What do you typically observe when you distillate ethanol?
In: Chemistry
I’m not a chemist, but I own a distillation apparatus for home chemistry, hopefully what I have to say is insightful.
I think what happens depends on your source of alcohol, such as a fermented mash, a low alcohol solution, or ethanol that you’ve used as a solvent and are now recovering to use again.
First you need to understand that ethanol and water form an azeotrope, which means that the temperature at which the solution boils depends on the percentage of alcohol. If I remember correctly it’s somewhere around 96% that has the lowest boiling point. As you heat the solution, the vapor escaping is part water and part ethanol, and in the case of heating a fermented mash it might also have methanol and acetone. If you have a reflux column, you can get higher percentages of alcohol in the distillate.
The longer you heat the solution, the more water will come over, resulting in a weaker distillate. It’s impossible to completely separate water and ethanol using distillation.
If you’re distilling to recover a solvent, then you’ll be more interested in what remains in the flask. If you’re distilling a fermented mash, some of what remains might still be good to use for fermenting again.
Nilered and nurdrage both have multiple informative YouTube videos from a chemists perspective, and there are countless videos from a brewer’s perspective.
When you boil a liquid (containing ethanol), the ethanol in it boils before the rest does. Collect the vapor, it is almost pure ethanol, the rest (which is not ethanol) will remain in your boiler.
Alcohol has a lower boiling point than water but that does not mean that when you heat a mixture of alcohol and water that all the alcohol boils off first. The mixture will ‘boil’ in such a way that the vapor will have a higher alcohol content and the remaining liquid will have a higher water content.
The liquid and vapor are then separated. The vapor with the higher alcohol content can be cooled and condensed back into a liquid. Voila, you now have a stronger drink!
The process can be repeated creating mixtures that are higher and higher in alcohol content. But alcohol/water mixture does have a limit. At 95%, the liquid and vapor have the same concentration upon heating so distilling cannot *completely* separate water from alcohol.
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