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Author: Subject: Anhydrous copper sulfate for drying and testing solvents
alchemizt
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[*] posted on 29-7-2022 at 18:11
Anhydrous copper sulfate for drying and testing solvents


I see that for 50% ethanol, adding white copper sulfate to it, the CuSO4 doesnt change colour until I heat the solvent to about 60C approx, then it starts to turn blue fast. Attempting to dry 96% ethanol in this way, I dont see much of a colour change. Even when heating, stirring, adding a little bit of water, it still does not hydrate much like it does in pure water of 50% ethanol. Can anyone who uses this method to test for water in solvents shed some light on this?
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Rainwater
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[*] posted on 30-7-2022 at 04:01


It takes time and stirring, the anhydrous form is not soluble in alcohol so its less soluble in a %50 mix than in pure water

The finer the salt has been ground up the more surface area and the faster the reaction takes place. The crystals have to rearrange themselves to fit the water molecules around them.


[Edited on 30-7-2022 by Rainwater]




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Tsjerk
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[*] posted on 30-7-2022 at 07:07


With some time given you can use CuSO4 to dry ethanol. Just know that no matter how long you dry, the ethanol will never become absolute. You can actually test ethanol being absolute as it will decolor hydrated CuSO4.

When you have absolute ethanol and add a small crystal of blue sulfate, it will turn the crystal white after 12 hours or so.

[Edited on 30-7-2022 by Tsjerk]
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