Fractionation is based on the differences between boiling points of components.
This is a distillation column that doesn't have a continuous feed. The material that is to be distilled will typically be in a round bottom still at the end of the column.
The reflux is the return of top product condensate from a distillation column back to the top of the column where it is able to flow down the column aiding with cooling and thus condensation in the column. It increases efficiency and enables a lower amount of theoretical plates to be used in the column.
Pressure is an important part in distillation because boiling points of different components to be separated depends on pressure, for normal distillation pressure is kept as 1 atmosphere but for components with high boiling points instead of rasing the temperature pressure is lowered till the vapor pressure of the components to be separated, hence the temperature to be raised becomes less, for example in vaccum distillation.
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HPLC Column is one type of tube containing a stationary phase react with mobile phase to detect peak