What is Rotary Evaporator Working Principle?

As a common evaporator in laboratory and industry, a rotary evaporator has been widely recognized for its excellent distillation and extraction performance. In the following, the working principle and structural features of a rotary evaporator will be introduced. I hope this article can help users make better use of a rotary evaporator.

Key Advantages in Use of a Rotary Evaporator

  1. That the centrifugal force and the frictional force between the wall of the rotating flask and the liquid sample result in the formation of a thin film of warm solvent being spread over a large surface.
  2. The forces created by the rotation suppress bumping. The combination of these characteristics and the conveniences built into modern rotary evaporators allow for quick, gentle evaporation of solvents from most samples, even in the hands of relatively inexperienced users. Solvent remaining after rotary evaporation can be removed by exposing the sample to even deeper vacuum, on a more tightly sealed vacuum system, at ambient or higher temperature (e.g., on a Schlenk line or in a vacuum oven).

What’s the Working Principle of a Rotary Evaporator?

A rotary evaporator is a kind of evaporation instrument, which is widely used in the chemical laboratory. It is suitable for reflux operation, rapid evaporation of a large number of solvents, concentration of trace components, and reaction processes that require stirring, especially for continuous distillation of large amounts of volatile solvents under reduced pressure.

The rotary evaporator, also called rotovap, is a common laboratory equipment consisting of: a motor, a distillation flask, a heating pot, condenser tubes and other parts.

  1. The evaporation flask is an eggplant-shaped or round-bottomed flask with a standard grinding mouth connection. The reflux serpentine condenser tube is connected to a pressure reducing pump.
  2. There is a three-way piston between the condenser tube and the pressure reducing pump. When the system is connected with the atmosphere, the evaporation flask can be removed. What’s more, the solvent will be transferred. When the system is connected to the pressure reducing pump, the system should be under reduce pressure.
  3. During the working process, the pressure should be reduced firstly, and then the motor should be turned to rotate the evaporation flask. In the end, the machine should be stopped and ventilated to prevent the distillation flask from falling off during rotation.

As the heat source for evaporation, a constant temperature water tank should be often provided. Through electronic control, the flask is rotated at a constant speed at the most suitable speed to increase the evaporation area. The evaporation flask was brought to a negative pressure state by a vacuum pump.

In short ,the principle of the rotary evaporator is electronically controlling the distillation flask to rotate at a constant speed at the optimum speed to increase the evaporation area. At the same time through the vacuum pump to make the evaporation flask in the state of negative pressure. The evaporation flask was heated in a water bath while rotating at a constant temperature, and the solution in the bottle was subjected to heat diffusion evaporation in a rotating flask under a negative pressure. The evaporation system can be sealed to a pressure of 400 to 600 mm Hg; the solvent in the distillation flask can be heated by a heating bath to heat up to the boiling point of the solvent; and the rotation can be carried out at a speed of 50 to 160 rpm to form a solvent film. Increase the evaporation area. In addition, the hot vapor can be quickly liquefied by the high efficiency cooler to accelerate the evaporation rate. The above is the introduction of the working principle of the rotary evaporator.

What’s the Structure of a Rotary Evaporator?

A rotary evaporator is mainly composed of six parts:condensing tube, collecting bottle, evaporating tube, rotary motor, vacuum system and bath pan.The condensing tube uses double serpentine condensation, adding a condensing agent such as dry ice and acetone to condense the sample; the collecting bottle effectively recovers the condensed sample, and the sample is cooled and collected through the collecting bottle; the evaporation tube first acts as a sample rotating support shaft, and secondly The sample is aspirated through an evaporation tube vacuum system; the rotary motor drives the evaporation bottle containing the sample by the rotation of the motor; the vacuum system is used to lower the pressure of the rotary evaporator system; and finally the bath is used to heat the sample with water or oil as a medium.

How to Use a Rotary Evaporator for Distillation?

Related Articles:

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Four Steps in Using a Rotary Evaporator

How does a Rotary Evaporator Remove Solvent

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