Smelly red phosphorus - Best way to clean it?

Quote: Originally posted by Rainwater

http://library.sciencemadness.org/library/books/brauer_ocr.p... Page 519 of this cool library book. Be sure to check it back in before its due. They got steep late fees there.

I started working on this yesterday, put all of my RP into a 1L flask, and filled the flask half way with 7% NaOH solution. It wasn't a violent reaction when I added the NaOH solution, but the smell was immediately evident. It smelled pretty terrible.

I put a reflux condenser on and put a hose adapter on the top, which I passed through some activated carbon to try to capture any of the smell (since I'm not entirely sure what it is). While the activated carbon did trap most of the smell I hadn't even refluxed it for 4 hours and there was a very weird looking yellow solid that started to collect in the tube. It smelled pretty terrible (same smell as what I smelled earlier).


Here are some other photos: https://imgur.com/a/XM0vy3P

Anyone have any idea what this could be? The RP i'm purifying isn't recycled at all, so its not from any previous reactions or anything. I wasn't expecting the purification process to left off anything that would settle in the tube like that. Im not sure how much of this will get released considering it's supposed to be refluxed for 24 hours.

I gave this another shot, but on a much smaller scale and with better preparation/research beforehand.

I took 7g of red phosphorus that was previously used to make iodomethane. After the iodomethane synth, it was washed very well then dried in a vacuum desiccator over some P2O5, but it still smelled a bit (which is kinda how I was gauging its purity, along with it's appearance):


I poured the 7g of rP into a 250mL erlenmeyer flask along with 100mL of 7% NaOH solution (using distilled water) and a stir bar, and setup for a 24 hour reflux:


Because of the release of phosphine, I also setup a gas washing bottle with some boric acid, this seemed to work much better than the bottle packed with activated carbon from my first attempt, lol. But the output was still leading to outside, along with the window being open just in case.

I couldn't do 24 hours straight, so I did 12 hours on two separate days.

After about ~10 hours or so, the color started to change to a darker kinda purple color, which I wasn't at all expecting:


After the first 12 hours, I turned off stirring/heating and let it settle. It was then apparent that the discoloration wasn't really due to the red phosphorus changing color, but the water which had turned slightly yellow/green (but still somewhat transparent):


But this may not be entirely correct, since you can see some of the phosphorus up on the sides still has the purple color:


The heating/stirring was resumed the next day, and the mixture got even more purple in color:


After another 12 hours, I turned off the hotplate and let the phosphorus settle to the bottom of the flask. The solution was decanted off, then the rP was washed several times with distilled water until it was no longer basic. Now with the yellow water removed, it's evident that the rP has darkened over the 24 hours:


100mL of distilled water was added to the erlenmeyer flask, and it was setup for another 24 hours of boiling. The only real difference I noticed now that I didn't see when I boiled it in 7% NaOH solution was that the red phosphorus seemed to whick up the sides of the flask, which didn't at all happen before. The heat/stirring was at the exact same settings as well so I doubt it splashed up on the sides any more than it could have in the NaOH:


After 12 hours of boiling in distilled water, the heat/stirring was turned off. To my surprise, once the rP had settled down to the bottom I could see that the water was a very nasty dark brown color:


The next day I decided that before I boiled it for another 12 hours, I would decant the nasty solution from the red phosphorus. It didn't say to do this in the literature, but I can't see what harm it would do.
After 100mL of fresh distilled water was added, the solution was setup for another 12 hours of boiling:


Once it had cooled down, I poured off the brown solution and washed the phosphorus several times with cold distilled water. Then decanted all the water and put the wet rP into a vacuum desiccator over some P2O5. When the rP had dried out, I could see that it had darkened considerably:



Also, not only had it darkened a lot, but it doesn't smell any better.

The "purified" red phosphorus now weighs in at 3.75g:


While I may have lost almost half of the red phosphorus, I wouldn't blame this on the procedure. Instead of vacuum filtering I decided to decant everything through the whole process, and sometimes the phosphorus would float on the water due to the surface tension, and I would just pour it off. So that's my fault (but I was going for purity here, not yield).


Here's one last picture of the red phosphorus next to the vial of which I pulled the P from for this purification procedure. You can tell the color has changed a great deal:



In summary - I don't think this procedure is very effective. I guess it could be user error, but it's such a basic procedure that I don't know what I could have possibly messed up. But I'm open to any constructive criticism :-)

Turn it into black phosphorus by autoclaving in ethylenediamine:
https://dlisv03.media.osaka-cu.ac.jp/contents/osakacu/journa...
https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10....

Yes, you read that right.

Quote: Originally posted by Rainwater

Sorry for the bad referral. I've never dealt with phosphorus but have performed about 30 procedures from that book with great results.

Quote: Originally posted by clearly_not_atara

Turn it into black phosphorus by autoclaving in ethylenediamine: https://dlisv03.media.osaka-cu.ac.jp/contents/osakacu/journa... https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10.... Yes, you read that right.

Quote: Originally posted by woelen

If I look at your original red P, then it looks quite pure to me. Red P always has a certain typical smell. Adding it to NaOH-solutions leads to reactions, in which you lose quite some phosphoprus and in which smelly compounds can be formed (PH3, and from that some ill-defined oxygen/hydrogen compounds of phosphorus can be formed. Red P is much less reactive than white P, but it is far from inert and reacts with quite some compouns, especially when oxygen from the air is allowed in as well. So, I would not hassle with the red P at all, unless it looks sticky and wet. In the latter case, I just would treat it with 0.5% NaOH for a few tens of minutes and then with distilled water.

Quote: Originally posted by PirateDocBrown

When you say it "smells absolutely horrendous", exactly how does it smell? Is it a phosphine smell? Some other smell?