Hanna Instruments HI 8510 - Manual (Page 22)

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ELECTRODE MAINTENANCE
PREPARATION
Remove the protective cap.
DO NOT BE ALARMED IF ANY SALT DE-
POSITS ARE PRESENT. This is normal with
electrodes and they will disappear when rinsed
with water.
During transport tiny air bubbles may form in-
side the glass bulb, and the electrode cannot
function properly under these conditions. Remove
the bubbles by "shaking down" the electrode
as you would do with a glass thermometer.
Reference
Filling Hole
Reference
Filling Hole
Fill Hole
Screw
Sensitive
Wire
Reference
Wire
Reference
Junction
Glass
Bulb
Glass
Bulb
Reference
Junction
Reference
Junction Reference
Junction
Platinum or
Gold tip Platinum or
Gold tip
Reference
Wire
Reference
Wire
Sensitive
Wire
Glass Body
pH Electrode
Plastic Body
pH Electrode
Plastic Body
ORP Electrode
Glass Body
ORP Electrode
Reference
Wire
Generally, if the ORP (mV) reading corre-
sponding to the pH solution value is higher
than the value in the table below, an oxidizing
pre-treatment is necessary; otherwise a re-
ducing pre-treatment is necessary:
pH mV pH mV pH mV pH mV pH mV
0 990 1 920 2 860 3 800 4 740
5 680 6 640 7 580 8 520 9 460
10 400 11 340 12 280 13 220 14 160
Reducing pre-treatment: immerse the elec-
trode for some minutes in HI 7091 solution.
Oxidizing pre-treatment: immerse the elec-
trode for some minutes in HI 7092 solution.
If no pre-treatment is performed, the elec-
trode will have long response times.
If working with refillable electrodes, always
check the internal electrolyte level and refillwith
HI 7071 solution, if necessary (the level must
be at least 2.5 cm below the filling hole).
If measurements are taken in solutions con-
taining sulfides or proteins, the cleaning of
the electrode junction must be performed (see
"Cleaning Procedure" section for details).
To check the correct functioning of the ORP
electrode, immerse it into HI 7020 test
solution and verify that the reading is within
200 and 275 mV.
After the test, rinse the electrode thoroughly
with water and proceed with the oxidizing or
reducing pre-treatment before taking any
measurement.
When not in use, the electrode tip should be
kept moist and far from any type of mechani-
cal stress which might cause damage. For
this reason, it is reccommended to store the
electrode with a few drops of HI 70300 storage
solution in the supplied protective cap.