Distillation is a common method for purifying liquid substances and separating mixtures. The boiling point of the compound can also be measured by distillation, so it also has a certain significance for the identification of pure liquid organic compounds.
The change of saturated vapor pressure of a substance at different temperatures is the basis of distillation separation. Heating the liquid to boiling makes the liquid into a vapor, and then the vapor is cooled and then condensed into a liquid. The combined operation of these two processes is called distillation.
The boiling points of the components of the liquid mixture must be very different, at least above 30℃ to achieve a better separation effect. Select the heating device according to the boiling point of the distilled liquid. When the boiling point of the distilled liquid is below 80oC, use a hot water bath to heat; when the boiling point of the liquid is above 100℃, use a simple air bath or an oil bath to heat the asbestos mesh When the temperature is above 200℃, use a sand bath, an air bath and an electric heating mantle.
In the distillation operation, the following points should be noted:
(1) Control the heating temperature. If a heating bath is used, the temperature of the heating bath should be several degrees higher than the boiling point of the distilled liquid, otherwise it will be difficult to distill the distillate. The more the heating bath temperature is higher than the boiling point of the distilled liquid, the faster the distillation speed. (2)However, the temperature of the heating bath should not be too high, otherwise it will cause the vapor pressure of the distillation flask and the upper part of the condenser to exceed atmospheric pressure, which may cause accidents, especially when distilling low-boiling substances.
The temperature should be strictly controlled during distillation because things that are too low can not be steamed out, and those that are too high can be steamed out, and may also cause the decomposition of the required substances, or the decomposition of undesired substances to generate new impurities! Prolonging the time can make the distillation process more adequate.
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