Metrohm 907 Titrando - Manual (Page 45)

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4 Karl Fischer titration
907 Titrando
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Table 3 Approximate sample size in grams (20 mL buret)
Water content of
the sample KF reagent 1 KF reagent 2 KF reagent 5
0.5% 0.4 - 3.6
1.0% 0.2 - 1.8 0.4 - 3.6
5.0% 0.04 - 0.36 0.08 - 0.72 0.2 - 1.8
10.0% 0.02 - 0.18 0.04 - 0.36 0.1 - 0.9
25.0% 0.02 - 0.14 0.04 - 0.36
50.0% 0.02 - 0.18
KF reagent 1: 1 mL KF reagent reacts with around 1 mg H
2
O
KF reagent 2: 1 mL KF reagent reacts with around 2 mg H
2
O
KF reagent 5: 1 mL KF reagent reacts with around 5 mg H
2
O
4.1.6.2 Working with liquid samples
Liquid samples are added with a syringe. The samples can be injected
two different ways:
￭ One uses a syringe with a long needle, which one immerses in the
reagent during the injection.
￭ One uses a syringe with a short needle and aspirates the last drops
back into the needle.
The best way for you to determine the injected sample amount is to
reweigh the sample.
Glass syringes should be used for the determination of traces and val-
idations. We recommend obtaining these from a specialized syringe
manufacturer.
Highly volatile samples and samples of low viscosity should be
cooled before sampling. Doing so avoids losses while working. The syringe
must, however, not be cooled directly, as condensation could form. For
the same reason, no air may be aspirated into a syringe into which a
cooled sample has been aspirated beforehand.
Samples of high viscosity can be thinned by heating. The syringe must
be heated as well. The same target can be reached by diluting with suit-
able solvents. In this case, the water content of the solvent has to be
determined and subtracted as blank value.
Viscous samples can be added to the measuring cell with a syringe
without needle. You can use the ground-joint opening for this. The best
way for you to determine the added sample amount is by reweighing the
sample.