SenTix
®
ORP-T 900(-P)
Activating platinum electrodes
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ba75845e03
02/2017
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Activating platinum electrodes
First-time
activation during
installation and as
required
For first-time activation use the activation powder from the SORT/RH reagent
set (component of the SORT/RH reagent set). Immerse the moist (but not
dripping) platinum electrode into the activation powder and rotate the elec-
trode several times in the powder. Then remove the activation powder under
flowing water with a soft brush (e.g. toothbrush).
Activation during
very long set-up
times
When changing from oxidizing to reducing test solutions and vice versa this
can result in set-up times that can take significantly more than an hour. In this
case pretreatment (activation) of the platinum surface can shorten the set-up
time. The type of pretreatment (reducing or oxidizing) is based on the pH
value and the ORP voltage (U
H
) of the test solution where the latter must be
estimated for the first measurement.
The type of pretreatment can then be determined using the following diagram
where U
H
is based on the normal hydrogen electrode:
Oxidizing pretreat-
ment
Immerse the platinum electrode for two to three
days in a sulfuric acid clorina solution (0,5 g clorina
powder, 100 ml H
2
O dist., 2-3 ml 20% sulfuric acid).
Clorina powder for producing the solution is
included in the SORT/RH reagent set.
Note: The diaphragm must not be immersed in the
clorina solution!
Reducing pretreat-
ment
When the electrode is ready for the test immerse it
in the RH 28 ORP buffer solution and wait for a sta-
ble measured value.
Detailed information on activating platinum electrodes, such as
how to produce the clorina solution, is given in the WTW applica-
tion report entitled R
EGENERATING
ORP
ELECTRODES
. The appli-
cation report is included in the SORT/RH reagent set.
1000
800
600
400
200
2
0
4
8
10
12
14
6
0
pH value
U
H
in mV
oxidizing pretreatment
reducing pretreatment
