quicksilver
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Density of Metal salts
I have experimented with materials which use various metal salts and am struck by what I consider to be an interesting phenomenon: The denser metals
(lPb, Hg) have different levels of sensitivity than less denser ones (Cu, Zn, Ni) in the context of energetic salts (azides, etc). With the less dense
being often more sensitive---- However there are exceptions continually. Copper azide is a very, very sensitive material (unusably so) but zinc azide
or nickel much less so. Atomic weights are quite close. What influence does density have on energetic materials? Or is that a question that is
inappropriatly generalized?
As an aside: I was considering Silver Styphnate and attempted to get some information. I found the formula & synth, and some very limited materal.
Most all of it was framed in the theoretical and comparison nature of it in terms of sensitivty.
As a silver salt it was LV sensitive and it's initiation ability was slightly better than the lead salt. I thought that the reason for lack of use and
persuit of this material was a cost element due to the price of silver nitrate as it's stability appears to be (like silver azide) fine when kept from
UV exposure. Like many silver salts I thought it would be very sensitive but like silver azide it was less so than Pb. Copper Azide is extremely
sensitive, yet an azide from nickel much less so. An azide from Tantalum (Ta) is so sensitive as to be almost unhandelable, yet it's close to lead and
mercury weight wise. What are these influencing factors?.
Has anyone ever heard of Silver Styphnate's commercial use as I have not....(?)
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12AX7
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Catalytic behavior I would guess. Zinc doesn't catalyze much.
As for tantalum, that's one of those left-side metals that doesn't like to combine with much besides carbon (i.e. carbide) and oxygen, and whose
soluble compounds tend to be acidic and hydrolyze (like TiCl4). I wouldn't be suprised if it's a bonding issue, combining with a relatively large
acid despite being a rather charged ion itself (Ta is what, +5?).
Tim
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The_Davster
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There are many more even more sensitive azides, cobalt azide is considered to be the most sensitive isolatable one, where as the normal palladium
azide cannot be obtained without explosion.
I believe the answer lies in crystal structure, however I am speculating. Different radii of the metal ion and azide ion lead to different crystal
lattices which are more or less succeptible to shock. But copper and nickel have the same ionic radii if I remember correctly, so radii could only be
a minor factor. But I imagine different crystal structures could form despite the same radii. I imagine the crystal structure of most azides are
known, comparison should be simple.
I have attached a book on azides, which you may or may not have read.
[Edited on 30-8-2006 by rogue chemist]
Attachment: Energetic Materials - Inorganic Azides (OCRed).pdf (2.6MB)
This file has been downloaded 790 times
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Rosco Bodine
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Barium styphnate is really the most interesting of these type alternative metal energetic salts which avoid the cost of working with silver and their
potential light sensitivity .
However , like lead styphnate it has poor initiating power by itself and must be mixed with lead azide or other rapid primary as an accellerant .
There are several " slow starting " primary explosives which are by themselves poor initiators because of slow self-accelleration , requiring critical
masses of several grams for the runup of the detonation wave to reach a full high order detonation , but once that velocity is reached then they are
efficient initiators , even moreso than lead azide alone .
Some of these complementary mixtures are more powerful initiators weight for weight than is pure lead azide . I have no specific data for the barium
styphnate / lead azide mixtures beyond the general information of the patent
attached . In PATR , page A576 , sand tests showed that a 40/60 mixture of lead azide / lead styphnate is roughly equal in brisance to pure lead
azide , and 60/40 is stronger still , and 80/20 is yet even stronger , so there is a range of mixtures which are useful . Evidently a similar
principle
applies to other composite synergistic mixtures of this sort .
Bismuth and Cadmium compounds are probably worth a look too . But I have not looked lately for any information on these .
[Edited on 30-8-2006 by Rosco Bodine]
Attachment: US3284255 Barium Styphnate - Lead Azide mixtures.pdf (135kB)
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quicksilver
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Thank you all so very much. This is very interesting material and I really apprieciate this stuff. -- There is more here than meets the eye!
I cleaned up my little lab and have been doing some experiments of late. I plan on posting some of the results of sensitivy tests (within milligram
amounts of course) - so I am off an running. I found a fantastic source of technical grade azide so within reason I can try most anything I can get a
metal salt of. 
My stuff on Ta said 5 also. It's unique; close to tungsten in mp but weight is simlar to gold. I have a few grams laying around. If you guys ever want
to U2U me and I'll share where I get some of my wierd stuff. My wife said "no more" so I need to stop collecting chems. 
[Edited on 31-8-2006 by quicksilver]
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The_Davster
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I am curious on the prep of tantalum azide, seeing as tantalum does not have the standard aqueous chemistry. Must be like TaCl5 and NaN3 in some
organic solvent or even the use of HN3. My knowledge of tantalum compounds are pretty limited, just the metal, simple anhydrous halides, the tantalate
and peroxotantalate compounds.
I always am in the mood for materials which are insanely sensitive, with no practical use, so please post results.
[Edited on 31-8-2006 by rogue chemist]
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woelen
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Rogue chemist, did you succeed in dissolving tantalum in acid? I always was thinking that this metal is insanely inert. I also hardly can imagine that
Ta(N3)5 can exist. That would mean one Ta atom at 15 N-atoms!!! That's really insane! I'm inclined to think that -- if -- some azide of tantalum
exists, then it is a combination with another anion, e.g. TaCl3(N3)2. Btw, these compounds all will be totally covalent. Ta(5+) does not exist as ion,
it is covalently bound in its compounds like Ta2O5 and TaCl5.
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The_Davster
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I have noted only very very slight loss of tantalum into hot aqua regia even when in contact for several days.
Brauer has the prep of tantalates and peroxytantalates from the oxide and fused alkali carbonate and hydroxide(and H2O2) respectivly.
All I have found this metal to do is turn to the oxide after extended heating at 1000C, and to really not like boron at 1200(might have reacted or
just made a really weak crystal structure at those temps, I could snap it with minimal force.)
[Edited on 31-8-2006 by rogue chemist]
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not_important
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HF is the only acid that does real damage to tantalum, through formation of fluoride complexes. It's pretty resistent to alkalia as well, fused Na/K
OH slowly attact it. The chloride can be made by heating the metal in a stream of chlorine, but the pentachloride is usually made by heating the
pentoxide in a stream of chlorine plus chlorocarbon such as CCl4.
The carbide can be made by heating the powdered metal with carbon to 1,700-2,100 C for half an hour or so. Heating the powdered metal in nitrogen
above 1,200 C for some time gives the nitride; the nitride is almost as inert as the metal itself. Sulfides can be made by strongly heating the metal
with sulfur.
Much of the remainder of the chemistry of tantalum is that of oxy-complexes of Ta(V), such as K8[Ta6O19], which is fairly soluble in water; more
complex heteropolyacid complexes are know. Once you have it reacted with oxygen, Ta tends to stay reacted with it. The oxide is much like the metal in
its chemical resistence; again only HF attacks it, out of the acids, fused alkali converts it to tantalates.
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