In the section on making Angel Water, I mentioned that potassium carbonate will pull moisture from the air into itself. It will also do this in an alcohol environment, as potassium carbonate (Salt) and alcohol (Mercury) are polar opposite to each other and cannot mix. We will use this to our advantage, as the potassium carbonate will hold back the water as the alcohol is being distilled off.
To do this, calcine 200g of potassium carbonate per liter of 95% alcohol, let cool down to a warm temperature, then pour your alcohol over it, close very tightly, and shake vigorously to ensure good mixing. Do this several times a day. Allow the mixture to stand at room temperature for at least a day, then distill at 85C. If you have a vacuum pump, this will help as it restricts exposure to air. Once the alcohol is chemically dried in this manner, it will act the same way potassium carbonate does, that is, it will pull moisture from the air into itself, even in a closed bottle, until it reaches roughly 96% again. It is a good idea, then, to use it as soon as possible.
Do not distill to the point where the potassium carbonate is dry, only go until the alcohol is just touching its surface in the boiling flask. Once this first distillation is done, it should be over 98%. A second distillation using 100g potassium carbonate as above will push it above 99.8%, and a third using 25g should yield perfectly dry, absolute alcohol.
There is a trick to recovering un–distilled alcohol from your distillations. Say you used 200g of potassium carbonate. Once the distillation is done, you can pour in nearly the same quantity of distilled water, say 190ml, shake it up, then let it stand for a few hours. You will find that the mixture has split itself into two distinct layers. The top part is the remaining alcohol, possibly coloured pink, and can be siphoned off using a syringe, to be redistilled later. The bottom part is potassium carbonate dissolved in water, and can be dried and calcined and reused later.
Guide by James Collins