Author Topic: Super-dry ethanol  (Read 4915 times)

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Super-dry ethanol
« on: December 13, 2002, 05:57:00 PM »
This is the Lund and Bjerrum method for preparing super dry EtOH.

* Fit a dry 2 litre RB flask with a double surface condenser and a calcium dry tube.
* Place 5 g of clean dry Mg turnings and 0.5 of I2 in the flask, followed by 50 - 75 mg of commercial absolute EtOH.
* Warm the mixture until the iodine has disappeared.  If a lively evolution of hydrogen does not set in, add a further 0.5 g portion of I2.  Continue heating until all  the Mg is converted into ethanolate
* Then add 900 ml of commercial absolute ethanol and reflux the mixture for 30 minutes.
* Distill off the EtOH directly into the vessel in which it is to be stored.

The purity of the ethanol exceeds 99.5 % provided that adequate precautions are taken to protect the distillate from atmospheric moisture.  The super-dry ethanol is very hygroscopic; it may be stored over a Type 4A molecular sieve.