User Guide

Instruction Manual Carbon Dioxide Electrode

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.(

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

Electrode Response

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.