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Fractional Distillation

Explain why packed and spinning band fractional distillation columns are more efficient at separating two liquids having close boiling points than are unpacked columns.

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The spinning band was first used to increase the efficiency of a fractionating process in the late 1930's.

Efficiency in a fractionating still is a measure of the degree of enrichment or rectification of one compound as it is being separated from others within the column. This separation is invariably achieved through the intimate contact between the vapors rising from the still pot and the liquid or reflux descending within the column. As this liquid/vapor contact occurs, the result is that only the most volatile material proceeds upward towards the receiver, while the less volatile material returns downward as a liquid towards the still pot. Thus, the efficiency of the separation process depends on the frequency and degree of contact between the ascending vapor and the descending liquid. As this contact becomes more intimate and frequent, the fractionation will become more efficient.

As a separating medium, a number of stills of the `packed column` type have employed various types of stationary fillers situated in the column in order to result in ...

Solution Summary

This solution explains the effectiveness of packed and spinning band fractional distillation columns.

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