D664_9 (17a) 04-2014
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Determination of meter
readings for the aqueous buffer
solutions.
To ensure comparable
selection of endpoints
when definite inflection
points are not
obtained in the titration
curve, determine daily
for each electrode
pair, the meter readings
obtained with aqueous acidic
and basic buffer solutions.
The response of different glass
electrodes to hydrogen ion
activity is not the same.
Therefore, it is necessary
to establish regularly
for each electrode system the
meter readings corresponding
to the buffer solutions
arbitrarily selected
to represent acidic
or basic endpoints.
Immerse the electrodes in the
pH 4 and the pH 11 aqueous
buffers, and stir each of them
for approximately five minutes,
maintaining the temperature
of the buffer solution
at a temperature
within 2 degrees
Celsius of that at which the
titrations are to be made.
Read the cell voltage
for each of them.
The readings so
obtained are taken
as the endpoints
in titration curves
having no inflection points.