alt Hacker News> This is actually a myth. I’ll have to see if I can find the papers I read but mass spectrometry has shown that methanol comes out throughout the entire process. The idea that things come out at their boiling temperature is a drastic oversimplification.
Please do find those papers! They may be describing a radical new chemistry that I'm not familiar with.
To be clear - methanol boils at 64C and ethanol boils at 78C. Are you suggesting that in standard distillation, there is still some non-trace methanol coming over at 78C? If I personally observed that in a laboratory setting, I'd quickly assume measurement error or external contamination.
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>To be clear - methanol boils at 64C and ethanol boils at 78C. Are you suggesting that in standard distillation, there is still some non-trace methanol coming over at 78C?
From what I remember, the highest concentration of methanol is in the tails. That should tell you everything.
*EDIT* Found the paper
https://op.europa.eu/en/publication-detail/-/publication/0b9...
https://en.wikipedia.org/wiki/Brownian_motion
Temperature is just an average, the individual molecules can have a higher or lower temperature and can therefore evaporate already below boiling point.
When you mix different liquids, all manner of complex things happen to their vapor pressure vs temperature curves.
Yes. It doesnt work the way you think. When you mix chemicals together and then boil, the result isn’t that simple.
Think of it this way: ethanol boils at 78.5. Water at 100. But when I’m distilling, the first stuff out of the still is coming out at like 80/20 ethanol to water, long before I’m near 100C. The later stuff still has some ethanol in it, even as I near 100C. (You can easily measure while distilling.)
So why would it be surprising that methanol behaved that way as well?
>They may be describing a radical new chemistry that I'm not familiar with.
It's probably pot still vs. reflux still. Chemists use fractionating columns to get better separation. Home distillers won't necessarily do so, so official advice has to assume they will not.
I mean—depending how much methanol was in the mix to begin with…
It’s been a long time, but I thought there was a whole Raoult’s Law thing, about partial pressures in the vapor coming off the solution combining in proportion to each component’s molar fraction * its equilibrium vapor pressure (at that temperature, presumably). Or something.
Point being, if you’re starting with a bunch of volatiles in solution, there’d be quite a bit of smearing between fractions boiling off at any given temperature/pressure. And you’d be very unlikely to get clean fractions from a single distillation anywhere in that couple-dozen-degree range.
Probably mangled the description, but isn’t that why people do reflux columns?
There are azeotropes - mixtures that distill together at a different temperature than either alone.
You can’t distill ethanol to higher than 95% because of the 95-5 ethanol-water azeotrope that boils at 78.2C, versus ethanol alone at 78.4C.
Methanol-water and methanol-ethanol don’t form an azeotrope so if properly done you can separate methanol via distillation.
I would assume it depends on what you are distilling.
If you are making brandy from clarified wine, it probably separates better than rotten grape mash.
It is still a continuum with some methanol molecules likely remaining even in the tails.
For all intents and purposes, the distiller's rule of thumb of throwing away the angels' share is still going to work because low methanol concentrations are never an issue —for the antidote for methanol is ethanol.
From what I understood ethanol and methanol form an azeotrope and boil together at a mixed temperature. And the going blind stuff is just prohibition propaganda both to make home distilled alcohol seem dangerous and to scapegoat the fact that the government was actively poisoning "industrial" ethanol.
Look at it this way: The boiling point of ammonia is -33 C. Would you drink a jug of household cleaning ammonia just because it's been heated to +20C?
But anyway, I don't think there's hazardous levels left after normal distillation+cutting, the reason for not buying booze from some guy behind a barn usually has more to do with lead contamination risks.
I suspect that the vapor of the mash is always a mix of the components, and even above the boiling point of methanol, it still produces a mixed vapor. At room temperature, all of the components produce some vapor and will evaporate. This continues as the temperature rises.
It's not clear to me that simple distillation of a methanol/ethanol mixture can produce either pure ethanol or pure methanol at any point, just as it's impossible to distill ethanol and water to pure ethanol (absolute alcohol) if the water is above a small percentage of the mixture.