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How does a rotary evaporator work?
The description in my textbook is too short and too abstract. Could someone give me a more detailed description?
Thanks a bunch!
- Anonymous2 decades agoFavorite Answer
A rotary evaporator is a device used in chemical and biochemical laboratories for the efficient and gentle evaporation of solvents. The main components of a rotary evaporator are a vacuum system, consisting of a vacuum pump and a controller, a rotating evaporation flask which can be heated in a heated fluid bath, and a condenser with a condensate collecting flask. The system works because lowering the pressure lowers the boiling point of liquids and thus the solvent. This allows the solvent to be removed without excessive heating.
Evaporation under vacuum can be performed in a standard distillation rig. However, the Rotavapor has a key advantage. As the evaporating flask rotates, the liquids are forced to the outside of the flask with the centrifugal force. This creates a larger surface area of the liquids and hence allows for quicker evaporation.
Rotary evaporators are highly effective at removing the majority of organic solvents during the extraction process but are not recommended for extractions that use water as a solvent due to its high boiling temperature.
The rotary evaporator was invented by Swiss company Büchi. The Büchi Rotavapor continues to be the most widely used rotary evaporator, and Rotavapor has become a synonym for such instruments. Other manufacturers include IKA and Heidolph.
The most common form is the benchtop rotary evaporator, though large scale (20 L) versions are available and are used by pilot plants in large pharmaceutical companies.
- Dave_StarkLv 72 decades ago
The above answer is mostly accurate -- the only quibble I have with it is the statement that "the liquids are forced to the outside of the flask with the centrifugal force" in paragraph 2.
First -- anyone with any knowledge of the rudiments of physics knows that there is no such thing as "centrifugal force" -- what most people call the "force" pushing outwards is, in fact, INERTIA.
In my own experience as a chemist, no rotary evaporator spins rapidly enough to have inertia force the liquid outwards to any significant degree. Most "rotovaps" are angled, rather than vertically oriented, and it is the surface tension of the liquid that causes it to "stick" to the rotating glass surface, thus increasing the surface area to speed evaporation.