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Author: Subject: Glacial acetic acid expands on freezing?
hodges
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[*] posted on 26-1-2023 at 14:54
Glacial acetic acid expands on freezing?


I purchased some food-grade glacial acetic acid. It arrived frozen due to the temperature outside. I notice it has expanded, apparently upon freezing. The plastic bottle is slightly swollen, and upon opening the top I can see that the liquid expanded all the way through the neck of the bottle before freezing.

I thought almost everything except for water contracted upon freezing.

I looked for a density chart. I did notice the unusual property of concentrated solutions having a lower density than some dilute solutions (even though both are greater than those of water). But I could not find a density vs. temperature chart.
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[*] posted on 26-1-2023 at 19:09


I think acetic acid and gallium are the only two common liquids that expand upon freezing, other than water.



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[*] posted on 26-1-2023 at 20:06


There's a small handful of examples besides water.... but I don't think acetic acid is one of them! Wiki/Merck say the liquid density is ~ 1.05 g/cm3 vs the solid density is ~1.27 g/cm3. I put mine in the freezer for a few minutes and got this:

frozenAceticAcidGlaciers.jpg - 101kB

not sure what to make of the swollen bottle!





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[*] posted on 26-1-2023 at 20:48


It does NOT expand of freezing. It shrinks. I have frozen it already few times in original glass bottles (>99%) to increase concentration and the glass survived every time. I was more worried on melting but also then the glass survived. I suppose tiny layer of melted acid was created between glass and frozen acid which prevented breaking glass on melting - luckily the melting starts from outside and not from the center. Also the volume significantly reduced during freezing and increased during melting, which was well visible by eye as the bottle was full before freezing and there was much more free space after freezing. I let bottles in fridge at +4 C for half a year, small periodical oscillations of temperature made solid acid to be at bottom and small amount of liquid on top which was then easy to pour out (unlike at the beginning when most of liquid trapped in the icy acid). I did the same as well with my 1,4-dioxane where at the beginning there was only a little of liquid visible but after months the volume of liquid is significantly bigger as the liquid which was initially frapped among crystals went slowly to the top.
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[*] posted on 27-1-2023 at 02:04


If it would expand, they would have a hard time selling it in glass bottles, or even plastic bottles.
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[*] posted on 27-1-2023 at 08:49


Glacial acetic acid definitelly does not expand when freezes. It freezes in my shed every winter in glass bottle without any accindent.
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[*] posted on 27-1-2023 at 09:29


I stand corrected.



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[*] posted on 27-1-2023 at 16:35


After sitting inside for about 24 hours, most of the acetic acid has melted. Indeed, the solid part goes to the bottom.

Not sure why the whole bottle was frozen solid yesterday, with the ice expanding even into the neck of the bottle. Perhaps someone transported it upside down (even though the box has an arrow on it, and was correct when it arrived on my doorstep. Perhaps air got stuck in it due to motion while transporting.

Today the liquid does not even come up to the top of the bottle (with some frozen part still present).
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