# Why doesn't the alcohol separate out of the rest of the booze? **URL:** \ **Category:** Factual Questions\ **Created:** [May 13, 2012, 11:01pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812 "2012-05-13T23:01:21Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Tim\_R.Mortiss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim_r.mortiss/32/142_2.png) [@Tim\_R.Mortiss](https://boards.straightdope.com/u/Tim_R.Mortiss)\ **Post date:** [May 13, 2012, 11:01pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/1 "2012-05-13T23:01:21Z")
Water has a density of about 0.9980 g/cm^3 at 20 degrees C. Ethyl alcohol only has a density of 0.785. In a booze like vodka, which is basically ethyl alcohol and water, why doesn’t all the alcohol float to the top? Just curious… ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [May 13, 2012, 11:07pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/2 "2012-05-13T23:07:51Z")
Ethyl alcohol has a very high chemical affinity for water and mixes and bonds with it nicely. It does not want to push the water out of solution. See > **[Hygroscopy](https://en.wikipedia.org/wiki/Hygroscopy)** > > Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g. changing in volume, boiling point, viscosity or some other physical characteristic or property of the substance. For example, a finely dispersed hygroscopic powder, such as a salt, may ... > [@](#): > > Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment. This is achieved through either absorption or adsorption with the absorbing or adsorbing material becoming physically ‘changed’ somewhat, by an increase in volume, stickiness, or other physical characteristic of the material, as water molecules become ‘suspended’ between the material’s molecules in the process. While some similar forces are at work here, it is different from capillary attraction, a process where glass or other ‘solid’ substances attract water, but are not changed in the process (for example, water molecules becoming suspended between the glass molecules). > > Hygroscopic substances include cellulose fibers such as cotton and paper, sugar, caramel, honey, glycerol, ethanol, methanol, diesel fuel, sulfuric acid, methamphetamine, many fertilizer chemicals, many salts (including table salt), and a huge variety of other substances. ---
**Author:** ![Dufus](https://avatars.discourse-cdn.com/v4/letter/d/c77e96/32.png) [@Dufus](https://boards.straightdope.com/u/Dufus)\ **Post date:** [May 13, 2012, 11:13pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/3 "2012-05-13T23:13:28Z")
[Miscibility](http://en.wikipedia.org/wiki/Miscibility) ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [May 14, 2012, 12:25am UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/4 "2012-05-14T00:25:15Z")
Why doesn’t salt settle out of salt water? When one compound dissolves in another, the molecules, atoms, or ions are attracted to one another. So the OH in the alcohol has water molecules hydrogen bonded to it hold ing it is the water. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [May 14, 2012, 1:01am UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/5 "2012-05-14T01:01:52Z")
the alcohol and water molecules all mixed up like being that way, even better than the alcohol being by itself. it is a lower energy state. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [May 14, 2012, 3:42am UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/6 "2012-05-14T03:42:30Z")
The unspoken part of the question is, “Oil and water have different densities and separate, so why don’t alcohol and water?” The reasons why water and alcohol stay mixed are given above, but the reason for oil and water to separate doesn’t have anything to do with the differences in their density. The difference in density explains only why the oil ends up on top. ---
**Author:** ![Tim\_R.Mortiss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim_r.mortiss/32/142_2.png) [@Tim\_R.Mortiss](https://boards.straightdope.com/u/Tim_R.Mortiss)\ **Post date:** [May 14, 2012, 6:23am UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/7 "2012-05-14T06:23:58Z")
Thanks, fellers! I understand the dissolving process (i.e., salt in water). Didn’t realize the same was happening with the ethanol and water. Ignorance fought! ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [May 14, 2012, 7:34am UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/8 "2012-05-14T07:34:58Z")
And giving a bit more of an explanation on why water and ethanol “like” each other, it’s because both have the ability to form hydrogen bonds. Bigger alcohols aren’t as good at this (the organic part gets in the way), but methanol is even better - it also has the nasty defect of being poisonous to humans, tho. ---
**Author:** ![Oly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/oly/32/8255_2.png) [@Oly](https://boards.straightdope.com/u/Oly)\ **Post date:** [May 14, 2012, 12:23pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/9 "2012-05-14T12:23:58Z")
Put in terms of the fundamental forces, the electromagnetic force comprising their intermolecular interactions is stronger than the gravitational force acting on the individual molecules. ---
**Author:** ![Hypno-Toad](https://avatars.discourse-cdn.com/v4/letter/h/b2d939/32.png) [@Hypno-Toad](https://boards.straightdope.com/u/Hypno-Toad)\ **Post date:** [May 14, 2012, 12:52pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/10 "2012-05-14T12:52:34Z")
Is Hygroscopy the reason why alcohol dehydrates a person so much? ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [May 14, 2012, 12:55pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/11 "2012-05-14T12:55:49Z")
No, that’s because the chemical reactions involved in degrading the alcohol use up water, and because often when people are drinking alcohol they’re not drinking as much water as they need. If your body is at a stage where it needs “two glasses of water” and you give it “two glasses of 25% alcohol”, you’re missing half a glass of water. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [May 14, 2012, 9:54pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/12 "2012-05-14T21:54:54Z")
But, I bet they actually do separate out a bit, just not much. Isn’t that the same principle by which uranium hexafluoride gasses separate out according to the atomic weight of the uranium atom, in centrifugal enrichment processes? ---
**Author:** ![Oly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/oly/32/8255_2.png) [@Oly](https://boards.straightdope.com/u/Oly)\ **Post date:** [May 15, 2012, 12:36pm UTC](https://boards.straightdope.com/t/why-doesnt-the-alcohol-separate-out-of-the-rest-of-the-booze/621812/13 "2012-05-15T12:36:40Z")
> [@Hypno-Toad](#): > > Is Hygroscopy the reason why alcohol dehydrates a person so much? This is in large part due, I remember learning, to alcohol suppressing the action of ADH, a hormone that increases water reabsorption by the kidney. When ADH action is down, water reabsorption is down, and I.P. Freely starts renting beer instead of buying it.