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Author: Subject: Formaldehyde => Paraformaldehyde
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[*] posted on 27-8-2005 at 16:24
Formaldehyde => Paraformaldehyde

This reaction has caught my attention. Aftering reseacrhing a bit I was able to find what I deemed to be an acceptable way of synthesisizing formaldehyde. Well, thats only part of the solution.

Doing a search here at Science Madness, I turned up the following:

Which is exactly what I wanted. Or rather, so I thought. There arent much details in that thread, and defiently no reports if the method even works.

While mostly about the purification of paraformaldehyde, it does go on about obtaining paraformaldehyde from hexamine. I know at the very least, I can get hexamine on ebay, for now anyway. Maybe later on I will look up synthesisizing hexamine, but thats just more work (as though all this isnt).

Searching on google and yahoo didnt yield much, however, I was able to find a lot of information about polymerization inhibitors. I found this intresting because it appears that formaldehyde would be easy to polymerize. For example:

"In water, formaldehyde polymerizes, and formalin actually contains very little formaldehyde in the form of H2CO monomer."

All that says is that polymerization occurs at low tempatures.

So basically, it *seems* as though this should be easy, since people goto such great lengths to prevent it.

I have a few ideas bumping around in my head but nothing concrete. Any help would be appreciated.


Oh and slightly (completely?) off topic...

Hexamine seems rather easy to make, just some formaldehyde and ammonia...


Most intresting... After reviewing some patents I have found numerous ways to make paraformaldehyde... However all require no less than 70% formaldehyde. Then I found the following:

"As a method for producing a paraformaldehyde of a high formaldehyde content (hereinafter referred to as "high concentration paraformaldehyde";), the following is known. That is, formalin containing about 37-50% of formaldehyde is subjected to a concentration treatment such as vacuum concentration to produce a highly concentrated aqueous solution of formaldehyde containing about 80% of formaldehyde, and the resulting highly concentrated aqueous solution of formaldehyde is cooled and solidified by means of a cooling apparatus and a pelletizing column to form paraformaldehyde containing about 78-83% of formaldehyde in the form of particles or flakes (hereinafter referred to as "conventional paraformaldehyde";). Then the resulting conventional paraformaldehyde is dried at a temperature not higher than the softening point of the conventional paraformaldehyde by means of hot air drying or far infrared ray drying [Japanese Patent Application Laid-open No. Hei 2-167244 (1990)]. "

Another patent mention distilling under a vacuum to achieve 80% purity... If possible, this would allow for a simple paraformaldehyde synthesis using NaOH as a catlyst (according to yet another patent).


[Edited on 28-8-2005 by Duster]

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National Hazard

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[*] posted on 19-11-2005 at 08:41

Maybe it would be possible to prepare an AN/ice bath, therein a flask with *slightly* diluted H2SO4, and the dilute(in my case 20%) formalin solution dropped in under stirring.... if polymerization does not start, some mg of AP might be added... :o

[Edited on 19-11-2005 by BASF]
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[*] posted on 4-12-2013 at 20:13
I just performed this procedure and it worked great

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[*] posted on 4-12-2013 at 21:28

By far the simplest way is by vacuum distillation. Pour you formalin solution into a large rbf, setup for simple distillation and pull vacuum with heating. Watch out for bumping (thats why you need a big flask), and once the formalin solution looks to be more viscous quickly disassemble the apparatus and pour the hot syrupy formalin solution into a beaker. As it cools it will thicken into a white jelly-like substance, it can be further dried over the desiccant of your choice. Aspirator vacuum is sufficient, and make sure you remove the concentrated formalin while the vessel is still hot! Otherwise it will solidify in the flask and take forever to get out. I have does this procedure numerous times and it works very well.
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