ABSTRACT
The dissolved oxygen (DO) in the sample diffuses through the membrane into the electrolyte which usually is an aqueous potassium chloridesolution. The theory of operation for the DO galvanic cell is the same as for gaseous samples. All oxygen detectors designed to handle gaseous samples can also measure the oxygen concentration in liquid streams, if components are provided to remove the gaseous oxygen from the liquid. The oxygen content of the electrolyte is brought into equilibrium with that of the sample. The electrodes are polarized by an applied voltage which causes electrochemical reactions to take place when oxygen contacts the electrodes. The cathode must be noble in order for the cathode potential to reduce molecular oxygen when the cell circuit is closed. Special cells are also available for measurement of oxygen in acetylene and fuel gases. The ideal membrane would be inert, stable, strong, permeable to oxygen, and impermeable to other ions and water molecules.
