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Instruction Manual 

 

Carbon Dioxide Electrode

 

 

10

temperature. Table 3 gives values for the "S" factor in the Nernst equation for the carbon dioxide 
ion. Gases are expelled from a solution at a faster rate as the temperature increases. 
 
 TABLE 

3: Temperature vs. Values for the Electrode Slope 

 
                Temp.(

o

C)              "S"  

                     0                

54.20 

                    5                 

55.20 

                   10                 

56.18 

                   15                 

57.17 

                   20                 

58.16 

                   25                 

59.16 

                   30                 

60.15 

                   35                 

61.14 

                   40                 

62.13 

 
Plotting the electrode mV potential against the carbon dioxide concentration on semi-logarithmic 
paper results in a straight line with a slope of about 56 mV per decade over the range 1X10

-4

M to 

1X10

-2

M.  (Refer to Figure 1.) 

 
For carbon dioxide concentrations above 1X10

-4

M, the electrode exhibits good time response (95% 

of total mV reading in two minutes or less). Response times are longer below this value and carbon 
dioxide loss to air may become a source of error. Samples above 1X10

-2

M must be diluted before 

measurement. Figure 2 indicates the time response of the carbon dioxide electrode to changes in the 
carbon dioxide concentration.