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Old 02-06-2019, 12:19 PM
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Science Interesting chemicals

A thread for posting occasional chemistry factoids.

Chlorine trifluoride ClF3 Is generally too dangerous to consider using. It's a green liquid at room temperature, and a colorless gas when warmed (though warming it isn't really a good idea). It's an incredibly strong oxidizing agent - much more so than boring old oxygen. It self-ignites and burns most materials, most of them explosively. It also corrodes things generally considered non-corrodible: iridium, platinum, and gold.

It burns most materials that oxygen can't: sand, asbestos, glass, tungsten, water, most fire retardants, concrete, the ashes of materials already burnt in oxygen, living flesh, ...

It can be stored in vessels made from steel, copper, nickel or quartz - but the vessels must be scrupulously cleaned and passivated. The only reason the metal vessels can contain the chemical is because it reacts with the metals forming a thin layer of insoluble metal fluoride - but any contamination allows the chlorine trifluoride to burn through the passivation layer faster than it can re-form, and so the container is quickly turned into a non-container.

The reaction with water is particularly violent and the products of the reaction include hydrogen chloride and hydrogen fluoride - in themselves fairly potent and alarming chemicals - and these are given off in the form of a steam or vapor due to the highly exothermic reaction.

In a nasty chemical accident at Shreveport, Louisiana, nine hundred kilograms of ClF3 were being moved across a factory in a sealed metal cylinder, kept very cold to reduce the risk of reaction. Unfortunately the cold made the metal brittle, and it cracked spilling the ClF3 everywhere. It burned through the one-foot thick concrete floor, and a further three feet of gravel beneath. The remains of the man moving the cylinder were found about a hundred-and-fifty yards away, blasted there by the force of the explosion - official cause of death was a heart attack.

Uses: It was tried in the 1940s as a rocket propellant, but kept setting fire to the rockets themselves, so was abandoned. The nazis tried to use it as a weapon, but it killed too many of their own chemists, and cost too much to produce. It is used (carefully, in small amounts) by the semiconductor industry to clean chemical vapor deposition chambers - it reacts with any slight contaminants on the walls of the chambers, burning them away: its high reactiveness is an advantage here as other lesser chemicals need to be activated by high temperature plasma to do the same work. It's used in the nuclear fuel processing industry during the production of uranium hexafluoride.
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Old 02-06-2019, 12:43 PM
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Default Re: Interesting chemicals

HF itself is an interesting chemical, hydrofluoric acid will eat through nearly anything, but it isn't nearly as volatile as ClF3. We used HF to do mineral assay for my boss' brother, who was a gold prospector in South Dakota. We dissolved ore samples with HF in a platinum dish ($900/ounce back in the late '70s), then diluted with water and ran them through the spectrometer to see what was in them. Yes, HF will even dissolve gold. I have no idea why platinum was immune to its effect. We stored it in a plastic bottle.
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Old 02-06-2019, 04:24 PM
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Default Re: Interesting chemicals

Sulphur hexafluoride SF6, on the other hand, is completely safe (well ... as safe as water ... don't completely fill your lungs with it).


The opposite of breathing in helium.
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Old 02-06-2019, 04:35 PM
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Default Re: Interesting chemicals

And let us not forget dioxygen difluoride (FOOF):

Quote:
Originally Posted by JoeP View Post
Oh yes, so I found this image:



(Holy cook.)

Which led me to this: Pressure Cooker at xkcd what-if
Quote:
What's the worst thing that can happen if you misuse a pressure cooker in an ordinary kitchen?
He goes way beyond "ordinary kitchen" though. Unless yours has fluorine available.

Quote:
Fill the cooker with oxygen up to 5 PSI, then pump in fluorine until it starts escaping through the safety valve. Put the vessel over an open flame until it reaches 700C (That’s C, not F. Yes, this will probably set off the smoke alarm.) Now, pump the hot gas over a liquid-oxygen-cooled stainless steel surface.

The procedure here is a little tricky, but if you do things right, the gas will condense into dioxygen difluoride (O2F2).
Which led me to this: Things I Won’t Work With: Dioxygen Difluoride | In the Pipeline

Also amusingly known as FOOF, from its molecular arrangement and its properties.

This handy substance will cause ice to spontaneously combust. (You can't get it warm enough to test it on water.)

Quote:
“Being a high energy oxidizer, dioxygen difluoride reacted vigorously with organic compounds, even at temperatures close to its melting point. It reacted instantaneously with solid ethyl alcohol, producing a blue flame and an explosion. When a drop of liquid 02F2 was added to liquid methane, cooled at 90K., a white flame was produced instantaneously, which turned green upon further burning. When 0.2 (mL) of liquid 02F2 was added to 0.5 (mL) of liquid CH4 at 90K., a violent explosion occurred.”
Quote:
And he’s just getting warmed up, if that’s the right phrase to use for something that detonates things at -180C (that’s -300 Fahrenheit, if you only have a kitchen thermometer). The great majority of Streng’s reactions have surely never been run again. The paper goes on to react FOOF with everything else you wouldn’t react it with: ammonia (“vigorous”, this at 100K), water ice (explosion, natch), chlorine (“violent explosion”, so he added it more slowly the second time), red phosphorus (not good), bromine fluoride, chlorine trifluoride (say what?), perchloryl fluoride (!), tetrafluorohydrazine (how on Earth. . .), and on, and on. If the paper weren’t laid out in complete grammatical sentences and published in JACS, you’d swear it was the work of a violent lunatic. I ran out of vulgar expletives after the second page. A. G. Streng, folks, absolutely takes the corrosive exploding cake, and I have to tip my asbestos-lined titanium hat to him.
We should get some FOOF to play with at :ff:. :foof:
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Old 02-06-2019, 07:06 PM
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Default Re: Interesting chemicals

Quote:
Originally Posted by Dingfod View Post
Yes, HF will even dissolve gold.

:nope:
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Old 02-06-2019, 07:42 PM
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Default Re: Interesting chemicals

Aqua regia, which is a mixture of hydrochloric acid and nitric acid, will "dissolve" gold. The Nitric acid, HNO3, gives the gold an oxidising agent kick and then the chlorine atoms combine with the gold. I guess HF might do the same job as HCl providing you added some nitric acid to it? But I don't know and wouldn't like to try! HF is nasty stuff and other strong acids are like dishwasher liquid in comparison.
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Old 02-06-2019, 08:18 PM
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Default Re: Interesting chemicals

Fluoride is actually the one halide that will not work.
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Old 04-23-2019, 07:18 PM
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Default Re: Interesting chemicals

Approximate chemical formula for a human. The formula gets the ratios about right, but you have to multiply all the numbers by about seven hundred trillion to get the actual number of atoms in a typical person.

H375,000,000 O132,000,000 C85,700,000 N6,430,000 Ca1,500,000 P1,020,000 S206,000 Na183,000 K177,000 Cl127,000 Mg40,000 Si38,600 Fe2,680 Zn2,110 Cu76,114 Mn13 F13 Cr7 Se4 Mo3 Co1

source: the book ElEMeNTaL by Tim James (that's where I read about Chlorine trifluoride too)
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