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vulture
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| Quote: |
The explosion limits of phophine in air are 1,6- nearly 100%, so exclusion of oxygen is essential to avoid blowing up the apparatus as soon as the
heating is begun. |
Not to mention its rather high toxicity...
[Edited on 2-2-2007 by vulture]
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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garage chemist
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Fume hood takes care of that, plus its smell is very strong and already noticeable at concentrations that do not pose immediate danger.
Of course, working with PH3 as intermediate is not the ideal way. A phosphine- free method is always preffered, but this is too difficult (high
temperatures) so we have to look for alternatives. Going via PH3 is the most promising one.
It is exactly the same as with making cyanides via HCN as the intermediate: it is easy and yields a very good product. The only downside is the added
danger.
But for cyanides, doable HCN-free methods exist, while for phosphorus, doable PH3-free methods do not seem to exist.
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unionised
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"The generation and decomposition of phosphine will have to be carried out in inert gas atmosphere "
That doesn't require an inert atmosphere; just a reducing one. A flow of H2 would do.
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garage chemist
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I think CO2 is easier to fill the apparatus with (heavier than air) than hydrogen. Also, if the atmosphere isnt oxygen-free there will be a more
powerful explosion with the hydrogen in there (the phosphine will ignite long before it starts to decompose, not to think of the phosphorus itself
which ignites at 50°C). Also, the hydrogen definately won't reduce any formed P2O5 from oxygen impurities in the gas back to phosphorus.
For those reasons I am sure that an inert atmosphere is required. A reducing one just won't do with phosphorus, because P is a stronger reducing agent
than hydrogen.
[Edited on 3-2-2007 by garage chemist]
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S.C. Wack
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Either that or the reduction of phosphate with hydrogen has been known for over 50 years, is mentioned in several books on phosphorus, is patented
(with some additional goings-on leading to other P cpds.), is mentioned in the very first page of the P thread, and linked to later on.
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garage chemist
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This contradicts with the statement in Ullmann that phosphorus will react with water vapor at high temperature to phosphoric acid and hydrogen.
The reduction of phosphates with hydrogen probably relies on the equilibrium shift by the high temperature which removes the phosphorus as it is
formed.
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guy
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If I did my calculations correctly,
21H2O + 3PO4(3-) + 8Al --> 8[Al(OH)4]- + 3PH3 + OH-
should have a Eo value of 1.09V. That's pretty good.
BTW, just to let you know, diphosphine is responsible for the explosive behavior, not phosphine. Diphosphine is analogous to hydrazine in structure.
[Edited on 2/3/2007 by guy]
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chemrox
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Elemental P comes in two common forms. Which one would be produced?
(This assumes the post is not a joke but I thnik it must be)
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guy
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| Quote: | Originally posted by chemrox
Elemental P comes in two common forms. Which one would be produced?
(This assumes the post is not a joke but I thnik it must be) |
White always occurs naturally. It takes more effort to convert to red.
And why does this sound like a joke? Its very probable that phosphine will at least be produced.
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guy
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Possible way to make aluminum phosphide?
16Al + 6Na3PO4 --NaOH--> 5Al2O3 + 9Na2O + 6AlP
Then treat AlP with water to get PH3 (this PH3 will be free of diphosphine, which is explosive).
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madscientist
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Something interesting:
| Quote: | | When triphenyl phosphate was reduced with a solution of LiAlH4 in carbitol, which was prepared as described in [9], the formation of red phosphorus
was observed and not even traces of phosphine were present. |
Attachment: phosphate ester reduction lialh4.pdf (216kB)
This file has been downloaded 1720 times
I weep at the sight of flaming acetic anhydride.
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Random
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5NaOH + 3NaNO3 + 8Al + 18H2O --> 8NaAl(OH)4 + 3NH3
2NaOH + 2Na3PO4 + 8Al + 22H2O --> 8NaAl(OH)4 + 7H2 + 2P
I think PH3 would form
NaOH + Na3PO4 + Al + H2O --> NaAl(OH)4 + PH3
this could actually happen
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zed
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Well, Madscientist.....Normally, using LiAlH4, ain't the preferred way to do anything.
But, Red Phosphorus is so hard to buy, or make by conventional means....This method really could be considered "Easy Phosphorus".
Too bad the Authors of your paper, seemed hell-bent on making phosphine, and didn't give much detail about their red phosphorus adventures.
As in....... "Darn it! We were trying to make Phosphine, but alas, we only got Red Phosphorus!"
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madscientist
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It made me wonder if other, more accessible reducers may effect a similar transformation. And I agree - it's too bad they failed to investigate
further!
I weep at the sight of flaming acetic anhydride.
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zed
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The result of many experiments, I fear.
Authors fail in achieving their original objective, but none-the-less...get results that
are extraordinarily interesting. But alas, generally, to no avail.
Scientific tunnel-vision, makes it impossible for them to see their triumph.
Give credit to the fellow that originally discovered Phosphorus. He was trying to refine Gold from urine, but ended up with Phosphorus instead.
He could see that he hadn't achieved what he wished to, but he was clever enough to also see that he HAD achieved something unique and valuable.
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