Hey, guys! If you’ve ever been into chemical methods of producing fluorine,
you’d probably seen some reactions of decomposition of higher metal fluorides that result in the formation of free fluorine.
In this video I’m going to show you a few reactions with these reagents,
and you’re also going to find out if this is really the way to get elemental fluorine in the laboratory
We’ll be starting with cobalt trifluoride.
This reagent is sensitive to air, and for this reason it is delivered in thick air-tight packages filled with inert gas
Cobalt trifluoride is a highly reactive light brown powder
And, as a comparison, this is pink cobalt difluoride
A bright-brown cobalt trifluoride powder turns dark-brown in air quite rapidly
and it becomes black the next day
Cobalt trifluoride reacts actively with water to produce hydrogen fluoride and oxygen,
and we can detect the latter by dropping a glowing splint in there
If we heat cobalt trifluoride in a quartz test tube, it will dissolve into cobalt difluoride and fluorine.
At this temperature fluorine will immediately react with quartz glass, and we won’t be able to see its pale yellow color.
However, I’m going to show you some reactions that will help to conclude its formation.
A hydrochloric acid reaction with cobalt trifluoride results in the evolution of chlorine and hydrogen fluoride,
and the formation of cobalt dichloride
Chlorine evolution can be detected by potassium iodide darkening due to the formation of iodine
Reacting with ammonia solution, cobalt trifluoride forms a precipitate hexamminecobalt(III)floride
If we mix silicon powder with cobalt trifluoride and set the mixture on fire, silicon will reduce cobalt to metal
and dissipate in the form of silicon tetrafluoride, meaning that the only product of this reaction will be pure cobalt
Take a look at this reaction in slow-mo.
These white-hot particles that are forming during the reaction are the essence of elemental cobalt
If we set a magnet to the cobalt that we just got, it will magnetize right away
Cobalt trifluoride forms cobalt difluoride and sulfur tetrafluoride in the reaction with sulfur
Being heated, the mixture of cobalt trifluoride and magnesium powder explodes
Cobalt trifluoride reacts less actively with titanium powder.
This reaction is especially beautiful to look at in slow mo
If we mix manganese difluoride with cobalt trifluoride and heat the mixture in an inert gas atmosphere,
we will get light purple manganese trifluoride
Manganese trifluoride, as well as cobalt trifluoride, is sensitive to air moisture,
and it’s also sensitive to light, hence it’s delivered in air- and light-proof package
It’s worth mentioning, that manganese trifluoride is not a higher manganese fluoride, as there is also manganese tetrafluoride.
If we leave light purple manganese trifluoride in air, it will be gradually turning brown
Manganese trifluoride reacts with water and manganese dioxide precipitate forms
Being heated, manganese trifluoride, as well as cobalt trifluoride, dissolves, forming elemental fluorine,
that we are going to detect now!
I took a quartz tube and created an inert gas atmosphere in it, using argon
I put two small piles of magnesium in this tube, and poured out some manganese trifluoride between them
Since manganese trifluoride forms free fluorine when it decomposes,
magnesium must react with it, as magnesium ignites in fluorine atmosphere
Now let’s watch at this process in slow-mo
And this is the reaction of manganese trifluoride with magnesium
Here I repeat the previous experiment, only this time I used thulium powder instead of magnesium
Thulium ignited because of the fluorine that was formed during the reaction
I also tried to decompose manganese trifluoride in a hydrogen atmosphere
since the reaction of fluorine with hydrogen proceeds explosively
And here’s one such explosion in slow-mo
Well, and now for the least active reagent of this video — cerium tetrafluoride
Unlike cerium trifluoride white powder, cerium tetrafluoride is a pale-yellow powder
Anhydrous CeF4 is an inert and extensively F-bridged polymer, doesn't change in the air,
that's why it's delivered in a standard plastic can without any additional protective elements.
It does not dissolve in water
When it was decomposing, I failed to ignite magnesium the way I did in the experiment with manganese trifluoride.
Maybe it has something to do with a very high decomposition point of cerium tetrafluoride,
as compared to this of some other similar cobalt and manganese compounds
On the other hand, the reaction of cerium tetrafluoride with magnesium looks pretty appealing in slow-mo.
Thanks for watching guys, and many thanks to my patrons
who keep supporting and helping me go on and make these videos happen.
I hope you enjoyed this video and now have a good idea of how higher metal fluorides decompose
See ya in the next video