The Cold Finger

Copper Cold Finger

This design is very easy to make, and useful when you want to insert a condenser in the top of an open tube. Its efficiency is poor due to the limited surface area, but may be improved by confining the vapor with a shroud keeping it close to the cold surface. It is most useful for small amounts of vapor, as in the processing of botanicals.

This design is simply made by sealing off the bottom of the outer tube (which is the "Cold Finger") and then inserting a long, open tube through the middle of a cork. A second short tube through the cork completes the water path. If you use a Cold Finger for a reflux condenser on top of a column, You can increase the efficiency by winding a copper tube around the shroud and soldering it in place. This is the "Gloved Cold Finger" mentioned in Chapter 3. This additional tube can be connected in series with the Cold Finger so the same water connection feeds both. If you do this, let the water flow through the Cold Finger first and then through the outside coil. This creates the greatest temperature difference at the part with the smallest surface area - the central Cold finger.

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Responses

  • leah
    How to build a cold finger condenser?
    8 years ago
  • diamanda
    How to make a reflux cold finger?
    7 years ago
  • james wolff
    How to make a copper cold finger?
    7 years ago

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