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Author: Subject: HMTD w/H2SO4?
GTOzoom
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[*] posted on 12-2-2007 at 08:55
HMTD w/H2SO4?


All over the internet I have read people saying "you can use H2SO4 no problem" or "H2SO4 eats at the HMTD so you can't"

I used up the last of my citric acid yesterday making a #8 cap, I need to make another batch this weekend. I have a ton of glacial sulphuric, but no citric acid. I simply want to get it cleared once and for all, CAN YOU USE H2SO4 TO MAKE HMTD? And if so, how much do you dilute the acid beforehand?

Thanks for the help, you guys seem to be very knowledgable people so I figured it can't hurt to ask.




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nitro-genes
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[*] posted on 12-2-2007 at 11:54


It probably depends on the amount of H2SO4 added. Carefull neutralization of hexamine with strong acids should be no problem given that the temperature is kept low and no excess acid is present. If you do use excess acid, the solution will have a faint smell of formaldehyde indicating that the hexamine is hydrolized to ammoniumchloride and formaldehyde, which condenses further to form methylamine and is probably what they mean by "eats at the HMTD". No or hardly any HMTD will be formed in this case...

I have never used sulfuric acid, though I have used a strong acid like HCl for preparing HMTD, which gave normal yields. Sulfuric shoul be possible as well, given that hexamine disulfate is reasonably stable...

[Edited on 12-2-2007 by nitro-genes]
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[*] posted on 12-2-2007 at 17:26


What is "glacial sulphuric" supposed to be? Only acetic acid can be "glacial".
BTW, I think acetic acid should work quite well in HMTD synthesis, as it is a weak acid like citric.




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[*] posted on 12-2-2007 at 17:50


IIRC (its been a while since I read on such mundane primarys) that the citric acid was necessary for the reaction as it is more than a catalyst, it is a reactant.

EDIT: The nature of this thread may make it detritus soon, such common energetics are not discussed here, depends how the thread goes.

[Edited on 13-2-2007 by The_Davster]




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[*] posted on 12-2-2007 at 19:31


Citric acid combines with the Ammonia liberated during the rxn which pushes the equilibrium to the right promoting the formation of HMTD.
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[*] posted on 13-2-2007 at 04:46


The NH3 produced during the reaction can be bound by any acid and as long the acid is not present in excess, the pH during the reaction will be relatively constant throughout the reaction and strong acids can be used as well. An excess of strong acid will result in a very low pH at the start of the reaction, favoring the hydrolysis of hexamine into other compounds, diminishing yields. Two moles of NH3 are formed for each mole of hexamine reacted, when the corresponding hexamine disalts are used these two moles of NH3 will combine with the two bound acids forming the ammonium salt which doesn't raise the pH like ammonia would...

[Edited on 14-2-2007 by nitro-genes]
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