682 THURAS: RECORDING SEA-WATER SALINITY 



ELECTRICAL CONDUCTIVITY OF SEA WATER 



The electrical conductivity of sea water was measured in the 

 sealed cell placed in a stirred bath. The temperature was main- 

 tained at 25°C. to within 0.01° C. The resistance capacity of the 

 sealed cell was measured with 1/10 N solutions of potassium 

 and sodium chloride.^ 



The electrical measurements were made by substituting an 

 accurate resistance box in place of the cell in one arm of a Wheat- 

 stone bridge circuit. The 60 cycle power circuit was used and 

 no auxiliary capacity or inductance was used to compensate for 

 the capacity of the cell. The resistance capacity was determined 

 with one sodium chloride solution and two potassium chloride 

 solutions. One of the potassium chloride solutions was specially 

 prepared by the chemical division of the Bureau of Standards 

 and the resistance capacity given by this solution has been 

 used to measure the conductivity of sea water. Following are 

 the capacities obtained with the three solutions at 18°C. using 

 a frequency of 60 cycles: 



I/ION, KCl prepared by the Bureau of Standards 5. 182 



1/lON, KCl prepared from Kahlbaum's pure salt 5. 181 



1/lON, pure NaCl 5. 178 



Unfortunately the specific conductivity of standard solutions, 

 at a frequency of 60 cycles, has not been measured. The re- 

 sistance capacities given above are therefore only apparent and 

 can be used to measure the specific conductivity of sea water 

 provided the change in resistance with frequency is the same for 

 a 1/10 normal solution of KCl as it is for sea water which has a 

 strength of about 1/5 normal. The resistance capacities ob- 

 tained with 1/10 normal KCl and 1/10 normal NaCl solutions 

 indicate that the change in resistance with frequency is the same 



2 The specific conductivity of these solutions at 18°C. measured by F. Kohl- 

 rausch and M. E. Mai thy in 1900 are 0.011203 and 0.009202 reciprocal ohms respec- 

 tively. As prepared by Kohlrausch the 1/10 N solution of KCl used in these 

 measurements contained 7.445 grams of KCl to one liter of solution at 18°C. and 

 the 1/10 N solution of NaCl contained 5.848 grams of NaCl to one liter of solution 

 at 18°C. All weighings were made in air and low conductivity distilled water 

 was used. 



