BUCHI Hydrolysis Unit B-411 - Manual (Page 19)

6 Operation
19 B-411/E-416 Operation Manual, Version E
6 .5 Choosing the heat output
When the preheating procedure is finished, the hydrolysis can be started. For this purpose we recom-
mend to switch the energy regulator to position 2 for four samples and to position 3 for six samples.
Depending on the boiling behavior, less heat can be provided when setting the regulator to position 1
or more heat can be provided by setting it to position 3.
6 .6 Hydrolysis
To carry out a hydrolysis proceed as follows:
Reduce the heat output (position 2 - 3) •
Insert the vessels containing the samples into the instrument •
Put the prepared glass sample tubes into the rubber couplings •
Close unused positions with the supplied stoppers Ø 45 mm on the suction tube •
Put the caps onto the digestion vessels and install the sample aspiration tube •
As soon as the sample starts boiling switch on the waterjet pump. •
The hydrolysis time depends on the sample. From the start of the boiling on it takes a minimum of •
15 and a maximum of 60 minutes (usually 30 minutes is an appropriate time).
Foaming can be suppressed by the addition of small acid injections
(HCl 4 mol/l). It is recommended to switch on the external pump
only after the samples are boiling evenly and no further foam is to be
expected. Thus a premature sample extraction is avoided.
Fig. 6.7: Hydrolysis
6 .7 Filtration
After expiration of the hydrolysis time, switch off the heating and
add hot distilled water (40 - 50 °C) to each digestion vessel to a
level of approx. 1 cm under the sample aspiration tube.
To filter the hydrolysate solution over the glass sample tubes, raise
the lift device to immerse the sample aspiration tubes into the solu-
tion. As soon as the contents of the individual digestion vessels are
completely transferred, rinse them with hot distilled water
(40 - 50 °C) portion by portion. The rinse volume until neutral
reaction is approx. 250 ml per sample.
Fig. 6.8: Filtration