The condenser

The alcoholic vapours are condensed by means of cold water running through a coil of copper tubing inserted in the stillhead. To make this coil use 16 feet or so of 3/i6" flexible copper tubing.** Such tubing is not usually stocked in the plumbing section of a hardware store but can be found in the automotive supply section since it is used for fuel lines. Even Vg" tubing can be found there if required, so don't be fobbed off by a salesman saying that W tubing is the smallest made. Make a hairpin from the 3/i6" tubing about 14" from one end with the two arms close enough to one another to fit inside the IV4" condenser jacket. Gently grip the hairpin vertically in a vise so as not to flatten it, put a short

Packing

Cooling coil

Packing

Needle valve

FIGURE 5. STILLHEAD

length of 3A" pipe over the short side of the hairpin to act as a mandrel, jam a piece of wood down inside to stop rotation and now wind the remainder of the 3/16" tubing around the outside. The whole operation will take about 5 minutes.

Note that the cooling water enters at the top of the coil in order to provide countercurrent flow of water and vapour. All heat exchangers work in this fashion and are much more efficient than when used with concurrent flow.

Several readers have asked about the top of the stillhead being open to the atmosphere. Shouldn't it be closed, they ask, to prevent vapour escaping? The answer is "no". The vapour rising up the column should be totally condensed to liquid, leaving nothing to escape through the top. If any vapour does manage to by-pass the cooling coil (detectable by putting your nose over the top and sniffing) then the coil hasn't done its job properly and you need more cooling surface or a lower water temperature.

The draw-off needle valve is attached to the underside of the horizontal portion of the stillhead by means of a short length of 1/4" tubing soldered to the stillhead, while the valve is attached to this tube by means of a compression fitting. This will avoid the necessity of having to heat the valve itself during soldering. In order to ensure a clear passage for the exiting liquid, and also to strengthen the joint, a useful tip is to attach it where the elbow overlaps the 1V4" tube (see Fig. 5). Before soldering the elbow in place drill a V4" hole in it where it will overlap the inside tube. Then solder the elbow in place. Position the short length of V4" tubing in this hole in the elbow, butting it up against the tube inside. Solder in place. Then drill right through the short length of tubing, penetrating the inner tube. This ensures that the draw-off tube is flush with the inside surface. If it stood proud the condensed liquid might flow around it instead of going down the hole.

The exit tube of the draw-off valve is shown in the diagram as being very short. The condensed alcohol emerging from the valve is quite hot, hot enough, in fact, for some people to put a small heat-exchanger on it to cool the alcohol before it falls into the collection bottle. A simpler method is to add a copper extension tube below the needle valve so that the alcohol is air-cooled before it enters the bottle. A long extension tube also allows you to place the collection bottle on a table. DO NOT use a length of plastic tubing for this purpose. Hot alcohol is a very aggressive solvent and will attack the plastic and make your alcohol cloudy.

** Note. If you cannot find any 3/16" copper tubing for the cooling coil you could use V4" tubing, a more common size. But if you do you will need to use 2" diameter copper tubing for the condenser housing since V4" tubing would flatten if you tried to wind it more tightly.

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