How deserve to acetic mountain be distilled by freezing when its freezing suggest is over the freezing point of water.

Examples on the web show the water part of the vinegar together ice and also the acid as a liquid but Wikipedia shows that freezing point of acetic acid is 16.6°C.

You are watching: What is the freezing point of glacial acetic acid


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The procedure you room describing sounds choose fractional freezing. Acetic acid is frequently purified through this method, for this reason 100% acetic mountain is often dubbed "glacial" acetic acid.

As an example of how this works, let"s think about a mixture that acetic acid and water.

Acetic acid has a freezing point of 16.6 oC. Water has actually a freezing allude of 0 o. They type a eutectic at -26.7 oC (although I execute not know the composition). The phase diagram probably looks something choose (but is not) the following.

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Phase Legend:

A = liquid solutionB = Solid solution of acetic acid in water PLUS liquid solutionC = Solid solution of water in acetic mountain PLUS liquid solutionD = Solid systems of acetic mountain in water E = Solid systems of water in acetic mountain F = Solid equipment of acetic acid in water add to Solid solution of water in acetic acid

A mixture the acetic acid and water the is roughly 72% acetic acid is cooled till it begins to freeze (solid blue vertical line), i beg your pardon happens about 2 oC. The phase alters from A (liquid solution) to C (Solid systems of water in acetic mountain PLUS liquid solution). The solid equipment is enriched in acetic acid contrasted to the initial liquid solution. The composition of the continuing to be supernatant liquid systems is enriched in water contrasted to the initial liquid solution. The composition of the heavy solution can be figured out by illustration a horizontal (red) line to the step boundary in between C and also E and reading under to 91% acetic acid. The composition of the remaining supernatant liquid solution can be identified by drawing a horizontal (green) heat to the phase boundary in between A and C and also reading under to 63% acetic.

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The supernatant step is removed and discarded, and the solid phase is enabled to melt. The process is repeated. Each successive freezing returns a new solid equipment that is enriched in acetic acid, till the purity is as high as you want it.

Note, that because water and acetic acid have actually a eutectic point, if we has actually started top top the left next of the eutectic point, the phases would have actually been reverse. The solid would be enriched in water and also the supernatant would have actually been enriched in acetic acid. The supernatant would be remove and kept, and the solid would certainly be discarded. The supernatant would certainly then be cooled and fractionally frozen again to additional enrich the supernatant in acetic acid until the eutectic allude is reached (at which point the composition of the supernatant is equivalent to the ingredient of the solid phase). If you desire to isolation acetic acid from a equipment that is mainly water, I would certainly distil the equipment until the ingredient is mostly acetic acid, and then fractionally frozen it.