Chemist1357
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Formic Acid Dehydration
Formic acid forms an azeotrope with water at 77.5%. I have this homemade but I need 85%-88%.
I can’t find any clear and easy way to dehydrate it further than 77.5% and I can’t buy 85% in Australia it just isn’t available anywhere and I
prefer to keep things otc.
Can you do it under vacuum or something? There’s always dumping a huge amount of anhydrous Copper(II) sulfate..
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Fery
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Industrially they use distillation of azeotrope at reduced pressure, IIRC something like 0,3 atm. But I suppose you need also a good column (like
insulated Hempel with Raschig rings) and variable adjustable reflux ratio distillation head for that.
https://www.researchgate.net/publication/343946284_Process_a...
I found also this for lab. preparation:
https://www.researchgate.net/post/How_do_I_remove_water_from...
You already have anhydrous CuSO4, other choice is B2O3
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draculic acid69
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Possibly go with the classics: mgso4 or CaCl2
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clearly_not_atara
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According to a paper found by Klute, formic acid can be dehydrated over anhydrous oxalic acid:
http://www.sciencemadness.org/talk/viewthread.php?tid=7012
Oxalic acid however is purchased as the dihydrate which in turn means you need to dehydrate it first. One method involves heating at 60 C in a retort
with a desiccant at the other end of the tube. Another is the use of alkanes with a Dean-Stark (toluene apparently does not work):
http://www.sciencemadness.org/talk/viewthread.php?tid=11153
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Fery
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If using anhydrous oxalic acid for concentrating formic acid works then you can maybe dehydrate oxalic acid dihydrate into anhydrous using silicagel
and desiccator. I once did that with a hope to dry my wet dihydrate crystals but after some time the crystals decayed into dust. The silicagel was
from a pack of effervescent vitamine tablets, nothing special.
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Texium
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In the past, I’ve dehydrated oxalic acid by azeotropic distillation with toluene and a Dean-Stark trap, followed by putting the resulting anhydrous
oxalic acid in a desiccator over anhydrous CaCl2 and paraffin wax shavings to keep it dry while absorbing any residual toluene.
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clearly_not_atara
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Quote: Originally posted by Texium  | | In the past, I’ve dehydrated oxalic acid by azeotropic distillation with toluene and a Dean-Stark trap, followed by putting the resulting anhydrous
oxalic acid in a desiccator over anhydrous CaCl2 and paraffin wax shavings to keep it dry while absorbing any residual toluene.
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Apparently toluene does work! :p
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Boffis
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Hi Chemist1357; I had this problem once and did some research into upgrading my formic acid and I found these two references I tried the azeotropic
distillation but was a pain though it does work.
Attachment: Anhydrous formic acid AmCJ Garner et al 1911.pdf (452kB)
This file has been downloaded 213 times
Attachment: phptP4SsQ (660kB)
This file has been downloaded 192 times
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Chemist1357
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| Quote: Originally posted by Boffis | Hi Chemist1357; I had this problem once and did some research into upgrading my formic acid and I found these two references I tried the azeotropic
distillation but was a pain though it does work.
How did you go about doing it? How much mmhg do you have to pull and what was the obtained concentration?
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