3 | Product description
Büchi Labortechnik AG
12/78
Operation Manual Rotavapor® R-250 Pro
3
Product description
3.1
Description of function
The instrument is a rotary evaporator with the aid of which single-stage distillation
can be carried out quickly without unduly stressing the product. The basis of the
process is the evaporation and condensing of solvents in a rotating evaporating flask
under vacuum.
The product is heated in the evaporating flask by the heating bath.
The rotary drive unit evenly rotates the evaporating flask.
◦ The rotation increases the surface area of the liquid which leads to an increased
evaporation rate.
◦ The rotation constantly mixes the product which prevents localized overheating
and delayed evaporation.
The vapor passes from the evaporating flask through the vapor duct into the
cooling section.
In the cooling section, the thermal energy of the vapor is transferred to the
coolant fluid so that the vapor re-condenses.
The resulting solvent is collected in the receiving flask and can then be reused or
properly disposed of.
Distillation under vacuum
Distillation capacity depends on the following factors:
Temperature of the heating bath
Pressure in the evaporating flask
Rotation speed of the evaporating flask
Size of the evaporating flask
Pressure in the evaporating flask:
A low pressure (below atmospheric) reduces the boiling point of the solvent. A lower
boiling point means the solvent does not have to be heated as much. Distillation
under vacuum is more efficient and gentler on the product.
Vacuum control:
A stable vacuum adapted to the application prevents undesirable solvent emissions
and bumping (boiling) of the product.
Heating bath temperature, coolant temperature and vapor temperature:
To ensure optimum distillation, it is important to make sure that the temperature
difference between the coolant and the heating bath is at least 40 °C. The
temperature of the rising vapor should be mid-way between the heating bath
temperature and the coolant temperature.
