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Author: Subject: Hexamine Pickle...
trezza
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[*] posted on 2-3-2011 at 10:15
Hexamine Pickle...


Hello everyone, I've been lurking for a while :P. Recently I attempted to purify the hexamine tablets used for a camping stove, here is the process I used.

I First took 1 hexamine tablet and crushed it to a table salt consistency with a mortar and pestle. This leaves me with around 14g of powder per tablet.

I poured around 75ml of warm water into a 100ml beaker and stirred in the hexamine powder and after 5 minutes I decided that all of the hexamine was dissolved and I filtered the solution to get rid of the left over wax.

I began boiling the solution with an alcohol burner and I found that as it got hotter, MORE hexamine crystallized out compared to when it was cooler. It also formed a skin on the top of the water which was preventing the steam from escaping, I had to keep stirring rapidly to break the skin and allow the steam to vent. I got down to about 20ml of solution and decided I would let it cool to see what was left, and as before the hexamine seems to be more soluble at a lower temperature, is this correct?

Also I have been searching for 98% sulphuric acid for some time now and have only found sources through lab supplies, or large quantities from industrial suppliers. I am too worried to ring and inquire or place an order because they all seem to state that they will only sell to businesses. I am in Australia, if any fellow Aussies could share their experience with buying from a chemical/lab supplier and the best way to go about it for a home chemist I would appreciate it, feel free to just send a PM.

[Edited on 2-3-2011 by trezza]
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hissingnoise
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[*] posted on 3-3-2011 at 06:23


I once tried purifying fuel tabs too --- in HNO<sub>3</sub> the "purified" hexamine began a runaway at >37°C so I drowned it.
For my trouble, and 35g hexamine I got about a teaspoon of very impure cyclonite!
Hexamine from H<sub>2</sub>C(OH)<sub>2</sub> and NH<sub>4</sub>OH is the way to go.
It'll still have that fishy smell . . .

I quite like the smell, and in all situations???


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hissingnoise
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[*] posted on 3-3-2011 at 06:57


If you can't find a reasonable quality H<sub>2</sub>SO<sub>4</sub> draincleaner in Oz try looking for battery acid.
Concentrating it is a pain but the additives it contains are oxidised by heating; SiO<sub>2</sub> will precipitate if SiC is present.


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trezza
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[*] posted on 4-3-2011 at 03:50


I don't mind the smell of hexamine, unless I put my nose right in the packaging then it's a bit much.
I have found 1L bottles of battery acid refill in an automotive parts store but I'm not very keen on purifying it. Heating H2SO4 to boiling point is too dangerous for my liking.
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hissingnoise
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[*] posted on 4-3-2011 at 04:19


I do (cough!) it in my (cough!) shed.
I use a large casserole dish for the large surface-area and when the normal bluish steam changes to a thick white, heavy vapour, it's done (cough!)!
Since you're in Oz, you could easily do it outdoors!
And while you're at it, you could check this out!

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trezza
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[*] posted on 4-3-2011 at 04:35


Quote: Originally posted by hissingnoise  
I do (cough!) it in my (cough!) shed.
I use a large casserole dish for the large surface-area and when the normal bluish steam changes to a thick white, heavy vapour, it's done (cough!)!
Since you're in Oz, you could easily do it outdoors!
And while you're at it, you could check this out!



What do you use as a heat source, I've been thinking one of those electric hotplates might do the trick
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hissingnoise
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[*] posted on 4-3-2011 at 04:57


Whoa . . .That's one big pic . . .

I use an electric ring salvaged from a old cooker.
I doubt that the unit pictured will reach the temperatures needed.
You'll need the sulphuric acid @ >300°C before it reaches 98%!

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[*] posted on 4-3-2011 at 05:03


Those ones can reach more than 500C, I once tried to melt some zinc (420C melting point) on my hotplate, without using the maximum available temperature, and it melted like a charm.
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[*] posted on 4-3-2011 at 05:07


trezza, that's kind of funny, as only a few days ago I bought myself a hotplate EXACTLY like that one. Only that it has one plate, not two.
For 12 dollars, new:D
I couldnt believe how cheap it was, that's why I bought it.

At full power it gets to 600C, measured by a thermocouple! Yes, that's red heat.
I don't expect it to last long, but what the hell, at that price, anyway i got a 2 year warranty.\
The thermostats on these cheap units usually fail first.
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hissingnoise
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[*] posted on 4-3-2011 at 05:26


Those units are for cooking!
If the plate doesn't reach red-heat - forget it!

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