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Author: Subject: Porous plate
Pumukli
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[*] posted on 23-12-2018 at 10:35
Porous plate


What is the so called "porous plate"?

I've been reading old (circa 1900) chemistry papers recently and found the above expression in numerous synthesis descriptions.

This plate is something what was used to purify things by placing them on porous plate and let it drain things off from these things.
I can imagine something like "pressing the crystalls between filter papers" in action but this porous plate thing is too much for my fantasy.

Btw. the plate is sometimes referenced as "porous ceramic plate". Was it some sort of non-recyclable filter? Or could it be cleaned after use?
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happyfooddance
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[*] posted on 23-12-2018 at 11:27


See "frit"
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Pumukli
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[*] posted on 23-12-2018 at 11:49


Yes, frit comes to mind, but they never mention"vacuum" or "suction" or "filtration" in connection with the plate.

These old chemists wrote quite detailed reports on their work and I think it means something that NONE of them mentioned so far these keywords. (I read at least 20 papers from different authors who used this plate.)

They just "put" things on these plates and miracle happens (or capillary action intervenes) and the substances purified.



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[*] posted on 23-12-2018 at 12:29


Yes, you just put your substance on the frit and magic happens (we call it chromatography). It happens because of the capillary action just like you said.

Sometimes just a filter paper will do.

Some other factors affect how well it works, such as the angle of the frit/paper and the humidity.
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S.C. Wack
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[*] posted on 23-12-2018 at 12:52


They sound difficult to clean and the subject has come up before. Coors does not define their white porous wares beyond ceramic. In the old days it was an unglazed "porcelain", perhaps different from Coors unglazed crucible porcelain in strength, starting content, or firing temp. You want to look in the old books on ceramics not chemistry.



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Pumukli
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[*] posted on 23-12-2018 at 17:09


After two more old articles where W.H. Perkin used these plates it seems that these were used instead of filter paper to dry crystalls. He put the crystalls obtained from a recrystallization on a ceramic plate and after a day they were dry. The plate absorbed all the "oils".

He also wrote that the oils contained another isomer of the product and in order to get it the plates were extracted in a Soxhlet apparatus.

Now I wonder if they were broken up before they were put in the extractor or they used XXL sized extractors in those days. :-)
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[*] posted on 23-12-2018 at 19:18


I wonder if one of the several typical types of sponges (for cleaning, cosmetics, etc.) might be useful in this capacity.

Surely it could be made better by a soak in a sodium silicate solution + a controlled dry.

Any mad scientist can scrounge a sponge and a few silica gel packets which is why I mention it here.


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[*] posted on 23-12-2018 at 20:35


I bought an unfired ceramic dinner plate for such use. It seemed to do the job of removing free liquid from crystals.

(greenware from a pottery craft shop)

[Edited on 24-12-2018 by Magpie]




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[*] posted on 24-12-2018 at 04:18


The smallest size of plate both today and 100 years ago was 150 mm.; Coors sells them 6 mm thick. Like an unglazed tile one might find at the hardware store? Do acids leach the Fe, etc. out of flowerpot material?



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