Continuous monitoring of gas streams:
Determination of trace level concentration of oxygen within a gas stream could be done through controlled potential analysis. A cell consists of a porous silver cathode and a cadmium anode. The reactions are
O2(g) + 2H2O + 4e ? 4OH - (cathode)
Cd(s) + 2OH - ? Cd(OH)2(s) + 2e (Anode)
The porous silver cathode serves to break up incoming gas into small bubbles, whereas the reduction of oxygen takes place quantitatively inside the pores. The hydroxyl ions created during reduction react along with the cadmium anode and forms a Cd (OH)2(s) product.
A special characteristic of this set up is which a galvanic cell is formed and therefore no external power supply is required. There is no requiring of a potentiostat controlling the potential of the working electrode. The current generates is passed by a standard resistor and the potential drop is recorded. An oxygen concentration is proportional to this potential and a digital show could denote the oxygen concentration directly. The set up could be used for the determination of oxygen in any gas stream and can detect oxygen concentration from 1 ppm to 1%.