BUCHI Multivapo P-12 - Manual (Page 50)

6 Operation
50 Multivapor™ Operation Manual, Version E
6 .3 Selecting the distillation conditions
To achieve optimal distillation conditions, the distillation energy supplied by the heating platform must
be removed by the condenser. To ensure this, operate the instrument according to the following
general rule:
Heating medium: 55 °C
25 °C
Vapor: 30 °C
20 °C
Coolant: max. 10 °C
How are these conditions achieved?
• Set the temperature of the instrument to 55 °C.
• Use a recirculating chiller to set the temperature of the coolant to max. 10 °C or use a dry-ice
condenser (type C) alternatively.
• The coolant flow is adjusted to approx. 600 – 800 mL/min.
• Define the operating vacuum according to the boiling point of the solvent which in this particular
example is 30 °C. The corresponding pressure can be deduced from the enclosed Solvent Table or
from the Solvent Library implemented in the Vacuum Controller V-850/V-855.
This rule can be extrapolated to higher temperatures, e.g. according to the following example:
Heating plate: 75 °C
25 °C
Vapor: 50 °C
20 °C
Coolant: max. 30 °C
Δ T ≥ 20 °C
Δ T ≥ 25 °C
Fig. 6.32: Schematic depiction of the relative temperature drop within the distillation setup
NOTE
The 25/20 °C rule indicates that during operation the displayed temperature does not correspond to
the temperature of either the vapor or the sample mixture. During distillation there is a temperature
drop relative to the display of approx. 10 °C for the sample and approx. 25 °C for the vapor.
The distillation conditions of the Multivapor are therefore not directly comparable to that of the
Rotavapor as the heat transfer in the latter, from heating bath to sample flask, is more efficient
compared to that observed in the Multivapor. At identical set temperatures, the actual temperature
of the Multivapor sample would be approx. 15 °C less than the Rotavapor sample.