eutech-instruments bromide epoxy Manuel D’Utilisation

Instruction Manual 

 

Bromide Electrode 

 

11

 

Total concentration (C

t

) consists of free ions (C

f

) and complexed or bound ions (C

c

) in solutions: 

                      

   

 

C

t

 

= C

f

 + C

c

 

Since the electrode only responds to free ions, any complexing agent in the solution reduces the 
measured concentration of ions. 
 
Bromide ions complex with some metal ions. Table 4 lists the levels of complexing metals causing 
a 20% error at 1.0X10

-4

M bromide. 

 
   TABLE 4:  Levels of Complexing Agents Causing a 20% Error at 1.0X10

-4

M Bromide 

 
 

 

 

Ion               

 

       Concentration 

 

 

 

Bi

+3

 

   

 

4.0X10

-4

M (80 ppm)   

 

 

 

Cd

+2

 

   

 

2.0X10

-3

M (200 ppm) 

 

 

 

 

Pb

+2

 

   

 

8.0X10

-3

M (1,600 ppm) 

 

 

 

 

Sn

+2

 

   

 

2.0X10

-2

M (2,400 ppm) 

  

 

 

 

Tl

+3

 

   

 

2.0X10

-5

M (4 ppm)  

 
Samples and standards should be at the same temperature since electrode potentials are influenced 
by changes in temperature. A 1

o

C difference in temperature results in a 2% error at the 1.0X10

-3

M 

concentration level. Because of solubility equilibrium on which the electrode depends, the absolute 
potential of the reference electrode changes slowly with the temperature. The slope of the electrode, 
as indicated by the factor "S" in the Nernst equation, also varies with temperature. Table 5 gives 
values of the "S" factor in the Nernst equation for the bromide ion. 

 
  TABLE 5:  Temperature vs Values for the Electrode Slope 

 
 

         Temp (

o

C) 

 

 

"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 recalibrated. 
 
The temperature range of the Eutech Bromide Ion Electrodes is 0

o 

- 80

o

C, provided that temperature 

equilibrium has occurred.