In Figure 3. a still is shown which, because of its offset design, we refer to as the "Mexican cactus". It consists of a 25 litre boiler surmounted by a 2V2 to 3 ft. length of IV4" copper tubing. This is the column. It will be packed with a suitable material (to be discussed later). At the top of the column is the stillhead where the vapours rising from the boiler are condensed to liquid and the liquid then split into two streams. The major stream, consisting of 90% of the condensed liquid, flows back down the column to the boiler while the other 10% is directed to the outside world via a small valve. Let us look at each part of the still in more detail.
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