Metrohm 899 Coulometer - Manual (Page 100)

9.1 Karl Fischer titration
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90 ￭￭￭￭￭￭￭￭
899 Coulometer
Problem Cause Remedy
The Control parameters
are not set correctly. ￭ Reset the Control parameters to default
values.
The titration time is
too long. The drift during condition-
ing is not stable. ￭ Wait before starting the titration until the
drift has become stable.
The parameter Start drift
is set too high. ￭ Set the Start drift lower.
￭ Adjust the Stop drift or use the Relative
stop drift.
The parameter Stop drift
is set too low. ￭ Set the Stop drift higher or use the Rela-
tive stop drift.
The water quantity is too
high. ￭ Observe the sample size and water con-
tents in accordance with Table "Recom-
mended sample sizes", page 31.
The Control parameters
are set incorrectly. ￭ Set the parameter Dynamics lower and
the parameter Max. rate higher.
The result is too
high. The coulometer cell is not
yet correctly conditioned. ￭ Shake the coulometer cell and wait until
the drift is stable.
The sample contains oxi-
dizable substances. ￭ Possibly use a KF oven.
￭ See technical literature.
The parameter Stop drift
is set too low. ￭ Set the Stop drift higher or use the Rela-
tive stop drift.
The drift correction is too
small (e.g. with the use of
a KF oven or with manual
drift correction). ￭ Start the titration as long as the gas flow
still exists between the conditioning vial
and the coulometer cell.
￭ Set the parameter Drift correction to
auto (= automatic drift correction).
The result is too
low. The sample releases iodine. ￭ Possibly use a KF oven.
￭ See technical literature.
The parameter Stop drift
is set too high. ￭ Set the Stop drift lower.
The drift correction is too
large (e.g. with excessively
high start drift, with fluctu-
ating drift or with manual
drift correction). ￭ Ensure stable and lower drift.
￭ Set the parameter Drift correction to
auto (= automatic drift correction).