1. Water treatment (sewage)-prechlorination & dechlorination
2. Metal finishing (CN destruct and chromate reduction)
3. Ozone treatment (commercial aquariums, water disinfection)
4. Bleach production
5. Poultry processing- disinfect the skin
6. Fruit and vegetable washing
7. Pulp bleaching (paper industry)
8. Chlorine addition (swimming pools, spas)
What Is "ORP"?
ORP is an abbreviation for for Oxidation Reduction Potential, also know as REDOX and is a useful measurement for monitoring and controlling chemical reactions.
Oxidation: addition of oxygen/ reduction of electrons
Reduction: reduction of oxygen/ addition of electrons
Characteristics of ORP
• non-specific measurement of total activity
• mV output allows automated control of chemical reactions
Typical examples of ORP uses include
• ozone or chlorine control
• chromate reduction or cyanide destruction
How Does an
Electrode Work?
An ORP measuring electrode is
identical to a pH measuring electrodes except a Nobel metal
is used in place of the pH glass as the measuring element.
Nobel metals are used because they will not enter into the
chemical reaction taking place. Other Nobel metals such as
gold or silver can be used, but platinum is the most
commonly used.
The reference is identical to the one used
in the pH electrode. It is a Ag/AgCl (silver/silver
chloride) wire in 3.5M KCl saturated with AgCl (silver
chloride). A second junction for protection of the
reference wire is common in industrial electrodes and is
referred to as a "Double Junction". A combination ORP
electrode works the same as a combination pH electrode. The
measuring electrode generates a millivolt output based on
the oxidising or reducing reactions taking place while the
reference electrode generates a constant millivolt output
The working range of an ORP electrode is +/- 2000mV. A pH
meter with a millivolt scale or ORP transmitter or
controller is used to display readings.
Temperature compensation
is not needed for ORP measurements
Examples of
ORP vs. various oxidising agents
