Comments on: At what temperature does vodka freeze?

Question: At what temperature does vodka freeze?

pompomtom — Mon, 17 Jan 2005 15:55:29 -0800

ChillFilter: At what temperature does vodka freeze?

We have a standalone freezer, which does a very good job. It doesn't seem to have a thermostat, and if I'm not careful with shelf-selection, I can look forward to having vodka somewhere between nicely viscous, and mostly frozen. I haven't yet had a completely frozen bottle... more often a large chunk of ice, and some oozing gel-like substance. So, how cold is my freezer (bonus points for answers in ºC!), and is the sludgy stuff significantly more alcoholic than the ice block in the middle?

By: Mayor Curley

Mayor Curley — Mon, 17 Jan 2005 16:05:43 -0800

Ethanol freezes at –110°C or something obscene like that. And it thickens more as it gets closer to that point. But you'd need to determine the density of your syrupy component to know the exact temperature (and not warm it while you measured.)

Your home freezer would have to be really something to be able to totally freeze alcohol. I'll bet that you're as close as you're going to get.

By: gwint

gwint — Mon, 17 Jan 2005 16:06:17 -0800

Well, the first result for "freezing point of vodka" on google yields:

80 proof vodka will freeze at approximately -26.95C or -16.51F. 100 proof vodka will freeze at approximately -40.43C or -40.78F (for why these numbers are approximate read the full post).

By: zelphi

zelphi — Mon, 17 Jan 2005 16:06:17 -0800

-40°C (says this)

By: sled

sled — Mon, 17 Jan 2005 16:22:54 -0800

It's freezing point depression, the formula is Delta T = K(sub F)m where Delta T is the change in freezing point, Kf is a constant (-1.86m/C for H2O), and m is the molality of the soln.

If you want to calculate the freezing point of Vodka go through the following exercise.

Assume 1000g of soln, we'll use 80 proof in this example, 40% ethyl alcohol (CH3OH) and 60% H2O. That means we'll have 400g of CH3OH and 600g (0.6kg) H2O.

First, obtain the number of moles of CH3OH in the soln to determine molaity. CH3OH has a molar mass of 46.7g/mol.

(Mass CH3OH) / (Molecular Weight CH3OH) = moles CH3OH

(400g CH3OH) / (46.7g/mol CH3OH) = 8.57 mol CH3OH

Next calculate the molality of the soln.

(Moles Solute) / (Mass Solvent) = Molaity

(8.57 mol CH3OH ) / (0.6kg H2OH) = 14.28m

Now, plug into the freezing point depression equation.

Delta T = K(sub F)m

Delta T = (-1.86m/C)(14.28m) = -26.56C

Therefore a soln of 40% ethyl alcohol and 60% water would have a feezing point of 0C + (-26.56C) = -26.56C

To convert to F use, C = (F-32) * ( 5/9) or F = -15.81F

Or the dirty way (change the 40 in that equation to proof/2).

By: Yelling At Nothing

Yelling At Nothing — Mon, 17 Jan 2005 16:33:47 -0800

Sled = wins.

By: five fresh fish

five fresh fish — Mon, 17 Jan 2005 17:14:06 -0800

Argh. Damn university kids think they know everything.

Well done, sled.

By: elpapacito

elpapacito — Mon, 17 Jan 2005 17:43:17 -0800

*evil evil*
I guess the formula refers to pure H2O ? Doubt there's pure H20 and pure CH30H in vodka....so i guess it's better to write "equals roughly" -26.56C rather then "equals"

/now less evil :)

Excellent explanation, among the best I saw in askmeta

By: pompomtom

pompomtom — Mon, 17 Jan 2005 17:44:26 -0800

Wow.

Thanks all, especially sled.

By: kenko

kenko — Mon, 17 Jan 2005 17:51:06 -0800

As for it being more alcoholic, fractional freezing is a cheap-ass alternative to distillation if you want to up the proof of something--the water freezes out first so the liquid left behind is more alcoholic.

By: Civil_Disobedient

Civil_Disobedient — Mon, 17 Jan 2005 19:11:05 -0800

sled: A+

By: gwint

gwint — Mon, 17 Jan 2005 19:18:37 -0800

Oh yeah, like you guys know what the "molality of the soln" means.

By: sfenders

sfenders — Mon, 17 Jan 2005 19:39:00 -0800

40% ethyl alcohol (CH3OH) and 60% H2O. That means we'll have 400g of CH3OH and 600g (0.6kg) H2O.

...? I thought that 40% was by volume, not mass.

By: ruwan

ruwan — Mon, 17 Jan 2005 20:14:02 -0800

Wow sled... props on remembering freshman chemistry. I was thinking "isn't there a formula for this?" and gave up and looked it up instead. 2 point to you.

By: rxrfrx

rxrfrx — Mon, 17 Jan 2005 20:52:26 -0800

sfenders, that's correct. ethanol, being something like 3/4 of the density of water, makes up less than 40% by mass of a 80-proof solution.

Put that smaller mass of EtOH into sled's math and you get about 21 °C in freezing point depression.

By: jmd82

jmd82 — Mon, 17 Jan 2005 23:45:41 -0800

EtOH? Man, now we're getting into Organic Chemistry...

By: rorycberger

rorycberger — Tue, 18 Jan 2005 01:48:00 -0800

so, now that we've established that....how much alcohol is likely in the sludgy stuff. And more importantly, how does it taste?

By: severiina

severiina — Tue, 18 Jan 2005 02:11:10 -0800

Small correction to sled's otherwise excellent answer.

... 40% ethyl alcohol (CH3OH)...
posted by sled at 4:22 PM PST on January 17

CH3OH = methyl alcohol (or methanol)
CH3CH2OH (or C2H5OH) = ethyl alcohol (or ethanol or EtOH)

Vodka (hopefully) contains ethanol.

By: biffa

biffa — Tue, 18 Jan 2005 02:18:56 -0800

sfenders, that's correct. ethanol, being something like 3/4 of the density of water, makes up less than 40% by mass of a 80-proof solution.

Does this take into account that alcohol/water solutions are denser than the pure versions of either?
sled was clearly doing back of the envelope bucket chemistry to explain the underlying science, stick with the textbook figures if you want to be precise.

By: pompomtom

pompomtom — Tue, 18 Jan 2005 04:50:55 -0800

so, now that we've established that....how much alcohol is likely in the sludgy stuff. And more importantly, how does it taste?

It tastes just fine, but then, I'm generally having it with kahlua.

(if I'm drinking it straight, I'm a few drinks past being a reliable witness...)

By: fvw

fvw — Tue, 18 Jan 2005 08:02:10 -0800

Based on experience instead of science: In a normal 4-star freezer, 37.5% vodka will freeze but 40% vodka will remain liquid.

By: mr_roboto

mr_roboto — Tue, 18 Jan 2005 11:45:07 -0800

so, now that we've established that....how much alcohol is likely in the sludgy stuff.

This isn't as straightforward as sled's calculation: you'd need a water/ethanol phase diagram to figure it out. I looked a bit for one, and couldn't find it online (at least not in the proper temperature range; people tend to be more interested in distillation). Apparently, Google Answers couldn't find one either. Check your nearest chemistry (or chemical engineering) library!

I think we can say confidently that the solid will be enriched in water, while the liquid is enriched in alcohol.