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Author: Subject: Preparation of elemental phosphorus
spong
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 Quote: Originally posted by Random I am interested in getting red phosphorus from matchboxes. What is the best way of doing it to make it almost pure?

See if you can find starting caps in sports stores, they're like the paper caps for cap guns except much larger. A pack of those could yield around a gram if you're careful.
They have a mixture of RP, KClO3 and S plus a binder.
soak them in warm water, scrape the wet powder out, keep adding boiling water and decanting to get rid of the KClO3, use acetone to wash the binder if the water hasn't got rid of it and then hot toluene to get rid of the sulfur.
I've got about 0.8g from a pack of caps I'm thinking of using as a chlorination catalyst so hopefully it'll be pure enough.
Rogeryermaw
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I've been reading posts for a few days now and there are some seriously brilliant people here. Some scary ones as far as safety is concerned but the general chemical knowledge has left me dumbfounded in some spots. Anyway it's nice to be on board and i hope i can offer help as much as i am getting from these forums. anyway i have built a small scale phosphorus retort that i will be firing up in a few days (whenever my calcium phosphate arrives). the vessel is 1 1/2" steel pipe 10 inch long capped at one end and the other reduced to 1/2" with a street 90 and a 6 inch drop to go into the collector. the drop will go into a container with a lid wit 3 holes. 1 for the spout, 1 for venting and the last for inert gas. i will post results as soon as i have some.

ya i know its cheating but i have the space for a truly nasty fire to get the heat i need (1100-1400 Celsius right?) I'm sort of out in the country and my neighbors burn trash and yard scraps so a fire will arouse no suspicions.

[Edited on 18-8-2010 by Rogeryermaw]
blogfast25
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Very interesting: finally someone who wants to scale up the ideas in this thread :-)

Important question: which reagent mix will you be using? Which reducing agent?

What will be the collector?

It's a large apparatus: I suggest you start with a quarter charge for first tests... Don't blow yourself up, it's not worth it.

Remember that your reaction may be self-propagating once initiated. That certainly seems to be the case with sodium metaphosphate/Al/SiO2 stoichiometric mixtures: You may want to reduce/quit heating once P4 starts coming over.

Will you argon flux the reactor prior to ignition?

[Edited on 18-8-2010 by blogfast25]
Rogeryermaw
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from everything i have read i shouldn't have to flush the reactor. it will be producing carbon monoxide which should burn the oxygen away at an early stage with these temps. i will, however inject inert gas into the collection vessel with a twofold purpose. if phosphorus is produced it will ignite as soon as it finds suitable oxygen so i will keep the atmosphere in the collector inert. the other possibility is that if i dont tend the fire, and the temp drops, the vessel may produce a suction. as long as the gas in the collector is inert then it can suck all it wants...it will just suck inert gas. i am considering using a paint can half full of water for collection because the lid is airtight and i can bolt the fittings on from the retort and the gas cylinder (considering CO2 because i have CO2 cylinders from my paintball gear) to keep the collector airtight except the 3rd hole which will exhaust excess inert gas. my reactant will be calcium phosphate, silica sand and charcoal for carbon. i thought about dehydrating some sugar with H2SO4 but according to industry production, purity is not all that important.

[Edited on 19-8-2010 by Rogeryermaw]

NEED RAIN!!! we have burn ban on so i can't conduct the experiment until we get some moisture but i will post pics of the entire process and share the results.

[Edited on 19-8-2010 by Rogeryermaw]
blogfast25
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 Quote: Originally posted by Rogeryermaw from everything i have read i shouldn't have to flush the reactor. it will be producing carbon monoxide which should burn the oxygen away at an early stage with these temps. [Edited on 19-8-2010 by Rogeryermaw]

That would indicate you're running Ca3(PO4)2 + C, right? Why not consider Al as a reducing agent? My own test with Na metaphosphate + Al + SiO2 (open crucible) was very successful.
Rogeryermaw
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the steel parts of the apparatus were only in the $20 range most of which if not all i'm sure will be reusable so i'm willing to try different mixtures to obtain results that will benefit the private chemist community...rotten dope heads ruined it for all of us. blogfast25 Thought-provoking Teacher Posts: 10340 Registered: 3-2-2008 Location: Old Blighty Member Is Offline Mood: No Mood  Quote: Originally posted by Rogeryermaw the steel parts of the apparatus were only in the$20 range most of which if not all i'm sure will be reusable so i'm willing to try different mixtures to obtain results that will benefit the private chemist community...rotten dope heads ruined it for all of us.

I think you'll find that removing post-reaction gunge (the 'slag') from your apparatus will be fairly easy with a power tool.

My own test with someone else's formula, here:

... was quite successful, albeit without capturing the formed P4. Na metaphosphate/Al/SiO2 lights up easily with some strong external heating and seems to burn right through (it generates a lot of heat once started).

Ca3(PO4)2 based mixes, whether reduced with C or Al and based on what I've seen and read, need higher heat and sustained heating to keep going.

Regards fluxing the reactor with Ar before use, I seem to have forgotten one of my own arguments I made against it! Assuming you generate a reasonable amount of P4, it will quickly scavenge any O2. The volume of your reactor is about 290 cm3, or 0.29 L, so even empty and at RT it would contain about 0.2 x (0.29 /22.4) = 2 mmol (millimol), the equivalent of 0.2 mmol of P4 (P4 + 10 O2 --> 2 P2O5) or about 0.03 g of P4!

Undoubtedly Hennig Brand on that famed day in 1669 didn't flush his retort either ;-) !
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That's what i'm counting on...once the residual oxygen is used up in the process, as long as the collector is inert and cool enough P vapors should solidify...i wonder if using an ice slurry in the collector would eliminate the need to have the spout submerged...that would solve the safety issue about water being drawn into the reaction vessel
blogfast25
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 Quote: Originally posted by Rogeryermaw That's what i'm counting on...once the residual oxygen is used up in the process, as long as the collector is inert and cool enough P vapors should solidify...i wonder if using an ice slurry in the collector would eliminate the need to have the spout submerged...that would solve the safety issue about water being drawn into the reaction vessel

I think you'll find it will solidify faster than you might wish: clogging of the spout may even be an unexpected problem. It might help to heat the spout to above the melting point of P4 at least...

Alternatively, get a thermocouple right after the reaction zone for better control. Always useful!

[Edited on 20-8-2010 by blogfast25]
Rogeryermaw
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clogging of the output spout has concerned me too... i don't want the whole thing to become a big bomb full of deadly scorching hot reactants and phosphorus... how about a slightly longer pipe running into the collector with the end of the pipe only 1/2" or so into hot water to keep the condensate in liquid phase? also the temps around the furnace should keep the material in the delivery tube liquid since steel conducts heat fairly well.
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This looks like a dangerous setup. A slight drop in temperature might cause underpressure in the reaction chamber. If water gets sucked back into the red-hot chamber it will cause an explosion. Once the reaction subsides OR you run out of charcoal the chamber will begin to cool down and then it has to be disconnected from the collector or disaster will ensue! You could make the spout somewhat longer and carefully insulate it with mineral wool to keep the P4 fluid. You could also try to attach a stainless steel funnel to the spout. Invert the funnel and put it into the collector so that its mouth is just barely under water - this will effectively avoid suckback.
un0me2
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I am currently looking at the synthesis of free, elemental phosphorus from phosphine (PH3), there is the thermal dissociation of phosphine (garage_chemists favorite - BTW I really would like a look at whatever anyone has on a thermite-type reaction giving a phosphine precursor).

There is also the reported reaction of phosphine with dimethylchloramine, which "reportedly" gives free, elemental phosphorus and dimethylammonium chloride (as reported here: http://pubs.acs.org/doi/abs/10.1021/ic50067a009). That would be an EXTREMELY interesting solution to producing elemental Phosphorus, as it would be feasible to produce elemental phosphorus using an RT hydrolysis of MxPx' salts to give PH3 (logically, there should be no need to dry it), pass the gas generated into a solution of dimethylchloramine (obviously an inert atmosphere would be vital). But at least there is not the need for the high-temperature on one end and then removal of the massive amount of excess heat.

Converting the elemental, presumably white, Phosphorus into the much more easily worked with Red Alletrope would probably be the next problem (pressure vessel, etc. I have several journal articles on the same).

There is also the reported combustion of phosphine (drying would be required) in an atmosphere of chlorine to give PCl5. I am trying to find some more details on that specific reaction, but if it is in fact the case (Buckholtz, et al's Patent would be proved).

In any event, a more amateur friendly synthesis of a phosphine precursor (I've attached one synthesis of Zinc Phosphide from Zinc Orthophosphate - hydrolysis of which in H3PO4 would give phosphine and zinc orthophosphate (ie. the precursor is regenerated by the hydrolysis reaction).

Attachment: Fluck.The.Chemistry.of.Phosphine.pdf (857kB)
This file has been downloaded 986 times

Attachment: Murali.Gopalam.Preparation.of.Zinc.Phosphide.pdf (393kB)
This file has been downloaded 654 times

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blogfast25
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@ rogeryermaw:

What do you plan for heating? Will the entire reactor bit be heated, in a furnace for instance? Or will you use bunsen burners?

As long as the spout isn't submerged, at least the risk of suckback is nil. You could perhaps used a thermos flask half-filled with iced water as collector?
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His P4 is going to hopefully drop into a vented paint can purged continuously with inert gas (CO2). I presume Roger will have water in the bottom of the paint can, yet provide a sufficient "air gap" so the spout end is not submerged. So suckback is not an issue.

As someone else pointed out keeping the retort spout at a high enough temperature to keep the P4 from solidifying is not going to be a problem if he has the other end red hot.

The single most important condition for a successful synthesis is good mixing - Nicodem
blogfast25
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 Quote: Originally posted by Magpie As someone else pointed out keeping the retort spout at a high enough temperature to keep the P4 from solidifying is not going to be a problem if he has the other end red hot.

Well, that all depends on the difference between the red hot zone and the spout itself... In continuous operation the spout would inevitably heat up. But at start up there will be some formation of P4 deposit.
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I'd be more concerned with slag plugging the outlet than P4. P4 melts quite easily. Therefore I recommend being careful to not overcharge the reactants.

Also, if the P comes out as a gas what's to keep some of it from leaving with the vent gas into the environment? Doing this outside, as already stated, and being aware of that possibility is recommended. Stay upwind.

The single most important condition for a successful synthesis is good mixing - Nicodem
Rogeryermaw
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Quote: Originally posted by blogfast25
 Quote: Originally posted by Magpie As someone else pointed out keeping the retort spout at a high enough temperature to keep the P4 from solidifying is not going to be a problem if he has the other end red hot.

Well, that all depends on the difference between the red hot zone and the spout itself... In continuous operation the spout would inevitably heat up. But at start up there will be some formation of P4 deposit.

so i'm thinking a good preheat below the reaction temp will reduce the chance of cold deposits, and the funnel with slight submersion is a good idea since it would increase the volume of water having to be drawn in causing it to surface and break the vacuum. i will be carrying this out in a force fed coal furnace, outdoors with gloves and protective clothing.
Rogeryermaw
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 Quote: Originally posted by Magpie I'd be more concerned with slag plugging the outlet than P4. P4 melts quite easily. Therefore I recommend being careful to not overcharge the reactants. Also, if the P comes out as a gas what's to keep some of it from leaving with the vent gas into the environment? Doing this outside, as already stated, and being aware of that possibility is recommended. Stay upwind.

THOSE are very good and scary points though i have considered the slag issue...i have entertained the ideas of some sort of fine steel screen near the last adapter but it may just burn away or cause other issue and have also thought of laying the pipe at a slight angle and making sure to leave an airspace at the top of the reactant mixture. as blogfast pointed out, i will likely try a small charge for the first run. depending on how it performs i have other pipe and fittings if the output needs to be longer.

[Edited on 21-8-2010 by Rogeryermaw]
blogfast25
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Good point by Magpie about the slag. The force fed charcoal furnace is all good, IMHO. If you load the reactor into the furnace at a small angle, spout at the higher end, blockage by slag shouldn't become an issue, IMHO. That and not over-charging.

I think the whole thing is a lot less dangerous than we might imagine but it needs to be done properly to succeed...
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 Quote: Originally posted by blogfast25 Good point by Magpie about the slag. The force fed charcoal furnace is all good, IMHO. If you load the reactor into the furnace at a small angle, spout at the higher end, blockage by slag shouldn't become an issue, IMHO. That and not over-charging. I think the whole thing is a lot less dangerous than we might imagine but it needs to be done properly to succeed...

I had my ceramic retort angled slightly downward to allow the liquid P4 to drain better. The slag from the Al/NaPO3/SiO2 run was foam-like, and I'm not sure that tilting the retort had much affect on it.

Try to get all your reactants dry so you don't generate any more phosphine than necessary.

In regard to potential danger, I felt that my handling of the retort following the run was really too dangerous. I want to make some more P4 someday but one of the reasons I stopped was the feeling that I really didn't have the situation under proper control.

The single most important condition for a successful synthesis is good mixing - Nicodem
blogfast25
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 Quote: Originally posted by Magpie I had my ceramic retort angled slightly downward to allow the liquid P4 to drain better. The slag from the Al/NaPO3/SiO2 run was foam-like, and I'm not sure that tilting the retort had much affect on it. Try to get all your reactants dry so you don't generate any more phosphine than necessary. In regard to potential danger, I felt that my handling of the retort following the run was really too dangerous. I want to make some more P4 someday but one of the reasons I stopped was the feeling that I really didn't have the situation under proper control.

Yes, my own Al/NaPO3/SiO2 mix in open crucible conditions also foamed, as the P4 escapes. It was also quite viscous. And continued to react after I'd switched the propane flame off. I wouldn't be surprised this mix could be initiated with the usual suspects, then allowed to propagate. Or ignited with Nichrome wire/current.

[Edited on 21-8-2010 by blogfast25]
Rogeryermaw
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yay! it's finally raining! maybe they will drop the burn ban so i can run this experiment.
un0me2
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Here is the paper I was waiting for on the reaction of dimethylchloramine and phosphine to give elemental Phosphorus. They start from Aluminium Phosphide & go via the production of phosphine therefrom.

Attachment: Highsmith.Sisler.A.New.Reaction.of.Chloramines.with.Phosphines.pdf (771kB)
This file has been downloaded 719 times

I just threw the synthesis of Zinc Phosphide up, starting from Zinc Phosphate(s). With strong phosphoric acid it should give Zinc Phosphate and dry Phosphine

Attachment: Murali.Gopalam.Preparation.of.Zinc.Phosphide.pdf (393kB)
This file has been downloaded 637 times

Now, I'm looking at that synthesis of Zinc Phosphide by thermal reduction with carbon and wondering why that couldn't be achieved in a MW. Carbon is a MW Susceptor and the hot carbon should reduce the Zinc Phosphate to the Phosphide by essentially the same mechanism as is done in the paper purely thermally.

All we need now is a decent route to dimethylamine - I do have the sneakiest suspicion that I have seen various agricultural products as methylamine salts.

EDIT

Whoops, apparently the Red Phosphorus is the allotrope that is formed. Really should have taken the time to read it better before I posted it - then again, kinda hard not to be excited Here is a paper on the preparation of the relevant methyldichloramine and dimethylchloramine by treating the relevant methylamine.HCl with calcium hypochlorite...

Attachment: Stevenson.Schomaker.The.Molecular.Structure.of.Dimethyl.Chloramine.and.Methyl.Dichloramine.pdf (693kB)
This file has been downloaded 708 times

[Edited on 22-8-2010 by un0me2]

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Rogeryermaw
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i found something that people in this thread may find very interesting. http://blog.modernmechanix.com/2007/08/02/arc-furnace-incase... this may very well be adaptable for phosphorus recovery. very cheap to build too.
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that man is not protecting his skin as he should be!
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 Sciencemadness Discussion Board » Fundamentals » Chemistry in General » Preparation of elemental phosphorus Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues