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Author: Subject: Preparation of Acetic Anhydride
Magpie
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[*] posted on 19-4-2019 at 07:00


No, I have never made HPO3 but would like to. What I made with H3PO4 was SO3. I posted this on the forum.



The single most important condition for a successful synthesis is good mixing - Nicodem
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Waffles SS
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[*] posted on 19-4-2019 at 07:07


Heating Phosphoric acid to 316c lead to Meta-Phosphoric acid.

You did exactly that:


Quote:

Preparation of HPO3

1. Set up the iron ring w/ceramic triangle or wire gauze on a ringstand at the elevation suitable for the Meeker burner. Place 600 mL beaker on the ring.

2. Add 135 mL of phosphoric acid to the beaker.

3. Apply the strongest possible heat to the beaker with the Meeker burner on MAPP gas.

4. Intensely heat the beaker until the melt turns red or 1 ½ hrs have elapsed, whichever comes first.

5. While the HPO3 melt is still hot pour it into a 250 mL rbf (the pot)

http://www.sciencemadness.org/talk/viewthread.php?tid=78495#...



[Edited on 19-4-2019 by Waffles SS]




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Magpie
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[*] posted on 19-4-2019 at 09:49


So I did! Thanks Waffles.



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Feriman
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[*] posted on 26-4-2019 at 21:43


I prepared some Ac2O by S2Cl2 method, then repeated experiment by adding my crude Ac2O as solvent to increase yield and purity,and result was good because the yellow color in my crude Ac2O from first experiment disappeared and I had more, but by a mistake some water was poured to my product and made it a milky color, I want to know what is purpose of milky color?

And glad to get any comment and idea about my experiment.

(My mistake): I connected outlet water of distillation condenser to a water aspirator and connected aspirator to vacuum adaptor of my distillation apparatus, at the end of experiment I closed inlet water so some water was pulled back in apparatus:(

[Edited on 29-4-2019 by Feriman]
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NZniceguy
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[*] posted on 29-7-2019 at 03:37


So I tried this method, making doubly sure that everything was dry and Sodium Acetate was fused and even fised again before use....I only had ten mls of Br2 so went with half of everything eg 1.7gm Sulphur and 33 gm Sodium Acetate.
I vacuum distilled and got around 25mls of a yellowy orange liquid.
I then set up for simple distillation and collected 3 fractions. One from 120 degrees C to 130 C which was about 12ml, another from 130C to 138C which was about 3ml and a third fraction from 138C which went up to 157C! Which was about 5ml
All 3 fractions have a distinct yellow colour and do not smell like Acetic anhydride. Also the high temp (above 140C) is obviously not right.
Is this sulphur contamination? If so what can I do to clean it up?
If not, what went wrong? What should I try different next time?
Thanks in advance.
Ps I have photos of the 3 fractions but am unsure how to upload them.

[Edited on 29-7-2019 by NZniceguy]

IMG_20190729_232706.jpg - 3.4MB
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NZniceguy
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[*] posted on 30-7-2019 at 01:35


Quote: Originally posted by NZniceguy  
So I tried this method, making doubly sure that everything was dry and Sodium Acetate was fused and even fised again before use....I only had ten mls of Br2 so went with half of everything eg 1.7gm Sulphur and 33 gm Sodium Acetate.
I vacuum distilled and got around 25mls of a yellowy orange liquid.
I then set up for simple distillation and collected 3 fractions. One from 120 degrees C to 130 C which was about 12ml, another from 130C to 138C which was about 3ml and a third fraction from 138C which went up to 157C! Which was about 5ml
All 3 fractions have a distinct yellow colour and do not smell like Acetic anhydride. Also the high temp (above 140C) is obviously not right.
Is this sulphur contamination? If so what can I do to clean it up?
If not, what went wrong? What should I try different next time?
Thanks in advance.
Ps I have photos of the 3 fractions but am unsure how to upload them.

[Edited on 29-7-2019 by NZniceguy]


I read that boiling a small amount of Potassium Permanganate in the combined fractions may get rid of the impurity. Does anyone have any idea if this is correct?
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Weka
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[*] posted on 7-4-2020 at 21:30


On magpies writeup, if the reaction taking place is 4NaOAc + 2S2Br2 --> 4NaBr + SO2 + 3S + 2Ac2O as per Thorpe then you would need 1 mol sulfur for 4 moles NaOAc (assuming the sulfur is recycled) whereas the original write up uses 1 mole for every 8 moles approx, which is more in line with the reaction proposed by Orshansky and Bograchov. I assume that this was decided upon based on higher yields for a 1:8 ratio. If you did achieve higher yields with a 1:8 ratio would that mean Thorpe may have proposed a more minor reaction path (It is made clear SO2 is released)?
Or was it due to some other problem that a 1:8 (1S:8NaOAc) molar ratio was used instead of a 1:4 (1S:4NaOAc) molar ratio?

Also, would the same reaction proceed with (Heavy) chlorine contamination in the bromine?




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Jenks
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[*] posted on 14-4-2021 at 10:22


I hope this inspiration can help. We know that HBr is easily oxidized, and it made me wonder... Instead of providing an equivalent of the nasty liquid bromine, might it be possible to find an oxidizing agent that would covert bromide back to bromine without oxidizing the sulfur? Then we would have the beauteous situation of supplying acetate, sulfur, oxidizer and a catalytic amount of bromide salt, and getting anhydride and SO2 as product. I wish we could just use iodide, as HI is even more easily oxidized, but apparently iodine and sulfur are reluctant to react.
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