ORP/Redox Sensors
The terms ORP or Redox are given to the voltage seen by the transfer of
electrons between atoms or molecules in a redox reaction. To measure potential
ORP/Redox it uses sensors made of metal, usually platinum, gold or silver.
These sensors are inert and applied in chemical reactions that operate only
by electron transfer. Such reactions occur with elements and compounds which
presents two or more oxidation states. With the exchange of electrons from the
redox system, the sensor receives a voltage equal to the electrochemical
potential of this system. The application of redox measurements to a practical
situation requires prior knowledge of some factors: - Presence of contaminants
that can compete with the main redox reaction (Pt, Ag or Au); - Approximate
values of ions activity coefficients, - Approximate speed of the reaction to
be controlled, - Necessity or not of the control pH. One form of control is
often used to maintain the redox potential above.