Rotary evaporators are now universally suitable for small and medium-sized experiments, and are essential instruments for laboratory experiments such as distillation, concentration, crystallization, purification, and separation. The experimental sample is distilled under reduced pressure in a spherical flask, and forms a thin film under the action of centrifugal force by rotating at a constant speed, thereby increasing the evaporation area and improving the evaporation efficiency. The sample recovery of rotary evaporators is not only related to the nature of the material, but also the way we use the rotary evaporator, which will also have a great impact on the recovery rate. The following is the effect of vacuum on sample recovery.
I. If the rotation speed of the rotary evaporator is too fast, the recovery rate will be affected. Too high vacuum will make the experimental target evaporate and lose with the solvent. In addition, please note that the solvent cannot be bubbled during rotary evaporation, and we can control it by reducing the temperature and the speed of rotation.
II. When the vacuum is too high, we can add a buffer bottle between the vacuum pump and the rotary evaporator, which can effectively prevent the test substance from being sucked into the vacuum pump. If you are using a diaphragm pump, there will be a knob near the meter head to roughly adjust the pressure in the system.
III. The temperature of the condenser is the key factor that influences the recovery rate. If the temperature of the condenser is too low, it will cause the evaporated test substance to accumulate in the condenser and fail to dissipate heat in time. The vacuum pump will suck the test substance in when it is working. In addition, what we need to pay attention to is that if our experiment is a substance like ether, we need to change the water in the pump frequently, otherwise it is easy to cause a fire.
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