The cell system is shown in Figure 1. Platinum electrodes are chemically inert, and do not take part in chemical reactions. Electrochemical reactions take place in the boundary layers of the electrodes. As soon as air that contains O3 molecules is bubbled through the cathode solution, the following total reaction occurs:
2 KI + 03 + H2O -> 2 KOH + I2 + 02
Iodine, I2, is formed and the I2 concentration of the solution starts to increase. If the external circuit is closed (switch S), reaction 1 is followed by reactions 2 and 3.
In the cathode chamber:
3 I - -> I3 - + 2 e-
In the anode chamber:
I2 + 2 e- -> 2 I-
These chemical reactions result in the following statement:
ONE O3 MOLECULE CAUSES A CURRENT OF TWO ELECTRONS
The current is measured with the OIF411 interface.
|The reaction occurs with all oxidants (such as NO2). The chemical reaction in sensor chambers is affected by the sensor dimensions, air bubbling rate, the total liquid volume of the sensor, and the temperature of the sensor solution. These factors introduce some basic errors and variance.|