The fractionating column consists of a 21/z to 3 ft. length of 1V4" tubing. The rule of thumb is that the height of a column should be at least 15x its diameter, which would mean a column height of 19" minimum, but why not be generous and add a few more inches. The higher the column the better (within reason), because it provides a larger number of solid/vapour interfaces up the length of the column and therefore more re-distillations. Two and a half to three feet is convenient but you won't wish to go much over 3 ft. or you will hit the ceiling!
At the top of the column (see Figure 3) an elbow is provided for the passage of vapour across to the stillhead condenser and for a thermometer to measure the vapour temperature. At the base of the column there is a series of adapters, including a 11/4" union, to go from the 11/4" diameter of the column to the 3/4" pipe fitting on the top of the boiler.
The column must be well insulated to ensure a stable temperature regime up the full length of the column while it is refluxing.
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