I've run across references to chlorine trifluoride quite a lot. It pops up fairly regularly on the Worldbuilding SE, and whatever idea people have with it is usually shot down very quickly - For obvious reasons.

One of the things that comes up in almost any web search about chlorine trifluoride is that it doesn't react with "candle wax" pretty much at all. (Example here)

Is this true? If it is, why? What is so special about candle wax that makes it immune to this substance that reacts extremely well with almost anything on, in, or around Earth?

(Worth noting: I'm not a chemist, so a basic overview would be appreciated in addition to any extensive scientific answer. Said extensive scientific answer is also appreciated because I'm sure there's others that would like the answer to this as well.)

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    $\begingroup$ I'm utterly amazed to find out ClF3 doesn't react with candle wax - can anybody give a better reference? A quick google shows up "Paraffin is by far the most frequently used candle wax on a worldwide basis today" at candles.org/elements-of-a-candle/wax and the paper "The explosive reaction of chlorine trifluoride with paraffin hydrocarbons" at sciencedirect.com/science/article/pii/S0082078406806053 $\endgroup$
    – Ian Bush
    Jun 26, 2018 at 21:26
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    $\begingroup$ pubs.acs.org/doi/abs/10.1021/jo00381a017 also says it reacts with saturated hydrocarbons. Only thing hampering the reaction^ might solid state and maybe low solubility of product, but it definitely reacts. $\endgroup$
    – Mithoron
    Jun 26, 2018 at 21:58
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    $\begingroup$ If it is true (and I doubt that) it is probably because there is a passivating reaction on the surface of the wax creating a layer of perfluorinated hydrocarbon (it is known not to react with PTFE). $\endgroup$
    – matt_black
    Jun 26, 2018 at 22:46
  • $\begingroup$ These are exactly the reasons why I asked. It didn't sound right, but it's so often cited that I want to know if it's true, and why $\endgroup$
    – Andon
    Jun 26, 2018 at 22:49
  • $\begingroup$ I know that a polyethene container can be treated with dilute F2 in nitrogen to give a flourinated surface. The idea is to get the best of both HDPE and PTFE by having a surface coating of PTFE on HDPE. I worry with candle wax that if it is heated then the PTFE like coating will be lost from the surface and the reaction will start again. $\endgroup$ Jun 27, 2018 at 6:14

1 Answer 1


I don't think paraffin would last long, since PTFE doesn't seem to last in the presence of CTF. From IGNITION! (John D. Clark), which you really, really need to read if you are interested in chlorine trifluoride or rocket propellents in general:

The results were excellent, but the difficulties were infuriating. Ignition was beautiful —so smooth that it was like turning on a hose. Performance was high —very close to theoretical. And the reaction was so fast that you could burn it in a surprisingly small chamber. But. If your hardware was dirty, and there was a smear of oil or grease somewhere inside a feed line, said feed line would ignite and cleverly reduce itself to ashes. Gaskets and O-rings generally had to be of metal; no organic material could be restrained from ignition. Teflon would stand up under static conditions, but if the CTF flowed over it with any speed at all, it would erode away like so much sugar in hot water, even if it didn't ignite. So joints had to be welded whenever possible, and the welds had to be good. An enclosure of slag in the weld could react and touch off a fire without even trying. So the welds had to be made, and inspected and polished smooth and reinspected, and then all the plumbing had to be cleaned out and passivated before you dared put the CTF into the system. First there was a water flush, and the lines were blown dry with nitrogen. Then came one with ethylene trichloride to catch any traces of oil or grease, followed by another nitrogen blow-down. Then gaseous CTF was introduced into the system, and left there for some hours to catch anything the flushing might have missed, and then the liquid chlorine trifluoride could be let into the propellant lines.


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