Sciencemadness Discussion Board

White phosphorus recovery

ChemistryForever - 24-2-2019 at 11:16

I had about 10 grams of white P. At that moment, I tried to store it under mineral oil, just like alkali metals, and I didn't realise that it can dissolve in it and that I should store it under water.
At first it seemed like it is ok under oil, but after opening the bottle about half year later, I realised that it had dissolved.
Is there any way I can recover it ?

SWIM - 24-2-2019 at 13:54



Might be able to get it out with a very short path distillation.

Falling film distillation if you've got the glass, or if not maybe just put it in a vacuum sublimator and perhaps the WP will collect on the cold finger.

I've never done this, but this is what I would try.

Assured Fish - 24-2-2019 at 15:34

Id be sceptical of you being able to distill out the phosphorous at 1 atmosphere. The oil will begin to smoke hevily and possibly decompose at those temps, leading to energy being eaten up.
If you try distilling or subliminating it please use an inert atmosphere.

There is also another option, you could bubble chlorine through the oil to prepare phosphorous trichloride and then distill that out.
The issue with this is there may be water in your oil which will destroy some of your PCl3 as it forms but unless your added water i suspect water contamination will be negligable.
Mineral oil shouldnt react as its mostly just long chain hydrocarbons.
If you try this then start on a small scale first.

j_sum1 - 24-2-2019 at 15:45

Pure speculation here. You might try a liquid-liquid extraction using CS2. Check first to see how miscible your oil and CS2 are.
Then again, carbon disulfide is probably more valuable than your WP. And you still have the non-trivial task of separating the CS2 from your Phosphorus without blowing anything up.

Sulaiman - 24-2-2019 at 16:34

I can't help with the recovery but unless you get a better suggestion - dispose of it.
whiteP and oil just sounds like an accident waiting to happen.

fusso - 24-2-2019 at 16:46

Quote: Originally posted by Sulaiman  
I can't help with the recovery but unless you get a better suggestion - dispose of it.
whiteP and oil just sounds like an accident waiting to happen.
What about burning before disposing? Oil/white P mixture burning may look cool:P

Sulaiman - 24-2-2019 at 16:54

Quote: Originally posted by fusso  
Quote: Originally posted by Sulaiman  
I can't help with the recovery but unless you get a better suggestion - dispose of it.
whiteP and oil just sounds like an accident waiting to happen.
What about burning before disposing? Oil/white P mixture burning may look cool:P

In this case I suspect that 'disposing' is 'burning'
- can't just put it with the trash/rubbish.

SWIM - 24-2-2019 at 18:16

Quote: Originally posted by Assured Fish  
Id be sceptical of you being able to distill out the phosphorous at 1 atmosphere. The oil will begin to smoke hevily and possibly decompose at those temps, leading to energy being eaten up.
If you try distilling or subliminating it please use an inert atmosphere.

.


What's wrong with using vacuum.
Like, you know, in a vacuum sublimator.

diddi - 24-2-2019 at 20:31

i feel solvent extraction is the best suggestion so far imo

happyfooddance - 24-2-2019 at 23:26

Quote: Originally posted by Assured Fish  
If you try this then start on a small scale first.


This is the best advice so far, in my opinion.

I am also just hypothesizing (I wish I had your problem but I have no elemental P), but what do you think would happen if you shook your mix with ice water? (de-gassed of course)

j_sum1 - 25-2-2019 at 00:18

That is a clever idea hfd.
It depens a lot on the solubility of WP in the oil and is unlikely to return a large yield. But it certainly would be a simple and safe option if it worked.

Herr Haber - 25-2-2019 at 05:17

What would you do with the WP enriched CS2 ?
Crash in water to recover phosphorus ?

woelen - 25-2-2019 at 06:02

I have very little hope for recovering the white P. The oil probably will be very high boiling and somewhat viscous. Even with vacuum you won't reach anything useful with that. Heating the mix will lead to decomposition of the oil and you need quite high temperatures to boil off white P.
You might even make PH3 when you heat the oil. I once made H2S from mineral oil and elemental S. I can imagine the more reactive P reacts with the oil, making PH3.
The expectations for solvent extraction also are bleak. The compounds, which dissolve white P to a reasonable extent also will be excellent solvents for mineral oil. E.g. CS2 is a perfect agent for dissolving long chain alkanes. I expect them to be completely miscible.
The only thing which may recover the P (but not in elemental form) is indeed adding chlorine (or bromine) and distilling off the PCl3. You could add more Cl2 or Br2 to make solid PCl5 or PBr5. The latter will crash out of solution from your oil. You then could rinse with low boiling ligroin to get rid of adhering oil and then evaporate. You'll have to exclude water meticulously. Also keep in mind that PCl5 and PBr5 are amazingly corrosive and up to now I did not find any bottle which keeps the stuff without issues for more than a year. I finally ended up ampouling my PCl5 in glass, even the red GL45 caps do not withstand this stuff for long.

You have to be equipped with good labware if you want to handle PCl3, PBr3, PCl5 or PBr5. These compounds are among the worst when it comes to storing them and handling them. Even nasties like bromine, conc. H2SO4 and conc. HNO3 are easy, compared to the phosphorus halides.

Probably just burning it up is the best thing you can do. Pour it over a sheet of paper tissue and light this tissue. Take a good distance from your house and assure no smoke can go to neighbors. I expect really dirty and nasty smoke, but the fire may be fun to watch.



[Edited on 25-2-19 by woelen]

Sulaiman - 25-2-2019 at 07:14

... in small batches - unless you don't mind a very large cloud.

The oil will make black smoke
but 10g of whiteP will produce a rather large cloud of white choking smoke.

chornedsnorkack - 25-2-2019 at 21:36

Quote: Originally posted by woelen  
I have very little hope for recovering the white P. The oil probably will be very high boiling and somewhat viscous. Even with vacuum you won't reach anything useful with that. Heating the mix will lead to decomposition of the oil and you need quite high temperatures to boil off white P.
You might even make PH3 when you heat the oil. I once made H2S from mineral oil and elemental S. I can imagine the more reactive P reacts with the oil, making PH3.

Can P4 solutions undergo polymerization to precipitate red P? Under which conditions? Can that be catalyzed?
Quote: Originally posted by woelen  

The only thing which may recover the P (but not in elemental form) is indeed adding chlorine (or bromine) and distilling off the PCl3. You could add more Cl2 or Br2 to make solid PCl5 or PBr5. The latter will crash out of solution from your oil. You then could rinse with low boiling ligroin to get rid of adhering oil and then evaporate. You'll have to exclude water meticulously.

If you don´t exclude water, your phosphorus halides would hydrolyze... to phosphoric or phosphorous acids, which would be polar and separate from oil.

DavidJR - 26-2-2019 at 04:38

Quote: Originally posted by chornedsnorkack  

Can P4 solutions undergo polymerization to precipitate red P? Under which conditions? Can that be catalyzed?

I imagine this might be a feasible approach. You could use a suitable UV lamp.