Sciencemadness Discussion Board

PTFE HF distillation apparatus

Gammatron - 17-9-2022 at 15:40

Hi everyone, just wanted to show off my HF generator I just finished. I got a 200ml PTFE reaction vessel on amazon, it is a perfect choice for this application. I used 10x12mm (ID, OD) tubing and drilled a hole 10.8mm into the side of the vessel and heated the tubing to force it into the hole. After heating again the tube expands to its original size and makes a very tight seal. The same thing was done to attach the condenser since adhesives & sealants aren't much of an option for PTFE. The reactor was wrapped tightly in copper wire to distribute the heat evenly and placed in a sand bath. The receiving flask is PP with a tightly sealing lid which is charged with water prior to running so it converts directly to HF acid.

I did my first test run with 50g of CaF2, I only got about 50% yield, the rest was still in the reactor but after 3 hours I finally shut it down. I added ice to the remaining sludge to cool and dilute it, it makes an excellent rust cleaner!

And please save me the horror stories and how you don't know anybody who will work with HF... I know it's nasty stuff but it's not about how dangerous it is, its about how you treat it.

307442335_3240533269597085_4190716246719054981_n.jpg - 388kB 306228538_765755918010356_255394012879265395_n.jpg - 435kB

[Edited on 9-17-2022 by Gammatron]

karolus28 - 17-9-2022 at 16:30

now this is something

Fery - 18-9-2022 at 03:19

Wow thanks for sharing !!!
So you reacted CaF2 with concentrated H2SO4? And produced liquid 100% HF, nice. Did you use something like ethylene glycol cooled to -10 C or even -20 C for the circulation in the condenser?

Gammatron - 18-9-2022 at 06:15

I do have Ethylene glycol in it in the form of antifreeze, this is mainly just so I can use a UV light to detect leaks. It is actually made from a repurposed water fountain so it only gets down to about 6 C. If I had a way to go lower then I would but it is sufficient to condense HF, also the end of the tube is submerged in the flask in the ice bath so that captures whatever makes it through. HF vapors are thick and I didn't see any escape the whole time.

Fery - 18-9-2022 at 09:48

Well done with the ice cooling. I think HF is lighter than N2 as well O2. Molar mass HF = 20 g/mol, molar mass N2 = 28 g/mol, molar mass O2 = 32 g/mol. But that's only theory, the only important thing is that you did well functioning apparatus, nice experiment and condensed HF !!!

Gammatron - 18-9-2022 at 10:51

Thanks for the compliments! I spent a long time trying to come up with a safe and effective method and while this could use improvements, a bubbler in particular, I think it is a good start.

Tsjerk - 18-9-2022 at 12:49

Nice, what are you going to do with it?

Gammatron - 18-9-2022 at 14:20

The main purpose is to make UF4 in my quest to refine uranium from ore but since I have it I'd also like to make some other cool compounds just for show. Two in particular are WF6, the densest gas and possibly some day when my skills are more advanced, SbHF6, the strongest acid.

j_sum1 - 18-9-2022 at 20:50

I would have guessed UF6 to be denser than WF6.

I admire your courage to work with HF. And your levelheadedness and lab skills to do so safely.

HF remains off my to-do list for the forseeable future.

Gammatron - 19-9-2022 at 05:16

UF6 is actually solid at standard conditions although it does sublimate. If I could find a synthesis that's doable in my lab then it may become a future project. I also could still be wrong about WF6 bring the densest gas as Wikipedia states that it's "one of the densest gasses"

Metallophile - 19-9-2022 at 06:56

This is awesome! I just bought a nice Fluorite sample from ebay, but I think I'll just leave it in the jar, and live vicariously through Gammatron's posts.

Herr Haber - 19-9-2022 at 08:41

Quote: Originally posted by Gammatron  
Thanks for the compliments! I spent a long time trying to come up with a safe and effective method and while this could use improvements, a bubbler in particular, I think it is a good start.

It's not something I would do but I really liked the simplicity of your aparatus.
I'm curious of what improvements you can come up with but at the same time I hope you dont need to much HF ;)

Gammatron - 19-9-2022 at 12:07

Stuff like this makes me wonder the level of danger that I would consider too much lol. If HF isn't bad enough, I've also filled a scuba tank to 1000 psi by pouring in liquid nitrogen and screwing the valve on.. ;)

The main improvement this needs is a bubbler at the exhaust to remove any fumes that make it all the way through, which I have plans for. Also a purpose made recieving flask since the one I am using in the picture is intended as my storage bottle. Other than that the apparatus performed perfectly, I need to figure out a way to achieve higher yield without having this thing running all day long. Starting materials are cheap but I am always short on free time to work on my projects.

Dr.Bob - 19-9-2022 at 15:51

If you want to try ClF3, that would be exciting. Even my fluorine chemist friend Ed decided that it was too hard to work with after trying to use it a few times for fluorinations (in monel equipment designed for fluorine work).

Gammatron - 19-9-2022 at 17:16

Well Mr Bob, you have enlightening me to something too dangerous to even consider working with.. but I will keep it in mind!

phlogiston - 20-9-2022 at 12:12

Very impressive, and I'm glad you do this and take the time to show it of here, so we can share in the joy of seeing these unusual experiments from the safety of our computer desks. Thanks!

In another thread, you mentioned you have 0.5 kg of NaF looking for a purpose. Would that not be suitable for the preparation of UF4 (so you don't -have- to prepare HF)? I imagine UF4 would precipitate upon adding a suitable reductor to a solution containing NaF and hexavalent uranium.

[Edited on 20-9-2022 by phlogiston]

Gammatron - 20-9-2022 at 12:34

Actually that is a very good point that never even crossed my mind. Every paper I've read and demonstrations I've seen uses HF so that's just what I thought was necessary. Cody's Lab used CuSO4 as a catalyst and then SO2 for the reduction. I'm not entirely sure the role of the CuSO4 because he's the only case I've seen it used. Anyways, I think I will try the reaction with the NaF, would certainly be a much easier option.

6dthjd1 - 24-9-2022 at 20:59

what did the lab smell like whilst distilling?

Lionel Spanner - 25-9-2022 at 14:16

That's impressive! It's a great bit of engineering, being both simple and highly effective.

It just goes to show that even the most hazardous materials can be handled safely, as long you know what you're dealing with and you have the right tools for the job.

Gammatron - 25-9-2022 at 15:37

Quote: Originally posted by 6dthjd1  
what did the lab smell like whilst distilling?

There was no smell, it was done in a fume hood. Even when I got up close to it to check the rate of distillate I didn't smell anything.


That's impressive! It's a great bit of engineering, being both simple and highly effective.

Thanks! Came up with a lot of ideas on how to do this and while being the most expensive method just cause of the cost of the reaction vessel this was by far the easiest and safest thing I came up with. This is due to do PTFE having complete corrosion resistance and no chance of introducing contamination where steel and lead might have issues.

ErgoloidMesylate - 14-5-2023 at 12:37

I recall doug 's lab doing ketene generation and one could wonder why he would try something so inherently dangerous, but then i found this: