How can acetic acid be distilled by freezing when its freezing point is over the freezing suggest of water.

Examples ~ above the web display the water section of the vinegar together ice and the acid as a liquid yet Wikipedia shows that freezing suggest of acetic mountain is 16.6°C.

You are watching: Theoretical freezing point of glacial acetic acid


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The procedure you space describing sounds prefer fractional freezing. Acetic mountain is commonly purified through this method, therefore 100% acetic mountain is often dubbed "glacial" acetic acid.

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

Acetic acid has actually a freezing suggest of 16.6 oC. Water has a freezing point of 0 o. They kind a eutectic at -26.7 oC (although I carry out not recognize the composition). The step diagram more than likely looks something prefer (but is not) the following.

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Phase Legend:

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

A mixture that acetic acid and water the is approximately 72% acetic mountain is cooled till it begins to frozen (solid blue vertical line), i beg your pardon happens approximately 2 oC. The phase changes from A (liquid solution) come C (Solid systems of water in acetic acid PLUS fluid solution). The solid solution is enriched in acetic acid compared to the initial liquid solution. The composition of the staying supernatant liquid solution is enriched in water compared to the original liquid solution. The composition of the heavy solution can be identified by illustration a horizontal (red) line to the step boundary between C and also E and reading under to 91% acetic acid. The ingredient of the continuing to be supernatant fluid solution deserve to be figured out by illustration a horizontal (green) line to the step boundary in between A and C and reading under to 63% acetic.

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The supernatant phase is removed and discarded, and the solid step is permitted to melt. The process is repeated. Each successive freezing returns a brand-new solid solution that is enriched in acetic acid, until the purity is together high as you want it.

Note, that because water and also acetic acid have actually a eutectic point, if we has started on the left next of the eutectic point, the phases would have actually been reverse. The solid would be enriched in water and the supernatant would have been enriched in acetic acid. The supernatant would be remove and kept, and also the solid would certainly be discarded. The supernatant would then it is in cooled and also fractionally frozen again to further enrich the supernatant in acetic acid till the eutectic allude is reached (at which allude the composition of the supernatant is identical to the composition of the solid phase). If you want to isolate acetic acid from a solution that is greatly water, I would certainly distil the systems until the ingredient is greatly acetic acid, and then fractionally freeze it.