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Author: Subject: How to dry tartaric acid to make it anhydrous?
beerwiz
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[*] posted on 21-11-2018 at 20:55
How to dry tartaric acid to make it anhydrous?


How to dry tartaric acid to make it anhydrous?

I tried drying it in the microwave for 5mins on high but it turned brown and started boiling, probably caramelized?

What's the best way of removing all water from tartaric acid to make it anhydrous?
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j_sum1
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[*] posted on 21-11-2018 at 21:48


What organic solvents does it dissolve in?
My instinct would be to use a Dean Stark trap – the same as you do for oxalic acid (using toluene as a solvent). (Here is Nile Red. Here is Nurdrage[.)
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beerwiz
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[*] posted on 22-11-2018 at 03:24


It's soluble in water, methanol, and slightly soluble in acetone.
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j_sum1
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[*] posted on 22-11-2018 at 03:55


What about ethanol?
The problem with using methanol is that there is no azeotrope with water.

You might also have success with vacuum dessication or the use of a dessicator.
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fusso
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[*] posted on 22-11-2018 at 05:18


The situation with oxalic acid is like this: PhMe dissolves neither oxalic nor H2O. If one can use azeotropic distillation using PhMe to dehydrate oxalic then what about other combinations of hydrates and immiscible solvents? There are plenty others to choose from, like DCM, EtOAc or EtOH but I'm not sure if tartaric will react with alcohols, acids or esters under such conditions, and Clevenger apparatus is needed for DCM.



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monolithic
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[*] posted on 22-11-2018 at 05:47


Maybe this is a dumb question, but wouldn't a conventional (non-microwave) oven at 120-130C for a few hours also work?
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[*] posted on 22-11-2018 at 09:11


Microwave ovens with chemicals are almost always a bad idea. It's not good to run them against very little load and since your compound is polar it will continue heating it to decomposition even after any water of hydration is gone. Not to mention they don't heat evenly. I've melted glass in a microwave by accident trying to dry calcium chloride before.

A conventional oven a healthy margin below the decomposition point of the anhydrous compound is the way to go, as monolithic suggested. If you can find a decomposition temp for the hydrate listed somewhere, try to stay a good amount above that.
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[*] posted on 22-11-2018 at 09:51


Microwaves are my favorite in the lab, sodium sulfate and magnesium sulfate for example are dried in a minute when put in a glass bowl with a glass bowl inverted on top as a lid.

The dry salts don't absorp microwaves and don't heat any further while being dry.

Oxalic acid dihydrate also works fine but sublimes from bottom to top glass, so not to much can be dried at a time. And the glasses should closely fit
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