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Temperature Settings for Rotary Evaporators: "Rule of 20"

By Carlton Hoyt, 02 March 2016

We often get asked: "What temperature should I set my rotary evaporator to?"

A good general guideline to follow is the "Rule of 20." This rule states that your bath temperature should be 20°C hotter than the boiling point or vapor temperature you are trying to achieve, and the coolant temperature should be at least 20°C cooler than the vapor temperature.

For instance: if you were trying to boil off a substance that has a boiling point of 70°C, you would want to set the bath temperature to 90°C and have the coolant in the condenser be 50°C or less.

If you'll be applying a vacuum, don't forget to check how the reduced pressure will effect your solvent's boiling point!

 

A complete rotary evaporator setup.