Sciencemadness Discussion Board

Ca+YF3 bad idea?

Conure - 26-5-2024 at 11:35

People say fluorides are dangerous to play with. YF3 is described as an irritant while CaF is described as non-toxic. What do you people say?

bnull - 26-5-2024 at 12:37

I'd say "Don't do that!"

Edit: OK, I think you deserve an explanation: fluorine is a bitch.

You see, chlorine is not much fun. You breathe it, you get a sore throat, perhaps a runny nose, but you'll be fine by the end of the week. I'm talking about micro scale here, not a "Ypres reenactment".

Fluorine is hell. It removes calcium from your blood and bones. Hydrofluoric acid, if you get splashed by it, you better have some calcium gluconate ready and pray to whatever Supreme Being you believe inNote; otherwise, you'll wriggle like an earthworm on hot asphalt for the rest of your short life. Say, a couple of minutes.

Please read carefully this thread: How hazardous is fluorine chemistry?

Note: Or invent your own on the spot if you believe in none.

[Edited on 26-5-2024 by bnull]

Edit 2: I'm being overcautious again.

You are trying to make metallic yttrium from YF3, right? If so, check out the old stuff in the Library. I would bet there is a safe procedure using Ca as reducing agent in one of those books.

@BromicAcid: Do you know if CaF2 forms a complex with YF3, or maybe even one of those odd oxide-halogenide combinations?

[Edited on 26-5-2024 by bnull]

BromicAcid - 26-5-2024 at 13:12

Calcium fluoride is non-toxic because it's pretty much insoluble. There's no way for the naked fluoride ion to enter your body since it's tied up. It's actually the calcium fluoride crashing out of the calcium channels in your heart that give you your heart attack.

Yttrium fluoride is also described as being insoluble. Probably why it's just listed as an irritant rather than just a poison. It's probably pretty low on the toxicity spectrum especially compared to highly soluble fluorides like sodium/potassium fluoride which are classified as poisons.

These two fluoride are about as tame as they come, though I still would not ingest them intentionally (or at least not in large amounts since I use a stannic fluoride toothpaste). These two fluorides are made dangerous though by reaction with strong acids which could liberate HF which is another creature all together.

Reacting YF3 with Ca though to give Y metal doesn't seem like much of a toxicity hazard (keep upwind of the fumes in case the fluorides start to volatize) but does worry me from an energetics aspect, sometimes these metal reductions can get a bit out of hand, where your calcium is going to melt and start to really let the reaction take off.

[Edited on 5/26/2024 by BromicAcid]

chornedsnorkack - 27-7-2024 at 00:31

Quote: Originally posted by BromicAcid  
Calcium fluoride is non-toxic because it's pretty much insoluble. There's no way for the naked fluoride ion to enter your body since it's tied up. It's actually the calcium fluoride crashing out of the calcium channels in your heart that give you your heart attack.

Yttrium fluoride is also described as being insoluble. Probably why it's just listed as an irritant rather than just a poison. It's probably pretty low on the toxicity spectrum especially compared to highly soluble fluorides like sodium/potassium fluoride which are classified as poisons.

These two fluoride are about as tame as they come, though I still would not ingest them intentionally (or at least not in large amounts since I use a stannic fluoride toothpaste). These two fluorides are made dangerous though by reaction with strong acids which could liberate HF which is another creature all together.

Precisely. Is human stomach HCl concentrated enough to leach dangerous amounts of HF out of CaF2?
Quote: Originally posted by BromicAcid  

Reacting YF3 with Ca though to give Y metal doesn't seem like much of a toxicity hazard (keep upwind of the fumes in case the fluorides start to volatize)

They would not. CaF2 boils about 2530 degrees, YF3 2230 degrees, Y 2930 degrees. The first component of mixture to boil off in case of overheating would be Ca, at 1480 degrees.
Ca compounds are not toxic when neutralized. But Ca vapour reacting with air would form dusts of CaO - which is the well known simple corrosive quicklime. Quicklime dusts are much worse than fluoride dusts.
Quote: Originally posted by BromicAcid  
but does worry me from an energetics aspect, sometimes these metal reductions can get a bit out of hand, where your calcium is going to melt and start to really let the reaction take off.

Melting at 840 degrees while alone.
For formation enthalpies at 25 degrees I get 1293 kJ/mol for CaF2 and 1718 for YF3. Which means that for 3CaF2 and 2YF3, it is 3879 and 3436 respectively - 443 left over. Will it overheat?
https://himikatus.ru/art/phase-diagr1/Ca-Y.php
Effectively immiscible with limited solubility even in melt.