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Date: | Wed, 17 Nov 2021 15:53:10 -0500 |
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> you can watch this process happen in a pan vaporizer. You charge the pan with dihydrate. As you heat the pan you see the dihydrate melt to a liquid. Immediately after melting you see the liquid foam as the water boils off. Then the liquid turns back into a foamed solid which is anhydrous oxalic acid. For quite some time, about a minute in my experience, with pan sublimers nothing much happens at all as the temp is too low to cause significant sublimation. Then rather suddenly you start to get a large cloud of fog over the pan as the anhydrous oxalic acid sublimes.
Yes, a good quality and expensive unit like the pro-vap has the mass to slow this process down, but the cheaper ones that sell much better because they are so much cheaper have a smaller mass, and a very rapid temperature rise that might be instructive to watch - the multi-stage process described above is less clear to the eye, and makes me wonder if the water is all gone quite so quickly as one might hope, and if there is any pause at 100c, or any drop in temp during the "foamed solid" phase.
The specific apparatus used, as usual, changes the experiment significantly.
> One of the refs I posted earlier pointed out that you could take the dihydrate and heat it at 70 deg C in an oven... That pressure build up can be a bit dangerous if you blow the lid and your face or body is in line with the lid and likely hot liquid flying up behind the lid...
Wow, I'm not sure that would be any improvement at all in "safety".
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