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Author: Subject: Experiments with the luminosity of white P
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[*] posted on 8-1-2005 at 15:12
Experiments with the luminosity of white P


I recently made 12g of white phosphorus from red P by sublimating it in a test tube.

The lowest 4 cm of the test tube were "bent" downwards in an angle of about 45° by softening with a propane torch and then bending it.
3g of red phosphorus were filled into the bottom of the modified test tube, it was closed with a one-hole cork stopper with a short length of glass pipe, the glass pipe was stuffed with glass wool.

The arrangement was held horizontally by a clamp on a stative, and the red P was strongly heated.
At first it caught fire, but this went out after a few seconds because the oxygen in the tube was consumed, so I had a nitrogen atmosphere in there.
In the straight portion, yellow translucent drops formed and ran down the tube and collected in a yellow puddle in the straight portion.
After all the red P was consumed, the tube was left to cool.
After it was at room temp, the cork stopper was removed and the long slab of white P was remover with a pincet.
This procedure was repeated several times.
The collected P was melted under a solution of K2Cr2O7 in dilute H2SO4 and stirred, it was divided into small droplets and then left to stand, it formed a single large drop which solidified.
It looks like solid honey or candle wax, yellow and a bit orange.
It smokes a bit when taken out of the water and glows in the dark.
(but not in my garage because it is too cold there! It only begins to glow at about 15°C)

The test tube was decontaminated by boiling 70% nitric acid in it.
The pincet was heated in a flame until it glowed red.
The water under which the phosphorus was stored was mixed with copper sulphate soln, to deactivate the P particles by formation of copper phosphide.

The bichromate mixture, which contained a lot of finely divided white P, was first heated with Ethanol until it turned green, to reduce the hexavalent chromium.
There was, as expected, a strong smell of Acetaldehyde.
The green soln was then mixed with copper sulphate to deactivate the P particles.
I'm going to precipitate the chromium with Na2CO3 as the carbonate.

Now I have the yellow pieces of P.

Look at this article, it is interesting:
http://41.1911encyclopedia.org/P/PH/PHOSPHORUS.htm

I have read about interesting experiments with its luminosity.
When a 2% solution of white P in glacial acetic acid is mixed with 3% H2O2, there is a strong chemoluminescence.
I'm going to try it out when I have Acetic acid.

You can boil a piece of P with water in a rb flask, there is a big "cold flame" where the water vapour exits the flask and contacts the air.

A solution of P in Ethanol glows in the dark, even when extremely diluted.

Does anyone know of other nice experiments with the luminosity of white P?
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BromicAcid
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[*] posted on 8-1-2005 at 18:11


Maybe just put some phosphorus in a large flask a quarter full of water, heat with phosphorus inside with rapid stirring to make a fine suspension of phosphorus, remove stir bar and re-cover flask, when you shake it, it should glow briefly then fade, shake again to do the same till all oxygen is used up. Might be a good way of making H3PO3.

Then again, this may not work, I think part of the phosphoresence may be due to the ozone which would probably not be produced significantly in this enviorment.

[Edited on 1/9/2005 by BromicAcid]




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[*] posted on 9-1-2005 at 11:57


I must be missing something. What do you to this routine with the dichromate/chromic acid for, other than potentially oxidising the white phosphorous?



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[*] posted on 9-1-2005 at 12:07


The chromic acid wash helps to remove impurities in industrially prepared phosphorus, they either rise to the top or are oxidized. But I wouldn't have thought that would be necessary for garage chemist as his phosphorus was obtained from other phosphorus that I'm assuming was pure.



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[*] posted on 9-1-2005 at 13:24


My phosphorus was a red viscous sludge, because it contained some (red!) phosphorus suboxide. This was oxidised by the chromic acid. The phosphorus turned from reddish to yellow, so it worked!
The document I linked above was the source of this method.
The chromic acid was still orange after washing the phosphorus with it, indicating no reaction with the white P.

As I now have a great fume hood, I will try to make PH3 from P and hot KOH solution.

I tried it about half a year before with very small amounts (pinhead sized bit of P, maybe 10mg) and it looked interesting:
a small bubble formed on the surface of the molten P and lifted it to the surface of the KOH, then the bubble bursted and instantly exploded with a white flame and some smoke, the P sunk again, a new bubble formed on it and the cycle repeated.
There was almost no PH3 smell, as all formed PH3 ignited on contact with air.

Does anyone know if the formed hypophosphite is toxic? If no, this would be a good and clean method of destroying phosphorus residues.

EDIT: I googled for "hypophosphorous acid toxicity" and found out that is essentially non- toxic!
It is rather difficult to prepare though:
first, Ba(OH)2 is reacted with white P, the excess Ba(OH)2 is removed with CO2, the dissolved barium hypophosphite ("phosphinate";) is reacted with H2SO4.

But the sodium salt is useful, too: it is a really powerful reducing agent! I'll try to find out what it can reduce.

[Edited on 9-1-2005 by garage chemist]
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[*] posted on 9-1-2005 at 13:54


PH3 is used for fumigation of rodents, and is quite toxic. Of course if it burns completely to P4O10 and H2O then these are (relatively) harmless.
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[*] posted on 11-1-2009 at 08:17


Sorry for the bump.

I tried the experiment GC suggested. I added a small piece of phosphorus to 3mL of GAA.
I heated to increase solubility, and shaked very carefully (the molten P may not come in contact with air).
It didn't seem a lot dissolved, a small blob remained.

Anyway...

Next I added about 2mL of about 3 to 6% H2O2 (not sure, this bottle maybe have decomposed a lot, but theres definately 15% H2O2 or more). I the H2O2 diluted 1mL to 5 mL with water.

All I get is a white turbid liquid with white fumes above it. No 'glow in the dark'.

I wonder what the white fumes are. It can't be white P, as that would ignite instantly. AFAIK, all oxidation products of P are soluble in GAA, as they are all highly polar, just like GAA.

Anyone has a procedure for the reaction in GAA? What did I do wrong?

[Edited on 11-1-2009 by Jor]
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