BUCHI KjelDigester K-449 - Manual (Page 36)

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6 Operation
KjelDigester K-446/K-449 Operation Manual
NOTICE
Risk of material damage due to wrong handling.
Improper handling of device components can cause a device damage.
1. Do not use cold water to cool down hot sample tubes after digestion.
2. Make sure that the rack containing the sample tubes is placed in and re-
moved from the digestion block with reasonable care.
3. Make sure that the rack is properly adjusted at the lift of the K-449, to make
the tubes smoothly slight into the openings of the digestion block.
4. Use digestion rods instead of use glass beads.
To vaporize larger amounts of water (10 – 200 mL), use digestion rods as this will prevent boiling
delays for optimal user protection from possible splashes due to boiling delays. Always use the
user protection shield installed at the rack.
The digestion time and profile depends on the substance to be digested. Information on this
can be found in the BUCHI Application Notes. If no BUCHI application is available, the digestion
method must be ascertained by means of experiments. If the solution has become clear, continue
to boil the solution for about 30 minutes. Once the samples have cooled off, the sample tube
can be connected directly to a BUCHI distillation unit or the KjelSampler for distillation.
Due to different heat transfer and air flows between the sample tubes and the heating block, not
all 20 samples boil simultaneously. However, as long as it is ensured that the digestion time and
digestion temperatures are sufficient, the different boiling times have no influence on the results.
If the digested samples are allowed to cool down for a long period of time, the samples might
solidify occasionally.
In this case, the sample must be liquefied again before it can be distilled:
∙by adding very carefully a small quantity of distilled water
∙by slightly warming it up in the KjelDigester
6.2 Start a digestion
1. For the K-446:
∙6.7.1 Digestion process, (6–39).
2. For the K-449:
∙6.8.1 Digestion process, manual mode, (6–40).
∙6.8.2 Digestion process, automatic mode, (6–41).
6.3 Set parameters for manual digestion
6.3.1 K-446
1. Press a [TEMP] and adjust the temperature by pressing c [+/-].
1. Press d [ENTER] to confirm the new value.
2. Press b [TIME] and adjust the time by pressing c [+/-].
3. Press d [ENTER] to confirm the new value.