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Author: Subject: Paraformaldehyde Purification
blazter
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Paraformaldehyde Purification

Since pure paraformaldehyde is not easily available for me OTC, I am limited to using what wally world stocks which is called "CampaChem". This comes in pouches with a very bright blue color. The powder which it contains is mostly very fine spherical prill looking material.

Previous attempts of purification through washing with various solvents like methanol or water were able to remove the majority of the dye, but not much of the detergent. This detergent has a nasty habit of leaving very tenacious soap scum residues on my glassware, which had to be removed with conc. HCl solution.

This brings me to the latest attempt. Being a bit rushed, no specific masses were taken, but this was more or less of a test run. The idea was to try and sublime the paraformaldehyde, and have it recondense on a makeshift coldfinger type condenser.

The apparatus was constructed from a fairly large bore test tube, and an old jam jar. A large enough hole was punched in the top of the jam jar lid to allow the test tube to pass through. The test tube was then affixed in place with a bit of electrical tape. It was also arranged so that it was a few cm above where the raw material would rest. Since it's winter there was an abundance of coolant just lying around in the form of snow, which was used to fill the test tube. A fair amount of the raw CampaChem was dumped into the jam jar, and the lid closed.

A hot water bath did not provide suffecient heating, so instead of going to the bother of making an oil bath, the works was simply placed inside a tunafish can directly on the hotplate.

After some heating, what appeared to be some water condensed on the test tube. The water probably was left in the jam jar or was introduced by the water bath by accident. Anyways, after some more time, a film began to deposit on the test tube as well as on the top of the jam jar. Unfortunatly a drop of water struck the hot glass and started a crack. At this point the heating was terminated.

The deposit is a dirty white, whith a slight hint of blue. Scraping it off the test tube is a bit difficult as it is very waxy, definitly amorphous. Either some of the dye sublimed, or the prills "jumped" a bit from the heating. The bottom campa chem has taken a on a reddish color which is a bit puzzling.

Does this seem to be fairly pure paraformaldehyde now based on the description? With any luck, it should react with household ammonia to form hexamine. Does anyone know if the standard 3% ammonia will be concentrated to work? Also, how would one go about extracting hexamine from the resulting aqueous solution? Thanks in advance for any advice.

Attached are some pics of the setup, as well as a pic of the result stuck to the test tube. Please excuse the crappy quality as they were taken with a 5\$ webcam.
The Ruler in the first pic is 6 in. long. The pic where the test tube is taken out of the the jar shows the deposit, though the quality of the image is low.

Attachment: Paraformaldehyde_Sublimation.rar (32kB)

Mumbles
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I believe your "out of can" picture is corrupt. It will not open. The other two will.

Seems like a valiant step in the right direction for the purification of OTC paraformaldehyde. About that ammonia. I think that the 3% should work, but you'd need quite a bit of it, and the efficiency will probably fall. I've never tried using paraformaldehyde for making hexamine but it should work in theory. If no crystals of hexamine form, and it will be harder to tell with the crystals of paraform in there too, try using a stronger concentration of ammonia.
Acid Test
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Apparentlly paraldehyde can be synthesised
from ethonol with a pallidium catalyst.
This is the industrial procedure and is
supposed to give good yields that are
basiclly anhydrous.
I know this because paraldehyde is used in
the pharmaceutical industry in Sweden

.....
Mumbles
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Do you know how to read or are you just drunk? You continuously post the most random things, that have nothing to do with the conversation at hand.
Mendeleev
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Why use a test tube, I would just put a small pyrex bowl which you can get at food lion on top of the jar, fill it with ice and do it that way. It gives you greater surface area. By the way in what section is the Campa Chem at Wal-Mart, I went there and I couldn't find it in the household cleaners aisle.

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Thermal
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Probably in the camping section. It's used for de-smelling RV toilets.
LUEshi is my god
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My attempt to reproduce blazter's sublimation experiment ended with the test tube being blown out of the jar lid and the blue shit erupting from the jar I used. I assume this to be cuased by steam buildup, as I noticed quite a bit of moisture condensing on the walls of the apparatus. I know the jar was completely dry, so I will dry the campachem powder in a dessicator before trying to sublime it again. However, a thought occured to me while watching the condensation dripping down the walls of the jar - would dissolving campachem in hot water decompose the paraformaldehyde to formaldehyde? And if so, couldn't one then distill off the formaldehyde, leaving the detergent, dye, and any other junk in the disinfectant stuff behind? Sorry for resurrecting such an old thread, but it seems like this would be a better method of purifying it if you only need formaldehyde (for hexamine synthesis, in my case) and not para.

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tom haggen
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Would it be possible to reverse the reaction, and obtain paraformaldehyde from hexamine? I assume this would have to do with shifting the equilibrium?

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neutrino
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Hexamine tends to decompose in acidic conditions, I believe into (para)formaldehyde and ammonia (actually an ammonium salt here).
tom haggen
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Kinda like this

7H2O + 4HCl + C6H12N4 --> 4NH4Cl + 6CH2O + H2O

If thats correct, what would be a good way to remove the ammonium chloride? Distillation would be obvious I suppose....
[Edited on 4-3-2005 by tom haggen]

[Edited on 4-3-2005 by tom haggen]

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tom haggen
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Does anybody think that this reaction would work?

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Natures Natrium
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 Quote: Originally posted by tom haggen Does anybody think that this reaction would work?

I have heard that this is the major route the reaction takes when the hydrolysis by HCl is rapid, ie high concentrations and temperatures. I have never seen an optimized procedure for it, however if one were to look at the write up that used to be on rhodiums page for the synthesis of methylamine then the above suppositions regarding reaction conditions seem plausible. This particular reaction is one in a long list of personal "to-do"s, so if you do attempt please report the results.

PS
It also seems to me, and this is purely hypothetical, that rapidly running concentrated HCl rapidly into a slurry of aqueous boiling hexamine and leading the released gas into chilled dH2O might be a good starting point for this reaction. Doesn't formaldehyde polymerise in cold, acidic H2O? Then the paraformaldehyde could be easily isolated via simple filtration. Hmm, just spouting some thoughts off the top of my head.

PPS As for the purification of the RV stuff, I think that idea regarding depolymerization in boiling H2O and subsequent distillation is probably the way to go. Not that I am claiming expertise, mind you, it just seems like a reasonable idea to me. It might take quite a bit of water to get it done though.

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Magpie
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I have seen janitorial strength ammonium hydroxide (10%) for sale at the hardware store.

The single most important condition for a successful synthesis is good mixing - Nicodem
tom haggen
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Yes the purification of the RV stuff seems like a good Idea. On roguesci they talked about thermal decompostion into formaldehyde for the use in a hexamine synthesis. However, I'm interested in paraformaldehyde for the fact that I want to synthesize PETN. Vulture seemed to think that the paraformaldehyde could be removed by distillation. But The topic doesn't seem to be very well covered.

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Hawkguy
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Sorry to open up an old thread, but eh, why not. An idear for Para formaldehyde preparation is to first prepare Formalin via hot Copper catalyst method. I've done it and it works fair. Then, Sulfuric Acid is added to the Methanol/ Formalin mixture, and the Formalin should polymerize. Since its insoluble in alcohol (Para formaldehyde), it should be possible to collect the product. Any ideas on how this could muss up?
Magpie
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I would like to obtain some paraformaldehyde. I tried to extract it from RV toilet chemical but was unsuccessful.

Formalin is easily bought over the internet, and I have about a liter for experimentation.

Could formaldehyde be extracted from formalin using methanol?

The single most important condition for a successful synthesis is good mixing - Nicodem
Loptr
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But methanol is miscible with water, how will you get the methanol/formaldehyde mixture?

This is funny since I believe I have actually seen procedures for extracting formaldehyde, but it was using water to do it.

EDIT: It seems that it is soluble in diethyl ether and benzene, so I would think other aromatic solvents as well. Something that isn't miscible with water.

[Edited on 5-5-2015 by Loptr]
Magpie
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 Quote: Originally posted by Loptr But methanol is miscible with water, how will you get the methanol/formaldehyde mixture?

Yes, I forgot about that. Maybe it could be salted out, say with K2CO3.

The single most important condition for a successful synthesis is good mixing - Nicodem
macckone
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Paraformaldehyde is made by dehydrating a basic solution of formalin. Formaldehyde gas is made by heating paraformaldehyde.
See patent us4550213.
Hawkguy
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