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Author: Subject: Practical guide for converting red P to white P
woelen

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Practical guide for converting red P to white P

I have taken the time to make some white P from red P. Many people might know that heating red P to a high temperature can give white P, but doing this in practice is not that simple. I had read a procedure on the German forum www.versuchschemie.de:

http://www.versuchschemie.de/topic,5774,-Wei%DFer+Phosphor.h...

This has inspired me to do a similar thing, with a slightly different setup.

The following page provides a method for making white P from red P in a relatively safe matter (albeit still quite a dangerous endeavor, know what you are doing!!).

http://woelen.homescience.net/science/chem/exps/RedP2WhiteP/...

In this way, I made approximately 3 grams of fairly pure white P. Sufficient for quite a few funny experiments

[Edited on 30-7-16 by woelen]

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Jor
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very cool
I Shame I cant do this, I cant accept such a large risk of fire

And by the way, when I click on a full list of experiments, this one is not on the list. I can only get to the exp by clicking this link, but not when starting on the homepage.
garage chemist
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Yes, that preparation of white P on versuchschemie.de was from me.
I have done much experimentation with white phosphorus, and a few syntheses with it, like PCl3, which I also documented on VC.

I eventually want to use the "quartz test tube in tube furnace" setup seen in my SO3 preparation in prepublication to prepare larger amounts of white P, so that I can make sizeable amounts of PCl3, a very interesting chemical that allows entering the realm of organophosphorus chemistry.

Instead of using carbon dioxide atmosphere, one can also simply leave the air in the test tube- the P vapor will initially consume any oxygen in the test tube, so that one essentially has a nitrogen atmosphere.

The "impurity in the red phosphorus" you describe is not carbon. There is no such impurity in your red P. The black solid you encountered is actually crystallized violet phosphorus. With continued strong heating, this will eventually completely sublimate, leaving no residue.
However, this requires much stronger heating than the sublimation of the red P. It is easy to accidentally melt the test tube in the process. This is the reason why one needs a quartz apparatus for sublimating larger amounts of red P.
For bending a quartz test tube (which are frequently offered on ebay) you need at least a propane/oxygen blowtorch.

Your website on white P looks extremely good. Keep up the good work, your experiment documentations are always great!

www.versuchschemie.de
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-jeffB
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Very nice demo, as always, woelen. If only I'd bought some red P ten years ago, when it was still available in the US...
Magpie
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Thank you woelen for providing such a practical guide for the making of this interesting and important reagent. And thanks to garage chemist for his original work and providing your inspiration.

I hope that someday I too will have some P. I know that I will have to make it myself due to the stigma associated with buying it in the US, even if a source could be found.
Ephoton
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nice woelen never checked your site out just add some gimp you say ;P now was that the
one thats in my chest or on my pc.

bash-2.05#

crazyboy
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Very nice. Good write-up. Besides having interesting properties what are the synthesis and experiments that can be done with white P that you referenced?

Jor
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You can make PCl3, wich is almost impossible to make with red P, because red P favours the step to PCl5.
woelen

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 Quote: Originally posted by Jor And by the way, when I click on a full list of experiments, this one is not on the list. I can only get to the exp by clicking this link, but not when starting on the homepage.
I'm not yet sure whether this page should be indexed or not. The experiment is very dangerous and it might bring less experienced persons to bad ideas, such as doing this experiment inside (this also happened on www.versuchschemie.de). Before it is indexed, at least a thorough reassesment of all risks is done by me and the page might change.

 Quote: Originally posted by garage chemist The "impurity in the red phosphorus" you describe is not carbon. There is no such impurity in your red P. The black solid you encountered is actually crystallized violet phosphorus. With continued strong heating, this will eventually completely sublimate, leaving no residue.
This sounds interesting. I have some of this black material drying in a petri dish now and will try some other experiment with this. Amazingly, it does not dissolve in an over-saturated solution of chlorine in water. Red P does (but always tiny black specks remain) and is oxidized. Maybe I keep a little of this material for my element collection. Unfortunately, I only have a few tens of mg of this material. The red P I have is labeled as 98% red P. The remaining 2% then is this black P?
I will change the page and remove the remark about the carbon. Thanks for your comments and info.

 Quote: Originally posted by crazyboy Besides having interesting properties what are the synthesis and experiments that can be done with white P that you referenced?
Some interesting experiments are:
1) Dissolve in CS2 and pour the solution over a piece of tissue paper. After a short delay the paper starts smoking and eventually catches fire.
2) Put a little piece under hot water and bubble oxygen gas or chlorine gas along the piece of white P. Spectacular flashes occur under water.
White P is interesting in many synths, both in inorganic and in organic chemistry. E.g. it can be used to make phosphine at a decent rate and at decent purity (by dissolving it in hot solutions of NaOH). It can be used in several organic syntheses (and no, I am not referring to the synthesis of meth ).

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YT2095
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IIRC, you can use some of this Black P (if thats what it is) as a Seed to make more, youll need a little Mercury as well, I think it acts as some sort of catalyst.
the good part is that if any of that residue IS Black Phos, you already have the hard to obtain part and can make More of it for your element collection.

here: "Black phosphorus is also produced by heating white phosphorus in the presence of a mercury catalyst and a seed crystal of black phosphorus. Black phosphorus is the least reactive, does not ignite easily and has the least commercial value."

taken from: http://nobel.scas.bcit.ca/resource/ptable/p.htm

[Edited on 2-3-2008 by YT2095]

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Waffles
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Quick thing- for a much less dangerous but still entertaining version of this, and where you still get white P, one can simply light a small steep pile of red phosphorus, sitting on graphite or something equally heat and chemical resistant, OUTSIDE, let it burn for a minute, then extinguish the fire by smothering it by hitting it with something flat and simultaneously spreading it out. You can then see a nice blue-white sparkly glow when you turn out the lights...more fun can be had if you spread the remainder very very thin on a large surface area, and rub your hand in it. Glowing blue hand! Touch the ground or something else with your hand...glowing blue handprint! Have someone else touch your handprint...another glowing blue hand! The stuff spreads around like an STD and it totally harmless in those amounts. Hooray!

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woelen

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Isn't it bad for your health if you cover a large area of your skin with white P? What you suggest here seems somewhat unhealthy to me. I like the idea, except the hand-rubbing part.

@Jor: The experiment page description is modified a little bit, more emphasis is put on the risks. It now is available from the index pages.

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Jor
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Why is white phosphorus so toxic? Is this just because it is so reactive? What does it 'do' in the body? If it so reactive you wouldnt be able to absorb it in the bloodstream, because it is already going up in flames.
not_important
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I remember reading that the smoke from burning phosphorous had been found to contain the P4 molecule, and that this allotrope was much stabler to oxygen than woyld be expected.

Phossy jaw was the occupational hazard of phosphorous. In part it may be caused by the phosphorous oxides, both acting as acids, as well as throwing the phosphate-calcium balance out of whack and otherwise interfering with phosphate systems.

Back when it was easy to get yellow phosphorous, its use as a poison typically added it to strongly flavoured food or condiments, to alcoholic beverages, or to medicines with high alcohol or chloroform content. Rat poison with several percent of phosphorous mixed with bran and molasses was a common source of yellow phosphorous; it was used as bought with no isolation being done other than possibly decanting or filtering to separate the bran after the phosphorous had dissolved in the liquid.

It causes damage to the liver and kidneys, both in the case of acute and chronic poisoning. It appears to damage cell membranes, possibly through free radical mechanisms. It's use as a poison can be detected days later, sometimes internal organs glow from their free phosphorous content when viewed in the dark, certainly in the dark. Distilling (steam) th free phosphorous from body tissues, and then oxidising it with HNO3 and converting it to phosphate for measurement, is a forensic technique.
ScienceGeek
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 Quote: Originally posted by woelen Some interesting experiments are: 1) Dissolve in CS2 and pour the solution over a piece of tissue paper. After a short delay the paper starts smoking and eventually catches fire. 2) Put a little piece under hot water and bubble oxygen gas or chlorine gas along the piece of white P. Spectacular flashes occur under water.

I made a video of White Phosphorous with point 1 and 2 included (for those of you who are interested)

[Edited on 6-3-2008 by ScienceGeek]

12AX7
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Nice!

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ScienceGeek
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Appreciate it =)

Very impressive not_important! You walk around remembering all this?
One could mention a more "trivial" fact as well: If one ingests White P4, you get what is called "Smoking Stool Syndrome".

-jeffB
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 Quote: Originally posted by ScienceGeek I made a video of White Phosphorous with point 1 and 2 included (for those of you who are interested)

Very nice! Since you clearly have access to both P and CS2 (lucky bum), would you be interested in trying another experiment I vaguely remember from one of the "Chemical Magic" books of my youth? It involved dissolving P in CS2, and adding a bit of mineral or vegetable oil (I forget which) to the mix. You'd then paint with it on paper. The CS2 evaporated quickly, but the oil protected the P, so instead of deflagration, you'd get a persistent glow, waxing brighter if you blew on the paper.

It always sounded like a really cool demo, but I missed my chance to order the necessary reagents. Probably just as well, actually -- I was always a little clumsy, and white phosphorus would have been VERY unforgiving.
PHILOU Zrealone
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Your white phosphorous must be very pure owing to its translucent waxy look.
In a school where I was supposed as stagiair to learn how to teach, I remember a teacher showing a large block of whithe P under water...it seemed white and brittle.
In fact when she tried to cut it on the table with a knife, it broke up in many pieces that did travel the chemical bench, the tiny pieces ranking from 1cm to 0.1 cm diameter over a few meter on the table started sporadically to burst in flame...that was cool except the white fumes of P2O5...even with open windows, pupils where taken by strong coughing.
********************************************
The black residue of black P is said to be conductor...while the white P isn't... a bit like graphite is while diamond is not but in a reversed fashion

[Edited on 6-3-2008 by PHILOU Zrealone]

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ScienceGeek
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That sounds really interesting, and plausible! I'll get right on it (when I have time), and post a video

Jor
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Very nice videos sciencegeek.

Thats a lot of silver nitrate !!!
woelen

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Sciencegeek, that video is very good. I also was considering making a webpage with experiments with white P. I already did the CS2/P experiment with a piece of paper, hanging between a pair of tweezers.

I also did the experiment with chlorine instead of oxygen. This gives the added nice effect that puffs of smoke are produced each time a bubble of chlorine reaches the surface.

One remark: The element is called 'phosphorus', not 'phosphorous'. The term 'phosphorous' is reserved for compounds, which have the element in the +3 oxidation state, e.g. phosphorous acid is H3PO3, while phosphoric acid is H3PO4.

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ScienceGeek
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You are completely right, woelen! Embarrassing mistake! (Not an easy element to spell though )

And would you do me a favor? Don't tell anyone else about it!

Picric-A
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nice write up on a very difficult (not to mention dangerous ) procedure!