eutech-instruments chloride epoxy Manuel D’Utilisation

Instruction Manual 

 

Chloride Electrode 

 

13

Chloride ions complex with some metal ions. Table 4 lists the levels of complexing metals causing 
a 10% error at 1.0X10

-4

M chloride. 

 
 TABLE 

4: Levels of Complexing Agents Causing a 10% Error at 1.0X10

-4

M Chloride 

 
 

 

 

 Ion 

 

   Concentration 

 

 

 

Bi

+3 

 4.0X10

-4

M (80 ppm) 

 

 

 

Cd

+2

  

2.0X10

-3

M (200 ppm) 

 

 

 

Mn

+2

  

2.0X10

-2

M (1100 ppm) 

 

 

 

Pb

+2

  

2.0X10

-3

M (400 ppm) 

 

 

 

Sn

+2

  

6.0X10

-3

M (700 ppm) 

 

 

 

Tl

+3

  

4.0X10

-5

M (8 ppm) 

 
Samples and standards should be within ±1C of each other, since electrode potentials are influenced 
by changes in temperature. Because of the solubility equilibrium on which the electrode depends, 
the absolute potential of the reference electrode changes slowly with temperature. The slope of the 
electrode, as indicated by the factor "S" in the Nernst equation, also varies with temperature. Table 
5 gives values for the "S" factor in the Nernst equation for the chloride ion. 
 
 TABLE 

5: Temperature vs. Values for the Electrode Slope 

 
 

 

     Temp. (oC)  

 

"S" 

    

0 

  54.2 

   10 

  56.2 

   20 

  58.2 

   25 

  59.2 

   30 

  60.1 

   40 

  62.1 

   50 

  64.1 

 
If changes in temperature occur, the electrodes should be re-calibrated. The temperature range for 
the chloride ion electrode is 0

o

-80

o

C, provided that temperature equilibrium has occurred. If the 

temperature varies substantially from room temperature, equilibrium times up to one hour are 
recommended. 
 

 
Plotting the electrode mV potential against the chloride concentration on semi-logarithmic paper 
results in a straight line with a slope of about 56 mV per decade.  (Refer to Figure 1.)