Water Quality
Parameters
ORP
Reduction and oxidation are two central chemical terms that describe the ability of chemical agents to accept (reduction) or donate electrons (oxidation). In aqueous solutions, the ORP (Oxidation-Reduction Potential) voltage can be measured using a standard hydrogen electrode as reference. The reducing or oxidizing properties of a solution first are a matter of the reactants. By using an ORP electrode this change in potentials would be recorded as a positive or
negative voltage.

ORP measurements monitor chemical reactions such as checking the denitrification of wastewater and disinfectant effect of detergents or the strength of plating baths.

Measurement of ORP voltage is carried out with ORP combination electrodes.
Similar to pH electrodes, these consist of a measuring electrode and a reference electrode. A metal electrode (normally a precious metal like gold, silver or platinum) is used in ORP combination electrodes in place of a glass membrane for carrying out the measuring function. The tendency for the chemical agents to accept or donate electrons determines the potential of the metal and thus the electrical potential of the combination electrode. ORP combination electrodes in use today contain a silver/silver chloride reference electrode, i. e. the indicated potential refers to this potential. Conversion to the standard hydrogen electrode system (UH) and that of the silver/silver chloride reference electrode is easily possible.

UH = UMeas + URef

ORP measurements can be carried out with all WTW pH/mV meters.