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Author: Subject: Metaldehyde isolation and purification?
Droso
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[*] posted on 20-12-2015 at 17:21
Metaldehyde isolation and purification?


Anybody here know how one could isolate metaldehyde from slug, snail pesticide? Its seems like an interesting compound that I wish to have in pure form.

The only problem is that there seems not much information about the concentration used on the poison nor the properties of this compound (solubilty, etc).

Thanks
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Etaoin Shrdlu
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[*] posted on 20-12-2015 at 17:54


Look up the SDS for the brand you have. It looks as though the compound is usually present in fairly low amounts. (<5%)
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nux vomica
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[*] posted on 20-12-2015 at 18:28


Wiki says that it sublimes between 110-120°c heating in a sealed container might work if you can keep between these temperatures.
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Texium
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nux vomica
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[*] posted on 23-12-2015 at 00:05


Thought I would try sublime some 15 grm per kg metaldehyde snail pellets I heated 60 grms at 180°c for one hour , got .55 of a gram of nice hair like metaldehyde crystals not the .9 grms in theory , still it seems to work.
Nux.

20151223_184148.jpg - 1.9MB

[Edited on 23-12-2015 by nux vomica]

20151223_190153.jpg - 1.5MB
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UC235
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[*] posted on 23-12-2015 at 00:11


I'm frankly impressed that such a simple method works so well.

Now the bigger question: is metaldehyde as aggravating a source of acetaldehyde as 1,3,5-trioxane is a source of formaldehyde?
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nux vomica
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[*] posted on 23-12-2015 at 00:57


I've been trying to get my head around the molar mass differences between acetaldehyde and metaldehyde.
If acetaldehyde is 44.05 grams per mole is 176.212 grams of metaldehyde (1mole) the equivalent amount to use in the place of liquid acetaldehyde in a synthesis.
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DJF90
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[*] posted on 23-12-2015 at 01:32


Seeing how metaldehyde is just a tetramer of acetaldehyde, you'd use the same amount on a mass basis (e.g. 1 g acetaldehyde is equivalent to 1 g metaldehyde).
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nux vomica
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[*] posted on 23-12-2015 at 01:52


Quote: Originally posted by DJF90  
Seeing how metaldehyde is just a tetramer of acetaldehyde, you'd use the same amount on a mass basis (e.g. 1 g acetaldehyde is equivalent to 1 g metaldehyde).


Thanks for that DJF90 I thought that might be the case.
What threw me was formaldehyde and paraformeldyhyde molar weights are only slighty different and they are one for one equivalents , the large difference between acetaldehyde and metadehyde made me think you needed more metadehyde to make a equivalent amount of acetaldehyde..
Thanks nux
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DJF90
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[*] posted on 23-12-2015 at 02:58


The difference with paraformaldehyde is that it is a polymer of undefined length, and so the molecular weight given for this material tends to be the same as that for formaldehyde.
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careysub
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[*] posted on 23-12-2015 at 08:39


Quote: Originally posted by nux vomica  
Thought I would try sublime some 15 grm per kg metaldehyde snail pellets I heated 60 grms at 180°c for one hour , got .55 of a gram of nice hair like metaldehyde crystals not the .9 grms in theory , still it seems to work.
Nux.



[Edited on 23-12-2015 by nux vomica]


Thanks for this. As it happens I just received some 10% metaldehyde slug bait, and was debating how to extract it. Perfect timing!
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Magpie
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[*] posted on 23-12-2015 at 10:13


Quote: Originally posted by DJF90  
The difference with paraformaldehyde is that it is a polymer of undefined length, and so the molecular weight given for this material tends to be the same as that for formaldehyde.


IIRC paraformaldehyde polymer chains are terminated with a water molecule. This would account for a slight difference in the MW of the monomer vs that of formaldehyde.

[Edited on 23-12-2015 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
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nux vomica
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[*] posted on 23-12-2015 at 19:21


Did another 60 gram run got 0.53 grams of metaldehyde theoretical .9 grams there was a amount of crystals that recombined with the top of the pellets though so I could get a better return. Nux

20151224_140600.jpg - 1.5MB20151224_140653.jpg - 1.6MB
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Magpie
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[*] posted on 23-12-2015 at 22:17


Nice work, nux.

It would be interesting to see what yield of acetaldehyde can now be achieved. However, for a synthesis it might be more efficient to use the metaldehyde "as is."

[Edited on 24-12-2015 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
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nux vomica
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[*] posted on 24-12-2015 at 02:54


Quote: Originally posted by Magpie  
Nice work, nux.

It would be interesting to see what yield of acetaldehyde can now be achieved. However, for a synthesis it might be more efficient to use the metaldehyde "as is."

[Edited on 24-12-2015 by Magpie]


Thanks magpie I would like to try to and make some Pentaerythritol but the alkaline conditions probably won't work with the metaldehyde.
It would have to be acidic to release the acetaldehyde if I am correct .
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