How can Bronze Age people make hazmat gear for chlorine trifluoride?

The ClF₃ is produced biologically, just as fruits produce acid or capsaicin. This alternate world just happens to have bacteria — and later, plants — that hit on the trick of using fluorine to produce toxins and novel organic compounds. This has some precedent in the real world. Just as the early civilized people produce gelatin, lye, and other chemicals through mixing, cooking, and processing natural feedstocks, they learned how to produce ClF₃ using especially useful biological precursors.

So, how can they make containers that hold it (to be thrown at enemies as a weapon) and how can the wielders of this weapon protect themselves?

Note in particular that chlorine trifluoride will ignite most organic and inorganic materials. You might suppose that the availability of fluorine-bearing molecules in the local biology will offer a solution, but the obvious Teflon is also ignited by the stuff.

Note: see this meta post


I'm not too picky about what “Bronze Age” means exactly. It covers a lot of time and different cultures in the real world. Only the general ideas: the people are well into agriculture, have metalworking but not the temperature and technique for Iron yet, wide-range trade, and inventions of “devices” like pottery wheels.

Clearly this alternate-reality culture will develop differently due to the fluorine biological resources. Taming ClF₃ (for warfare) might enable the iron age immediately thereafter. So, don’t worry about the exact age and culture — it will be made up anyway.

Let me re-iterate: the plants/bacteria/whatever do not secrete ClF₃ directly. I realize that it doesn’t offer obvious evolutionary value. Rather, the plants produce “usable flourine compounds”, so that primitive people can produce the stuff by mixing and cooking (and waving of hands).

  • $\begingroup$ can you be more specific about what bronze age means to you? The term bronze age is not really defined well by historians and much less by you. Otherwise, have you read the wikipedia article? "Vessels made from steel, copper, or nickel resist the attack of the material due to formation of a thin layer of insoluble metal fluoride". So copper and nickel is known to your civilization I guess? Maybe only copper, but that should be enough, right? Also, a lot of bronze age civilizations had gold available to them. $\endgroup$
    – Raditz_35
    Commented May 6, 2017 at 11:21
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    $\begingroup$ It was just a little unclear when you wrote 'The ClF₃ is produced biologically' which was a little misleading. $\endgroup$ Commented May 6, 2017 at 14:36
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    $\begingroup$ @cobaltduck Are you sure it's a good idea to coat yourself in what is basically fuel, when dealing with chemical so oxidising that it can burn sand? It's every bit as great idea as coating yourself in dynamite to work with fire, which is to say, not very good. $\endgroup$
    – M i ech
    Commented May 6, 2017 at 15:18
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    $\begingroup$ This sounds a little like the chemical equivalent of "How to stop my unstoppable bad guy" questions. $\endgroup$
    – FreeElk
    Commented May 6, 2017 at 15:29
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    $\begingroup$ Given science-based tag, this question has no answer except "they can't". $\endgroup$ Commented May 6, 2017 at 23:56

7 Answers 7


Let us accept that these folks have enough ClF₃ handy that they want to make war by throwing it about. Let us consider first principles and move from there to the construction of hazmat gear.

ClF3₃ is very reactive because the F is more electronegative than oxygen. Things which do not burn because they are terminally oxidized (example: water) react because the F can displace the O.

Just as terminally oxidized substances cannot burn in oxygen, by definition terminally fluorinated substances cannot be additionally fluorinated. So, as pointed out, a coating on bronze vessels and bronze armor of the fluoride would be fine, and also easy to make because these people have plenty of an excellent fluorinating agent. As regards the elegance of solution, I quote Tom Sawyer from Huckleberry Finn.

“WORK? Why, cert’nly it would work, like rats a-fighting. But it’s too blame’ simple; there ain’t nothing TO it. What’s the good of a plan that ain’t no more trouble than that? It’s as mild as goose-milk. Why, Huck, it wouldn’t make no more talk than breaking into a soap factory.”

Let us consider a solution more in keeping with the overall tone of this work of fiction: over the top awesomeness! I wondered what other terminally fluoridated substances might be available or easy to make and hit upon fluorspar, or calcium fluoride.

Colorful crystals

Terminally fluoridated, CaF₂ is impervious to Cl₃F. Fluorospar is common and occurs as crystals, which come in a range of beautiful colors. I propose that these fluorine-throwing peoples could make awesome multicolored scale mail out of flakes and chunks of fluorspar, and allow the CL₃F to drip off and onto the ground, where it will react away.

Yet even this fine solution is a little lacking, I think. It might be hard to find enough fluorspar crystals to make armor, even in this unusual and apparently fluorine-rich world.

Can these people make their own fluorspar? Of course! Chalk, limestone or any calcium, treated with ClF₃ will terminally fluorinate all components. Limestone will turn to CaF₂ and volatile CF₄; not sure about the oxygen but I think it would leave as CO₂. The CaF₂ thus made would be a chalky insoluble white paste.

I propose the most elegant solution would be to dispense with the armor concept and cumbersome accoutrements altogether, and instead coat the naked body with a thick layer of CaF₂ paste. ClF₃ will bounce harmlessly off. It would be easy to thicken up one's protective coat of fluorspar paste as events necessitate.

eye protection

There remains the eyes. It is hard to see if thick white paste is applied to them. For this the crystalline form of fluorspar will still be necessary. AND awesome looking.

enter image description here

breathing protection

The final issue is to provide respirator protections for these naked crystal-eyed warriors. Here is how that can be accomplished, at the cost of aesthetic purity.

From an article on disposing of ClF₃ from nepis.epa.gov:

scanned text

Based on this, the respirator would have 2 stages. The outer is of finely particulate salt (NaCl). The ClF₃ strips off the Na to form inert NaF. Chlorine from NaCl and ClF₃ is released as gas. The second stage is a regular charcoal respirator like the WW1 soldiers used — charcoal adsorbs Cl fine.

I suppose the fluorspar lenses could be built into the mask. Naked white-caked people wearing these freaky masks would still meet Tom's criteria, I think.


Fluorite crystals apparently cropped from “FLUORITE — Illinois State Mineral” in Rocks and Minerals Magazine, January-February 2013.

Mud image adapted from a still from “Mud Paint Performance #23” by Route 207 Films.

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    $\begingroup$ I suppose breathing is also optional while handling the stuff? $\endgroup$
    – Cort Ammon
    Commented May 6, 2017 at 22:45
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    $\begingroup$ @Cort Ammon. Ah yes; it is a gas. I will assume these people keep their Cl3F chilled in liquid form, in with the champagne. In fluorspar crystal decanters. $\endgroup$
    – Willk
    Commented May 6, 2017 at 23:09
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    $\begingroup$ yes! Very nice and a good general explaination. I suppose having organisms containing fluorine may cause more instances of fluorspar occuring within limestone deposits. $\endgroup$
    – JDługosz
    Commented May 7, 2017 at 6:45
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    $\begingroup$ @Will The boiling point of ClF3 is 11C. If the only thing protecting you from inhaling it's vapors is that you are planning on not spilling it. There's no point in having any other protective equipment because you will be screwed anyway as soon as you loose containment. Remember it burns on contact with oxygen, and it's byproducts require significant protective equipment in their own right. $\endgroup$
    – sphennings
    Commented May 7, 2017 at 14:17
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    $\begingroup$ You mean CaF2, not Ca2F. Calcium has two electrons in the outer shell and fluorine has 7 ( I.e. can accept 1). $\endgroup$
    – Spencer
    Commented Oct 26, 2019 at 21:39

Look - WE can't make ClF3 hazmat gear, so it's a pretty safe bet Bronze Age folks won't either. And biologically-produced ClF3 is just laughable. There simply aren't any organic substances it won't oxidize/fluorinate. It reacts violently with water, for heaven's sake. Not to mention sand, concrete and gravel. Exposure to water immediately produces hydrofluoric acid, so you'll need to specify that your microbes are part of a fluorine-based biology. And since such a biology would be wildly toxic to any surrounding organic systems, it's pretty clear that such a system would violate the Highlander Rule, "There can only be one."

But if you're going to hand-wave (at supersonic or maybe hypersonic or even superluminal speeds) and actually produce the stuff, copper vessels will hold it just fine. You have to flush the vessel (and the inside of its lid) with ClF3 vapors first, in order to produce a fluoride layer. Otherwise introduction of the liquid will cause a spontaneous combustion with the metal which is essentially impossible to extinguish other than by throwing the pot into a lake while avoiding ANY contact with the smoke. I expect that any contact with CuF2 vapors will produce HF, and inhalation will produce HF in the lungs.

And once you've got it in the pot, you must keep the temperature below 53 F, since that's the boiling point. In fact, biological processes typically don't work well below 50 F, or at least not quickly, so any bacteria will be very inefficient in terms of production rates.

  • $\begingroup$ Furthermore, while it is certain that biochemistry of this world will be different, properties of ClF3 suggest that biochemistry resistant to ClF3 is flat out impossible. Any form of biochemistry requires long chains, we use carbon which ClF3 considers fuel in nearly any form. Silicon based biochemistry is not an alternative as ClF3 burns SAND (oxidised silicon!). Same with pretty much any element known to create long and complex molecules - ClF3 is something that any and every type of life in the galaxy would consider extremely dangerous. $\endgroup$
    – M i ech
    Commented May 6, 2017 at 15:25
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    $\begingroup$ Can Bronze age people reliably control temperatures to get them down to 53F? $\endgroup$
    – FreeElk
    Commented May 6, 2017 at 15:25
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    $\begingroup$ @FreeElk - As long as they live near glaciers, sure. Ice storage houses date back to 1780 BC, And very dry areas can produce low temperatures (below freezing) readily. Romans produced ice by exposing water to the sky at night using radiative cooling, and wrapping the ice in straw during the day. Of course, this was in Northern Africa, not Italy. $\endgroup$ Commented May 6, 2017 at 15:32
  • $\begingroup$ The living cells don’t produce ClF₃. They produce some fluorine-containing molecules that make it possible for the people to make it in some simple way involving available chemicals and fire. Your first paragraph (and the last) is arguing something that’s not what the question states! $\endgroup$
    – JDługosz
    Commented May 6, 2017 at 19:25
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    $\begingroup$ @JDługosz sadly I agree that if you are willing to handwave how reactive Cl, F and ClF3 are in living organisms and how dangerous is to produce it, then you can really, really easily handwave all else like storage and hazmat suits, and your question has little purpose. And if you don't want this high levels of handwavium, then well explained "no" is an answer. $\endgroup$
    – Mołot
    Commented May 7, 2017 at 9:59

The key background

From your wikipedia articles on ClF₃:

Vessels made from steel, copper, or nickel resist the attack of the material due to formation of a thin layer of insoluble metal fluoride.

And Bronze age:

An ancient civilization is defined to be in the Bronze Age either by smelting its own copper and alloying with tin, arsenic, or other metals, or by trading for bronze from production areas elsewhere.

It seems we have copper as a viable substance. The other key point is that the metal react and then form a barrier which no more ClF₃ can pass through.

One thing to note before we start, is that modern guidelines for handling suggest not to, at any point, risk it leaking and:

Where possible, automatically transfer liquid, gaseous, or solid Chlorine Trifluoride from drums, cylinders or other storage containers to process containers. But, for the sake of your story, lets do what we can (though a few deaths in the manufacturing/use would probably assist accuracy).

Possible protection

A copper container could be used to hold the gas. Ideally you don't want the gas to escape since there is very little you can do (even now) to avoid it. There is the advantage of it being a particularly heavy gas and so any containers should be stored as low down as possible - basements, dungeons...whatever fits your story — with a canary alarm (or animal of your choice) kept close to the entrance.

Any armour used would also have to be copper with a copper fluoride coating in joints. Beneath this copper fluoride should be a layer of thick leather as the substance is still thought to be fairly toxic.

The biggest problem would be avoiding breathing it in or contact with the eyes. Glass is obviously a big no go and no other transparent materials existed at the time. Either you chuck your men in unprotected (the more likely scenario at the time) or you make a full copper suit and weld someone into it to protect their head...and train them to do the job blind.

Once the gas has leaked* the best course of action is to move slowly, the dense gas will stay low down unless disturbed by movements — running will likely do this (advantage on the battle-field when the enemy are panicking though).

*Assuming you're wearing the armour described earlier so the gas doesn't react with your feet and doesn't do anything particularly dramatic with the floor.

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    $\begingroup$ "the dense gas will stay low down unless disturbed by movements" No it bloody won't. Any organic material it contacts will burst instantly into flame, or at least react with the utmost rapidity.. $\endgroup$ Commented May 6, 2017 at 20:33
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    $\begingroup$ As far as I was taught, "bloody" above is pretty factual, not a curse word. Just saying. Once gas leaked, just don't be there or it'll be bloody. That's why we prefer automata and staying away irl. $\endgroup$
    – Mołot
    Commented May 7, 2017 at 10:04

Using some of the resistant metals that were around, like copper and such, are helpful, however, there could be a solution within your world's evolution.

If this is produced naturally, to start with in a less toxic version, then there may be things that have evolved to be biologically resistant to the substance, at least in other forms.

It won't be quite to the level of the finished product (which will be MUCH more corrosive), but these changes and resistances will likely be crucial to developing anything that has even a ghost of a chance as far as CIF3.

We don't have anything like that on earth, but then again, it's not produced here naturally much either.

I'd do a combo platter--so use the metals that you know are resistant, and then take a look at the biology of the animals that interact with the plants.

In the real world, capsaicin hurts most animals, but doesn't really bother birds. And there are berries which birds can eat but are totally poison to most mammals. (Since those berries travel well in a bird's digestive system, to be spread but not in a mammal's, it makes sense that this would be so.)

Fluorine is highly toxic and reactive. And yet, your plants will be able to contain and release it. This may be part of your answer. If your plants in any way have a symbiotic relationship with other animals (like bees and birds do with plants) those animals may well have their own resistances which might be able to be used by your bronze age people. If there's something that feasts on your plant (could even be a slug or something) that could have a natural resistance.

I say, don't look to what Bronze Age people could do in our era, because you'll be out of luck there. Instead, take your answers from what your world has to offer. This Fluorine change will produce many and varied evolutions which may well hold the key.

If you want something specific, look to how it's handled today. The answer is low temperature. So your biologic would be something naturally occurring that cools down to those temperatures. We have nothing like that on earth, and it would be a very strange biology indeed. You've got to go full sci-fi here, using known science and handling, as a basis, and then veering hard into sci-fi territory.

The biological precursors being more prevalent in nature might be helpful in finding something naturally resistant, even if it is something that must be boiled down or concentrated and what not. Even in less caustic chemical form, an advantage still might be find naturally. Otherwise, my answer is that it isn't possible. Because there really is nothing on earth that would work.

  • $\begingroup$ From blogs.sciencemag.org/pipeline/archives/2008/02/26/… "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" So, evolutionary adaptation - not so much. $\endgroup$ Commented May 6, 2017 at 18:00
  • $\begingroup$ «capsaicin hurts most animals, but doesn't really bother birds.» yea! Just a week or two ago my Sichuan mother-in-law looked on astonished as Diamond munched on a ~hot~ pepper without a care. $\endgroup$
    – JDługosz
    Commented May 6, 2017 at 19:48
  • $\begingroup$ @WhatRoughBeast Even having precursors prevalent in nature might result in an unforeseen biologic that we've never seen or thought of. It's not something we have, even remotely, and it would have to be complex in ways that we haven't seen. $\endgroup$ Commented May 6, 2017 at 20:10
  • $\begingroup$ @JDługosz Edited. I wish I could get more specific, but the answer is not here on earth, not for Bronze Age, anyway. $\endgroup$ Commented May 7, 2017 at 3:02
  • $\begingroup$ «but the answer is not here on earth, not for Bronze Age, anyway» Well, Will found something! $\endgroup$
    – JDługosz
    Commented May 7, 2017 at 6:51

WhatRoughBeast is right about the chemistry, I am afraid. The entire reason these compounds are so fun is because while elements fluorine, chlorine, and oxygen can be made to form compounds with each other, they very strongly prefer to bond with almost anything else with the usual exception of the noble gasses. They can't be produced by "heating stuff up" or by any other non-magical method available to a bronze age civilization. A biological process is actually possible IMHO, but I think we all agree it would take genetic engineering or divine interference to make it happen on a useful scale.

Now you could of course hand-wave™, super-luminal speeds or otherwise, but you really, really should not do so here. Why? Because a bronze age civilization does not have the chemistry needed to know what elements the stuff they use is composed of or what its chemical formula is.

How and more importantly why were you planning on telling people the "burning stuff" is actually chlorine trifluoride? Or that the local biology contains fluorine compounds? The whole point of hand-waving™ is that you skip explanations not relevant to the actual story or setting. Combining it with superfluous level of scientific detail is never a good idea. Especially when anyone you show the result will either ignore it with glazed eyes or react much like WhatRoughBeast did.

So if you want to hand-wave™ do it properly, just focus on the actual observable effects and ignore the mechanics apart from maybe a general sanity check.

Alternately, if what you wanted to know about was chlorine trifluoride just accept the chemistry will not work the way you want it to.

Sorry if you found this offensive, unfriendly, unproductive or so on. It is not intentional, but telling someone you think their idea is a fundamentally flawed one with any kind of useful detail seems to always carry that risk. And unfortunately trying to make the answers somehow useful is the entire point on this site.


They use whatever the organism in question uses to keep from being killed by its own toxin, likely transporting the whole organism which is processed on demand. Some details about what kind of organism contains the stuff would be important for more detail.

considering the practices of the time they likely would use no protection and just use slaves or children for handling and just accept high mortality.

  • $\begingroup$ I was thinking along those lines but then in the comments the OP said no, I explained that the plants contain precursors. Admittedly the question was unclear but it seems the plants don't actually contain the chemical in it's form we want to use it in. $\endgroup$ Commented May 6, 2017 at 16:48

Under normal conditions, making this hazmat gear is impossible. I didn't choose Stoff-N (Chlorine trifluoride) as an anti-tank weapon for my story for nothing, and remember, it can ignite itself, and running with a full bronze set, without any openings in it is:

A: Impossible.
B: You will likely be suffocated because of the deprivation of oxygen in your hollow bronze statue before Stoff-N gets you.
C: Or you'd be just simply fried to death.

Stoff-N isn't just some whimsy ineffectual napalm, it's the distilled essence of the Chemist's nightmare, it will burn through 90 cm's of gravel just to get you, even its residues are more than enough to melt away tanks, and emulate WW1 a bit. This chemical was too much, even for the meth addicted, Hitler to use.

What idiot would plan to stuff these things into genetically engineered lemons, then fire it from longbows, just to decimate a german tank?! (aside from Cave Johnson)

Thankfully, there is still hope:

Dr. John Drury Clark said:

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.

Stoff-N is for bombs and not for flamethrowers, so you can get out of the "blast radius" if you're a good runner, just don't forget to wear a tight clothing and always keep a rag with yourself, that you can use to filter the air a bit, but don't forget to throw it away ASAP.

Your best chance is making a large umbrella (no Resident Evil references here) that you can immediately throw away when it gets into contact with Stoff-N.

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    $\begingroup$ This is confusing — the first paragraph suggests a disposable shield as opposed to a full resistant shield, which is a good idea. But then the rest of the post is disorganized and doesn’t elaborate on that idea. Instead, it mentions an air tight bronze armor suit (?) , and then goes off on a tangent from there. I suggest you keep the first sentence and throw away the rest; write something that follows from this opening. $\endgroup$
    – JDługosz
    Commented May 14, 2017 at 11:32
  • $\begingroup$ Well, the good news is that switching the sentences is good from an English Composition point of view. The introductory paragraph should introduce the topics that follow. $\endgroup$
    – JDługosz
    Commented May 14, 2017 at 15:35
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    $\begingroup$ The bad news is that you’ve focused on a non-answer and left the germ of a good (unique) answer falling by the wayside. Saying that bronze armor won’t work is not an answer. Saying that there’s no good answer is not an answer and contradicts both other good answer posts and your own umbrella idea! Take what’s now the last paragraph and throw away the rest. Develop that unique solution into an answer — you can discuss the difference between ablative and impervious shielding and show that the former is being overlooked. $\endgroup$
    – JDługosz
    Commented May 14, 2017 at 15:40

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