Freezing Vodka

[phelixoflaherty]

Brought back 2 bottles of Vodka from Poland (Hols). Fired them in the freezer with along with a bottle of smirnoff. The smirnoff froze. The other 2 didn't.
Why so?

[Micky Dolenz]

Higher alcohol content I would think

[rubadub]

^^yep^^

There was a recent thread with a guy with freezing vodka. I have had captain morgans 35% go slushy. Most red smirnoff in offies here will be 37.5% while most vodkas abroad will be 40% or more. It seems to be a fine line, I never get 37.5% freezing in my freezer, but it is only a fridge freezer.

Also somebody could be nicking it and diluting it, a very common problem!

[grenache]

We have a freezer in work and we put all our vodka into it (Smirnoff included). None of it ever freezes. OP must have gotten a dodgy bottle.

[rubadub]

Originally Posted by grenache

OP must have gotten a dodgy bottle.

Or his freezer could be colder than yours.

[cHaTbOx]

The change in freezing point of the solution is the freezing point depression constant of water (-1.86 C per mole solute per kilogram solvent) multiplied by the solution's molality.

In one litre

• 40% bottle , 400 grams of the solution would be the alcohol and the remainder, 600 grams, would be pure water.
• In 37.5% , 375g alc , 625g water
• In 35% , 350g alc , 650g water

Molarity of ethanol is 46g/mole

• 400g/46g=8.69565217391
• 375/46= 8.15217391304
• 350/46= 7.60869565217

The molalities of the solution are:

• (8.69565217391 mol alcohol / 0.6 kg) = 14.4927536 molal
• ( 8.15217391304 mol alcohol / 0.6 kg) = 13.5869565 molal
• ( 7.60869565217 mol alcohol / 0.6 kg) =12.6811594 molal

So

• 40%= 14.4927536 * -1.86C = -26.9565217 C
• 37.5= 13.5869565 * -1.86C = -25.2717391 C
• 35%=12.6811594 * -1.86C = -23.5869565 C

But this is if the ethanol was pure , ethanol purity is limited to 95-96% due to due to the formation of a low-boiling water-ethanol azetrope.
Also Ethanol is about 20% less than the density of water so taking it's volume as weight means there is another error .
So these results are probably a few degrees off.

Sorry for all the science , hopefully it's right.
To put it simply , the more alcohol the lower the freezing point.

[rubadub]

Very interesting stuff, I did want to see the science behind it.

Originally Posted by cHaTbOx

Sorry for all the science , hopefully it's right.

As you mention the density alcohol is less. Also as it decreases in temp it will change in density again. A guy a week or so ago though he got too little vodka in his bottle, but was forgetting it reduces in volume once cold.

Also to further complicate things if you add 1 litre of 90% alcohol to 1 litre of water you do NOT get 2L of 45% alcohol, as you would expect. The volume will be less than 2L and it won't be 45%. They are different sizes at a molecular level, it is like saying a bucket of sand mixed with a bucket of tennis balls will fill less than 2 buckets. In saying that the effect is not very much, but the densities should be taken into account. I never knew how it was calculated before.

[cHaTbOx]

Originally Posted by rubadub

Also to further complicate things if you add 1 litre of 90% alcohol to 1 litre of water you do NOT get 2L of 45% alcohol, as you would expect. The volume will be less than 2L and it won't be 45%. They are different sizes at a molecular level

The OH- component of alcohol interacts with the H+ of the water molecules. These bonds attract each other to the point of making hydrogen bonds. These bonds result in a tighter molecular formation, reducing the volume of the combined liquids.

It's why cocktails don't mix completely

[Carawaystick]

Originally Posted by cHaTbOx

• 40%= 14.4927536 * -1.86C = -26.9565217 C
• 37.5= 13.5869565 * -1.86C = -25.2717391 C
• 35%=12.6811594 * -1.86C = -23.5869565 C

This shows that different ABV will have a reasonable spread of freezing point, If your freezer was -24.5degC, then only one bottle of lower alc smirnoff would freeze.
I would have expected shennanigans before the numbers show it's fairly plausible.