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Alucard
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Never measured exact value, but I would say about 20% by weight solution of EF in water may be formed, or up to 1/4 by volume EF/water (I mean 1/4 EF
and rest 3/4 is water).
BTW you can easily salt out EF by using NaCl. I never measured exact effectivity of salting out process, but NaCl works anyway, a decent amount of EF
may be salted out from water though.
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unionised
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Quote: Originally posted by Cou  | Wikipedia says hexane doesn't form an azeotrope with water. https://en.wikipedia.org/wiki/Azeotrope_tables'
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It's been pointed out that Wiki doesn't say there isn't an azeotrope, it just doesn't say that there is one.
But it's useful to recognise that anypair of miscible liquids will form an azeotrope.
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Fery
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Hi Boffis, very nice !!! Thx for report There is no azeotrope in ethyl formate - water system (read the pdf which I attached previously, there are 3
esters preparation from which 2 form azeotrope with water and this one doesn't). But partial pressure of water at 54 C is nonzero and a little of
water distills. This is why I used 500 cm hempel column with raschig rings as the final step because I have never achieved 100% dryness of any ester
using Na2SO4 - every ester which forms azeotrope with water always started to distill as emulsion (only just few first ml were always turbid, which is
also good as it dehydrates the remaining ester to dryness). I use Na2SO4 as drying agent because I have it 5 kg in stock, which seems to be far more
than I'll manage to use in my whole life. I have few kg of MgSO4.7H2O but I don't have any motivation to dehydrate it (because of the amount of
Na2SO4). I have also few kg of anh. CaCl2 - this drying agent seems to be at least little soluble in esters so crystals of CaCl2 (perhaps in some
hydrate form) always visible as a distillation residuum but that never hurts.
[Edited on 7-8-2020 by Fery]
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zed
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Has little to do with this discussion, but my house is infested with tiny little biting ants, that stink to the heavens when killed. Crushing even
one produces a strong Ethyl Formate odor. I've grown to dislike it, almost as much as I dislike them. Though it does give me something to do in the
morning. I'm fond of leaving a few dirty dishes out overnight. Come morning, they are swarming, and ready to meet Mr. Boiling hot water.
Too bad Ethyl Formate isn't a rare and valuable reagent. I would distill the little pirates.
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Boffis
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While working up the residue from the distillation flask to recover the remaining formic acid as sodium formate I was surprised by the small amount
recovered. Assuming the 1060ml of ethyl formate was 100% it represents about 13 moles of formic acid while the original acid should have contained
about 26 moles there should have been 13 moles or about 600g of formic acid left in the still. However, the sodium formate recovered indicates less
than 7 moles (recovered 314g ofsodium formate).
This suggest that the acid was a lot less than 85%!
To test this I purchased 1L of fresh 85% acid and repeated the preparation exactly as before. It has been running now for 24 hours and I have
recovered 1800ml of crude product and the still head it still only reading 56 C and the pot temperature is still below 90 C. The rate of addition is
now down to about 1 drop every 2 - 2.5 second which is less than 1 ml per minute (higher addition rate causes the stillhead temperature to rise
rapidly) and the distillation recovered about 1ml per minute so I am, based on previous experimental experience, approaching the end.
Interesting, I am not sure where my old formic acid came from, I have had it for many years. Maybe it doesn't keep well.
[Edited on 11-8-2020 by Boffis]
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Boffis
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[Edited on 11-8-2020 by Boffis]
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Boffis
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I have now worked up the products from my ethyl formate preparations. The 1L of fresh acid gave after 24 hours of slow dsitillation roughly 1850ml of
crude product and 750ml of still residues. The crude product was treated this time with precipitated calcium carbonate (5g), filtered and then dried
with 100g of MgSO4. It was then distilled with the partially processed product from the previous preparation which had been further dried with 50g of
MgSO4 (about 1L) to yield roughly 2.2 L distilling at 54 C +/-0.5 degrees!! The fraction distilling below 53.5 C was vanishingly small and the next
fraction 54.5 to 56.0C was about 300ml leaving a small residue in the flask which I will probably work up to recovery the alcohol in it but it is
>250ml.
I also investigated the flask residue from the esterification, the 750ml was neutralised by adding 25g portions of reagent grade strontium carbonate;
3 were required to neutralise the remaining formic acid. The undissolved carbonate was filtered off, washed, dried and weighed= 11.85g so the weight
of SrCO3 consumed was about 63g or about 39g of formic acid. Evaporating down in stages to a small volume gave 84g of strontium formate dihydrate in
large glassy orthorhombic prisms (theory about 91g). These figures show that the final flask residue contained only about 5.3% formic acid w/v. This
is an insanely efficient procedure, well done Fery!
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