re- lease of hydraulic fluid from release valve 7. The second upward stroke is then accomplished by a repetition of the procedure for raising the piston, described above. The pressure can be reduced in a controlled manner by opening drain valve 4. The high-pressure vessel is shown in Figure 5. It is a jacketed or compound cylinder of tapered shrink construction. Since in a vessel of this de- Sign the inner cylinder is in compression and the outer one in tension, very great strength results. Bridgman's "'shrunk-on" method of supporting tapered vessels is based on the same mechanical principle (4) The hydraulic fluid is transmitted through the bottom of the pressure vessel. From the closure, the conductivity cell is suspended in the vessel's cavity, which is 9-3/8 inches in length and 1 inch in diameter. In order to reduce the total volume of fluid which must be compressed, the remainder of the vessel's cavity is filled with a loose-fitting filler-bar. This filler-bar must be crosscut in the bottom to prevent it from acting as a check valve. Figure 6 shows an enlargement of the closure of the pressure vessel. At moderate pressures the mild steel ring and the lead back-up ring extrude and act as seals. One electrical lead is sealed with a cone and is insulated. The closure itself, which is in electrical contact with the remainder of the high=pressure equip- ment, acts as the second lead. The outside lead from the closure must be con- nected to the grounded terminal of the conductivity bridge. 2. Safety Precautions On all sides of the high-pressure apparatus not protected by the equip- ment's steel-plate cabinet, a movable sectional shelf of a ''Homosote"-plywood sandwich was erected. Personnel on the floor above were protected with a 1-inch steel plate mounted on a strong frame directly above the closure. A laboratory shower and additional dry-chemical fire extinguishers were installed, warning signs were posted, and face masks and gloves were provided. As an added safety precaution, a special, less flammable hydraulic fluid was obtained. (See below.) 3. Hydraulic Fluids White gasoline is commonly used as the hydraulic fluid in high-pressure equipment. As a safety precaution, we used a less flammable fluid (Univis P-38) for runs at less than 100, 000 psi. Univis P-38 (Humble Oil & Refining Co.) is an ester=type hydraulic fluid which was developed for military aircraft and large gun recoil mechanisms. Unfortunately, it becomes highly viscous and therefore un- usable above 120, 000 psi. Arthur DUittle Inc. S-7001-0307 | aes } Lp ~Y _ = Kc Ss a } os wey yy 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 thermoregulating 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-type 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 electroiyte .( ) In order to avoid these difficulties, the special capillary-type cell (Figure 8) was designed with an electroiyte-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 electrolyte-filled cell Arthur D Little Inc. S-7001-0307 | ~~ ELECTRODES FILLING PLUG MOVABLE PLUG EXTRACTOR TAP FIGURE 8 13 LIQUID BOUNDARY ELECTRODE SNARL CAPILLARY ELECTRODE SNARL CAPILLARY-TYPE CONDUCTIVITY CELL (GCC-2) Arthur DHittle, Inc. $-7001-0307 14 is insensitive to the exact configuration of the electrode snarls. Another advantage of a capillary-type cell is that the correction of the cell constant for both chang- ing temperature and pressure is relatively simple. Since initial experiments suggested certain useful alterations in the design of the first glass capillary cell, GCC-1, a new cell, GCC-2, was con- structed (Figure 9). The arms of this cell are bridged with a glass brace for added strength. Moreover, the volume of the reservoirs relative to that of the capillary and electrode compartments has been increased, in order to prevent the electrolyte level from falling below the upper electrode when high pressure is applied. In order to reduce polarization, an aqueous chloroplatinic acid-lead acetate solution and procedure described by Creighton(7) were used to platinize the platinum electrodes of both cells. We found that we could not platinize the electrodes of the capillary cell in the cell. Hence the platinum wires were platinized outside of the cell. The cell was then filled with solid NaCl up to the bottom of the upper electrode compartment. The platinized wire was fed into that arm of the cell through plastic "spaghetti, " in order to avoid buckling in the reservoir, and was pushed into the solid NaCl to form the initial kink. Once the initial kink, which prevents the wire from entering the capillary, is formed, the rest of the electrode snarl can be formed without difficulty. The solid NaCl is next removed, and the electrode snarl in the lower electrode compartment formed by feeding the pre-platinized wire in through "spaghetti." D. CONDUCTIVITY BRIDGE A Shedlovsky conductivity bridge(8) with a Wagner earth connection, based on the design of the bridge successfully used at the Sterling Chemistry Laboratory of Yale University for precision electrical conductivity measure- ments, has been constructed. The over-all arrangement of the principal com- ponents is shown in Figure 10, and the details of a Leeds & Northrup Campbell- Shackleton shielded ratio box are shown in Figure 11. Arthur DUittle Inc. S-7001-0307 15 BRACE RESERVOIR ELECTRODE SNARL ELECTRODE SNARL FIGURE 9 CAPILLARY-TYPE CONDUCTIVITY CELL (GCC- 2) Arthur A AUittle Inc. S-7001--0307 16 GENERAL RADIO 397 AMPLIFIER AND FILTER INPUT OUTPUT LEEDS & NORTHRUP. 4754 AC-DC DECADE RESISTOR RCA WO-33A * IOSCILLOSCOPE LEEDS & NORTHRUP 1553 CAMPBELL-SHACKELTON A’ GENERAL RADIO GENERAL RADIO 1203-B 1210-C R-C POWER SUPPLY OSCILLATOR FIGURE 10 CONDUCTIVITY BRIDGE CELL U7/ | OSC | TRANSFORMER DETECTOR FIGURE 11 CONDUCTIVITY BRIDGE, SHIELDED RATIO BOX Arthur A Hittle, Ine. S-7001-0307 18 IV. EQUIPMENT CALIBRATION A, TEMPERATURE MEASUREMENT In order to measure the thermostatic bath temperature to 0.005°C, a copper-constantan thermocouple was constructed. The emf's produced were measured with a Leeds & Northrup Model K-2 potentiometer, and the corre- sponding temperatures read from graphs that have been prepared. Measurements comparing the temperature of the hydraulic fluid in- side of the cavity of the pressure vessel with the temperature of the surrounding oil of the thermostatic bath were made. The results, given in Table I, show that, within the limits of experimental error, the temperature of the conductivity cell immersed in the hydraulic fluid inside the pressure vessel is the same as the bath temperature. Measurements were also made at 0 and 5°C. Within the deviation of the measurement, bath and cavity were at the same temperature. The tem- perature deviations within the bomb were significantly less than those in the bath, due to the thermal inertia of the massive pressure vessel. Measurements dis- closed small (less than 0.5°C) temperature differences between the bottom and surface of the bath at different distances from the heating and cooling elements. TABLE I COMPARISON OF TEMPERATURE IN CAVITY AND BATH (°C) Number of Measurements In Bath In Cavity Ist day 6 24.533 +0.019 6 24.170 + 0.050 10 24.405 = 0.001 8 24.453 + 0.026 24.385 24.405 (AT =+0.020°C) 2nd day 6 24.755 +0.001 7 24.768+ 0.011 5 24.780 + 0.001 24.767 24.768 CME = 4-0001°C) 3rd day 10 24.787 = 0.004 8 24.790 = 0.000 5 24.790 + 0.000 24.789 24.790 (AT = +0. 001°C) 1 52.80 53.75 (MP =0).05°C) 1 54.96 54.10 (AT = -0.86°C) 1 57.78 57 78 (mar = ©,00°C) Arthur D Hittle Inc. S-700 1-0307 ——— 9 B. LEAD CORRECTIONS The measured electrical resistance of the shielded leads from the con- ductivity bridge terminals of the closure is 0.46 + 0.02 ohm. The resistance of the leads of the conductivity cells was calculated from their length and handbook values of the resistivity of No. 24 platinum wire. The lead corrections thus ob- tained for each cell are summarized in Table II. The dependence of the lead cor- rection on temperature and pressure is negligible. TABLE II LEAD CORRECTIONS (25°C) Leads and Length of Total Cell Closure Pt Leads Pt Leads Correction (ohm) (inches) (ohm) (ohm) Teflon Jamieson 0.54 10 OFZ 0.66 (TJC-1) Glass Capillary 0.54 13 0.16 0.70 (GCC-1) Glass Capillary 0.54 11 0.14 0.68 (GCC -2) The resistance of the solution-filled conductivity cell, Re , is given by ROS IR ekg (1) where Ry, is the resistance as measured on the bridge, and L is the appropriate total basis correction from Table II. Go eG SIVAMEMING Considerable shielding and grounding difficulties were encountered, but have been for the most part removed. In particular, the conductivity bridge and the manganin cell recorder were interfering with one another. When the cell is in Arthur D Little, Inc. S$-7001-0307 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, Rm» 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 III CELL STABILITY Deviation in Time the Measured Temperature Solution Cell Period Resistance, Ry, (°C) (M) (hr) (%) 25.05+ 0.03 O.Mok Wen « 19 0.062 25.05+ 0.04 1.00 Kel? GCC-1 2.4 0.012 25.05+ 0.03 0.20 Ka? @6Geil 158 0.007 D7 OL22 O04 0.20 Kc1* GCC-1 18 0.034 DARO MORON 0.10 Kcl° GCC-2 1 0.008 a. In contact with Univis P-38. b. Open to the air. c. 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 .(9) 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 ,(10) Jones Arthur D Little, Inc. S-7001-0307 21 and Bollinger(11) 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 cps 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-1. 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, Re, was calculated from the relation 1 1 : : R Ro Re ©) 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 Reick (3) 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. Arthur D Little Ince. $-7001-0307 De TABLE IV FREQUENCY DEPENDENCE OVER THE RANGE 200 TO 20, 000 cps A. Total Resistance of the Teflon Jamieson Cell (TJC-1) Temperature Electrolyte Total Electrical Resistance, ohms (°C) (M NaHCO3) Outside Bomb Inside Bomb 27.19 £0.08 0.10 43.98 + 0.40 - 27.45 £0.04 0.10 - 43 .56+0.10 (0.96% lower inside oa) X65 10 2 O08 0.010 394.28+0.21 - ME 19 22 © 02 0.010 - 392.01+0.16 . (0.55% lower inside bomb) B. Total Resistance of the Glass Capillary Cell (GCC-1) 27 Ol =O Ol 0.50 236018 EO = Dip OA ORO 0.50 DIST SHO BoM (0.95% lower inside bomb) 27! OO) x2 O07 0.10 7/,, @29) ar BS) = Die ON Gat OR O02 0.10 = 17,000 = 10 (0.42% lower inside bomb) Arthur D Uittle Inc. S-7001-0307 — 23 400 | 0.010M NaHCO3 Soln. (26.18°C) 300 200 nOmAte RESISTANCE (ohms) 100 80 60 SO 40 O.100M NaHCO3 Solin. (27.29°C) 30 20 0.0 0.4 0.8 2 1.6 2.0 24 28 3.2 3.6 4.0 RECIPROCAL OF FREQUENCY (10%/f,cps*) FIGURE 12 FREQUENCY DEPENDENCE OF THE TEFLON JAMIESON-TYPE CELL (TJC-1) Arthur A Hittle, Ine. S$-7001-0307 24 30,000 20,000 O.10M NaHCO3z Soln. (27.00°C) 10,000 8000 TOTAL 6000 RESISTANCE (ohms) 4000 3000 0.50M NaHCO3 Soln. (27.02°C) 2000 1000 © 00 0.4 0.8 12 ° 16 2.0 2.4 28 3.2 3.6 40 RECIPROCAL OF FREQUENCY (107/f,cps') FIGURE 13 FREQUENCY DEPENDENCE OF THE GLASS CAPIDEARY = YPE CELE (GCC=1) ooo eC Se © Sno OsOcORORS j=) Electrolyte (M KCl) .0100 .0100 .0100 ~0100 .0100 .0100 .0100 -0100 .0100 .0100 ~0100 .0100 .0100 .00100 -00100 .00100 - 100 . 100 ~00200 .00200 Temperature (°C) 03 03 00 O1 03 08 00 25.05+ 25.09+ 25.042 25.04~ 25.024 24.984 Daron oOo oe Se © 25.03 0.04 13.0422 18.02+ 19) G22 18.09+ 18.05+ ie 9 Ont .05 oaldl 00 09 06 O1 S2OROFOR OSE 17.99+ 0.07 18.08+ 0.14 18.09+ 0.01 17.99+ 0.08 18.05+ 0.04 1, Ose 0.283 18.19+ 0.09 18.14% 0.04 17.98 0.01 17.90+ 0.10 17.94 0,04 TABLE V RESISTANCE INSIDE AND OUTSIDE THE BOMB Total Resistance, ohms In Bath 145102 == OLO 141.28 *0.02 141,.28+0.03 IAN Oil 2002 TAL QD =O, 10 In Bomb 141,21 0.08 141,27 =0.02 141.29+0.01 141.26 + 0.03 (same in bomb and bath) 159,.94£0.19 159.86 + 0.02 159.88 + 0.04 159.89 + 0.03 159.59 +0.05 159.59 + 0.03 159.41 +0.18 159.53 + 0.08 235) Number of Measurements NwWawu uv & e Ut Ov CO NI CF (0.23% smaller in bomb than in bath) 1480.14 + 0.47 1477.68 + 0.09 1478.91 41.23 1479.53 + 0.04 1479 .53 (same in bomb and bath) 17.89+0.01 7) ot) (0.45% smaller in bomb than in bath) 730807, == ONS 730.07 (0.22% smaller in bomb than in bath) 17.81 +0.03 4 6 17 Bil 728.46+0.01 3 8 728.46 Arthur D Little Inc. S-7001-0307 26 TABLE VI REDUCTION OF MEASURED RESISTANCE Total Resistance % Reduction Electrolyte Cell in Bomb in Bomb (ohms) KCl TJC-1 18 0.45 NaHCOo3 ea 44 0.96 KCl TjJC-1 141 0.00 KCl wGell 160 0.23 NaHC03 TJC-1 392 0.55 KCl TjJC-1 728 0.22 KCl MiGoll 1, 480 0.00 NaHC0O3 GCC-2 Dey B39 7, | 0.95 NaHCO3 GCC-2 17, 629 0.42 0.42 + 0.27 Arthur D Little Inc. S-7001-0307 27 In order to measure Rg directly, the resistance of the cell (TJC-1 filled with 0.1 M KCl) in the pressure vessel was measured with an ohmmeter (the bridge could not be balanced) with the grounded lead between the closure and the cell electrode disconnected. The measured resistance was 5000 to 5700 ohms, corresponding to a value of C of 280 to 320. This was considered good agreement. The variation of C with pressure cannot be measured, but is presum- ably negligible. In the pressure runs, the cell constant at 1 atmosphere is cal- culated directly from R¢ and the value of C determined by measurements inside and outside the bath using the appropriate electrolyte (the manner of calculating cell constants is discussed in greater detail below). The cell constants at given pressures are then calculated on the basis of this cell constant. Thus C becomes absorbed in the cell constant, and the value of the specific conductance becomes very insensitive to the value of C. For example, for 19.376°/o0o0 chlorinity sea water at 4.82°C, with cell GCC-2, the measured value of C is 125, and at a pressure of 20, 000 1b/in.2 the corresponding value of the specific conductance is 0.03811 ohm-! cm™!, If the value of C is increased fivefold to 600, the specific conductance be- comes 0.03816 ohm=!cm7-!, a change of only 0.13%; and if C becomes infinite, the specific conductance becomes 0.03817 ohm~! cm= F, PLUG POSITION AND LIQUID LEVEL EFFECTS Although the movable plug of the Teflon Jamieson cell (TJC-1) is located remotely from the electrodes (see Figure 7), there is a detectable influence of plug position on the measured resistance (12) This effect was measured at 25.2°C and 1 atmosphere, and the following relationship was found to obtain: SR (1 + 0.00262 d) (4) where Re is the resistance of TJC-1 when the lower end of the plug is flush with the lower end of the cell's wall, and d is the displacement (in inches) of the plug. As the pressure is increased, the electrolyte in the cell is compressed and the plug is displaced. Assuming that the variation in cross sectional area of the cell with pressure is negligible, equation (4) can be rewritten in terms of pressure as Ri gow - 0.0105 k'P) (5) where the pressure, P, is in atm and k’ is the mean compressibility of the elec- trolyte in atm7!, When the electrolyte is water, at 20, 000 lb/in.2 the denomi- nator on the right of equation (5) has the value 0.993. Arthur D Little, Inc. S-7001-0307, ae 28 At 25°C, and with 1.0 MKCl as electrolyte, the measured total re- sistance of the glass capillary cell GCC-2 varied by less than 0.003% as the electrolyte level in the cell was varied from the top to the bottom of the reser- voir. Inasmuch as this error lies within the experimental deviation, the con- clusion is drawn that the measured resistance is independent of the position of the hydraulic fluid-electrolyte interface in the capillary-type cell. G, DETERMINATION OF CELL CONSTANTS Cell constant measurements were made with the cells both in the bath and within the pressure vessel. Measurements and computations involving KCl were based on the procedures and results of Jones and Bradshaw, (13) while for NaCl and sea water the cell constants were computed from the specific conduct- ances reported by Chambers, Stokes, and Stokes, (14) and Thomas, Thompson, and Utterback.(15) The results of these measurements are summarized in Table VII. In the case of the Jamieson cell (TJC~-1), the measured cell constant was only in fair agreement with that calculated from cell dimensions, probably due to the nonparallelism of the electrodes; in the case of the glass capillary cells (GCC-1) and (GCC-2), the agreement was good. The deviations in cell constant in Table VII are somewhat greater than is desirable in conductivity measurements of the highest precision. Also, for GCC-2, the values determined using KCl are about 8% greater than the val- ues determined using sea water or 0.500 MNaCl. In the case of GCC~-2, the large cell constant and the upper limit of the conductivity bridge's capacity pre vents cell constant determinations using dilute KCl solutions. Because of these difficulties and the spurious parallel resistance effect discussed above, in order to get entirely self-consistent results and to make the present results compatible with the 1 atmosphere values now being used by oceanographers, we decided to base our calculations on cell constants as determined immediately before and after each pressure run and using the electrolyte of the run. In the case of the sea water run, this procedure makes the correctness of the specific conduct - ances we report contingent upon the 1 atmosphere values reported by Thomas, Thompson, and Utterback.(15) The accuracy of the results of Thomas, Thompson and Utterback has been questioned on several occasions. In particular, Pollak(16) has suggested that their results may be in error due to a Parker effect. In the event that more accurate values for the specific conductance of sea water become available, the values which we report for specific conductances can be readily corrected simply by multiplying by the factor K,/Kjty» where K, is the new value of the specific conductance and K;ty is the value reported by Thomas, Thompson, and Utterback at the same chlorinity and temperature. The values of the constants in the em- pirical equations which we will generate subsequently for expressing the specific conductance at elevated pressure in terms of the 1 atmosphere value will be un- affected, inasmuch as the above correction factors out. Arthur D Little, Inc. $-7001-0307 CELL CONSTANT DETERMINATIONS Cell Temperature (°C) TJC-1 0.93+ 0.03 Solita O12 15 A702 O02 1E.2C O10 IB20 O05 18.03+ 0.07 18.20+ 0.10 25 .00+ 0.02 25 .00+ 0.00 Zon O02 O03 25.03+ 0.06 DS O22 O10 25.40+ 0.05 25.06+ 0.02 25,0022) 0/011 25 O22 O02 25.13+ 0.09 25 .40+ 0.05 BS OO O08 85 2022 ©, ii 4498+ 0.03 GCC-1 25.25+ 0.04 DB W522 O02 25.60 0.00 25.004 0.08 TABLE VII Electrolyte 19.376°9/o00 sea water 19.376°/o00 sea water 19.376°/o00 sea water 0.001 0.002 0.010 0.100 19, 3769/00 sea water 0.010 0.010 0.010 0.010 0.010 0.020 0.100 0.200 0.200 1.00 1.00 0.010 0.010 0.010 0.100 1.00 1.00 M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl M KCl 29 Cell Constant (cm-l 0. OF 198 6 SIL 178 B95 nl), 194 200 200 5 MSY, »185 ol L95 6 IOS) ~ 193 sl) 205 203 187 184 88 90 45 43 oO Oo 8 2 2 98 2 2eo2 © 6&6 ©o@ Oo Co Oo 2G Oo © CG CO I \o 75 79 79 216 227 0.193+0.0 0.196 + 0.004 Arthur D Uittle, Inc. S-7001-0307 ~-- +e. 30 Cell GCC-2 Temperature pes Chm So oS 2 oOo © (°C) 18 0. PTE Os 08 =O. 00 0. 0 = 0. 2 ON = Og LEO. OLE O, 568 2 0. 03 = 0. .00 +0 O1z 0; 23 £0. .06£0 AO 0, OO; R950 05 10 07 00 02 06 20 14 02 15 10 02 02 07 02 05 08 -O1 TABLE VII (Continued) Electrolyte 19 .3760/00 sea water 19.3760/o00 sea water 17.619/o0 sea water 9.68°/00 sea water 1.00 M KCl 19.376 9/oosea water 17.61°9/00 sea water 9.68°/00 sea water 17.61°/o00 sea water 9.68°/00 sea water 0.100 MKC 19.376 °/oo sea water 19.376 °/oo sea water 17.61°/o0 sea water 9.68°/00 sea water 0.100 M KCl 1.00 M KCl 0.400 M NaCl (cm!) 164 164 165 163 165 164. 162. 165. 96 oil IOs 7/2 OY) 0 6 7D ¢ 166. 180 164 167 168 166 7) 0 WO Lien AROS 01 9 7/7) (0) I/O) < Il 38) 9) 1 2 NOS} (0) 22 kos) Josea Arthur DULittle Inc. S-7001-0307 ———=_=_[_[_— sO C—~—SC—C 31 Due to limitations of time, we were unable to perform a complete check on the work of Thomas, Thompson, and Utterback, although there ap- pears to exist enough question concerning their work to warrant its repetition with carefully designed conductivity cells. H. PRESSURE DEPENDENCE OF CELL CONSTANTS The geometrical dimensions of the conductivity cells and hence their cell constants will vary as the hydrostatic pressure exerted on the cells is var- ied, due to the compressibility of the materials of which the cells are constructed. The electrodes in the Jamieson cell are remote from the ends of the cylindrical cell, and, as a consequence (except for the effect of the position of the movable plug, discussed above), will have a negligible influence upon the value of the cell constant. Figure 14 represents a cross section of this cell in the region of the electrodes. The inside radius of the cell is r, the distance between the parallel plate electrodes is d, the surface area of the electrodes is A (A= S2, where S is the length of the edge of the square electrode surfaces), and e is the length of the leads from the electrodes to the cell walls. Now d = 2r - 2e (6) The linear compressibility, At /4,, of platinum at 30°C given by the International Critical Tables(17) is 6 12 2 Mbp = Od 10 = 0.68% 10 2, (7) where P is the pressure in atmospheres . The linear compressibility of Teflon may be approximated by 1/3 of the volume compressibility, (A V/V). Thus (6) becomes d, = 2r, (1 - 1/3 (AV/V) - 2e, (1 - 0.124 x 10° P +0.63 x 1 1) (8) and the cell constant becomes -6 51D Bey |b 1/3(AV/V)| -2e,(1-0.124x10" P+ 0.68x10 "P*) gy k SsS——> SS ep [s, (1 - 0.124 x 10°°P + 0,63 x 10 7p”) 2 Arthur D Little Inc. wit (SOON O20 Tall alah FIGURE 14 JAMIESON CELL, CROSS SECTION 33 The elastic properties of platinum change by less than 0.01% per degree centigrade; therefore, the temperature dependence of A4/{ has been ignored. Unfortunately, the behavior of Teflon under compression appears to be complex, involving a 2.3% contraction in volume at 5000 atm at room temperature (17, 18,19, 20) The pro- posed phase diagram for Teflon is shown in Figure 15. Values of A V/V for Teflon at the appropriate pressures and temperatures were read from a plot of the data of Weir(21) (Figure 16). Over the pressure range of our experiments, changes due to change in the dimensions of platinum parts were relatively small, so when S and r are expressed in cm, equation (9) becomes ky = 2x, fi - 1/3 avn | = i OW7 (10) As mentioned above, r 1 was determined from conductivity measurements imme- diately prior to the application of pressure. Examination of the results summarized in Tables IX to XI (see Section VI) shows that the variation with pressure of the constant of TJC-1 is quite appreci- able and represents about a 6% decrease at 30, 000 Ib/in.2,. In the case of the glass capillary cell, the USS SLE depend nee of phen cell constant takes a very simple form i ( os we Biehl SD QO Loo NUR Pw oY & ( 9 \ i Fe CL sue 10 P), (11) where P is now in lb/in.2. When P is expressed in bars the constant becomes 1.57x 107°, In contrast with the pronounced pressure dependence of the Teflon cell constant, the constants for the glass cells increase only a few tenths of a percent at 20, 000 lb/in.2 Although the Teflon and glass cells have entirely different pressure dependencies of their cell constants, results obtained with these two types of cells were in surprisingly good agreement (see Figure 22). I, EQUILIBRATION In our first experiment the electrical resistance of a 0.010 M KCI solu- tion was measured as the pressure was continuously varied from 15 to 100, 000 lb/in.2 and back to 15 lb/in.2. The pressure was varied rapidly, and the run was completed in about two hours. Serious hysteresis was observed (Figure 17); that is, the curve did not retrace itself as the pressure was decreased. This hysteresis was attributed to failure of the system to thermally equilibrate. This possibility was experimentally checked and confirmed. Arthur D Little Inc. S-700 1-0307 34 The heat of compression of a fluid dQ am dv (#) oG a T P is usually positive; thus, heat is released when a fluid is compressed and ab- sorbed when the fluid is allowed to expand. If compression or expansion is © rapid, and heat conduction into the surroundings is slow, then the process will be an adiabatic one, and the temperature will increase or decrease, respec- tively .* In the present experiments, rapid compression will result ina momentary increase of temperature and a corresponding transient decrease of measured electrical resistance (see Figure 18); rapid decompression will give rise to a transient increase of resistance (see Figure 19). These experiments indicated that re-establishment of thermal equilibrium requires about 20 min- utes. In all subsequent experiments, resistance readings were made following each pressure change until a constant was obtained. Arthur D ULittle, Ine. ___ $ 7001-0307 _ 35 PRESSURE 7 (103 atm) 4 Oo 10 20 30 40 50 60 70 80 90 TEMPERATURE (°C) (EN PRR TI SR RTE ET TIGR BT TE CE TF SET FIGURE 15 PROPOSED PHASE DIAGRAM OF TEFLON (C. E. Weir, J. Research Nat. Bur. Standards, 50, 95 (1953)) Arthur MD Hittle Ine. $-7001-0307 36 COMPRESSION (-AV/V; ) 0.16 0.14 O12 010 0.08 0.06 0.04 002 000 — O 2000 4000 6,000 8000 10000 PRESSURE (atm) FIGURE 16 RELATIVE VOLUME CHANGES FOR TEFLON (C. E. Weir, J. Research Nat. Bur. Standards, 53, 245 (1954)) 37 140 O.O10M KCI in TUC-1, 1000cps, 25.0°C 130 120 | TOTAL RESISTANCE (ohms) 110 100 90 | O 20000 40,000 60,000 80.000 100,000 PRESSURE (Ibs/in?) O 1000 2000 3000 4000 5000 6000 PRESSURE (bars) FIGURE 17 HYSTERESIS DUE TO FAILURE OF SYSTEM TO THERMALLY EQUILIBRATE Arthur D. Little Inc. S$-7001-0307 38 130 128 O.OIOM KCl in TJC-1, 1000cps, 250°C 10,000 Ibs/in2 Towa, UN RESISTANCE (ohms) a 112 20,000 Ibs/in2 60,000 Ibs/in? TIME (minutes) FIGURE 18 EQUILIBRATION TIME AT PRESSURE - PRESSURE APPROACHED FROM ABOVE 39 10,000 Ibs/in@ 20,000 Ibs/in® TOTAL RESISTANCE (ohms) O.010M KCL in TJC-1, 1000cps, 35.2°C 50,000 Ibs/in? O 5 10 15 20 TIME (minutes) FIGURE 19 EQUILIBRATION TIME AT PRESSURE - PRESSURE APPROACHED FROM BELOW Arthur D.Little Pune. S-7001-0307 40 V. THE EFFECT OF PRESSURE ON THE ELECTRICAL CONDUCTIVITY OF AQUEOUS POTASSIUM CHLORIDE SOLUTIONS The molal conductance of an aqueous solution 0.010 m in KCl wee measured at 25, 35, and 45°C over the pressure range 15 to 100, 000 Ib/in .2 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/in.2 the present results are in satisfactory agreement with the results reported earlier by Hamann aud, Strauss .(23) Discrepancies in the two sets of data appear above 60, 000 ib/in. 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: 1. Our 25°C curve more closely paralleis 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 KCi with pressure is initially in agreement with the relative change in resistance measured by Adams and Hail .(24) With respect to the latter consideration, Adams and Hail, 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 26, 800 lb/in.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 (1/ ( Ap/ Ay)- Until the variation of the cell constant with pressure becomes significant, the in- itial slopes of Rp/Ry and Ay/ Ap should be the same. Up to 5000 lb/in. 2a plot of the present values of A\4/ Ap ae 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’ Arthur DAittle Inc. S-7001-0307 41 values of Ay/ Ap versus P has a slope whose absolute value is one half the value of the other two plots. Hamann and Strauss mention that their results also differ (by several percent at 10,000 atm) from those of Zisman, (25) and they attribute this discrepancy to contamination of Zisman's solutions by direct contact with his kerosene pressure fluid. The conductance of KCl first increases with increasing pressure, goes through a maximum at about 30, 000 lb/in.2, and then decreases (see Figure 21). Solutions of other strong salts show similar behavior .(25) Hamann attributes the initial increase to the increase in the number of ions per unit volume as the solu- tion is compressed, and the subsequent decline to decreasing ionic mobility with increasing viscosity of the solvent .(12, 23) we shall see subsequently that this explanation is probably an oversimplification . Arthur D Little, Inc. S-7001-0307 42 220 200 180 160 MOLAL CONDUCTANCE 140 (gm-ohm--cm-mole~') 120 100 O G. JONES AND B.C. BRADSHAW, J. Am.Chem. Soc.,55, 1780 (1933) X H.E.GUNNING AND A.R. GORDON, 7 J. Chem. Phys., 10,126 (1942). eo 10 20 30 40 TEMPERATURE (°C) FIGURE 20 MOLAL CONDUCTANCE OF AQUEOUS 0.010 m KCl SOLUTIONS 50 (1b/in .2) 15 5, 000 10, 000 15, 000 20, 000 30, 000 40, 000 50, 000 60, 000 70, 000 80, 000 90, 000 100, 000 TABLE VIII 43 MOLAL CONDUCTANCE OF 0.010 m KCl SOLUTIONS* Pressure (bars) .1.03 (atm) = = = 11 Molal Conductance in gm-ohm "sem anole (25°C) 141 145 150 155 ilsy7/ 158 US 155 (35°C) 170 (45°C) 199 *For dilute solutions, molality and molarity are approximately equal. Arthur DLittle Ine. S-7001-0307 44 220 2004 180] MOLAL CONDUCTANCE (gm-ohm“-cm7'- mole”) 160 140% O PRESENT RESULTS X S.D. HAMANN AND W. STRAUSS Trans. Faraday Soc., 51,168 (1955) 80,000 100,000 20,000 40,000 60,000 PRESSURE (Ibs/in*) O 1000 2000 3000 4000 5000 6000 PRESSURE (bars) FIGURE 21 MOLAL CONDUCTANCE OF 0.010 m KCl SOLUTIONS 45 VI. THE EFFECT OF PRESSURE ON THE ELECTRICAL CONDUCTIVITY OF SEA WATER The standard sea water used in the present experiments was P39 (8/1/61), obtained from the I.A.P.O. Standard Sea Water Service of Charlottenlund Slot, Denmark. Its chlorinity, Cl, was 19.376°/o0; its salinity, S, calculated from the definition(26) J 2 O08 = (S05) Cll, (13) was 35.00°/o00. In addition, sea water solutions of 17.61°/o00 and 9.68 °/o0o0 chlorinity (31.81°/o0 and 17.50°/oo salinity) were prepared by weight dilutions . Inasmuch as deionized water of specific conductance less than 1 x 10-9 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 ib/ 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 Ib/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 AK/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. Arthur D Little Ine. S-7001-0307 ~ ewes vou 46 TABLE IX SPECIFIC CONDUCTANCE OF 19.376°/00 CHLORINITY SEA WATER Cell Specific Pressure Resistance Constant, k Conductance, K (1b/in .2) (bars) (ohms) (cm7l) (ohm=lem-1) Run No. 8, 0.93 + 0.03°C, TJC-1 Sells .1,03 7.18 0.216 0.0301 4,500 310 6.78 0.213 0.0314 8, 000 550 6.52 0.209 0.0321 12, 000 827 6.24 0.208 0.0332 15, 000 1, 030 6.12 0.207 0.0338 20, 000 1,380 5.92 0.206 0.0349 RIM INO. Wil, Oi 2 OWS, GEe-2 15 1.03 5630 164.0 0.02913 5, 000 344 5396 164.1 0.03034 10, 000 689 5228 164.3 0.03143 15, 000 1, 030 5100 164 .4 0.03224 20, 000 1,380 5043 164.5 0.03268 25, 000 1, 720 4973 164.6 0.03310 RUM NO> O, Soli 2 O.19G, IjiCGeal 15 1.03 6.77 0.227 0.0335 2, 000 138 6.97 0.224 0.0341 4,000 276 6.36 0.222 0.0349 6, 000 413 6.21 0.221 0.0356 8, 000 551 6.08. 0.219 0.0360 10, 000 689 5.94 0.218 0.0367 12, 000 827 5.82 0.217 0.0373 14, 000 965 5.74 0.216 0.0377 16, 000 1, 100 5.67 0.216 0.0381 18, 000 1, 240 5) OS) 0.215 0.0388 20, 000 1,380 5.00 0.214 0.0389 25, 000 1, 720 5.39 0.214 0.0397 30, 000 2,070 5.28 0.213 0.0403 25, 000 1, 720 5.41 0.214 0.0396: 22,500 1,550 5.43 0.214 0.0342 21, 000 1, 480 3.47 0.214 0.0389 19, 000 1,310 cos 0.214 0.0393 13, 500 930 5.70 0.216 0.0379 15 1.03 6.77 0.227 0.0335 Arthur D Aittle, Inc. S-7001-0307 47 TABLE IX (Continued) Cell Specific Pressure Resistance Constant, k Conductance, K (1b/in. 2) (bars) (ohms) (cm=1) (ohm-! cm-!) Run No. 12, 4.82 +0.06°C, GCC-2 15 1.03 4960 165.1 0.03329 2, 000 138 4870 165.2 0.03392 _ 4, 000 276 4786 165.2 0.03452 5, 000 344 4738 165.2 0.03487 6, 000 413 4668 165.3 0.03541 — 8, 000 551 4631 165.3 0.03569 9, 500 654 4576 165.3 0.03612. 10, 000 689 4580 165.4 0.03611~ 12, 000 827 4491 165.4 0.03683 * 14, 000 965 4444 165.4 On03722 16, 000 1, 100 . 4409 ml 165.5 0.03754 ~ 18, 000 1, 240 4380 165.5 0.03778 20, 000 1,380 4345 165.6 0.03811 15 1.03 4958 165.1 0.03330 RuniNow7alsa920) 0026 amy 15 1.03 4.59 0.198 0.0432 3, 000 207 4.46 0.194 0.0435 6, 000 413 4.32 0.192 0.0445 9, 000 620 AD) 0.190 0.0451 12, 000 827 4, 1 0.188 0.0457 15, 000 1, 030 - 4,03 0.186 0.0461 18, 000 1, 240 3.96 0.185 0.0467 20, 000 1,380 3.91 0.185 0.0473 40, 500 2,790 307 0.184 0.0489 Run No. 13, 15.04£0.01°C, GCC-2 15 1.03 3880 166.7 0.04300 2, 000 138 3805 166.7 0.04381 4, 000 276 3733 166.8 0.04468 6, 000 413 3685 166.8 0.04526 8, 000 551 3640 166.9 0.04585 10, 000 689 3604 166.9 0.04631 12, 000 827 3577 166.9 0.04666 14, 000 965 3545 167.0 0.04711 16, 000 1, 100 3525 167.0 0.04738 20, 000 1, 380 3492 oye 0.04785 Arthur D Little, Inc. $-7001-0307 ~ wwe vy 48 TABLE IX (Continued) Cell Specific Pressure Resistance Constant, k Conductance, K (1b/in.2) (bars) (ohms) (cm7!) (ohm-! cem-1) Run No. 10, 24.914+0.02°C, GCC-2 15 1.03 3160 167.1 0.05288 2, 000 138 3115 167.1 0.05364 5, 000 344 3075 167 .2 0.05437 6, 000 413 3072 167.2 0.05443 7, 900 517 3054 167.2 0.05475 9, 000 620 3032 167.2 0.05515 10, 000 689 3015 167.3 0.05549 12, 000 827 3003 167.3 0.05571 14, 000 965 2988 167.3 0.05599 16, 000 1, 100 2976 167 .4 0.05625 18, 000 1, 240 2966 167.4 0.05644 20, 000 1,380 2953 167.5 0.05672 Arthur D Uittle Inc. S-7001-0307 49 TABLE X SPECIFIC CONDUCTANCE OF 17.61°/o00 CHLORINITY SEA WATER Cell Specific Pressure Resistance Constant, k Conductance, K (1b/in. 2) (bars) (ohms) (cm-l) (ohm>lcm-!) Run No. 21, 0.08 £0.07°C, GCC-2 15 1.03 6175 165.0 0.02672 2, 000 138 6080 165.0 0.02714 4, 000 276 5985 165.1 0.02759 6, 000 413 5885 165.1 0.02805 8, 000 551 5785 165.2 0.02856 10, 000 689 5695 165.2 0.02901 12, 000 827 5615 165.2 0.02942 14, 000 965 5945 165.3 0.02981 16, 000 1, 100 5490 165.3 0.03011 18, 000 1,240 5440 165.4 0.03040 20, 000 1,380 5410 165.4 0.03057 RuniNow 20) 5-01 3052026, GEC=2 15 1.03 5420 165.9 0.03060 2, 000 138 5320 165.9 0.03118 4, 000 276 5222 166.0 0.03179 6, 000 413 5135 166.0 0.03233 8, 000 Sol 5060 166.1 0.03283 10, 000 689 4995 166.1 0.03325 12, 000 827 4952 166.1 0.03354 14, 000 965 4926 166 .2 0.03374 16, 000 1, 100 4875 166 .2 0.03409 18, 000 1, 240 4865 166.3 0.03418 20, 000 1, 380 4825 166.3 0.03447 25, 000 1,720 4789 166.3 0.03473 30, 000 2, 070 4775 166.5 0.03487 40, 000 2,760 4790 166.7 0.03480 Arthur DAittle, Inc. S-7001-0307 50 TABLE X (Continued) Cell Specific Pressure Resistance Constant, k Conductance, K (1b/in .2) (bars) (ohms) (cm*1) (ohm>! cm-1) Run No. 18, 15.01+0.02°C, GCC-2 15 1.03 4246 162.8 0.03833 2, 000 138 4184 162.8 0.03891 4, 000 276 4134 162.9 0.03940 6, 000 413 4093 162.9 0.03980 8, 000 551 4063 163 .0 0.04012 10, 000 689 4029 163 .0 0.04046 12, 000 827 4002 163 .0 0.04073 14, 000 965 3975 163.1 0.04103 16, 000 1, 100 3951 163.1 0.04128 18, 000 1, 240 3926 163 .2 0.04157 20, 000 1,380 3902 163 .2 0.04182 Run. No. 22, 24'.83,= 0.07°C, GCGC-2 15 1:03 3455 168.0 0.04963 2, 000 138 3422 168.0 0.04909 4, 000 276 3387 168.0 0.04965 6, 000 413 3356 168.1 0.05009 8, 000 551 3324 168.1 0.05057 10, 000 689 3297 168 .2 0.05102 12, 000 827 3271 168.2 0.05144 14, 000 965 3249 168 .3 0.05180 16, 000 1, 100 3230 168.3 0.05211 18, 000 1, 240 3217 168 .4 0.05235 20, 000 1,380 3207 168.5 0.05254 25, 000 1,720 3187 168.5 0.05287 30, 000 2, 070 3180 168 .6 0.05302 Arthur D Little, Inc. S-7001-0307 51 TABLE XI SPECIFIC CONDUCTANCE OF 9.68 2/00 CHLORINITY SEA WATER Cell Specific Pressure Resistance Constant, k Conductance, K (Ib/in.2) (bars) (ohms) (cm=1) (ohm=+cm7!) Run No. 15, 0.00 £0.00°C, GCC-2 15 1.03 10653 163.9 0.01539 2, 000 138 10475 163 .9 0.01565 4, 000 276 10275 164.0 0.01596 6, 000 413 10090 164.0 0.01625 8, 000 551 9925 164.1 0.01653 9, 000 620 9840 164.1 0.01668 10, 000 689 9760 164.1 0.01681 12, 000 827 9625 164.1 0.01705 14, 000 965 9510 164.2 0.01727 16, 000 1, 100 9420 164.2 0.01743 18, 000 1, 240 9340 164.3 0.01759 20, 000 1,380 9280 164.3 0.01771 Run No. 17, 4.94 +0.14°C, GCG-2 15 1.03 9272 164.9 0.01779 2, 000 138 9100 164.9 0.01812 4, 000 276 8950 165.0 0.01844 6, 000 413 8830 165.0 0.01869 8, 000 551 8700 165.1 0.01898 10, 000 689 8575 165.1 0.01925 12, 000 827 8470 165.1 0.01949 15, 000 965 8330 165.2 0.01983 16, 000 1, 100 8300 165.2 0.01990 18, 000 1, 240 8240 165.3 0.02006 20, 000 1,380 8200 165.3 0.02016 Arthur DLittle, Inc. S-700 1-0307 52 TABLE XI (Continued) Cell Specific ____Pressure = Resistance = Constant, kK © Conductance, K (1b/in .2) (bars) (ohms) (cm71) (ohm~! cm=!) Run No. 16, 14.83 +0.15°C, GCC-2 15 1.03 7217 165.2 0.02289 2, 000 138 7124 165.2 0.02319 4, 000 276 7038 165.3 0.02349 6, 000 413 6960 165.3 0.02375 8, 000 551 6875 165 .4 0.02406 9,,000 620 6845 165.4 0.02416 10, 000 689 6810 165.4 0.02429 12, 000 827 6735 165 .4 0.02456 14, 000 965 6675 IOS) of) 0.02479 16, 000 1, 100 6620 OD) o®) 0.02500 18, 000 1, 240 6575 165 .6 0.02519 20, 000 1,380 6530 165 .6 0.02536 Run No. 14, 25.06 +0.02°C, GCC-2 15 1.03 5861 166.6 0.02843 2, 000 138 5798 166 .6 0.02873 4, 000 276 5740 166.7 0.02904 6, 000 413 5690 166.7 0.02930 8, 000 Sol 5640 166.8 0.02957 10, 000 689 5596 166.8 0.02981 12, 000 827 5562 166.8 0.02999 14, 000 965 5530 166.9 0.03018 16, 000 1, 100 5477 166.9 0.03036 18, 000 1, 240 5468 167.0 0.03054 20, 000 1;380 5447 167.0 0.03066 Arthur DULittle Inc. S-7001-0307 33 15.04°C 15.20°C SPECIFIC CONDUCTANCE (ohm-'cm-') O 5,000 10,000 15,000 20,000 25,000 30,000 PRESSURE (!bs/in®) O 500 1000 1500 2000 PRESSURE (bars) BSE SC cn Pt Se ALA UNE SPRMNEN RAE ROE YES ORAL OLN POG SILL ED A TRIM STA Baa IE Ba IE TSR SL DTI ss EO a PE TT ES a SE) FIGURE 22 SPECIFIC CONDUCTANCE OF 19.376°/o00 CHLORINITY SEA WATER Arthur D.Little Ine. S-7001-0307 54 F 24.83°C 0.050 0.045 —O 15.01°C 0.040 } SPECIFIC CONDUCTANCE (ohm-1cm-1) 0.035 | 0,025 (0) 5,000 10,000 15,000 20,000 25,000 PRESSURE (Ibs/in*) O 500 1000 1500 PRESSURE (bars) I ES case SER NNER SOS SORT EE A SOO ICRU TST SE SNS IER SCIEN Se IT] FIGURE 23 SPECIFIC CONDUCTANCE OF 17.69/00 CHLORINITY SEA WATER 55 0.035 0.030 = O 25.06°C SPECIFIC CONDUCTANCE 0.025 (ohm-! cm-") —. 14.83°C 0.020 | 0.015 0 5,000 10,000 15,000 20,000 25,000 PRESSURE (Ibs/in*) O 500 1000 1500 PRESSURE (bars) FIGURE 24 SPECIFIC CONDUCTANCE OF 9.69/00 CHLORINITY SEA WATER Arthur A Aittle Inc. S-7001-0307 56 TABLE XII SLOPES OF SPECIFIC CONDUCTANCE VERSUS PRESSURE CURVES Run No. Temperature (°C) 19.376 °/oo Chlorinity Sea Water 8 0.93 £0.03 11 MOi8 0.08 9 Si 22 O12 12 4.82 + 0.06 7 15,20) = © 02 13 15.04 £0.01 10 24.91 40.02 17.61°/o00 Chlorinity Sea Water 21 0.03 2 0.07 20 5.01 £0.20 18 SMO ORO2 oy) DGB 22 O07 9 .68°/o0 Chlorinity Sea Water 15 0.00 +0.00 17 4,.94$0.14 16 14.83 £0.15 14 25.06 £0.02 AK/A P (ohm=!em=lb= lin 2) 7 7 60 x 10. 36x 10° 27 .20 x 10 =] -98 x 10 Ae 10 ! =F -00 x 10 “Y 53 x 10 mS Co RS mS CO Tf i) B= 10 2 Koopa lone sss 2 a7 -38 x 10 1 oe SS SS) 2.43 +0.23 x 10° 1A 10° e710 ! 1.44x 10” 10x 10 © Hp 2 OA x ig 7 1.45 +0.06 x 10°! Arthur D Uittle Inc. __$-7001-0307 _ 57 S12 3.0 | 28 26 24 SLOPE AK/APX107 22 (ohm-'cm-"Ibsin2) 20 | SLOPE =1.17X1078 18 CHLORINITY (9/00) FIGURE 25 VARIATION OF SLOPE WITH CHLORINITY OF SEA WATER Arthur A Hittle Inc. S-7001-0307 58 Over the pressure range 15 to 10, 000 lb/ in.2, the observed results can be represented by a simple empirical relation Soa = Sime * Sake ) that is to say, the specific conductance at any pressure in this range can be cal- culated from the value at 1 atmosphere and the same temperature and chlorinity and an additional term which is the product of a constant (for a given chlorinity) and the pressure. With a further sacrifice in accuracy but gain in generality, in- asmuch as this constant, Cc; or AK/AP, appears to be a linear function of chlo- rinity, equation (15) can be rewritten -8 ; Ko Tcl = Kitci te oily x 1@ “El P (16) where P is the pressure expressed in lb/in.2. Although it is less accurate than the original data, we believe that expression (16) will be of considerable practical use to oceanographers. Equation (16) probably can be extended within reasonable limits beyond the temperature (0 to 25°C) and chlorinity (9.68 to 19.376 9/00) ranges of the present experiments; however, it becomes increasingly inaccurate as the pressure is extended beyond 10, 000 Ib/in a As the sea water is subjected to pressure, due to its compressibility its volume will decrease, and thus the concentration of the electrolytes it contains will increase. The specific conductance of a solution increases with increasing concentration of electrolytic solute; however, as Table XIII and Figure 26 show, the observed increase in specific conductance with pressure is much greater than one would expect simply on the basis of the decreased volume of the solution. (27) TABLE XIII COMPARISON OF CALCULATED AND OBSERVED SPECIFIC CONDUCTANCES — (19.376 chlorinity, 35.03 salinity sea water at 0°C) From From Empirical % Compress~ % Pressure Observed Expression Deviation ibility Deviation (1b/in 2) (bars) iN5) 1 0.02906 0.02906 = 0.0291 = 5, 000 340 0.03020 0.03038 0.6 0.0295 2.3 10, 000 690 0.03125 0.03171 1.4 0.0297 Soil 15, 000 1, 000 0.03218 0.03303 2 (6) 0.0299 Tod 20, 000 1, 400 0.03325 0.03436 4.5 0.0301 9.6 a. Observed data extrapolated to 0.0°C. Arthur D.Hittle, Ine. S-7001-0307 SPECIFIC CONDUCTANCE (ohm-' cm-") 59 0.034 0.033 0.032 OBSERVED 0.031 0.030 CALCULATED FROM COMPRESSIBILITY DATA 029 me O 5,000 10,000 15,000 20,000 PRESSURE (Ibs/in*) O 500 1000 PRESSURE (bars) Fal SOS AST AE WAS A SIS SD aA LR STEED a FIGURE 26 OBSERVED AND CALCULATED SPECIFIC CONDUCTANCES OF 359/00 SALINITY SEA WATER AT 0°C Arthur A Hittle, Hine. S-7001--0307 60 In Table XIII the fourth column contains specific conductances calcu- lated from the empirically determined equation (15), which takes the form K, = 0.02906 + 2.65 x 10 P (17) When P is expressed in bars, Kp becomes equal to 0.02906 + 3.84 x 10-° Pp. The values in column six of Table XIII were obtained by interpolation of chlo- rinity-specific conductance data of Thomas, Thompson, and Utterback .(15) The chlorinities were calculated from salinities using equation (13), and the salinities in turn were computed from the relation (Salinity) , = (Salinity) iene Ve (18) where V, is the relative volume of the sea water at pressure P compared with its volume at 1 atmosphere (28) The relative volumes were obtained from the relation Ve = Vp Miyiepes = =r SIP (19) where the values of 6 used are those of 35°/oo salinity sea water at 0°C, as given by the International Critical Tables .(29) In addition to NaCl, sea water contains other species (see Table XIV), and some of these may form weak electrolytes. In general, the ionization of weak electrolytes and hence their contribution to electrical conductivity increases with increasing pressure (30) TABLE XIV COMPOSITION OF SEA WATER(3) Ion Concentration (gm/kgm) Na+ 10.556 Mg++ e272 Ca++ 0.400 K+ 0.380 Sr++ 0.013 Gly 18.980 SO4 2.649 HCO3_ 0.140 Bias 0.065 Arthur D Little Inc. S-7001-0307 61 The weak electrolyte present in largest amounts in sea water is MgSO4, whose dissociation constant has a value of 4.4 x 1073 at 25°C (32) > $e 2 ‘3 Se ee MgsO, < Mg + SO, r KMigsO, = (Mg ) (SO, ) (20) In order to test the hypothesis that the unexpectedly great increase in the conductance of sea water with pressure might be due to a conductive contribu - tion from the enhanced ionization of weak electrolytes such as MgSOy, the specific conductance of an 0.50 M NaCl solution, containing no other added electrolytes, was measured as a function of pressure. The results are shown in Figure 27. In the 15 to 10, 000 Ib/in .2 pressure range, the curve is nearly linear and has a slope of 2.03 x 10-7 ohm=! cm! ib-!in.2. The slope calculated from equation (16) using the chlorinity corresponding to 0.50 M NaCl is 2.08 x 10°7 ohm7! cm Ib-!in.2. Inasmuch as these two slopes are in agreement well within experi- mental error, the unexpectedly rapid increase in the specific conductance of sea water with pressure evidently cannot be attributed to a conductive contribution from the ionization of a weak electrolyte such as MgSO,4. The conductance of electrolytic solutions depends on the viscosity of the medium. As viscosity increases, the mobility of the charge-carrying ionic species decreases, and the observed decrease in specific conductance at the higher pressure is undoubtedly due to the increase in the viscosity of water under high compression (33) Water and dilute aqueous solutions are anomalous inas- much as their viscosity versus pressure curves initially exhibit a shallow mini- mum .‘?4) This viscosity anomaly has been attributed to the breaking up of the residual ice structure of liquid water. An increase in the temperature or the addition of electrolytes tend to remove the anomaly. The observed conductance anomaly might be attributable to this viscosity anomaly. Adams and Hall 24 discuss the pressure dependence of the relative resistance of NaCl solutions, and, in addition to the viscosity effect just mentioned, suggest that the degree of dissociation of strong electrolytes such as NaCl, as in the case of weak electrolytes, may also increase with increasing pressure. Inasmuch as dilute NaCl solutions are supposed to be 100% dissociated at 1 atmosphere, the mean- ing of this suggestion is not entirely clear unless one evokes the concept of a weak ion pair. Because of difficulties involved in determining the variation of their cell constant with pressure, Adams and Hall(24) reported only relative resist- ances, i.e., the ratio of the resistance at pressure P to the resistance at 1 at- mosphere. When the present results (Figure 27) are expressed in terms of relative resistances, they are seen to be in good agreement with the results of Adams and Hall (Figure 28); and their results in turn are in agreement with the earlier findings of Korber. 35) This agreement is reassuring, especially in view of the less than satisfactory agreement in the case of KCl at 25°C (Figure 21). Arthur DHittle, Ine. S-7001-0307 62 TOPN &@ 05 °0 AO AONV.LONGNOD OISIOddS L£¢ Fa NdI4 ($40q) SYNSS3Yd OS2 00S er O (,u!/sqi) SYNSS3ud ; ‘Ol } 000°9 000+ 0002 fo) 000'21 OOOO! _ 0008 _ 5 Seas 2v00 8700 (;-Wd ;- Wyo) SONVLONGNOOD 914104dS 6v00 OSOO ISOO 63 O PRESENT DATA, 0.50M(2.9%) NaCl, 24.95°C X ADAMS AND HALL (2.87%) NaCl, 25°C 0.99 0.98 RELATIVE RESISTANCE (Rp/R)) 0.97 096] 0.95 0.94 O 4,000 8,000 12,000 16,000 PRESSURE (Ibs/in®) O 250 500 750 1000 PRESSURE (bars) FIGURE 28 RELATIVE RESISTANCE OF NaCl SOLUTIONS Arthur A. Hittle, Ine. $-7001-0307 64 I) 16. 17. REFERENCES . Nat. Research Council - Nat. Acad. Sci., Publ. 600 (1959). . Ibid., p. 149. However, B. V. Hamon, J. Marine Research (Sears Foundation), 16, 83 (1958), has reported what he described as "tentative" measurements of the pressure coefficient of the electrical conductivity of sea water. P. W. Bridgeman, Pro. Am. Acad. Arts Sci., 72, 45 (1936). ale @eamicsou Chem ehysiye2 lel 3.65@ll953). . S. D. Hamann, Physico-Chemical Effects of Pressure, Butterworth's Sci. Publ., London, 1957, pp. 120-121. H. J. Creighton, Principles and Applications of Electrochemistry, John Wiley & Sons, Inc., New York, pp. 77-78 (1924). - T. Shedlovsky, J. Am. Chem. Soc., 52, 1793 (1930). See G. Kortum and J. O'M. Bockris, Textbook of Electrochemistry, Elsevier Pub. Co., Amsterdam (1951), vol. II, p. 563, et seq., and the references cited therein. H. C. Parker, J. Am. Chem. Soc., 45, 1366, 2017 (1923). G. Jones and G. M. Bollinger, J. Am. Chem. Soc., 53, 411 (1931). So ID). nema, O> Clea, fo LAI. G. Jones and B. C. Bradshaw, J. Am. Chem. Soc., 55, 1780 (1933). . J. F. Chambers, J. M. Stokes, andR.H. Stokes, J. Phys. Chem., 60, 985 (1956). D. Thomas, T. G. Thompson, and C. L. Utterback, J. conseil, Conseil permanent intern. l’exploration mer, 9, 28 (1934). M. J. Pollak, J. Marine Research (Sears Foundation), 13, 228 (1954). E.W. Washburn (ed.), International Critical Tables of Numerical Data, McGraw-Hill Book Co., Inc., New York (1926), vol. III, p. 48. Arthur D Little Inc. S-7001-0307 —— “ a 18. i) « 20. Zak 22. Dore 24. PRD) 0 78) Zadl « 28. BS) 6 30. oils 32. 33. 34. 35. 65 P. W. Bridgeman, Pro. Am. Acad. Arts Sci., 76, 55, 71 (1948). C.E. Weir, J. Research Nat. Bur. Standards, 45, 468 (1950). C.E. Weir, J. Research Nat. Bur. Standards, 50, 95 (1953). C.E. Weir, J. Research Nat. Bur. Standards, 53, 245 (1954). See A. Defant, Physical Oceanography, Pergamon Press, New York (1961), vol. I, pp. 123-129, for a discussion of the oceanographic significance of and formulas for the adiabatic temperature change with depth in the sea. S. D. Hamann and W. Strauss, Trans. Faraday Soc., 51, 168 (1955). L.H. Adams and R. E. Hall, J. Phys. Chem., 35, 2145 (1931). w.A. Zisman, Phys. Rev., 39, 151 (1932). H. U. Sverdrup, M. W. Johnson, andR.H. Fleming, The Oceans, Prentice- Hall, Inc., Englewood Cliffs, N. J. (1942), p. 51. For a discussion of the possible errors in the literature values of the com- pressibility of sea water, see V. A. Del Grosso, Conf. Phys. & Chem. Properties of Sea Water (Easton, Md., 1958), Nat. Research Council - Nata Acad Scie, bubl. G00((959) pperlsoa195. Although expressed in terms of weight, salinity is a concentration unit; de- creasing the volume is therefore equivalent to increasing the salinity, all at constant weight . ICT, vol. I, p. 440. S. D. Hamann, op. cit., pp. 129-131. H. U. Sverdrup, op. cit., p. 166. H. W. Jones and C. B. Monk, Trans. Faraday Soc., 48, 929 (1952). n . D. Hamann, op. cit., pp. 122-124. R. Cohen, Ann. Physik, 45, 666 (1892). F. Korber, Z physik. Chem., 67, 212 (1909); 77, 420 (1911); 80, 478 (1912). Arthur D Little Ine. S-7001-0307 Ae ret ER Re Deak, ek NS CAMBRIDGE * CHICAGO « NEW YORK * TORONTO SAN JUAN +e WASHINGTON® ZURICH « EDINBURGH SANTA MONICA e SAN FRANCISCO # MEXICO CITY.