How to Deal with Low Evaporation Speed of Rotary Evaporator

How to Deal with Low Evaporation Speed of Rotary Evaporator


Rotary evaporator, also called rotary evaporation machine, is a commonly used equipment in laboratories. It consists of a motor, distillation flask, heating pot, condenser, etc., and is mainly used for continuous distillation of volatile solvents under reduced pressure, which is applied in chemistry, chemical industry, bio-medicine and other fields.

 The principle of rotary evaporator is: under vacuum conditions, heating at a constant temperature makes the rotary bottle rotate at a constant speed, and the material forms a large area film on the bottle wall, which evaporates efficiently. The solvent evaporates, then it is cooled by a high-efficiency glass condenser and recovered in the collection bottle, which greatly improves the evaporation efficiency. Rotary evaporator is especially suitable for the concentration and purification of biological products that are easily decomposed and denatured at high temperature.


When we experiment with a rotary evaporator, due to the difference in the boiling point of the internal and external solutions, if the aqueous solution is used for the experiment, the evaporation efficiency may be low. In this case, what should we do to solve the problem?


The slow evaporation speed of rotary evaporator can be solved by the following methods:

1. Check whether there is any problem with the vacuum pump and its joints, and whether the seals of each part of the equipment are damaged and causes the vacuum too low. A good vacuum can effectively suppress the boiling of the aqueous solution and improve the efficiency of evaporation and condensation.

2. You can add some alcohol to the solution to extract the water in the solution, which can effectively improve the efficiency. You can also add toluene to form an azeotrope, and then use a rotary evaporator to remove water.

3. Reduce the temperature of the cooling water in the condensing system to below 0℃, and it is recommended to use a low-temperature coolant circulating pump, which has a large cooling capacity and a fast cooling speed. The use of a low-temperature coolant circulating pump can solve the slow evaporation speed of rotary evaporator well.

4. Reduce the amount of solution to be evaporated each time, and it can be divided into several times. Although a small amount of method is more troublesome, it can significantly improve the efficiency.

Post time: 2021-04-12

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