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Author: Subject: Preparation of elemental phosphorus
BromicAcid
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[*] posted on 19-9-2004 at 08:13


Doesn't trisodium phosphate have an impractical temperature of melting? My chem book says that it looses its last water of hydration at 200C but that it decomposes upon melting, I'm assuming into sodium pyrophosphate, which has a melting point of around 800C.

I've read of the method to produce iron phosphide by heating phosphate, iron, and silica and the iron phosphide sinks to the bottom. However converting this to phosphine and reducing seems to be a bit too much work considering the prep for phosphorus from this step is to simply heat iron phosphide with sulfur, or iron sulfide.

From the patents that I found phosphine is usually generated in the lab by the action of water on magnesium phosphide. If magnesium were easy to come by I have no doubt that one could easily make magnesium phosphide by heating a mixture of phosphate, silica, and excess magnesium, however it is not so easy to come by in a reliable form.

In my newest chemistry book it describes the analytical process to determine arsenic content of an unknown sample. Many here are probably familiar with it, ash the sample containing arsenic then dissolve the sample in HCl. The H3AsO4 thus formed is treated with SnCl2 and reduced to H3AsO3, this is in turn reduced with zinc metal according to the reaction:
H3AsO3 + 3Zn +6HCl ---> AsH3 + 3ZnCl2 + 3H2O
So essentially a dissolving metal reaction.

I wonder if dissolving a phosphate in HCl and adding excess metallic tin to the reaction mixture might yield a decent quantity of phosphine? It would preform both reactions simultaneously, however it might be difficult to control.

Just some thoughts.

Edit: Just tried mixing HCl, Sn, and Ca2(PO3)3, upon mixing the HCl with calcium phosphate the solution turned yellow, upon adding the tin the solution decolorized to clear, but shortly thereafter turned black. I caught the faintest whiffs of phosphine but may have been entirely mixtaken due to the biting smell of HCl that overpowered everything. Got the test tube sitting in the sun to see what I end up with, it was odd that it turned black.

Edit #2: If a dissolving metal reduction will reduce nitrate to ammonia or nitro to amine, and the same/similar readuction reduces arsenates to arsine, it would only make sense for a similar reduction for phosphates to phosphine.

[Edited on 9/19/2004 by BromicAcid]




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Theoretic
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[*] posted on 24-9-2004 at 05:38


"Doesn't trisodium phosphate have an impractical temperature of melting? My chem book says that it looses its last water of hydration at 200C but that it decomposes upon melting, I'm assuming into sodium pyrophosphate, which has a melting point of around 800C."

No, it doesn't. Na3PO4 can only decompose into Na4P2O7 if it loses Na2O, which I'm sure isn't going to happen.




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BromicAcid
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[*] posted on 24-9-2004 at 08:41


Anhydrous Trisodium Phosphate melting point information:

Melts at 73 - 75 C
Decomposes at 75C
Melts at 1340 C
Decomposes at 75C
Becomes anhydrous at 212F Melts at 75C

So, I'm confused as to what it decomposes to, as if it just lost its water of hydration it would simply state that.

[Edited on 9/24/2004 by BromicAcid]




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[*] posted on 24-9-2004 at 17:49


According to Lange's 15th, Na<sub>3</sub>PO<sub>4</sub> (anhydrous) melts @1340*C. The 12-hydrate melts @ 73.4*C and looses 11 H<sub>2</sub>O @100*C. No decomposition is mentioned,
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[*] posted on 24-9-2004 at 18:21


That is quite the prohibitively high temperature. I found something interesting though regarding the use of sodium phosphate, particularly in the production of phosphides.

Supposedly according to an older chemistry book I was browsing around today, the only way to make tungsten phosphide is to electrolyze a mixture of tungsten oxide in molten Na3PO4.

But then again electrolyzing calcium phosphate in cryolyte supposedly yields phosphorus directly.

[Edited on 9/25/2004 by BromicAcid]




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[*] posted on 1-10-2004 at 08:28


Ca3(PO4)2 dissolves in HCl? Very interesting! Though I would suggest Fe rather than Sn, much more available and dissolves slower than Sn, thus more of the H atoms are utilized due to less chance of recombination at low concentration.
Fe could be used for direct reduction of molten sodium whateverphosphate, more available than zinc and would work the same way, though a weaker reducer.
For carbon reduction, I suggest NH4H2PO4, this would convert to ammonium metaphosphate (AMP), thinly powdered sugar would be thrown in and dehydrated by the metaphosphate and produce a very fine active form of carbon (taken from the CS2 thread), the dihydrogenphosphate (ADHP) thus formed would dehydrate back to metaphosphate, this would be reduced by the active carbon much more actively than by ordinary powdered charcoal. These would be the reactions:

1) NH4H2PO4 => NH4PO3 + H2O

2) 6NH4PO3 + C6H12O6 => 6C + 6NH4H2P2O7

3) NH4H2PO3 => reaction 1)

4) NH4PO3 => reaction 2)

5) 2NH4PO3 + 6C => 6CO + 2NH3 + H2 + 2P




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biggrin.gif posted on 1-10-2004 at 11:32


A sidenote: what to do with the off-gases after condensing the phosphorus? You could burn them, although that would be a waste (but it would be interesting to see the flame colour, since NH3 burns pale green-yellow, CO blue, H2 colourless :P). You could lead them all to a hot tube with CuO and get copper powder and harmless waste gases (CO2, H2O, N2). Or you could lead them to a very hot ceramic (or with ceramic bits) tube and make HCN from the NH3 and CO, as well as water vapour. After condensing HCN + H2O in ice-cool water, the remaining CO and H2 (in ratio 4CO/H2) could be led into molten NaOH to make sodium formate. The hydrogen left over can be led into a condom and stored. :D Although I'm only half joking, since condoms, when they are first manufactured, are filled with 25 l of air to test for strtength, so one could easily accomodate a mole of H2 (22.4l), the amount that would be left over from a 446 g batch. Then you could take the condom, tie it, attach it with a long gasoline-soaked thread to a brick somewhere in a field, ignite the thread and watch. The thread will ignite, the condom will float into the air and explode in the sky with a big boom when the flame gets to it.
Thus every single reaction product is utilised. :D




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[*] posted on 7-10-2004 at 09:28
elemental phosphorus making


Hello everybody!!
this is my first message on this list. I am actually Italian, and I am studying for a PhD in chemistry in the UK, so I apologise if my English is a bit rusty.
Regarding making phosphorus. I have been 'obsessed' with making white phosphorus for a long time. I have actually succeded making about 100 mg of white phosphorus in my landlady's garden a couple of months ago but never tried again since. That night I was so happy I couldn't go to sleep. I obtained a nice yellow 'drop' at the bottom of my condenser which solidified as the water temperature dropped. When I got the pebble out with a spoon, it smoked in air, smelt badly of garlic and yes, it shone green in the dark. It didn't catch fire though, even when pierced with a toothpick. The consistency is that of soft wax. I used a mixture of KH2PO4 and homemade willow charcoal with no sand. The retort was made by 'incapsulating' a 10 ml lab glass vial with 'fire' cement and cooking this in the kitchen oven at 250 C for 1 h. The spout was a piece of copper tubing sealed on the retort with the same fire cement, (this comes as a ready-made putty in my local hardware store). The furnace design is very simple indeed: I have made a refractory kiln with a blowing pipe attached to a 'cold-shot' powerful hair-drier. The furnace was fired with BBQ charcoal. I have successfully melted iron in this, so I guess the temperature at full regime, must have been in excess of 1300 C (it looked so bright it would hurt my eyes to stare at it).
I have tried with thicker glass jars, without success. I guess the glass, which replaces the silica, melts inside the fire cement 'mold' and acts as a flux aiding the melting of the phosphate. The usual reduction reaction then occurs. It took 30 min or so at bright white heat for the first spontaneously flammable bubbles to break the surface of the water in the condenser. They produced white-bright little flames, so I guess some phosphorus got lost in that way. I am now thinking of repeating the experiment with ground glass powder in a slighlty bigger retort.
I still have my pellet of P4 in a small jar or water. It now sits proudly on my desk.

Remember to keep the retort size as SMALL as possible so that it will be easier to achieve and sustain internal high temperatures, and:
do NOT use metal retorts. Too much heat is simply transferred away to the spout and then to the water in the condenser.
Do not use gas torches unless you have an acetylene/oxygen source. Go for a nice charcoal/air furnace which you can make with an old bucket and refractory mix (and a nice hair-drier from your mum/girlfriend/granny...)

Phosphorus-makers of the world ! Get out there NOW and start making phosphorus!!

Phosphorus1
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[*] posted on 20-10-2004 at 00:21


If you are ready to rock n’ roll, but lack in a strong heat source, you can do a neat trick or two.
1) Inject a little oxygen in the flame of your good old propane burner.
2) Make a hydrogen flame. The temperature is 1000 C – 2000 C. Plus, it flows around thing very easily, it’s very fluid and relatively long, it will flow around your vessel and heat it evenly.




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[*] posted on 29-10-2004 at 02:17


In some textbooks I've met with maybe one of the most common method for laboratory phosphorus preparation. I wonder if you know of that.
In substance this method is based on reduction of phosphate, but this phosphate is here sodium ammonium hydrogen phosphate Na(NH4)HPO3. As for reducing agent zinc dust was mentioned but Mg or Al will sure work as well. I've never tried this though I've prepared some sodium ammonium phosphate. If anyone try this with success please tell me.

reaction(I can be wrong):

Na(NH4)HPO3 = heat= NH3 + H2O + NaPO3

4NaPO3 + 5Zn = 2P + 5ZnO + Na4P2O7

totally:

4Na(NH4)HPO3 + 5Zn = 2P + 5ZnO + Na4P2O7 + 4NH3 + 4H2O
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[*] posted on 29-10-2004 at 18:10


I second that. Just cut a little notch out of the side of a >1982 US penny, hold it with a pliers so that the notch faces downward, and then heat it with a propane torch. When the copper skin of the penny becomes wrinkly, jerk the pliers slightly, and a blob of molten zinc will plop out of the copper shell. I suggest doing this procedure outside, above a non-flammable surface (concrete). Also, the zinc will splash a bit, so wear protection.

[Edited on 30-10-2004 by FrankRizzo]
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[*] posted on 29-12-2004 at 06:49


Has anyone actually tried out Theoretic's method -- maybe melting down some zinc with TSP from the local hardware store into a flask of cold water? sounds neat - toxic as hell but neat :D
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[*] posted on 29-12-2004 at 10:20


Since this has come up again, this is Rossel's Berichte ref. It is the Al reduction mentioned early on. Unfortunately his Zn ref in Bull. Soc. Chim. isn't so available to me.

Attachment: berichte_P_from_Al_reduction.pdf (210kB)
This file has been downloaded 2103 times

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[*] posted on 29-12-2004 at 14:41


S.C. Wack: That's VERY interesting.
The resource says that when sodium phosphate ("NaPO3", obtained by heating NH4NaHPO4) is heated with aluminium powder, elemental phosphorus is directly evolved without the formation of hydrogen phosphide.
Addition of fine SiO2 to the mix improves the yield.
However, the aluminium must not be too fine, or the reaction becomes violent.

Al + NaPO3 + SiO2 is the ideal mixture, it also reacts at the melting point of NaPO3, which makes a strong heat source unnecessary.

The synthesis of phosphorus is not so important for me though, as I once bought 100g of red P from Ebay (was expensive as hell though :mad: ).


[Edited on 29-12-2004 by garage chemist]
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neutrino
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[*] posted on 29-12-2004 at 17:13


Out of curiosity, how much was it? By the way, NaPO<sub>3</sub> is sodium <i>meta</i>phosphate.
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[*] posted on 29-12-2004 at 20:32


Which is the exact method I use to make phosphorus (the one that works best at least) the name you'll most often find NaPO3 under is sodium hexametaphosphate, it makes a cyclic structure if you see the drawing of it so it is better represented (NaPO3)6 the preparation of (NaPO3)6 is also covered in Gmellin (I think I butchered that name) which I scanned in earlier in this thread.



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[*] posted on 9-4-2005 at 22:06


Read a little on this subject and keep reading over and over that you must use "acid calcium phosphate" Ca(H2PO4)2 made by adding sulfuric to the neutral insoluble calcium phosphate Ca3(PO4)2 or the phosphorus simply won't reduce - maybe everyone knows this already but just checking
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[*] posted on 12-4-2005 at 16:09


has anyone tried melting zinc in sodium metaphosphate yet? sounds so interesting - dangerous as all getout but interesting :)
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[*] posted on 12-4-2005 at 17:14


The 'acid calcium phosphate' is also known as calcium superphosphate, it is made by adding sulfuric acid to calcium phosphate till the precipitate re-dissolves again, calcium phosphate itself does work but the temps are somewhat higher, calcium superphosphate = home production, calcium phosphate = industrial, at least in my opinion.

Zinc does work as a reducing agent, yields are lower then with aluminum reduction from what I've read and just as with aluminum or magnesium reduction yields are also lowered from the reaction of the phosphorus produced with the zinc present to form the phosphide. Although I didn't check into it I have to wonder about the stability of magnesium phosphide, aluminum phosphide and zinc phosphide to heat, if they decompose at elevated temperatures >800 then there would be no need for silica in the reaction because they should just decompose, right?

And while I'm posting to this topic, someone (I will if no one else gets around to it) should attempt the reaction I mentioned earlier on this page of heating iron, a phosphate and silica in a crucible, the iron if in excess reacts with the phosphate and iron phosphide sinks to the bottom of the crucible forming a seperable hunk. Heating this iron phosphide with sulfur (which would imply low temperatures considering there is no mention of pressure) furnishes the distillation of phosphorus.




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[*] posted on 12-4-2005 at 21:48


heck both zinc and tin are better reductants than phosphorus - i might try to use a roll of solder for this
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[*] posted on 13-4-2005 at 15:50


Heres a coupla things I want to try...

According to a patent, can't remember which one right off, good results were obtained when the chemicals to be reduced were ball milled together and compressed into 1 inch or so "briquettes" via hydrolic press at some 15 tons of pressure. A nice side benifit other than good yields was that reduction was completed at 1250C whereas on an industrial scale it is just getting going.

Other thing I want to do is instead of dumping the WP vapor into water, is to have a long pipe as the condenser, with a one way check and ball valve on the end. That way when the RXN is over, the entire vessel can be sealed keeping the atmosphere anoxic, and hopefully keeping the WP from self igniting. When its time to take out the WP, inert gas can be pumped into the end the end with the ball valve while the other unscrewed from the vessel.

Speaking of removing WP... it is soluable in carbon disulfide (which is a nasty substance of its own). So after the condenser is removed and another ball valve screwed on, some carbon disulfide can be introduced into the condenser and sloshed around effectively washing it out.

Well so you got ur WP in the carbon disulfide... what then? Easy, keep it in a glass jug, and sit it out in the sun for a few days. The sun will react with the dissolved WP particles turning them into RP. RP is insoluable in carbon disulfide and it will precipitate and fall out of the solution onto the bottom of the jug.

Easy... lol. :D
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[*] posted on 13-4-2005 at 20:55


jimmyboy, solder is tin/lead, not tin/zinc. Unless you've got lead free solder which is ~95% tin, the rest being silver, copper and sometimes indium.
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[*] posted on 13-4-2005 at 21:12


Could any body clear up some of my confusion please? If I were to do this which calcium phosphate should I buy, the monobasic calcium phosphate Ca(H2PO4)2 H2O, dibasic calcium phosphate CaHPO4 or calcium phosphate Ca3(PO4)2? I got a little mixed up, so sorry if this looks stupid, but better be sure. Thank you.



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[*] posted on 13-4-2005 at 23:07


Not so twospoons

http://www.kappalloy.com/tinzinc.html

although yes the more common ones do not contain zinc - i think they also use this alloy for alumaweld rods

[Edited on 14-4-2005 by jimmyboy]
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[*] posted on 14-4-2005 at 00:05


Either that, or aluminum-zinc alloys (essentially potmetal). Which would also work quite well as fuel.

Tim
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