How does vacuum level affect the degree of change in boiling point?
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Does increasing the vacuum level increase the boiling point difference between components with originally similar boiling points? Or it’s not certain; it depends on the specific substance?
Analyze specific substances individually. But there are other methods to separate substances with similar boiling points...
The boiling point is the temperature at which boiling occurs in an open system; it is a constant value that serves as a reference for a property. There is no concept of boiling point in a closed system; a closed system is governed by vapor pressure. When the system pressure is lower than the saturated vapor pressure at the corresponding temperature, the material evaporates. Increasing the vacuum level can lower the temperature required for the material to vaporize; however, it’s not certain whether this will improve the separation of different components
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You are referring to the effect of pressure on the separation efficiency of materials. The greater the pressure, the lower the separation degree; the lower the pressure, the higher the separation degree. The separation degree indicates the ease with which materials can be separated
In other words, vacuum can improve separation efficiency compared to normal pressure, right?
It can only be said relatively speaking. The boiling points are already quite similar; as a result, changes in pressure do not cause significant differences in boiling points, so other separation methods can be used to address this issue. For example, in extraction: a third medium is introduced, which is soluble with one of the media but has a significant difference in boiling points.