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Author: Subject: Preparation of elemental phosphorus
Sauron
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[*] posted on 24-12-2006 at 06:31


Brauer p.522, "bright red" (vermillion) P from Hg and PBr3.

55 g Hg
51 g PBr3

Heated two days at 100 C in a sealed combustion tube with constant shaking, one additional day at 130 C then one more day at 170 C. Worked up rather elaborately to free it from Hg (I) bromide and Hg (II) bromide. I have to calculate the working pressure but assuming it is not more than 60 psig then this could be done in a 500 ml Parr shaker with an Ace-threaded bottle (not neoprene stopper) and a heating mantle. The scale 6-7X the above without filling the bottle more than half. If the P is for chlorinating to PCl3 I'd omit the workup and use the crude product; the PBr3 if any and the mercury bromides will be removed in the purification of the PCl3. As a guess this ought to fetch about 100 g red P per run and that's a reasonable return for the labor. Where I am PBr3 is obtainable while the red P and esp the P-chlorides are verboten.

If you don't have a Parr shaker type hydrogenator, you can use a mag stirrer, and put a shield around the assembly as you should with any pressure operation.

Anyone want to guestimate the working pressure inside this 500 ml vessel with c.330 g Hg and 306 g PBr3 @ 100-170 C?

If it is too much for the glass (which can really take about 150 psig) then a steel autoclave is the way to go, but I bet a Parr bottle will take anything that a sealed glass combustion tube would.

[Edited on 25-12-2006 by Sauron]
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[*] posted on 24-12-2006 at 06:56


Footnote to above

Hg d 13.5 g/ml, b.p. c.350 C

PBr3 d 2.88 b.p. 175 C

I reckon that the scale can be 10X Brauser's, 550 g Hg and 510 g PBr3 won't take up even 40% of that 500 ml vessel. The yld of red P ought to be on the order of 125-150 g -- I haven't calculated the mass percent of P in the PBr3 but it ought to be something not too far off 25%.

Looks like the entire reaction is conducted at well below the b.p. of both reactants and all the PBr3 is long gone before the temp gets raised to just under the b.p. of that reactant on the fourth day.
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[*] posted on 24-12-2006 at 08:02


If all you want is PCl3, wouldn't it be a lot simpler just to chlorinate Ca3P2 or Mg3P2 from carbon reduction of the phosphate?
Also white P will transform to red P with a few days heating under CO2 when held right at its boiling point.
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[*] posted on 24-12-2006 at 10:08


Dun me for a coward but I'd rather not have to work with WP "willie peter" unless given no choice. In my case I have several kg of Degussa Hg and several Kg of Merck PBr3 and a Parr 500ml shaker so, this procedure represents the path of least resistance. And I can buy more Hg and PBr3 if I need them.

I have a 2" x 12" tube furnace but it only goes to 1100 C. Even that is somewhat above the capabilities of Vycor tubing, but inadequate for the white P preps. But even if that were not the case I'd sooner dance across Cambodia wearing snoshoes, if you see what I mean.

However don't let me rain on your parade. I will observe with interest from 10,000 miles away. :)
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[*] posted on 24-12-2006 at 11:55


OT:

Hey Sauron, did you go through the turstiles sideways? :P

Don't know if you know that joke...

Tim




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Eclectic
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[*] posted on 24-12-2006 at 14:42


I wasn't suggesting you make red P from white P, only pointing out that you don't need pressure. I don't see how hot PBr3 and mercury in a Parr shaker is much safer.

Also, did you miss the Ca3P2 or Mg3P2 with Cl2 bit? You don't NEED elemental P. A metal phosphide will do.

[Edited on 24-12-2006 by Eclectic]
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[*] posted on 24-12-2006 at 18:12


No, I missed that, it's a long thread. I read the first few pages, then found that procedure in Brauer and as it only involved materials and apparatus I have on hand, decided to post it. I will happily study the rest of the thread.

Aren't phosphides commercially available? Or are you just cost-cutting? Also Mg powder is I think restricted here. I recall when I bought a few Kg of Mg turnings for Grignard there was some issue about this because the sales person was a bit sensitized about Mg powder. Al powder is probably OK as long as it's not the microfine stuff used for aluminizing HE.

The mercury-PBr3 does not look to be spectacular. There's no offgassing (no HNr product) so only pressure is vapor pressure of the Hg and that of the PBr3. At 100 C this won't be (I think...must look it up) anything like the rated 4 atm or the actual limit of the vessel which is about 9 atm. As the rxn proceeds the mix goes into solid phase and the partial pressure of red P and of the Hg(I)Br are calculable at 100, 130, and 170 C where this finishes up. So unless there's a huge exotherm involved in the formation of the mercury bromides (seems unlikely and can be looked up) this rxn does not seem very dramatic.

HOWEVER I will keep an open mind and study the thread much more fully. Thanks for your comments.
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[*] posted on 24-12-2006 at 20:30


I peeked at Alfa's catalog. Calcium phosphide (tech grade) is an off the shelf item, 250 g is well under $100. It is the preferred reagent for PH4 generation.

I do not know what transportation difficulties there might be but the cost does not seem to me to be a serious barrier I also don't know what govt formalities (if any) there are for export or import.

Brauer documents the aluminothermic preparation of this material as well as the preparation directly from the elements.
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[*] posted on 24-12-2006 at 20:35


Quote:
Originally posted by 12AX7
OT:

Hey Sauron, did you go through the turstiles sideways? :P

Don't know if you know that joke...



Tim


Sorry, Tim, I missed that. Don't know the joke. These days I have trouble fitting through turnstiles in any orientation.
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[*] posted on 24-12-2006 at 20:59


If you chlorinate a metal phosphide you should get the metal chloride and PCl3. Reduction of phosphates to phosphides does not need as much heat as freeing elemental P?

I'd think a big slug of mercury banging back and forth in a glass container would have a similar effect as hitting it with a hammer...
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[*] posted on 24-12-2006 at 21:39


The shaking can be replaced with a spinbar and a mag stirrer, if the stress of the Hg in a shaker is too much for the glass. I am sure the object of the exercise is just to keep the reactants in contact, obviously they will initially be in two layers and unless mixed products forming at the intrerface could effectively isolate the reactants from each other.

Did anyone actually find a reference or procedure for chlorinating an alkali, alkali-earth or other metal phosphide? Or is this an educated guess only? Sometimes these things just don't go the way they "should" don't they? See my thread regarding speculative chlorination of P2S5 (P4S10).

Brauer's entry for technical Ca phosphide suitable for making phosphine is aluminum powder ground from shot and calcium phosphate ground and mixed. An ignition mixture is used, set off with Mg ribbon, ignition mixture unspecified but I'd guess anyoen familiar with thermite reactions will know it. I seem to recall sodium peroxide and barium oxide maybe? Anyway all this in an iron crucible with a cover. The scale was in hundreds of g so we are talking a large iron crucible. The phosphide produced cannot, according to Brauer, be freed from alumina slag, they are simply broken up and ground together after cooling. Given the reactivity of the phosphide with atmospheric moisture I'd think a dry (glove) box would be indicated, the air inside should be dessicated but an inert atmosphere isn't required.

I have a large glovebox, never thought I'd be doing an aluminothermic rxn in it. But I would think that something needs to be done to minimize or eliminate PH4 formation. Apart from the toxicity, stench and pyrophoricity issues it represents a waste of P product.

Given all of that I'd sooner buy the phosphide if I don't run into a headache over shipping or importation.

Let me know if the chlorination of a phosphide is a known rxn.
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[*] posted on 25-12-2006 at 03:24


I checked some numbers and it appears I overestimated the % P content of PBr3. It's only c.11%. Therefore the theoretical recovery assuming a perfect process and perfect technique is only about 110 g of P from a Kg of PBr3. In real world terms maybe 50-75 g.

Therefore, I no longer think the Hg-PBr3 route is very economically appealing.

Looking at the aluminothermic process the same way well, Al is cheap, and so is calcium phosphate. I do note that the technical calcium phosphide is rated as having 8% active P. Going by the formula that would be 20% P if the stuff were pure. One source claims an assay of only 23.7% calcium phosphide in their product.

Besides Alfa, calcium phosphide (tech.) is also sold by Aldrich, Fluke and Riedel-Haas.

If the actual P content by weight is 8% then this is similar to the 11% above for PBr3. If it is 20% then it is substantially better The latter is unlikely. A Kg of the phosphide costs about the same as a Kg of PBr3. A toss-up.

Of course is one is making his own phosphide from cheap phosphate that is a different story. Al is cheap. In my location though as I mentioned Mg is not an option at least not as powder. I do seem to recall a procedure in Org.Syn. for making a finely divided highly reactive form of Mg from ordinary turnings. I will have to review that. Maybe that can be modified to produce Mg powder in a dry form. Worth a look-see.
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[*] posted on 25-12-2006 at 05:51


This might help those who can't obtain Mg powder but note that the product is highly pyrophoric (!) if exposed to air when dry. I would therefore advise working up (to dryness) in a glove box with an atmosphere of dry Argon. Note that sodium metal and NaI work in place of K/KI if the quality of the reagents is adequate, and that while activity for the Grignard rxn is reduced, pyrophoricity may also be reduced, which is desirable, and would not be a hindrance to the use of this Mg in the reduction of calcium phosphate. I see no reason why this procedure should not scale up well.

Org.Syn. Coll. Vol. 6, p.845 (1988); Vol. 59, p.85 (1979).

Active magnesium. A 200-ml., three-necked, round-bottomed flask equipped with a Teflon-coated magnetic stirring bar, stopper, rubber septum, and condenser connected to an argon inlet (Note 6) is charged with 1.5 g. (0.038 g.-atom) of freshly cut potassium (Note 7), (Note 8), and (Note 19), 2.01 g. (0.0211 mole) of anhydrous magnesium chloride (Note 9), 3.55 g. (0.0214 mole) of anhydrous potassium iodide (Note 10), and 50 ml. of tetrahydrofuran (Note 11). The mixture is stirred vigorously (Note 12) and heated to reflux with an electric heating mantle (Note 13). A black precipitate starts to form within a few minutes. After 3 hours at reflux temperature, the reduction should be complete (Note 14), producing active magnesium as a black powder that settles very slowly when the stirring is stopped (Note 15).

Notes:

7. Purified grade potassium from J. T. Baker Chemical Company has been found by the submitters to give the most consistent results. The checkers used potassium metal from Allied Chemical Corporation. Very impure potassium or sodium generally gives magnesium powder with much reduced reactivity. Sodium may be used in place of potassium provided that the boiling point of the solvent chosen (Note 11) is higher than the melting point of the metal.
8. The potassium is usually cut into two or three pieces under hexane or heptane and placed wet in a tared flask that has been purged with argon. The flask is evacuated, removing the hydrocarbon, filled again with argon, and weighed to determine the exact amount of potassium. The amount of potassium used by the checkers varied from 1.4 to 1.6 g., the weights of the other reagents being adjusted proportionately. With this procedure the pieces of potassium are shiny and relatively free from oxide coating. Alternatively, the potassium cuttings may be wiped free of solvent, quickly weighed in air, and placed in the flask. The submitters recommend that the first procedure be used.
9. Anhydrous magnesium chloride from Alfa Division, Ventron Corporation, was used as supplied by both the submitters and checkers. The submitters have subsequently had success with anhydrous magnesium chloride and bromide purchased from Cerac, Inc., P.O. Box 1178, Milwaukee, Wisconsin 53201. The checkers were unsuccessful in several attempts to prepare suitably active magnesium from analytical grade anhydrous magnesium chloride, purchased from Research Organic/Inorganic Chemical Corporation. The submitters stress that the reagent must be anhydrous. It may be stored in a desiccator containing anhydrous calcium sulfate and, if required, dried overnight in an oven at 120°. Anhydrous magnesium chloride cannot, however, be prepared by heating the hexahydrate under vacuum, since hydrogen chloride is released before dehydration is complete. The submitters have prepared active magnesium from anhydrous magnesium bromide and iodide; however, highly insoluble magnesium salts such as the fluoride or sulfate are not reduced. A small excess of magnesium chloride is used in this procedure to ensure that the potassium is completely consumed. The submitters have also provided the following unchecked procedure, which is suitable for preparing both anhydrous magnesium chloride and bromide. The magnesium turnings and 1,2-dibromoethane used were purchased from J. T. Baker Chemical Company and Aldrich Chemical Company, Inc., respectively. A 200-ml., three-necked, round-bottomed flask equipped with a magnetic stirring bar, two stoppers, and a condenser connected to an argon inlet (Note 6) is charged with 0.35 g. (0.014 g.-atom) of magnesium turnings, 50 ml. of tetrahydrofuran (Note 11), and 3.0 g. (0.016 mole) of 1,2-dibromoethane. The suspension is warmed gently, initiating the reaction. After the initially exothermic reaction subsides, the mixture is heated at reflux for 50 minutes. The solvent is evaporated under a reduced pressure of argon or nitrogen, leaving a white solid. The flask is then evacuated and heated in an oil bath at 150° for 1 hour. The dry magnesium bromide is ready for preparing active magnesium in the same flask.
10. Potassium iodide (>99% purity) from Allied Chemical Corporation or Mallinckrodt Chemical Works is finely ground with a mortar and pestle, dried overnight in an oven at 120°, and stored in a desiccator. The molar ratio of potassium iodide to magnesium chloride is not highly critical and may vary from 0.05 to 2.0. However, the optimum ratio is 1:1, as specified in the procedure. If the potassium iodide is omitted, the black magnesium powder produced reacts with bromobenzene at −78°. However, since the magnesium prepared in this way does not react with fluorobenzene in refluxing tetrahydrofuran, it is evidently less reactive than that produced in the presence of potassium iodide.
11. The submitters purified the tetrahydrofuran prior to use by distillation from lithium aluminum hydride. For a warning concerning potential hazards of this procedure, see Org. Synth., Coll. Vol. 5, 976 (1973). The checkers distilled the solvent from the sodium ketyl of benzophenone. The submitters have found that diglyme and 1,2-dimethoxyethane are also effective solvents. The reactivity of the magnesium obtained with 1,2-dimethoxyethane as solvent is slightly reduced. Hydrocarbons, amines, and dioxane proved to be ineffective solvents, owing to the insolubility of the magnesium salts and consequent incomplete reduction.
12. Efficient stirring is essential for the generation of highly reactive magnesium. If the stirring is not effective, the reduction may not be complete after the 3-hour reaction time. The remaining unreacted potassium is a fire hazard during the isolation of the product. If the scale of the reaction is increased, measures should be taken to ensure that effective stirring can be maintained throughout the reaction period. The submitters recommend that, as a precaution, the scale be increased gradually.
13. The mildly exothermic reduction may result in excessive foaming which carries potassium particles up into the condenser. This problem is avoided by using a relatively large flask (in this case, 200 ml. instead of 100 ml.) and by carefully controlling the temperature at the beginning of the reduction.
14. The reduction appears to be essentially complete in 30–45 minutes. However, a reaction time of 3 hours is recommended to ensure complete consumption of the potassium (Note 12).
15. Although the submitters have found that the active magnesium may be stored under argon for several days, they advise that the preparation be used within a few hours to obtain the maximum reactivity. Most of the reactions carried out by the submitters with the active magnesium were performed in the same flask and solvent used for the reduction. Attempts to evaporate the tetrahydrofuran and replace it with different solvents resulted in magnesium suspensions of reduced reactivity. The active magnesium may be conveniently transferred to another reaction vessel, if desired, as a slurry under an atmosphere of argon.
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[*] posted on 25-12-2006 at 07:39


PCl3 from a metal phosphide is a procedure in Kings Survival Chemistry. Many of the procedures in Kings look suicidal, but this one seems reasonable. I think they use charcoal reduction of calcium phosphate to get the phosphide.

Metal phosphides are used as an agricultural pesticide for gassing burrowing creatures with phosphine. A license is required to purchase in USA.

If your government does not allow you to purchase PCl3, is it legal for you to make and use it? Not that government rules have to be rational...
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[*] posted on 25-12-2006 at 08:12


Quote:
Originally posted by Eclectic
PCl3 from a metal phosphide is a procedure in Kings Survival Chemistry. Many of the procedures in Kings look suicidal, but this one seems reasonable.


It, indeed, seems reasonable but Kings chemistry survival guide should not be used as realiable source (but rather as idea book) because, apart of dangerous, it contains also lot of synths that will give very low yield although they are described as proper high-yield procedures.

Other more reliable sources are needed or someone should try this synth to see what actually happens.

[Edited on 25-12-2006 by chromium]




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[*] posted on 25-12-2006 at 08:38


A license is required from the Ministry of Defense to import or manufacture chemicals on a certain list. That includes PCl3 PCl5 POCl3 and elemental P (white and red). It does not include the corresponding Br compounds or PI3 for that matter. This country (Thailand) is a signatoree of the CWC and so has definite treaty obligations regarding CWC scheduled chemicals. It is not a member of the Australian Group which seeks to expand the coverage of the CWC but so far is just advisory. The Thai MOD list is lengthier than either, but a lot of what is on there is obsolete (obscure WWI arsenicals, no not the Lewisites, I mean things like cacodyl chloride.) Anyway, if I make and use a small qty of PCl3 to make TMP (also on the list) and use it to make the totally unregulated BEDT-TTF who's going to give a damn? I'm not going to stockpile the naughty precursors and I'm not engaged in anything nefarious (no drugs, no energetics, and no chemical weapons.) The trouble these days is that you can't perform a great many procedures that are really routine any more without requiring something verboten.

Banned solvents

CCl4
CHCl3
1,2-dichloroethane
1,2-dibromoethane

banned chlorinating reagents

SOCl2
POCl3
PCl3
PCl5
SO2Cl2
SCl2
S2Cl2

Other banned basic reagents

Acetyl chloride and acetyl bromide
Acetic anhydride
bromoacetic acid and ethyl bromoacetate
ethyl chloroacetate
ethyl iodoacetate

and so on.

Bromine and dimethyl sulfate are on the list but for some reason are still being sold. I am told that the govt does not care as long as the quantities purchased are not excessive (maybe 1 or 2Kg/month).

Chlorine and sulfur dioxide are proscribed. Fluorine and anhydrous HF are proscribed. Chlorosulfonic acid is proscribed.

Dimethylamine is on the list.

Chloroacetyl chloride is not prohibited, but is effectively impossible to ship any more.

It certainly could have been on the list because of its use in Friedel-Crafts acylation of benzene to make CN (phenacyl chloride tear gas, Mace, chloroacetophenone.) Bromoaacetyl bromide IS on the list for that reason, phenacyl bromide is more potent.

So the list is (as usual) rather arbitrary.

Examples of the obscure and irrelevant on the list:

Selenium mustard
Tellurium mustard -- which turned out not to be vessicant at all
sym-dichlorodimethyl ether

Anyway any practicing synthesist has got to spend his/her time dodging all these "unobtainiums" -- here's an example from peptide synthesis. Standard reagent for global deprotection of peoptides in Fmoc strategy is a 5% soln of piperidine. And now almost everywhere in the world, even university labs need to waste administrator time filling out bureaucratic forms to attest that the piperidine is not to be diverted to making PCP. This is even true in countries where there is no abuse of PCP and no clandestine (or other) production. What good is this? Piperidine is not hard to make.

This is all a huge nuisance. And I doubt that it's in aid of anything. Example: acetic anhydride. Because of Thailand's proximity to Burma and Laos heroin production Ac2) is a huge no no here. So even school labs can't have small quantities.

But that hasn't slowed down heroin manufacture one little bit. So what is it in aid of? What good does it so?

No one should feel guilty about bending such a rule.

If I need it I make it and I use it. I don't keep it around and I don't sell it on the black market. I wouldn't know how to make contact with the black market. If I did I wouldn't have any trouble getting red P would I?

Surely these are sentiments shared by most of the people on this board, yourself included?
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[*] posted on 25-12-2006 at 08:47


I never heard of Kings Survival Chemistry. It sounds like a contemporary descendant in spirit of The Anarchist's Cookbook from the 60s (I am an old fart). I used to read that and laugh at the idea that anyone would be foolish enough to take those instructions seriously. We used to joke that the govt must have put it out to kill off clueless radical wannabe bomb makers.
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[*] posted on 25-12-2006 at 09:06


Calcium phosphide as a rodenticide: yes that was clear from Googling it. It also has been employed at some point in the past as an incendiary in aerial bombs. Also in signal flares.

Apart from the technical issues and the cost and the questions unsnaswered on shipping and importation here, I see no reason not to try this.

Same goes for chlorination of P2S5. I started a thread on that, but so far it's gone unnoticed, maybe due to the holidays. I have the stuff on hand, top quality from Merck. When chlorinated will it fall apart to PClx and SxCly? Or will it give a more complex product SxClyPz. I dunno. Anyway it's OT here.
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[*] posted on 25-12-2006 at 09:57


You could try carbon reduction of calcium phosphate in your tube furnace, followed by chlorination in situ. I'd be interested to know if the procedure actually works.

A potential problem might be the formation of a stable adduct of PCl3 with the metal chloride.

This is the ONLY prep in Kings that actually seemed reasonable to me. There is a copy on the FTP site I think...
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[*] posted on 25-12-2006 at 10:21


I seem to recall that there are certain phosphrus compounds that upon hydrolysis fall apart to red P among other products. I will look for th source and see if any of them are accessible by purchase or preparation.

I can also hire local people cheap to cut up vast numbers of matchbook covers like 100,000 of them. If I retrieve 1 mg red P per cover, there's 100 g for the cost of that labor plus some technical acetone (sold here in 22 L tins.) I realize this is footling but, anything else is looking like becoming a magnum opus.
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[*] posted on 25-12-2006 at 11:45


red P is not souble in aceton, in fact, i dont know any solvent
afaik the P only is on the striking surface, not on the match itself
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[*] posted on 25-12-2006 at 12:44


Yes I am well aware. I toss the matches. The match boxes have two striking surfaces and that's where the red P is. The acetone is to dissolve the glue and liberate the P from the adhesive. Time and agitation help. The fine suspension of P gets filtered and the P is ready for cleanup. It is not a high tech procedure.

But thanks for your advice.

What to do with about 5-10 million leftover matches? Laboriously recover a few hundred g antimony trisulfide? Not worth the effort.
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[*] posted on 25-12-2006 at 14:45


Ain't there P4S3 (or P3S4?) in there too? Oughta be something that can be done with it, maybe does it decompose i.e. "dry" distill to P4 + liquid S?

Tim

[Edited on 12-25-2006 by 12AX7]




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[*] posted on 25-12-2006 at 15:38


I already posted on this in the phosphorus chlorides (inexplicably in Organic Chemistry). I think there is a Russian reference somewhere with Zn reduction.

"I seem to recall that there are certain phosphrus compounds that upon hydrolysis fall apart to red P among other products" - I wouldn't think so. But thanks for posting the long preparation for Rieke magnesium. I'm sure we're all going to be rushing to use potassium to make magnesium with your help, or buying his inexpensive products from his company. And thanks to everyone for adding yet another valuable page to this thread.

The [_rl=]words[/_rl] is not working. It used to.

Review http://ep.espacenet.com/advancedSearch?locale=en_ep , typing in C01B25/01, C01B25/02, or C01B25/10 in the European Classification field, if you really want to know P chemistry.

[Edited on 25-12-2006 by S.C. Wack]
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[*] posted on 25-12-2006 at 18:35


Why the apparent sarcasm, S.C.Wack?

I pointed out the note in that procedure that says that Na works in place of K. I doubt I am the only one who has been stymied in buying Mg powder. I am not a shill for any supplier. I'm just another chemist trying to make little ones into bigger one like the rst of us.

Potassium is too expensive and too much of a pain to handle. I have 250 g of it sitting under parafin oil and it cost me dearly. On the other hand I have about 6 Kg Na on hand. Which metal am I more likely to use?

Thanks for the pointer to your post on Zn, which I will go see.

I did find the ref I was after, there are simple P compounds that fall apart to red P and other products but so far none of them appear to be of practical preparative value. If you are interested I can write them up but, it sounds like you would prefer I keep my insights to myself.

I do not fathom the hostility you are putting out.

But, I do appreciate all your work on the Library. So have a happy New Year.
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