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DBL%20Hendrix%20small.png College chemistry, 1983

Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: Twitter: Dereklowe

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February 26, 2008

Sand Won't Save You This Time

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Posted by Derek

In a comment to my post on putting out fires last week, one commenter mentioned the utility of the good old sand bucket, and wondered if there was anything that would go on to set the sand on fire. Thanks to a note from reader Robert L., I can report that there is indeed such a reagent: chlorine trifluoride.

I have not encountered this fine substance myself, but reading up on its properties immediately gives it a spot on my “no way, no how” list. Let's put it this way: during World War II, the Germans were very interested in using it in self-igniting flamethrowers, but found it too nasty to work with. It is apparently about the most vigorous fluorinating agent known, and is much more difficult to handle than fluorine gas. That’s one of those statements you don’t get to hear very often, and it should be enough to make any sensible chemist turn around smartly and head down the hall in the other direction.

The compound also a stronger oxidizing agent than oxygen itself, which also puts it into rare territory. That means that it can potentially go on to “burn” things that you would normally consider already burnt to hell and gone, and a practical consequence of that is that it’ll start roaring reactions with things like bricks and asbestos tile. It’s been used in the semiconductor industry to clean oxides off of surfaces, at which activity it no doubt excels.

There’s a report from the early 1950s (in this PDF) of a one-ton spill of the stuff. It burned its way through a foot of concrete floor and chewed up another meter of sand and gravel beneath, completing a day that I'm sure no one involved ever forgot. That process, I should add, would necessarily have been accompanied by copious amounts of horribly toxic and corrosive by-products: it’s bad enough when your reagent ignites wet sand, but the clouds of hot hydrofluoric acid are your special door prize if you’re foolhardy enough to hang around and watch the fireworks.

I’ll let the late John Clark describe the stuff, since he had first-hand experience in attempts to use it as rocket fuel. From his out-of-print classic Ignition! we have:

”It is, of course, extremely toxic, but that's the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively. It can be kept in some of the ordinary structural metals-steel, copper, aluminium, etc.-because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.”

Sound advice, indeed. I'll be lacing mine up if anyone tries to bring the stuff into my lab.

Comments (79) + TrackBacks (0) | Category: Things I Won't Work With


1. Fred on February 26, 2008 11:25 AM writes...

Everyone should have a “no way, no how” list.

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2. Thomas McEntee on February 26, 2008 11:57 AM writes...

According to the Kirk-Other Encyclopedia of Chemical Technology, 4th Ed, during WWII, Germany ran a 5-ton per day pilot plant to produce ClF3. Chlorine trifluoride oxide (ClF3O) is another extremely powerful oxidative fluorinator. The initial report on its synthesis was published in 1970; this report describes the UV-initiated reaction chlorine trifluoride with oxygen and fluorine. Another is chlorine trifluoride dioxide (ClF3O2, first synthesized in 1972. A key paper to read regarding oxidative fluorinators--including the xenon fluorides and krypton difluoride--is the study "A Quantitiative Scale for the Oxidizing Strength of Oxidative Fluorinators", Karl O. Christie and David A. Dixon, JACS, 114, 2978-85 (1992)

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3. Feiser N. Feiser on February 26, 2008 12:22 PM writes...

Ah, the old sand bucket. Was out in the hall outside the undergraduate labs. Might have been there since benzene was linear. Top was decorated with cigarette butts, dried gum, bits of paper. Then one day down the hall the THF still is being cleaned out - long over due. Thick clumps of whatever ketyl becomes. Inside, a bright shiny prize of sodium metal that disagrees with the optimistic and impatient grad student's use of straight ethanol as cleaning aid. Fire erupts. Extinguished by CO2. Humid day, icy glass, beads of water form and follow gravity down. Into and onto sodium metal. Fire erupts. Extinguished by CO2. Repeat several times until it dawns that CO2 will eventually run out. Send terrified lab mate down the hall to fetch savior: sand bucket! Weight of bucket: about 200 lbs. Skinny grad student risks hernia rushing it back to lab, arrives exhausted, collapses in victory like Pheidippides. Firefighting grad student drops damned CO2 tank, plunges bare hand into sand bucket. Screams in pain - sand has been accreted by age into protoconcrete, impermeable to human flesh, spatulae, metal rulers, etc. Fire meanwhile burns itself out. Sand bucket replaced for next sucker.

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4. jose on February 26, 2008 12:50 PM writes...

"I am become death, the (liquid) destroyer of worlds."

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5. Mark on February 26, 2008 12:55 PM writes...


That made my morning! What a fine combination of chemistry, history, and comedy.

I get the soundtrack to an old Stooges short in my head when reading that...

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6. Wavefunction on February 26, 2008 1:27 PM writes...

"Ignition" totally rocks! What a rambunctious journey through liquid rocket fuel propellants. Too bad it's out of print.

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7. Brooks Moses on February 26, 2008 2:54 PM writes...

It does sound like a book that I'd really like to read. It would be nice if Dover would find a slot for it in their reprint catalog!

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8. BACE on February 26, 2008 3:51 PM writes...

On a different note, what do you think of this:

People will die from paying the cost, not of the disease.

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9. In the back stacks on February 26, 2008 5:36 PM writes...

get yer ignition here

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10. milkshake on February 26, 2008 7:26 PM writes...

I was in lab where they analysed oxygen isotopic content in silicates and other minerals.

They had a big tank of BrF3 there. It made an impression on me - you take dry sand and gas it with brominefluoride and off goes O2

Oh, and the apparatus was a benchtop, the tank parked right next to it. it had an exhaust but no fume hood in sight :)

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11. Fred on February 26, 2008 7:46 PM writes...

Interesting that this should show up on a day we are discussing difficult fires: Ethanol fires from rail and tanker accidents are more difficult to extinguish than gasoline fires. Ethanol dissolves the foam commonly used to fight fires.

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12. Anonymous BMS Researcher on February 27, 2008 9:00 AM writes...

When my father was in high school some fellow students started a thermite reaction in the chem lab. It burned its way through several floors and finally went quite a ways into the concrete floor of the basement (from my father's descriptions I'm visualizing the scene in Alien when the creature's blood burns through the decks of the spacecraft). Fortunately, no people happened to be directly in its path...

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13. tom bartlett on February 27, 2008 9:50 AM writes...

"When my father was in high school some fellow students started a thermite reaction in the chem lab. It burned its way through several floors and finally went quite a ways into the concrete floor of the basement"

Must have been a pretty big quantity.

Anyway, ClF3 sounds way cool. Xenon Fluorides are also good candidates for the "no way, No how" list.

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14. milkshake on February 28, 2008 1:09 AM writes...

XeF2 is actually a nicely behaved heavy salt-like solid, not very reactive. You can but it from Aldrich but it is dear.

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15. TNC on February 28, 2008 2:52 AM writes...

Baran actually used XeF2 in a recent synthesis.

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16. Thomas McEntee on February 28, 2008 6:45 AM writes...

Milkshake: As of January 2005, XeF2 also was offered for sale on the English-language web site of Russia's Kurchatov Institute and recommended for uses in the surface treatment and improving wear-resistance for styrene-butadiene rubbers, acrylonitile-based rubbers, EPDM and isoprene-based rubbers.

An interesting synthesis of XeF2 suitable for students was described by JH Holloway in 1966 (J Chem Ed) in which a sealed Pyrex bulb containing fluorine and xenon is placed in sunlight. After a period, tiny crystals of XeF2 are observed to form.

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17. A-nony-muse on February 28, 2008 9:39 AM writes...

What, no one chose to comment on the burning RAW CHICKEN FLESH pics in the Air Products MSDS for ClF3??? That's not something you see every day!

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18. Derek Lowe on February 28, 2008 9:41 AM writes...

I've used XeF2 myself - a rather penetrating smell, which I sampled despite trying not to. It's the higher xenon fluorides, I believe, that are a bit rambunctious. I'll probably add them to the list, too, and do a post on 'em. . .

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19. MedChemSF on February 28, 2008 12:08 PM writes...

A-nony-muse: I was more impressed with the flaming nitrile glove.

I can imagine chicken on fire, but I don't think I've ever thought about what it would take for a chemical to set my gloves off.

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20. Kevin on March 3, 2008 1:59 PM writes...

I hate to admit it but I've worked with both. I've even seen someone redesign a TGA to handle these gases. Funny, thro the HS2 worried me more.

Catalyst design can be messy at times.

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21. Mike on March 3, 2008 2:18 PM writes...

Careful. You are going to give the Truthers another idea about how the government brought down the WTC towers, WTC 7, and what really caused the Tunguska blast.

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22. Jim on March 3, 2008 2:19 PM writes...

Reminds me of a Captain Marvel comic book story from (probably) the late 1940s where Captain Marvel was fighting some evil genius who had created a universal solvent. This chlorine trifluoride sure sounds almost as scary.

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23. MB on March 3, 2008 2:33 PM writes...

The Nazis also experimented with loading chlorine trifluoride into artillery shells to use against the Maginot fortifications. One of those babies slamming into your pillbox could ruin your whole day.

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24. Huycbald on March 3, 2008 3:44 PM writes...

I just love it that there are people in the world who can answer the question, "Will anything set sand on fire?" And, in the affirmative, no less.

Great stuff!

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25. Douglas Pratt on March 3, 2008 5:56 PM writes...

I have a beloved copy of "Ignition!" right here. Did y'all know that Dr. Clark was a well-known member of the Baker Street Irregulars? He wrote the famous essay "Watson was a Woman," offering proof that Dr. Watson was really Irene Adler. A truly amazing man. The introduction to "Ignition!" was written by Isaac Asimov. By the way, in the chapter where he discusses chlorine triflouride, Clarke mentions that someone nanaged to synthesize enough chlorine pentaflouride (!) to characterize...

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26. Robert on March 4, 2008 9:10 AM writes...

I just found your site, and I have to say that these "Things I Won't Work With" segments are both hilarious and informative. I'm a cheist myself, though most of my work has been quality control with analytical instruments, so I'm not familiar with all the reagents and processes being mentioned. But I'm certainly learning interesting new things by looking them up. (Not to mention leanring what to stay the hell away from!) Anyway, I hope you keep up with these. you've certainly earned a bookmark from me!

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27. Clayton E. Cramer on March 4, 2008 4:13 PM writes...

This brings back memories of sitting on an airliner talking to a sales engineer for a chemical company. He was completely unaware of what happens when you combine fluorine gas and water. Yikes!

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28. Bob Holness on March 10, 2008 9:51 AM writes...

So in this case we need a metal filing bucket?

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29. SFOtter on March 10, 2008 3:19 PM writes...

Years back, when I worked as a machinist, we occasionally had to mill blocks of magnesium for semi-conductor mfgs.

Some apprentice decided he could cut faster than the programmer had set and ratcheted up the speed & feed rate.

The resulting fire destroyed a $40k Matsuraa mill and part of the floor.

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30. Irritant on March 20, 2008 2:03 AM writes...

I believe this is what Chuck Norris has for breakfast when he has a sore throat.

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31. Spooge on June 28, 2008 10:22 PM writes...

The first reagent in the Krol Blade.

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32. Chunkstyle on July 14, 2008 10:12 PM writes...

As I recall, ClF3 was simply dropped on London by those same Nazis, who built the 5 ton/day plant for it. Pretty nasty, when the compound itself is the bomb...

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33. Seriously on September 26, 2008 2:38 PM writes...

I've worked with ClF3 before, had excellent results with maintaining LP-CVD process chamber and no accidents when handled properly. Get careless and you can get burned. Handle with respect, and the benefits are miraculous.

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34. Rissa on October 24, 2008 6:16 PM writes...

"Suitable extinguishing media: None."

Says it all really.

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35. Yanes on January 28, 2009 1:10 PM writes...

We use bromine triflouride in the the oilfield, nasty similar oxidizer. Pretty potent mental image: burning snow.

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36. Eric on March 18, 2009 11:39 AM writes...

How, pray tell, did they figure out that ClF3 is toxic? I mean, besides the whole catching-fire-to-raw-flesh-or-water thing.

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37. Ilya on March 22, 2009 4:53 AM writes...

So this is the stuff that aliens (from the film) had for blood...

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38. Michael Chermside on March 25, 2009 3:56 PM writes...

How on earth do you synthesize that stuff?! Not that I'd want to try...

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39. milkshake on March 25, 2009 6:06 PM writes...

obviously they had to find some material that does not get eaten by it. I suppose they used some metal alloy that coats itself with a protective layer of fluoride. The starting material, fluorine gas is bad enough - on contact it speedily burns through the skin like a flame...

By the way Teflon was invented in WWII as the only material that can withstand uranium hexafluoride in the gas diffusion enrichment plant.

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40. anonymous on March 26, 2009 12:16 AM writes...

#36 Eric- I'll give you three guesses, and the first two don't count.