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Mercury Azides. I’ll Get Right On Those For You.

Azides have featured several times in the Things I Won’t Work With series, starting with simple little things like, say, fluorine azide and going up to all kinds of ridiculous, gibbering, nitrogen-stuffed detonation bait. But for simplicity, it’s hard to beat a good old metal azide compound, although if you’re foolhardy enough to actually beat one of them it’ll simply blow you up.
There’s a new paper in Angewandte Chemie that illustrates this point in great detail. It provides the world with the preparation of all kinds of mercury azides, and any decent chemist will be wincing already. In general, the bigger and fluffier the metal counterions, the worse off you are with the explosive salts (perchlorates, fulminates, and the others in the sweaty-eyebrows category). Lithium perchlorate, for example, is no particular problem. Sodium azide can be scooped out with a spatula. Something like copper perchlorate, though, would be cause for grave concern, and a phrase like “mercury azide” is the last thing you want to hear, and it just might be the last thing you do.
As fate would have it, though, none of this chemistry is simple. You can get several crystalline forms of mercuric azide, for one thing. The paper tells you how to make small crystals of the alpha form, which is not too bad, as long as you keep it moist and in the dark, and never, ever, do anything with it. You can make larger crystals, too, by a different procedure, but heed the authors when they say: “This procedure is only recommended on a small scale, since crystalline α-Hg(N3)2 is very sensitive to impact and friction even if it is wet. Heavy detonations occur frequently if crystalline α-Hg(N3)2 is handled in dry state”.
Ah, but now we come to the beta form. This, by contrast, is the unstable kind of mercury azide, as opposed to that spackle we were just discussing. These crystals are not as laid-back, and tend to blow up even if they’re handled wet. Or even if they’re not handled at all. Here, see if you’ve ever seen an experimental procedure quite like this one:

After a few minutes, the deposition of needle-like crystals starts at the interface between the nitrate and the azide layer (β-Hg(N3)2). After some time,
larger crystals tend to sink down, during this period explosions frequently occur which leads to a mixing of the layers, resulting in the acceleration of crystal formation and the growth of a mat of fine needle-like crystals. . .

Hard to keep a good smooth liquid interface going when things keep blowing up in there, that’s for sure. Explosions are definitely underappreciated as a mixing technique, but in this case, they are keeping you from forming any larger crystals, a development which the paper says, with feeling, “should be avoided by all means”. But it’s time to reveal something about this paper: all this mercury azide stuff is just the preparation of the starting material for the real synthesis. What the paper is really focused on is the azide salt of Millon’s base [Hg2N+].
Now that is a crazy compound. Millon’s base is a rather obscure species, unless you’re really into mercury chemistry or really into blowing things up (and there’s a substantial overlap between those two groups). A lot of the literature on it is rather old (it was discovered in the early 1800s), and is complicated by the fact that it usually comes along as part of a mixture of umpteen mercury species. But it really is a dimercury-nitrogen beast, and what it’s been lacking all these years – apparently – is an azide counterion.
There are two crystalline forms of that one, too, and both preparations have their little idiosyncracies. Both forms, needless to say, are hideously sensitive to friction, shock, and so on – there’s no relief there. For the beta form, you take some of that mercuric diazide and concentrated aqueous ammonia, and heat them in an autoclave at 180C for three weeks. No, I didn’t just have some sort of fit at the keyboard; that’s what it says in the paper. I have to say, putting that stuff in an autoclave has roughly the same priority, for me, as putting it under my armpits, but that’s why I don’t do this kind of chemistry.
But the alpha form of the Millon’s azide, now that one takes some patience. Read this procedure and see what it does for you:

Nitridodimercury bromide [Hg2N]Br (0.396g, 0.8mmol) is suspended in a saturated aqueous solution of sodium azide NaN3 (dest. ca. 3mL) at ambient temperature, resulting in an orange suspension which was stirred for ten minutes. The solution is stored at ambient temperature without stirring under exclusion of light. After one week, the colourless supernatant was removed by decantation or centrifugation and the orange residue was again suspended in a saturated aqueous solution of sodium azide NaN3. This procedure was repeated for 200 to 300 days, while the completion of the reaction was periodically monitored by PXRD, IR and Raman spectroscopy. . .

So you’re looking at eight months of this, handling the damn stuff every Monday morning. The authors describe this procedure as “slightly less hazardous” than the other one, and I guess you have to take what you can get in this area. But the procedure goes on to say, rather unexpectedly, that “longer reaction times lead to partial decomposition”, so don’t go thinking that you’re going to get a higher yield on the one-year anniversary or anything. What way to spend the seasons! What might occur to a person, after months of azidomercurial grunt work . . .surely some alternate career would have been better? Farm hand at the wild animal ranch, maybe? Get up when the chickens would be getting up, if they’d made it. . .head out to the barn and slop the wolverines. . .hmm, forsythia’s starting to bloom, time to neuter the hyenas soon. . .
No, no such luck. The hyenas will have to remain unspayed, because it’s time to add fresh azide to the horrible mercury prep. Only three more months to go! Sheesh.

44 comments on “Mercury Azides. I’ll Get Right On Those For You.”

  1. The Aqueous Layer says:

    I love this from the abstract:
    Always look on the bright azide of life: The synthesis of Millon’s base azido salt [Hg2N]N3, and the metastable β-Hg(N3)2, along with their full characterization is possible for the first time and closes an open gap in azide chemistry.
    Yes, that gap in azide chemistry certainly needed to be closed, unless that azide detonates, forming an even larger gap…

  2. Anonymous says:

    Youtube is full of entertaining metal azide videos!

  3. Calvin says:

    Just look for the 30g detonation of lead azide on YouTube. Perky.
    Derek. I love these posts. Keep ’em coming.

  4. slowday says:

    Wonder if the reviewers checked their yields…

  5. Inner-Self-Connected Vader says:

    What is it about these posts that makes me want to go out and do azide chemistry? I think that, inside every former Boy Scout, there lurks a pyromaniac…

  6. The Aqueous Layer says:

    Just look for the 30g detonation of lead azide on YouTube. Perky.
    That was simply awesome. The mannequin wearing goggles was a nice touch.

  7. Myma says:

    Thank you, Derek. I needed a little more mirth in my life today.

  8. barry says:

    the rule at Organic Syntheses used to be that they wouldn’t publish a prep until/unless it had been reproduced on the mole scale. Then they reduced that to the 100mmole scale. I don’t suppose any such standards apply to inorganic azide papers?

  9. A few more of these and you are going to be accused of disturbing the peace and inciting the mob.

  10. Anonymous says:

    Great post Derek, thanks so much!

  11. The Iron Chemist says:

    Horrified to read that they apparently did most of these syntheses on a gram scale. The term “deathwish” keeps coming to mind.

  12. jtd7 says:

    Nothing excites my intellect like a novel insight that is undeniably true, and this post brought me one: “Explosions are definitely underappreciated as a mixing technique.”

  13. Jim says:

    Does the world need mercury azide? Or any more heavy metal azides? That this is going on in an academic laboratory disturbs me. Please leave this to the military. Also, it seems like most papers dealing with explosives come out of Germany.

  14. As a chemist-turned-account-manager who spent three years of her life purifying a protein that lost its activity in EVERY SINGLE COLUMN WE USED, the whole 200-300 day thing with the potential of DYING makes my graduate career look much less traumatizing.

  15. LMM says:

    Footnote 18 hints that — unbelievably — they repeated the autoclave protocol more than once.
    Apparently any excess starting material will also crystalize, yielding large mercury (I) azide crystals. Helpfully, Footnote 18 cautions us that, quote, “the slightest provocation [of these crystals] … will always lead to a violent detonation, thereby decomposing the whole batch.”
    Well, crap. Not only did that take out the hood and my eyebrows, I now have to repeat the whole damn procedure all over again.

  16. Helical Investor says:

    When part of your graduate studies going to sleep with the police scanner on … look for another advisor.

  17. paperclip says:

    “Hey, just curious, how long will you be needing the autoclave?”
    “Um, three weeks.”
    “Three weeks?! Good grief, what type of broth needs three weeks to be autoclaved?”
    “Um, I’m not working with a broth…”

  18. JosSmos says:

    @13 This is exactly what should be possible in academia. There is not an idea stupid enough for academia. Nowadays we have (only) a few highly specialized groups in the world doing this type of research, and those stupid ideas get backed by a LOT of experience and reasoning. These people are not your average hillbilly stuffing a pipe, and you should credit them for it.
    BTW, can you imagine the risk analysis for this work in your average BigPharma or CustomSyn Inc.?
    Oh, and that includes the military, as they are happy to source this work to academic groups through grants.

  19. Hap says:

    How does someone come up with these type of procedures? Was there a literature prep for related compounds, and they just (gingerly) adapted to this work, or (more likely) did someone search around to find conditions that would work?
    When even reactions that work might blow up, finding conditions that work seems not only onerous and dangerous, but unmanageable. It’s one thing trying 1500 conditions to oxidative dimerize a diazofluorene when the failures (probably) wouldn’t have blown you up, and so you might have been able to perform the reactions combinatorially. With this, the failed reactions might blow up the others, so most of what makes combinatorial testing possible isn’t here. It’s like dancing in a minefield, in the dark, blindfolded.

  20. Anonymous says:

    #18 – I do give them credit. They have some brass balls and I presume they know what they’re doing. However, I still don’t understand why this work was necessary. Is it worth the risk? A researcher could die doing this work. Other than the authors’ claim that this fills a gap in azide chemistry, what was the takeaway from this work? Were people clamoring to have this gap filled? It all just seems unnecessary for what could result in a scientist without a hand (or worse).

  21. JosSmos says:

    @20 I guess that their “gap in azide chemistry” is a bit over the top and may serve the need for a high IF. Nevertheless, true discovery can lie in the darkest of places. And to go to these places is a worthy goal.
    Yes, a researcher may die in this type of work, but they are aware of the dangers and will do everything to estimate this danger and counter the risk, and are well trained to do so. A lot of other chemists may not look at their compounds with such scrutiny, e.g. Karen Wetterhahn back in the days.

  22. Slomo says:

    Getting funding for a project like this is almost a bigger feat than carrying out the chemistry

  23. Anonymous says:

    A lot of other chemists may not look at their compounds with such scrutiny, e.g. Karen Wetterhahn back in the days.
    It should be noted that Karen Wetterhahn did everything correctly. It was only after her death that her colleagues investigated the permeability of mercury and discovered it to be much more permeable than the glove company claimed. Prior to that, those gloves were widely believed to be appropriate protection.

  24. Anonymous says:

    Next stop fulminating gold and silver chemistry – both nitrides. I played with this kind of stuff as a kid about 50 years ago in my back yard lab. Looking at them wrong could make either explode. The heavy metal azides and fulminates were far safer to handle but not as easy to make. For inquiring minds, a new book titled “Primary Explosives” from Springer covers some of this chemistry in great detail. It seems the world of these kinds of energetic materials has not stood still over the past 50 years. There is a lot of novel high energy chemistry that remains to be explored for those needing a little danger in their lives.

  25. Jens says:

    @20: here in Germany one of the requirements for finishing university and earning a “Doctor” title is doing and documenting some original research – rehashing/copying somebody else’s work has resulted in some careers being over even years after the fact, so there’s more scrutiny nowadays.
    “Filling gaps” can use others’ research as guidelines while being original enough to be valid.

  26. Ken says:

    Quote from 12 “Nothing excites my intellect like a novel insight that is undeniably true, and this post brought me one: “Explosions are definitely underappreciated as a mixing technique.””
    You have a kindred soul here. That was one of the funniest chemistry-related statements I’ve ever read.

  27. srp says:

    I can only imagine that the groups doing this work think of themselves as members of a rarefied elite who are proud to do things others could or would not. Like being in the Delta Force. What I’m not sure about is how much the risk itself is an attraction–does a BASE jumper lurk inside certain chemists?

  28. Oldnuke says:

    I’m just waiting to hear about Klaptoke’s adventures making plutonium azides… Let’s hope he doesn’t get a visiting scholar’s post in Los Alamos. gr

    1. David Edwards says:

      Apparently, someone has actually made neptunium and plutonium azides. There are brief references to this in this document. Page 189 covers neptunium azide complexes (and notes that there are a range of these, with some interesting difficulties both in formation and characterisation), whilst page 404 briefly covers plutonium azide complexes.

      Since the work in question is of French origin (thought written in English), sadly, Klapötke wasn’t involved. Though I suspect he’d enjoy solving the puzzle of making the higher oxidation state azides, which apparently is still awaiting a reproducible solution.

  29. joeylawn says:

    Other interesting Nitrogen compounds (if they could be made) are Octaazacubane (N8) – I nickname that one “Nate”, and ‘Ammonium Triazide’ N(N3)3.

  30. Interesting read! I used to be into synthesizing all kinds of explosive compounds when I was younger and lived out in the country!

  31. Anonymous says:

    I once tried to make nitroglycerine in my parents garage, but I got impatient and added everything too fast. The nitration got out of control and the garage filled with toxic brown fumes, so I never made it. Probably just as well.

  32. D.J. says:

    So if these things are insanely unstable and explosive, but they’re so unstable you can’t use them as regular explosives…..why do people keep making them? Perhaps it’s in the spirit of pure mathematics, simply to know.
    It’s neat to see all these posts, certainly, but I’m wondering why all these papers get published if they’re never going to make the stuff again? Or perhaps it’s to show how they got there for reproducibility, but then since they made it, no-one else has to, and people can see what’s been made already?

  33. cookingwithsolvents says:

    @8, yes they did do it in huge scale. The first or second issue of inorg syn has huge synthesis of Na(Hg) and several different big-scale syntheses of HN3, NH3N3, NaN3, etc. Vol 1 has HN3 and vol 2 has an improved procedure that directly makes KN3.
    My PhD group had the series in the group room and sometimes I’d peruse over lunch. Learned a lot of ‘in theory you could make it’ chemistry that makes me appreciate aldrich, strem, and all the other suppliers. Especially for metal halide compounds, which I use regularly and would really hate to have to make for myself.

  34. Hobbes says:

    I move to have Azides in general be renamed to “detonation-bait”. When people think the solution is to stuff more nitrogens onto something, start running, fast.

  35. Anonymous says:

    Who needs carbon anyway??

  36. Nature Lover says:

    This could get to be expensive with replacing the spectrometers. Or since I left undergrad/grad school 40 years ago do they armor them now? I guess if one can safely remove a minute amount this is not an issue. Obviously they had not too much of an issue but
    I could see the grant request for 8 duplicate machines for attrition…

  37. daryl says:

    I enjoyed reading the 1950 tomes “The Chemical Elements And Their Compounds” by Sidgewick.
    Read the section on the team exploring Perchloric Esters. They wore iron masks.

  38. Nick says:

    Does Millon’s base have an azidotetraazolate (CN7) salt yet? Someone should get on that.

  39. Anonymous says:

    @Derek: “Explosions are definitely underappreciated as a mixing technique…”
    I couldn’t help but be reminded of the Monty Python sketch where Graham Chapman extolled the virtues of dynamite in the practice of medicine:
    Doctor: This is where Mrs. Shazam was so wrong. Exploding is a perfectly normal medical phenomenon. In many fields of medicine nowadays, a dose of dynamite can do a world of good. For instance, athlete’s foot – an irritating condition – can be cured by applying a small charge of TNT between each toe.

    Doctor: Now, many of the medical profession are skeptical about my work. They point to my record of treatment of athlete’s foot sufferers – eighty-four dead, sixty-five severely wounded and twelve missing believed cured. …

  40. silverpie says:

    OK, take a negative ion that’s on the order of cyanide in the things-that-will-kill-you-quickly list, add a positive metal ion that rates high on things-that-will-kill-you-slowly-and-painfully… and then the combination tends to explode? Strike 3, I’m out of there!

  41. The WiZard is in says:

    Copper perchlorate?! Perfectly harmless, you
    can buy it OTC. Tetraamine copper chlorate
    can be prepared as a primary explosive.
    Yea old Schumacher, Perhclorates: Their Properties
    Manufacture and Uses. Reinhold, 1960.
    (I own a UMI reprint) notes that —
    p. 48 Antimony perchlorate – decrepitates
    strongly when heated above 60o C.
    SR Brinkley, Jr. Am Chem Soc J 62:3524,
    December, 1940.
    The Instability of Silver Perchlorate
    While breaking the cakes buy gentle pressure
    in a mortar, a sample detonated with
    extraordinary violence .
    Making small Xtls of for instance lead azide
    is de rigueur, e.g., “dextrinated” lead azide
    though dextrin is no longer used, CMC is.
    AD-A011 026
    Proceedings of the Symposium on Lead and Copper
    Azides on 25th=-26th October 1966
    Explosives Research and Development Establishment
    Walthan Abbey
    119 pages. Free DL from the usual source.
    If you want to impress your friend you can grow
    large Pb azide xtls.
    Fair & Walker Eds.
    Energetic Materials
    Volume 1
    Physics and Chemistry of the Inorganic Azides
    Plenum Press 1977
    People who like this book would also like —
    Bowden & Yoffe
    Fast Reactions in Solids
    Academic Press 1958
    Noted in passing —
    A SL of pages. 1960.
    Free DL from the usual place.
    At no extra charge —
    The most singular properties of this
    salt [potassium chlorate] consist more particularly in the violent
    mode of action it exhibits with combustible
    bodies. This may even be considered as
    surprizing, when compared with those
    afforded by all the other known
    saline substances. The super-oxigenated
    muriate of pot-ash seems to include the
    elements of thunder in its particles. A
    chemist can produce effects almost
    miraculous by its means, and nature
    seems to have concentrated all its
    power of detonation, fulmination,
    and inflammation in this terrible
    Antoine-François de Fourcroy (comte)
    A general system of chemical knowledge,
    and its application to the phenomena of
    nature and art.
    Volume 3 Section fifth
    Concerning Alkaline and Earthy Salts
    Blowing shit up since
    when blowing shit up
    wasn’t cool.

  42. loupgarous says:

    One word for you, young feller… “waldoes.”

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