BUCHI Rotavapo R II - Manual (Page 35)

6 Operation
35 R II Operation Manual, Version E
6 .4 Distilling
To start operating the instrument, the following conditions have to be fulfilled:
• All electrical connections are established correctly.
• All sealing are inserted correctly.
• All joints are greased.
To start operating the instrument, proceed as follows:
• Switch on the instrument.
• Allow cooling water with a temperature not higher than 20 °C to flow through the condenser at
approx. 40–50 L/h.
• Set the heating bath temperature to the desired value as described above and wait, until the
heating medium has reached its operating temperature.
• Fill the solution you want to distill into the evaporating flask and make sure it does not exceed the
filling weight of 3 kg.
• Mount the evaporating flask.
NOTE
Choose the pressure in such a way that the boiling point of the solvent is 40 °C (see solvent table).
• Set the rotation speed.
NOTE
If the last distillation was an automatic one and you now want to carry out a manual distillation, turn
the knob for the rotation speed to its leftmost position first before setting the rotation speed by
turning the knob to the right. Otherwise the instrument will not start operating.
• Use the quick-action jack to submerge the flask into the bath.
• After the set vacuum has been reached, wait for about 1–2 minutes to see whether distillation
begins.
• If the distillation does not start, optimize the parameters (decrease the pressure gradually or
increase the bath temperature).
Both possibilities lead to an increased distillation capacity, see also chapter 6.5.
6 .5 Optimizing the distillation conditions
Depending on the solvent being distilled the distillation might have to be re-optimized. In the opti-
mized case, the condenser should be steamed up to between 2/3 to 3/4, see figure below.
If this is not the case, there are two possibilities to optimize the distillation:
• When the heating bath has reached 60 °C slowly reduce the pressure. Thus, the boiling point of
the solvent is reduced and Δ T
1
increases resulting in an increase of distillation capacity.
• When the heating bath has reached 60 °C increase the bath temperature. Thus Δ T
1
increases
resulting in an increase of distillation capacity as well.
NOTE
When the bath temperature is increased, not all of the additional energy is used for distillation but a
major part is discharged into the environment due to the increasing difference between heating bath
and the ambient temperature.