Lab 855 Glossary
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12 Glossary
12.1 pH/ORP
Specialist
term
Description
Asymmetry see zero point
Diaphragm The junction is a porous body in the housing wall of refer-
ence electrodes or electrolyte bridges. It arranges the elec-
trical contact between two solutions and makes the
electrolyte exchange more difficult. The expression, junc-
tion, is also used for ground or junction-less transitions.
Electromotive
force of an
electrode
The electromotive force U of the combination electrode is
the measurable electromotive force of an electrode in a
solution. It equals the sum of all the galvanic voltages of the
electrode. Its dependency on the pH results in the elec-
trode function, which is characterized by the parameters,
slope and zero point.
ORP The ORP is caused by oxidizing or reducing substances
dissolved in water if these substances become effective on
an electrode surface (e. g. a gold or platinum surface).
pH value The pH value is a measure of the acidic or basic effect of
an aqueous solution. It corresponds to the negative
decadic logarithm of the molal hydrogen ions activity
divided by the unit of the molality. The practical pH value is
the value of a pH measurement.
Slope The slope of a linear calibration function.
Zero point The zero point of a pH combination electrode is the pH
value at which the electromotive force of the pH combina-
tion electrode at a specified temperature is zero. Normally,
this is at 25 °C.
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