Redox electrode is a precious metal electrode. It was used to carry out potential measurement, and at the same time can't take part in the chemical reaction process, that is to say it is to the control of chemical. So here can only choose platinum, gold or silver precious metals.
As the reference electrode is like pH measurement with Ag/AgCl reference system.
Insert a Redox platinum needle electrode into the solution of chlorine, in platinum needle is a phase boundary layer formed between surface and surface, known as "Helmholtze electric double layer". The phase boundary layer is equivalent to a capacitor, its one end is connected to a platinum needle, the other end is connected as pH measurement and the reference electrode. The capacitance will be due to the electrochemical potential difference between platinum needle and solution for charging. And solution of the potential depends on the concentration of the logarithmic ratio Log COX/CRED the sum total of all ions and the water potential difference.
At the same time platinum will be oxidation, and depends on the concentration of oxidant 3 ~ 4 atoms from forming on the surface layer thickness of platinum oxide. The oxide layer on the one hand, conduction electrons, that is to say, hinder the Redox process measurement. But the oxide layer at the same time establish a oxidation memory, when the chlorine content is lower will cause delay measurement.
The more dilute test solution, the longer the delay process. Under the condition of high content of Redox buffer, this process can be ignored.
This effect can also be used in front of the two cans of examples to explain. A jar full of water, another jar is empty. If the connection pipe diameter is small, the two cans of water balance process is slow, fast conversely. Electrode table
The rough also can bring the measuring of inertia. This is because of rough surface concave pit will also be stored effect, thus make
The process of ion exchange.
The surface of the Redox electrode should try to keep bright and clean.
As a result of the action of the electric double layer "" Helmholtze as a capacitor, so in when there is a potential change
Charging current flows, electrochemical balance so far has been arrived. If this compound layer measuring amplifier is not zero current method is adopted to measure the electric potential, will not achieve electrochemical equilibrium. At this point, the measured value will be constant drift, and under certain conditions, the electrode surface and chemical changes may occur.