Sciencemadness Discussion Board

Hexamine fuel tablets purity

Fusionfire - 31-8-2011 at 00:21

Hi guys,

Are hexamine fuel tablets a good source of pure hexamine for the purposes of making explosives (RDX, HMTD)?

This wiki doesn't say anything about their purity:
http://en.wikipedia.org/wiki/Hexamine_fuel_tablet

There is a passing reference to some impurities here:
http://en.wikipedia.org/wiki/Hexamethylenetetramine
Quote:
Together with 1,3,5-trioxane, hexamethylenetetramine is a component of hexamine fuel tablets used by campers, hobbyists, the military and relief organizations for heating camping food or military rations.


Assuming the tablet is impure, how does one go about purifying it?

The brand of fuel tablets I have are Mil-Com ones (see picture); there is no ingredients list on the box.

Attachment: mil_com_hexamine_tablets.pdf (219kB)
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boonga - 31-8-2011 at 03:11

Hey Fusion, I too stumbled upon this same situation. The local camping stores had a variety of fuel tablets and after some snooping around the brand "HEXA" contains practically 99%+ hexamine. Simply crushing the tablet, weighing the mass (which was around 70 grams) and placing it in 100ml of water, all bar roughly 0.25g didnt dissolve. Hexamine's solubility in 100ml of water is 85.3g per Litre soo technically it should of all dissolved. Nevertheless the insoluble material (in its very small proportion) hasn't caused a problem in any reactions since finding the brand, hopefully you have a brand similar. As for purifying i am clueless, the tablets are pure white and seem to have a very thin waxy coat (this is perhaps the impurity?who knows?) but no materials list, nor msds can be found online. For now it will have to do :D

hissingnoise - 31-8-2011 at 06:25

The fueltabs I have are uncoated but there's obviously some kind of dextrine-like binder as the tabs hold together well.
I had no problem preparing HMTD but I got a runaway when going for RDX.
It happened midway through the addition so I had to drown; I got minimal RDX.
I was using RFNA so I don't know if the binder interfered or if dissolved NO<sub>2</sub> was the culprit . . .
For max purity, a hexamine/NH<sub>4</sub>OH solution should be carefully evaporated to dryness.


Fusionfire - 31-8-2011 at 06:50

Quote: Originally posted by boonga  
Hey Fusion, I too stumbled upon this same situation. The local camping stores had a variety of fuel tablets and after some snooping around the brand "HEXA" contains practically 99%+ hexamine. Simply crushing the tablet, weighing the mass (which was around 70 grams) and placing it in 100ml of water, all bar roughly 0.25g didnt dissolve. Hexamine's solubility in 100ml of water is 85.3g per Litre soo technically it should of all dissolved. Nevertheless the insoluble material (in its very small proportion) hasn't caused a problem in any reactions since finding the brand, hopefully you have a brand similar. As for purifying i am clueless, the tablets are pure white and seem to have a very thin waxy coat (this is perhaps the impurity?who knows?) but no materials list, nor msds can be found online. For now it will have to do :D


The little undissolved bit may have something to do with the long dissolution times of hexamine compared to inorganic salts. I have a bottle of saturated hexamine solution that I kept shaking like a maniac to get it to dissolve at its stated solubility limit. In the end I gave up, forgot about it, left it on the shelf and a few months later it is 100% dissolved :D

Roger86 - 3-9-2011 at 09:02

Quote from wikipedia ' 1,3,5-Trioxane is a white solid with a chloroform-like odor. '

Do the tablets smell like chloroform?

hissingnoise - 3-9-2011 at 11:38

Trioxane, the trimer of formaldehyde burns well but hexamine has a higher output.
Hexamine always smells fishy (amines)!