killswitch
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Crystallization, purification, storage, and related topics
[Any general tips on storage, purification, and handling are appreciated here, in addition to discussion of the specific issues in this post.]
Recent experiences with TNP have led me to become more interested in these topics. Having received my product in the form of a flaky yellow cake, I
attempted to increase the density by melting it in a beaker on a hot plate. It appeared that I had at least 100ยบ C of leeway between the melting
point and the detonation temperature, and with my infinitely-variable temperature control knob I decided to give it a go. While the flakes did
coalesce somewhat, there appeared to be pockets of gas forming on the bottom of the beaker where it contacted the plate. Placing a larger beaker over
it to contain the evolving vapor, I observed colorless droplets forming on the glass. When the picric acid cooled, gaps remained at the bottom of the
mass. All in all, out of ~10 grams of product, 1.6 vanished during my various attempts to increase the density, suggesting that the vapor was TNP
boiling or subliming. In future, I intend to achieve high density through old-fashioned evaporation.
As regards to storage, I keep most of my compounds in acetone solution (neutralized, dehydrated, and recrystallized at least once beforehand). Does
the acid-catalyzed breakdown of nitric esters occur in such media? If so, is its progress impeded? And if it is, to what degree?
On a related note, how does one promote the formation of large crystals (of MHN, R-salt, RDX, etc.) in acetone media?
I also wonder how best to form a solid crystalline blend of MHN and R-salt. Would evaporating an acetone solution of the two result in a well-blended
crystal, or would the composition tend towards larger molecules at the center with the more soluble substance deposited closer to the surface?
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quicksilver
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It's very difficult to make generalizations with this issue as each material has unique properties. Nitric esters in the form of double-based
smokeless powders have several features that allow decades long shelf life. In that instance, the material is made as pure as humanly possible; the
use of stabilizers, lack of exposure to oxygen, temperature extremes and UV are some of the significant issues. However some esters from solid
alcohols (MHN, ETN, SHN) require significant re-crystallizing to even begin to approach a level of purity in which to begin the process.
Many times the total shielding from oxygen via submergence in neutral fluids (such as Kerosine, paraffin oil, etc) may be needed and alterations in
temperature stopped totally in such as mercury fulminate, bulk tetrazine, etc and placed in a darkened refrigerated environment.
Bring a material into a solvent might help it's longevity but there are only so many materials that will dissolve without alteration.
Variances in weight of a completed synthesis often indicate a less-than-pure product as frequently accompanied by the retention of water. That is one
reason why any solvent should be considered carefully.
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