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I remember reading about ethanol that's able to be found trapped within rocks, but I sincerely cannot find the source, so here I am.

I'm trying to understand how that works. I want to magnify it in my setting for the purposes of some very specific cultural phenomena I won't get into but basically what I'm asking is, how can large amounts of ethanol be found within rocks? Primarily, water soluble minerals that generally form in deposits. I don't think free-standing alcohol would suffice as I am certain it would simply evaporate.

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    $\begingroup$ You can easily find an aqueous ethanol solution trapped in a stone recipient if you go to certain more up-market pubs. $\endgroup$
    – AlexP
    Jan 2, 2023 at 23:38
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    $\begingroup$ Or you can just have your alcohol on the rocks instead ;) en.wikipedia.org/wiki/On_the_Rocks $\endgroup$ Jan 3, 2023 at 5:30
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    $\begingroup$ Are you sure you didn't read about ethane, a component of natural gas? Those organic chemistry names are all so inconveniently similar... $\endgroup$
    – Cadence
    Jan 3, 2023 at 10:20
  • $\begingroup$ There is at least one giant cloud of methanol in space, don't know if that helps. $\endgroup$
    – Grooke
    Jan 3, 2023 at 13:06
  • $\begingroup$ If you're looking for natural sources of ethanol, you might want to consider vegetables such as corn, sugarcane, pineapple, potato. These yield bio-ethanol byproducts. Might work depending on your story. $\endgroup$ Jan 3, 2023 at 18:18

4 Answers 4

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I wish I had better news...

Ethanol is a naturally occurring substance resulting from the fermentation by yeast of fruit sugars. (Source)

Why do we use corn? Because we can produce so honking much of it compared to the higher sugar content of fruit that the lower efficiency of corn becomes irrelevant.

I tried to hunt Google for any reference to ethanol or alcohol being trapped in rocks. I came up with nothing.

If ethanol occurs underground, it would occur due to the decomposition of biomass and wouldn't last very long. I kinda doubt any alcohol could last very long bound in any rocky substance. Even if it did, I'd imagine that it would evaporate long before it could be captured via (*ahem*) ore processing.

On the other hand, I'd like to recommend The Alcohol Textbook. Download that throwing-weight document and turn to page 41, then start reading. You'll get a better-than-average overview into ethanol and potential future sources.

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    $\begingroup$ I will remind you that In the Big Rock Candy Mountains You never change your socks And the little streams of alcohol Come trickling down the rocks $\endgroup$
    – Willk
    Jan 4, 2023 at 19:08
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Molecular sieves / zeolites

AFAIK, JBH is right; there are no alcohol containing rocks in nature. Jed Clampett can't shoot 3 raccoon lengths to the left and become a beer baron.

This answer won't give you a great alcohol rock, but it can work with a little effort.

There are minerals that will adsorb small amounts of alcohol and hold it strongly enough that it is not readily eaten by bacteria. They are zeolites and/or synthetic molecular sieves.

You either need to dehydrate natural zeolite at 170 degrees celsius and then soak the alcohol in, or make the synthetic zeolites and do the same thing. Synthetics have to be manufactured in autoclaves using organic templating agents, but they hold a lot more booze.

If they have the opportunity to hold water instead, they will take it, so getting them dry is necessary.

To release the alcohol, heat the zeolites at just above alcohol boiling temperature and capture the gas, or slowly seep water through it, displacing the ethanol as water adheres to the binding sites.

Other inorganic sorbents like activated carbon or special clays might work, but probably not as well.

Sodium ethoxide

You can react alcohol with sodium hydroxide to make sodium ethoxide. It's a white solid that's effectively 70% alcohol by weight. It's what used to be on those little refreshing KFC napkins many years ago (in my country anyway).

Add the correct amount of an acid (e.g. citric acid) and you will get an alcohol solution, potentially even a strong one.

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    $\begingroup$ KFC napkins? Is that right? what was the purpose? It is a pretty strong base (WP mentions it forms an alkali solution with pH as high as 15.5) corrosive and caustic... I'm not sure I want to wash my hands it in, no matter how oily the chicken was. $\endgroup$
    – James K
    Jan 3, 2023 at 10:38
  • $\begingroup$ I'm pretty sure that only the sodium ethoxide makes it into the napkins. Not even KFC wants their customers to have burnt lips. $\endgroup$
    – user53931
    Jan 3, 2023 at 15:58
  • $\begingroup$ @JamesK, yes, it was sodium ethoxide. But only a tiny quantity, not enough to destroy the fat in your hands normally, let alone in their post KFC state. The ethoxide would react with a tiny bit of fat, or water forming soap +alcohol, which would strip the fat off your hands and feel nice and cold. $\endgroup$
    – user86462
    Jan 3, 2023 at 19:16
  • $\begingroup$ @JamesK If there had been much more in them, they would have burned your hands just like you're envisioning. And yes, they did really irritate your lips if you wiped them and they weren't covered in grease. $\endgroup$
    – user86462
    Jan 3, 2023 at 19:25
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As other answers have pointed, out a sustained process for producing and entrapping alcohol in rock would be difficult to explain, but perhaps a one-time natural catastrophe could fit your story line.

Consider a large orchard or natural formation of fruit bearing plants where in late summer/early fall there is a lot of fermenting fruit on the ground that is subsequently covered by a land slide. Sealed off from oxygen, the fruit ages like a fine wine for decades until the seam is discovered in the hardened sandstone.

There may be other compounds present that would disrupt the flavors or make the fruit go bad during this time, but something to consider depending on how chemically accurate you wish it to be.

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There are methane pockets in permafrost, coal seams, and all the usual places you'd find natural gases. There are methods, using zeolites (like Sean said), to convert methane to methanol that might occur naturally. Of course methanol is not the thing you want, it's the "bad" alcohol.

Either way the only way that pockets of ethane/ethanol or methane/methanol would last any length of time would be in protected environments that would either have high pressure (think geysers that spray oil and gas when punctured) or low temps (frozen under ice or permafrost). The freezing point of ethanol is around -110C (at 1 bar) so it would have to be cold like the poles of Mars.

The stuff is volatile so would end up out-gassing or evaporating given any chance.

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  • $\begingroup$ The adsorption onto zeolites devolatilises alcohols and makes them unavailable to organisms, so if you had a gigantanormous zeolite deposit, you might solve those problems. I'd forgotten about methane cracking though. That actually gives a (slightly implausible) natural route to an alcohol rock: zeolites form in hot, wet, high p conditions. Water leaves, zeolites dehydrate. Ethane enters and under very high pressure and temperature turns into ethanol. $\endgroup$
    – user86462
    Jan 4, 2023 at 0:31

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