Summation of the Sciencemadness Phosphorous Thread

May 6, 2012

 

Historical and modern preparations of elemental phosphorus from phosphates are straightforward yet inconvenient for an amateur chemist because they require very high temperatures, provided by charcoal/coal fired furnaces in old methods and by electric arcs in newer ones.

- Polverone(1)

 

The phosphorous thread is long overdue for summation.  Beginning on page 15(2) replies to the thread began including a disclaimer from individuals that they "didn't have time to read" the thread before posting.  In many cases even if this disclaimer was not applied it was apparent that the ideas individuals presented were simply rehashes of old material that would have been obvious if they had just taken the time to read the thread.  This summation covers all replies in the thread to May 6, 2012 and covers 36 pages of posts totaling 897 individual posts.  It is being compiled for the 10th anniversary of Sciencemadness as I feel this thread is particularly significant in the amount of effort put fourth by fellow forum members. 

 

Now for my own disclaimer.  I am somewhat well versed in the literature preparation of phosphorous and have read this thread beginning to end several times.  I also have my own literature references that I will add in parts to backup information already presented.  However all of this is being done through my own lens so to speak and some spelling/grammar has been corrected.  This summation does not substitute for actually going through and reading the thread.  Some information that did not seem important to me may be important to someone else.  Point being I tried to include what I felt was of value, weather this holds true for all instances however remains to be seen.  Pictures from the thread are not included in this summary however all references are hyperlinked to their actual thread where the pictures can be viewed.  Please, I hope you enjoy this and hopefully it will provide guidance to any reader in the future and spare them some headache in the process.

 

-Bromic

 

Table of Contents:

Section 1 - Production of phosphorous from organic phosphate sources

Section 2 - Production of phosphorous from inorganic phosphate sources

- Carbon as a reducing agent

- Aluminum / magnesium as a reducing agent

- Hydrogen

- Zinc

- Other reducing agents

Section 3 - Production of phosphorous from phosphides/phosphine

- Making phosphides

Section 4 - Production of phosphorous from phosphoric acid

- From carbon using microwaves

Section 5 - Miscellaneous methods to produce phosphorous

 

Section 1

Production of phosphorous from organic phosphate sources

 

Organic phosphate sources include bones, urine, excrement, plant matter, anything that once was living or came from a living being.  The earliest isolation of phosphorus was indeed from organic phosphate sources and it was only later that phosphorus was obtained from inorganic phosphates such as calcium phosphate.  Organic phosphate sources are of advantage due to their availability although the downside can be low phosphate recovery and always when working with organic material, stench.

 

Bone meal is available from many  lawn and garden centers as an organic phosphate source but it must be ashed before use.  Bone ash itself is also available from artists supplies where it is used for pottery as well as for some other specialty uses.  After which the phosphate is usually extracted by reaction with sulfuric acid followed by filtering.  This is known as the wet method of producing phosphoric acid.  However after that point the phosphate is removed enough from an organic source that I would categorize it under one of the other headings. 

 

In the opening post of the thread, Polverone gives an excellent summary of the standard process of phosphorus production using organic materials(1):

 

In the 1800s and earlier, phosphorus was prepared by a number of processes. The earliest was that of Brandt, who prepared it from human urine and charcoal. Later methods were variations on the theme of "heat bone ash with charcoal at high heat." The ashes of bones contain considerable phosphorus, combined with calcium and oxygen, that can be reduced to the elemental state with enough heat and a suitable reducing agent (carbon).

I will summarize the method given in Muspratt:

Animal bones are strongly heated in air until all organic matter has been destroyed. The bones are powdered and to every 3 parts of powder are added 2 parts concentrated sulfuric acid and 16 to 18 parts water. This causes some of the calcium in the bones to be converted to calcium sulfate, which can then be removed by decantation/filtration.

The liquid thus obtained is evaporated to a thick, syrupy consistency. It is mixed with one-fourth its weight of charcoal powder, and then it is raised to near-red heat to make it perfectly dry. The mass is transferred into a stoneware or iron retort in a furnace. The retort has a copper tube connected to a heated underwater receiver where the phosphorus can condense without oxidation (and without solidifying and blocking the tube); the gases that bubble to the surface are sent back to the chimney of the furnace by a second, smaller copper tube. The furnace temperature is gradually increased to white heat.

First comes off steam, then hydrogen and carbon monoxide and dioxide, and finally, at bright red heat, phosphorus begins to come over, accompanied by phosphine and CO/CO2 (it is difficult to be sure about some of the exact products because of the archaic and sometimes inaccurate terms used in the text).

Muspratt does not say precisely how long all of this takes, but Wagner's Chemical Technology (1872) indicates that heat was maintained for a long time, up to 48 hours.

 

Although the process starting from bones has been rendered obsolete in industry a recent example(3) of it's use as a demonstration has been found.  The translation of that text(4) is provided below as the original text is in German.

 

Cleaned, boiled and dried chicken bones are burned with a bunsen burner on a fireproof surface and directly heated with the flame until they have turned into white ash.

2g of this bone ash are mixed with 0,5g magnesium powder and 0,5g kieselgur.
The mix is heated in a test tube which is plugged with a glasswool plug. After the reaction has finished, it is left to cool and the glasswool plug is removed in a darkened room and observed closely.  A glow is visible on the glasswool.

When the residue in the test tube is mixed with water, gas bubbles are evolved which self-ignite on contact with air. They are phosphine.

 

In both of these cases it is the unrefined calcium phosphate found in bones that acts as the phosphate source although they differ greatly in the selection of reducing agent. 


Section 2

Production of phosphorous from inorganic phosphate sources
 

Although the emphasis of this section is on different reducing agents for inorganic phosphates, the reducing agent is only one half of the equation (I'm not using that term literally).  The phosphate is just as important as the reducing agent when it comes to making the reduction work as some phosphates are considerably more easy to reduce than others.  Still, in the spirit of categorizing things I am sorting these by reducing agents used.  And there are almost as many different reducing agents as there are phosphates that people have tried.  Please just keep in mind however that one phosphate cannot be swapped directly for another, the reaction might not work at all or it might go much too fast (think deflagration). 

 

  Carbon as a reducing agent

 

Carbon is one of the most time tested reducing agents of phosphates.  The original alchemical preparation relying on urine and other detritus succeeded in making phosphorous due to all of the organic material present which broke down to the carbon needed to carry out the reduction. On the whole carbon reduction requires more intense and sustained heat than other methods of phosphorus production although carbon has the advantage of being as widely available as phosphates themselves.  

 

The reaction between carbon, silicon dioxide, and tricalcium phosphate (the standard phosphate ore) at temperatures of up to 1500°C in an arc furnace(1) is still the standard method to prepare phosphorous.  Although the problem posed to the at home chemist with this operation is great and succinctly addressed in this quote from Polverone(1) "Building a suitably airtight, nonconducting, refractory vessel for an arc furnace is something well beyond my current engineering skills/resources..."  The reactions occurring in this method of preparation can be shown as:

 

Ca3(PO4)2 + 3SiO2 + 5C ---> 3CaSiO3 + 5CO + 2P(gas)

 

Successful attempts to prepare phosphorous using carbon as a reducing agent usually employ the highest of temperatures in the field of phosphorous production.  One of the earliest successes detailed in the thread came from Phosphorous1, his exploits are below(5):

 

I used a mixture of KH2PO4 and homemade willow charcoal with no sand. The retort was made by 'encapsulating' 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 slightly 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...)” 

 

 Although many people have used metal retorts for this process the point made above is valid, unless the whole retort is placed inside of a kiln or the like it does do well to conduct heat away and the heat from a torch is feeble at best to get the reaction going.  The following quote is much more illustrative of attempts on in this thread to make phosphorous(1):

 

I have, a couple of times, tried straightforward phosphate reduction with charcoal and heat. The vessel is a steel pipe with a screwed-on cap at one end and a screwed-on nipple at the other. The nipple has a section of copper pipe inserted in it and sealed with furnace cement. I filled the pipe with a mixture of diammonium phosphate and charcoal on the (admittedly dubious) premise that the ammonium salt would have a lower decomposition temperature and might help the reaction along. Plus it was the only pure phosphate I could find on short notice.

I heated the apparatus with a large gas laboratory burner and had a vessel of warm water to dip the copper pipe into. On my first attempt, I got a lot of strange/unpleasant smelling gases and water condensation at first (I wasn't going to submerge the tube until I was sure something interesting would come out). I also saw some gas leakage around the threads on the pipe. When it looked like the reaction wasn't going anywhere, I removed the nipple/copper tube assembly. I then heated the tube some more just for curiosity's sake. Toward the end I started to see something interesting. The mixture was melting and bubbling out of the tube a bit. I could heat this portion directly with the gas burner, and when I got it red hot I started to see a rather distinctive flame come out of voids in the material. It looked like the flames I'd gotten by igniting red phosphorus (obtained from match box strike strips) and it had the same smell.

After that minor encouragement I figured I'd clean things out and try again, more patiently this time. However, it turns out that whatever hot diammonium phosphate and charcoal turn into, it is hard, insoluble, and tenacious. I had to painstakingly chip/smash slag out of the pipe with a metal rod.

On my second attempt, much later, I kept the copper tube underwater the whole time and tried to be patient with the heating. The gas burner took a while (15 minutes?) to heat the tube up to red heat, and even then could maintain that heat only where the tube directly contacted the flame. It never got hotter than a medium-red. There was a considerable amount of junk deposited in the water - mostly copper salts created by hot/moist exit gases - but no phosphorus that I could see.

 

As mentioned previously, the selection of phosphate is just as important as the selection of reducing agent.  Supposedly phosphorite can be reduced with carbon at 500 to 600°C(59), Strepta performed experiments using aluminum phosphate which has a lower temperature necessary for reduction, 1100°C according to the literature(6).  Strepta's apparatus consisted of a quartz tube heated by ni-chrome wire with a helium sweep though it was later suggested that his helium, being balloon grade, contained sufficient oxygen to decimate his yield(7).  Although a portion of the thread describing the experiment is quoted below(8) I highly recommend reading Strepta's detailed experimental description complete with photos to which the figures listed below point to:

 

The reaction to be tried was: 2AlPO4 + C ==> 2Al2O3 + CO2 + 2P. The authors used equal weights of AlPO4 and C although this results in a large excess of C by stoichiometry, possibly to ensure that all of the AlPO4 is reduced.

I added 4.5 g of dried AlPO4 to 4.5 g of carbon black and mixed this in a coffee grinder for two minutes. I was only able to get 4.7 g (of the 9g total) of this mix into the reaction tube as I wanted it no more than half full. More could have been added by reducing the headspace above the mix and/or by tightly packing the mix.

4.7 g of reactants would represent .6g available P at 100% yield. With a yield of 70% this amount would be reduced to about .4g.

Experimental

When finally assembled and ready, I started the gas flow and let it run about 10 minutes before ramping the temperature to 650 C. After allowing the initial transient to settle, I continued to ramp the temperature in 100 deg increments every 5 minutes. As the temp transitioned from 1050 to 1150 C, the exit portion of the tube darkened and the exhaust gas bubbles burst into flame as they surfaced in the beaker. I continued the temp ramp to 1250 C. After a few minutes at this temp, the probe readings (monitored at the 595 output) became erratic, dropping to as low as 600 and to as high as 1400. I suspected a poor connection in the circuitry or a failure of the 595. After a few minutes, I shut the power off to the controller but left the gas flowing and allowed the tube to cool. As it cooled the readings became steady again and at 250 C I removed the insulation and quartz tube from the galvanized pipe section and unwrapped the kaowool. As I unwrapped the tube it broke into two pieces. (Fig 7) The area under the heating element was extensively cracked, and through handling, another section broke off. I removed the tc probe and found that the Ni-Chrome sheathing had melted and the melt had largely gathered into three globules. One of these had a vitreous solid adhering to it –this appeared to be a piece of melted quartz.

Some phosphorus was evident in the exit section of the tube (Fig 9) but this was not recovered. About 2.7 g of the original 4.7 g of reactants was recovered (Fig 8) and this had not fused but was still a loose powder as described in the article.

Conclusions

It appears that AlPO4 is reduced by carbon in the vicinity of 1100-1150 C as described, although I was not able to confirm the % released (claimed as 72-83% after 1 hr) as the apparatus itself was also reduced to junk. It also appears that a carbon reaction, presumably with O2, is responsible for the extreme temperature excursion experienced.

Another interesting variation (though adding additional layers of unnecessary complexity) of the process(27) (28) involved concurrently passing hydrogen chloride through the mixture of bone ash and carbon.  Of interest is that the reaction appears to take place at red heat.

Improved method of extracting- Phosphorus from Bones.

—LeGenie Industrial describes a process recently patented by II. Cari Mantrand, of Paris, for extracting phosphorus from bones more economically than by the processes heretofore employed. The calcined bones, reduced to a fine powder, are mingled with a sufficient quantity of pulverized charcoal to combine, as carbonic oxide, with all the oxygen of the phosphate. The mixture is placed in an earthenware cylinder varnished on the inside, filling the cylinder to three-fourths of its capacity. The cylinder is then heated red hot, and a current of hydrochloric acid gas is blown into it. The phosphate of lime is immediately decomposed, forming chloride of calcium and carbonic oxide, while the liberated phosphorus is evaporated and driven through a copper tube, which leads into a vessel of cold water, where the phosphorus is condensed. The chloride of calcium, disembarrassed of the charcoal, in contact with sulphuric acid, regenerates hydrochloric acid for a new operation. The labour of pulverizing the bones may be saved by digesting them with a solution of hydrochloric acid; using for this purpose the water of the condenser from the preceding operation.

 

Aluminium / magnesium as a reducing agent

 

The allure of using aluminum for the reaction of phosphates is two fold.  First off, the reaction is exothermic.  Initially it was thought through thermodynamic calculations that the reaction would be self-sustaining although that seems not to be the case as it has not been ignited by a thermite boost(23), still it does overall decrease the energy burden that needs to be supplied.  Secondly the reaction imitates at a lower temperature.  These two boons look great on paper but the temperatures involves still lie on the extreme end of home chemistry and the engineering hurdles are still nearly as significant as they are for the production of phosphorous from the reaction of phosphates using carbon. 

 

The form of the aluminum has been simultaneously cited as unimportant (due to it being a liquid at reaction temperature) to critical, various sources of aluminum from aluminum cans to german pyro dark have been cited as being used for these reactions. 

 

In theory each of these reaction involving aluminum could instead use magnesium.  Magnesium should give higher reaction temperatures (leading to self-sustaining reaction) and possibly a lower initialization temperature however work using magnesium has been limited.  One example is cited in the section on organic phosphates above(3) where the demonstration reduces bone ash to elemental phosphorous using magnesium powder.  One possible complication however is that formulations often include silicon dioxide to displace a portion of the phosphorous and under reaction conditions the magnesium reacting with the silicon dioxide to give magnesium oxide and elemental silicon is a real possibility.

 

Still, all told aluminotheric reduction of phosphate are the only reactions to yield significant and reproducible amounts of phosphorous.  Additionally throughout the bulk of the thread these reactions also take advantage of a specific phosphate, sodium hexametaphosphate.  This material is available over the counter for water softening purposes and contains a high percentage of phosphorous coupled with a low melting point of ca. 550°C(9).

 

In a reference(10) quoted by Polverone(11) the following details are given in a reference over 100 years old:

 

Action of Aluminium on Phosphorus Compounds—Phosphorus vapour when led over powdered aluminium, heated to a dull red beat in a current of hydrogen, combines with it with incandescence, forming a dark greyish-black unfused mass, which is decomposed in contact with moist (normal) air, forming PH3, and leaving a greyish-white powder. It is decomposed also by water, aluminium also by water, aluminium hydroxide and a brownish-black residue being left ; and by acids and alkalis, which dissolve it almost completely with evolution of PH3. The compound remains unaltered when heated in air.

At more or less elevated temperatures, all phosphoric, acid compounds (meta-, pyro-, and ortho-salts alike) are decomposed by aluminium. Metaphosphates, however, undergo the most complete change, according to the equation—

6NaPO3 + 15Al = 6NaAl02 + 2Al2O3 + Al5P3 + P3

The addition of silica effects the release of the remaining phosphorus, thus :—

6NaPO3 + 10Al + 3SiO2 = 3Na2SiO3 + 5Al2O3 + 3P2

Calcium and magnesium salts are as efficacious as those of sodium, but the superphosphates of commerce are not available for the production of phosphorus in this manner. If, however, bone ash be decomposed by hydrochloric acid instead of by sulphuric acid, a material suitable for the purpose is obtained.

Hence phosphorus may be produced, with almost quantitative completeness of yield, at relatively low temperatures...

 

A similar quote from Gmelin provided by garage chemist(16) states: "NaPO3 produced by melting NH4NaHPO4 is mixed with Al powder and heated. Already at red heat, the mass begins to glow and emit P vapors. Other phosphate salts can also be used, even the Ca and Mg salts."  Yet another reference(12) given by pROcon(13) from the same era gives a better indication of what is meant by 'low temperatures' in the above quotation:

 

The applications of aluminum in the arts multiply with much the same rapidity as do those of electricity. The Berichte describes a new method of preparing phosphorus by its use as a reducing agent. The process is so simple that it can easily be illustrated on the lecture table. Hydrogen ammonium sodium phosphate is fused in a porcelain crucible until it is changed into sodium metaphosphate; aluminum turnings are then dropped into the liquid, and the freed phosphorus bursts into flame. Now, if the experiment is tried with a glass tube, instead of a crucible, a slow current of hydrogen being passed over the mixture of the salt and aluminum, the phosphorus distills into the cooler part of the tube without the formation of any phosphoretted hydrogen. The residue consists of alumina, sodium aluminate, and a phosphide of alumina - Al2P2.

By these steps in the process only 30 per cent of the phosphorus in the mineral used can be obtained; but the phosphide is decomposed entirely by heating it with silica, and this may be added at the beginning of the experiment and the reaction proceeds without difficulty and without loss.

It is advised that for the lecture table a combustion tube a yard long be used; two and a half parts of aluminum, six parts of sodium metaphosphate (obtained from heating previously the hydrogen ammonium sodium phosphate) and two parts of finely pulverized silica are placed in the tube, a slow current of hydrogen is passed through, and heat is applied until the reaction begins. This is shown by sudden incandescence, and phosphorus is seen to condense in globules on the cooler part of the tube, at the end where hydrogen escapes.

Instead of this phosphate, any ordinary phosphate may be used, but experimenters are warned not to use the superphosphates containing calcium sulphate mixed with them, such as are used for fertilizing purposes, because the sulphate is suddenly decomposed by the aluminum with an explosion when a certain temperature is reached.

 

Whereas the form of the aluminum used in the reaction varies greatly, the forum of the silicon dioxide is stated explicitly to be finer than sand.  Finer than can be ground.  The finest available.  The silicon dioxide will not liquefy at the temperatures that the reaction initiates at.  Although coarser grades have been used, fumed silica, diatomite, kieselguhr(19) and other very fines sources are usually recommended.  This is considered one of the hurdles to overcome to get good yields with this reaction and usually necessitates prolonged heating and also deters the reaction from being self-sustaining.  However boron trioxide may work in place of silica.  The advantage being a much lower melting point(14).  If too much aluminum is used and no silicon dioxide is used only the phosphide will be formed and no phosphorous will be released(19).

 

Boric acid can be used in place of silica

6NaPO3 + 10Al + 3B2O3 = 6NaBO2 + 5Al2O3 + 3P2

the boric acid melts at about the same temperature as the sodium metaphosphate, the sodium metaborate also has a slightly lower melting point than the silicates.

I did this as a recreational exercise decades ago, no pressing need for phosphorus so I didn't go for production data. Using a mix of Ca and Na metaphosphates with B2O3 and SiO2 resulting in some fairly low melting glasses and seemed to work OK with carbon as a reducing agent; I assume because the reaction mix was fairly fluid throughout the reaction giving better contact between all the reactants. On the other hand it is not self-heating.

 

This bit of information was successfully applied by Strepta(15) on a future run:

 

I tried boron trioxide (from boric acid by heating) in place of silica according to:
6NaPO3 + 10AI + 3B2O3 = 6NaBO2 + 5Al203 + 3P2 and had better yield in terms of less solid residue (ash) after the reaction.

Stoichiometry of the above equation calls for a ratio of calgon/Al/silica of 2.93/1.29/1. I mixed it accordingly and ground it thoroughly in a mortar. The B2O3 is quite hard after it cools and a bit of work is required to pulverize it. The end result is a mix which acts as a fluid, rocking back and forth if swayed and spurting to the top of the tube if the bottom is rapped sharply on a hard surface. Again I took 3 grams of this mix and heated it at the bottom of a pyrex test tube, the other end of which was wrapped with a damp piece of paper towel. CO2 was used a a protective atmosphere and the exhaust was routed through a half full 100 ml cylinder of H2O.


Heating of the tt was via a meker burner. The first noticeable difference in using B2O3 was that the edges of the mix began to shrink and curl before the reaction started, a result of the B2O3 starting to flow.

Once initiated the reaction was, again, self-sustaining, but noticeably slower -12 to 15 seconds- than the 3-4 seconds previously observed with silica.

Yield of P was .265 g from .512 available (identical result from 2 tries). The ash, however, was smaller and almost identical mass in both tries. The residual was .500 g less the initial mass (2.500 vs 3.000). If all the difference is attributed to released P, the efficiency of the reaction is ~98%. the missing 50% P could possibly be lost as P2O5 (quite a bit of gas escapes from the 100 ml cyl. during the reaction.

 

In practice the reaction mixture expands after liquefaction to an estimated 3-4 times the original volume(18) by the end of the reaction.  The slag solidifies at a very high temperature and as such if it reaches the outlet it will plug the outlet.  Making sure the reactants are dry also reduces lost yield to phosphine.  It is also noted that phosphorous comes over last and that the best yields are obtained on prolonged heating.  Another discovery in the thread was that adding a small amount (6-7 wt%) of sodium chloride to the reaction mixture may help 'cut the reaction time in half'(20).  This was postulated to be caused by lowering the viscosity of the melt although it was also noted that the final product obtained from runs using sodium chloride as a flux looked to be of a lower purity(21).  This and many of the other practical notes were documented by Rogeryermaw during his series of reactions following this process. 

 

It should be noted that these reactions all leave behind gross or at least a minimum of phosphide contamination.  As such the presence of phosphine/diphosphine (spontaneously flammable and highly toxic) during the cleanup is a distinct possibility(17) this is complicated by the amount of manipulation needed to clean out the reaction vessel where the slag leftover solidifies to a glass-like consistency. 

 

In terms of application of these teachings here are some selected successful attempts, first from Magpie(22):

 

Today I made a small amount of P according to the following reaction:

6NaPO3 + 10Al + 3SiO2 --> 3Na2SiO3 + 5Al2O3 + 6P

Stoichiometric ratios of the reactants were mixed in a mortar. The Al was 100-200 mesh, the SiO2 200 mesh pottery grade, and the NaPO3 was technical grade. My basis was 5g of P.

I have been wanting to try this for some time but have not been able to find a suitable luting compound to join a ceramic retort to a glass adaptor. I finally settled upon the best candidate that would give me a truly positive seal, yet was releasable following the experiment. This is Permatex high temperature RTV silicone. Previous testing with a ceramic tile/glass slide showed that an RTV seal can be destroyed in about 2 hours with con sulfuric acid at 125C, thereby allowing recovery of the glass piece.

After loading the retort the 24/40 glass adapter was attached using the RTV and allowed to cure overnight. Today the retort was backfilled with argon, placed in a tube furnace, and a 400 mL beaker of water located to provide a water seal for the adaptor outlet.

Over a period of 3 hours the temperature of the furnace was brought up to a maximum of 1300C. Most of the time there was just a periodic large bubble evolved indicating expansion of the gas in the retort. However, at times the bubbling would stop, be erratic, or even form a vacuum of about 1/2" water. During the last 100C or so it seemed like no gas was formed, or any vacuum either.

P never did drop into the receiver as I had intended. When I removed the insulation from the adaptor I found a small pool of solidified P, tainted red from the RTV. Using a bunsen burner I melted the P, picked up the furnace and drained the 4 or 5 drops of waxy, heavy P into the receiver.

 

 Next from Gurson who was able to perform this project at school for a special assignment.  Please check out the original post(25) for a beautiful photograph.

 

12NaPO3 + 20Al + 6SiO2 = 6Na2SiO3 + 10Al2O3 + 3P4

The products reacting were 40 grams in total. NaPO3 was obtained from heating NaNH4HPO4. The remaining glassy stuff was crushed (damn hard it was) and dried in a drier at 80°C. SiO2 were not especially small particles, just made it with HCl and NaSiO3. Al was 100 um.

The reaction vessel looks a lot like BromicAcids's second one. But where he goes for a 'gass ball valve' (or something like that) I used a overpressure of nitrogen of 1.1-1.2 bar.
The reaction vessel is 20 cm long, throughcut 5cm. The steel is 5mm thick. A small pipe for the nitrogenflow is welded on the reaction vessel. That pipe is 6mm through, and 10 cm long. The bottom of the reaction vessel is welded airtight. (It's just closed, don't know how to say that in english.)
The drainpipe for the gasses and P4 was screwed on the top of the reaction vessel. The drain is 20mm through. It is has a 90° bow. From the end of the vessel to the bow is the drain 15 cm, after that 40 cm long. Less heat was transferred to the water then we expected.

 

I used a acetlylene burner for the heating. It melted the outside of the reaction vessel, so you had to be careful not to burn a hole in your reaction vessel.

 

We put the end of the drain under boiled distilled water. In patent 2,050,796 it stated that dissolved oxygen in the water would oxidise the P4, so I boiled it and put in a PE bottle for usage.

The vessel was first heated 15 mins to 400°C to get rid of the H2O which would form PH3/P2H4. (Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol 8) We also added some carbon (tip from Gmelins' to prevent phosfine forming)

After we heated it for about 2 hours the P4 started to came over. The water was becoming a bit whitey, what was supposed to be colloidal white P. After a while some solids were formed on the bottom. The heat was turned off after 3 1/2 hour.”  Gurson (207)

 

The maximum yield of a reaction mixture of 40 grams was 8 grams White Phosphorous. We were able to isolate some 5 grams of white P (measured under water, volume is x ml, should weigh x grams but weighs x+y grams, so y could be white P), and also 1.6 grams of Red P (from whiteP+UV -> RedP)
So the yield was.. 82,5%

 

Finally an early attempt by Cyrus(25), one of the first on the forum that actually isolated phosphorous:

 

Today I tried to make some elemental phosphorus, using trisodium phosphate as a fine powder (all ground by hand, my hand hurt for a while, I must be holding the pestle wrong or something), fine silica, and aluminum, in the form of snipped up wires. There was an excess of Al because I figured it was the reactant that would get mixed and used the most inefficiently.

I heated about 50 g total reactants in the distilling apparatus described in my furnace thread for about 2 hours on "hellfire" :). (the part of the apparatus in the furnace was glowing reddish orange. The only difference from the apparatus I used than the one shown in that thread was that instead of bubbling the exit gasses through a tin can soldered on, which I tried but wouldn't hold water, I put another 90 deg elbow on the end of the pipe and a short section pointing upwards, this part was filled with water.

As the thing was heated, phosphine (so I think) started coming out of the end as a white mist, so I burned it off with my propane torch, it made popping sounds and the mist disappeared.

After this, the water started getting milky, so I figured there was some phosphorus in there, but at the very end of the run, I heated the water up until it boiled, and then dumped what I supposed would be a water/phosphorus mix into a tin can filled with water. All that came out was water. Since the furnace ate a handful of wood or two every few minutes, I had to stoke the fire a LOT, and the only way to add more fuel was to take off the lid, set it down on some bricks, add more fuel, and then put the lid back on. Every time I did this some of the water spilled out. I don't think phosphorus is a good grass fertilizer. :)The furnace is still cooling down (I also fired some pottery) which takes about 5-10 HOURS! Thusly, I cannot check for more details. :(

Although Cyrus didn't initially think he had obtained any phosphorous the next day he found some hidden below the water in his setup(26) although most of it had been floating on the water of clinging to the walls. 

 

 

Hydrogen

 

Hydrogen is able to reduce most phosphates at temperatures significantly less than the temperatures required for aluminothermic or carbon reduction.  Temperatures ranges have been quoted from 350-750°C for these types of reactions(29).  As the reducing agent is fixed for this section the selection of a phosphate is all the more important and the temperatures required vary widely as referenced below(30).

 

For the low-temperature production of phosphorus, the most interesting candidates appear to be phosphates of lead, bismuth, and antimony. The case of silver phosphate is rather interesting too, as its reduction first yields finely divided metallic silver plus phosphoric acid, which appears to be catalytically reduced in the presence of the silver to give free phosphorus.
 
 Other metals may be reduced at even lower temperatures, but they give phosphides or phosphites, depending on metal and conditions, never free phosphorus. I daren't wonder how much harder the reductions would be with hydrocarbon gases in place of hydrogen... yet I do wonder, given the difficulties of preparing pure dry hydrogen from metal and acid as opposed to cracking the valve on a gas line or cylinder.

 

Of course the major complications are getting dry hydrogen and then after that working with this extremely inflammable gas.  There is also the danger of creating phosphine. 

 

Although the general procedure for isolating phosphorous from phosphates by reduction with hydrogen has been around for over a hundred years, most of the experimentation has focused on a more recent patent designed to produce isotopically labeled phosphorous from lead phosphate.  Evil_lurker summarized the patent procedure(32) as this:

 

According to the patent, lead phosphate or Pb3(PO4)2 is reduced under hydrogen or methane (natural gas comes to mind) with hydrogen resulting in the highest yields and methane about 50% of that.

The reaction consists of three stages:

1. The Pb3(PO4)2 is heated up to 300C to drive off any existing water.

2. Once the temp hits 300C the hydrogen is turned on and the tempurature slowly raised to 500C. The hydrogen reduces the Pb3(PO4)2 by ripping off the oxygen molecules and forming Pb3P2, aka lead phosphide.

3. Upon the cessation of evolution of water, the furnace is again slowly raised up to somewhere between 650-800C. According to the patent, small amounts of PH3 are liberated at around 600C. This makes sense, the Pb3P2 probably starts to break down somewhere around 600C and thus liberates PH3, which subsequently start to be reduced to H2 and elemental P at around 650C, so basically at the beginning of the reduction temp the phosphine being liberated is not hot enough to break down.

 

 

Still, the reduced reaction temperature makes this extremely tempting for many experimenters although few have made the attempt.  The most focused attempt to date by Strepta(31) is quoted below:

 

“I attempted the reduction of Pb3(PO4)2 according to the method (H2 reduction of Pb3(PO4)2 @ 700C) in the patent by Rupp, et al. I made a quartz tube furnace from a section of .8” i.d. quartz tubing overwound with nichrome wire from a toaster oven. It is shown in the first photo, with 115v volts applied.

 

The actual color of the energized nichrome was orange, the violet effect apparently a combination of the photo flash and the emitted light. A firebrick has been drilled lengthwise (1 inch dia) through which the quartz tube is fitted and acts as insulation. The temperature in the tube is monitored with a Fluke P 80 inconel immersion type probe embedded in the Pb3(PO4)2 and connected to an ExTech temp meter. The input and output ends of the tube are fitted with natural cork stoppers which stand up to the heat far better than rubber. The cork to glass tube joint is sealed with silicon rubber. To further ensure that the system remains sealed, the ouput tube is run into a beaker of water and produces visible/audible bubbles when everything is working correctly.

The tube is charged with Pb3(PO4)2 also made according to Rupp (except for the ultrasonic agitation). The Pb3(PO4)2 was dryed in an oven and ground to a flour –like consistency using a coffee grinder.

 

The hydrogen is generated by electrolysis using sulfuric acid-water at battery acid concentration, ie, sg =1.275. The anode and cathode are both made from sheet lead (from Home Depot). The cathode is a 3 inch high section spiraled inward for max surface area. A 3 inch wide funnel is mounted over the cathode to capture the H2 and funnel it into a 10 in. long tube which is terminated with a rubber stopper. A glass tube carries the hydrogen out and another hole in the stopper permits a piece of #10 Cu wire to complete the circuit to the cathode. The anode is also sheet Pb and sits immediately above the cathode.

Transformer & rectifier/fan

The 10 inch collection tube permits the generator to produce a sufficient “pressure head” to bubble the H2 through the subsequent H2SO4 and CaSO4 dryer sections.

The container is a tall glass flower vase. When operated (typically @ 6 amps) for an hour, the solution becomes too hot to handle. It also progressively darkens as it produces the brown precipitate, PbO2, as can be seen in the sequence of photos. A strong odor of ozone is apparent during operation.

 

In the experiment shown, about 12 g of the Pb3(PO4)2, prepared as described as above, was placed into the quartz tube against a wad of fiberglass insulation to hold it in place.

The hydrogen generator (6.6 amp) is started and run for about 10 minutes before the heating coil is energized. Heating is begun slowly, keeping the temperature below 400C for the first hour. You can see the moisture from the drying and later reduction condensing in the far section at the output of the quartz tube.
H2O Condensation

After the H2O no longer appears at the end of the tube, the temp is raised to 700 – 750C.
A red film deposit near the output of the tube appears first. Later and further away a yellow film appears. There was also a popping sound and some smoke from bubbles (PH3?) breaking the surface of the water in the beaker.

Last picture is apparatus being disassembled. Only a film of P was produced—no quantity of any significance. The viability of this as a practical technique for producing even laboratory amounts (a few grams) remains to be demonstrated.

 

Mellor in the Sciencemadness library(33) covers many of the older methods of phosphorus production however the reduction of phosphate ores with hydrogen is mostly absent.  However in one of his later supplements the following information is supplied(34):

 

...many phosphates can be reduced by hydrogen at temperatures between 300° and 750°C.  Metals which do not form phosphides, or give phosphides which are easily dissociated by heat, are the most susceptible to this reduction.  In these reactions the metals is formed and the oxygen of the phosphate is quantitatively converted to water.  Lead phosphates are particularly easy to reduce by hydrogen.  For example, pyromorphite, 3Pb3(PO4)2*PbCl2, starts to react at 300°C and is completely reduced at 850°C.

 

Also from the same source the decomposition temperatures of various phosphates with hydrogen are listed with bismuth phosphate being the lowest (425°C), silver phosphate being second lowest (425°C), antimony phosphate (450°C) third lowest and lead phosphate fourth lowest at 575°C.

 

Zinc

 

Zinc has been proposed by several posters for various advantages, real or not.  Theoretic runs though the advantages(35) as he sees them in the thread: "zinc can be a gob instead of a powder, it's a much less vigorous reducer than Al and so the reaction can't get out of hand, there are two components instead of three (phosphate and zinc as opposed to phosphate, Al and SiO2), the reaction isn't stopped by a tough oxide layer, is faster and goes much nearer to completion."  However  some of this may be complicated by the volatility of zinc oxide(36).  Still, there are literature references to the use of zinc in this reaction although it's ability to compete with other reducing agents is dubious(37) as seen in the following quote:

 

The Franck patent that the aluminum reduction method is based upon also mentions the use of zinc as a reducing agent. I have seen a mention much earlier, in the 1855 book Outlines of Chemical Analysis: Prepared for the Chemical Laboratory at Giessen By Heinrich Will, Daniel Breed, Lewis (Google Books) that metaphosphoric acid or metaphosphates will liberate phosphorus when heated before the blow-pipe with a bit of zinc.

I have verified without recovery (like the aluminum sheet experiment) that chopped bits of zinc will cause the liberation of phosphorus from hot fused metaphosphates. Even lead will do it. I think the critical point in going from demonstration to production isn't going to be the reducing power of the metal (within reason), but ensuring that the kinetics and conversion efficiency are optimized for production. Good mixing may strongly influence that (good mixing, or ensuring that oxides are fluxed away to keep exposing fresh metal to the melt).

 

 

Other reducing agents

 

The following methods were mentioned in passing during the course of the discussion.  They were not investigated any further although they may prove useful.  The work has simply not been done.

 

Madscientist (38) -

Vulture mentioned in another thread that CaC2 would make a good reducing agent in such a reduction as phosphate reduction.

I suspect that sodium polysulfide would work well in a phosphate reduction.

4Na3PO4 + 2Na2S2 ----> 8Na2O + 4SO2 + P4

 

 Sedit (40) -

Has anyone ever experimented with fusing Hexasodium metaphosphate with Sodium acetate? I did a little while ago just messing around and the mixture liquefied rather quickly and a strong smell of garlic was released. It seemed like the NaOAc was acting as a rather good carbon source and a flux because once the melt was fluid there was a large release of Phosphorus at a pace much faster the I have seen in the past using a number of the following.....powdered carbon, powdered Aluminum, Magnesium(the most potential IMO) I can't help but wonder if Sodium acetate could become very helpful in creating White phosphorus.

 

 

Section 3

Production of phosphorous from phosphides/phosphine

 

The forum has seen much discussion regarding phosphides and phosphine however no practical attempts have been made due to the intense toxicity, delayed effects, and spontaneous flammability.  Garage chemist seems to be one of the greatest proponents of this method(41) (45).

 

Heating PH3 results in the splitting off of hydrogen to form solid, yellow lower phosphines. At higher temperatures, I am sure those will completely decompose into the elements.
As phosphorus has a boiling point of 280°C and you will be working at a much higher temperature, the P will condense as a liquid on the tube walls as the reaction gas exits the hot zone. Just like the unreacted 900°C sulfur vapor from my CS2 synthesis condensed as it left the tube furnace.

 

Disproportionation of phosphine is appealing because preparation of phosphides may prove easier than making phosphorous directly from phosphates and an active metal although no one has yet to attempt to prepare phosphides intentionally.  Beyond thermolysis the methods of converting phosphine to phosphorus as discussed in the thread are few.  One recent example however involves the reaction of phosphine with dimethylchloramine(42)(43)(44).

 

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.

 

Another option to decompose phosphides to phosphorous that has been discussed is the high temperature decomposition of phosphides directly to phosphorous although no literature references have been mentioned(46):

 

I think that at the very least the following will occur, considering that cupric chloride decomposes relatively easily into cuprous chloride and chlorine:

4Cu3P2 ----> 4Cu3P + P4

 

Another attack at copper phosphide involved the availability of copper-phosphorous rods for welding.  These rods contain a phosphorous/copper alloy and it was suggested that similar to dissolving phosphorous in lead and electrolyzing the lead away to leave behind red phosphorous it could be done using these rods(47).  Later research however revealed(48) that the phosphide would oxidize at the anode giving dissolved hypophosphate solution. 

 

Additionally phosphine will also react with aqueous solutions of nickel salts forming nickel-phosphorous alloys however the use of these alloys in the isolation of phosphorous is unknown(49)(50).

 

Preparation of phosphides

 

Providing there is a reasonable way to prepare phosphorus from phosphine there is a need to make phosphides for feed stock.  That being the case there has been some discussion on making phosphides intentionally.  Some phosphide preparations are available over the counter for control of moles and the like although these only contain a few percent of phoshide at best.  In some countries different versions are available however where the phosphide is prepared by a thermite-like reaction between phosphate and aluminum(19), these would make a better feed stock for this phosphine if available additional information can be found in this quote by garage chemist(52)

 

The patent you attached is about the usage of phosphine as a poison against rodents, and about a mixture that creates calcium phosphide in-situ in order to avoid the strict legal regulations that alkali and earth-alkali phosphides are subject to due to their highly poisonous nature and ready hydrolysis to phosphine even with aerial moisture.


A mixture of an alkali or earth-alkali phosphate, like Ca3(PO4)2, and aluminum powder, burns similar to thermite when ignited and leaves a slag that consists of Ca3P2 and Al2O3.

 
With moisture of air, earth or by contact with liquid H2O, 1g of the slag that burning a mixture of 43% Al and 57% Ca3(PO4)2 gives produces 72ml of gas (PH3) that imparts a lethal phosphine concentration to 3 - 5 cubic meters of air.


Due to the admixture of Al2O3, the mixture hydrolyses much slower than pure calcium phosphide.

 

Phosphide mixtures prepared by aluminothermic reduction however are going to be nearly impossible to separate so would need to be used as the slag obtained from the reaction(53).  However there are several literature references for phosphides such as zinc phosphide(42)(51) as follows:

 

In our lab Zn3P2 was prepared by thoroughly grinding a mixture of 3.8 g pure Zn3(PO4) 2 and 1.6g specpure carbon in a pulverizer. The powder was then transferred to an alumina boat which  was subsequently heated in a vacuum furnace. After completion of the heat treatment the samples were quenched to room temperature by blowing cold air over them for about 5 min. A schematic diagram of the tubular vacuum furnace designed for this purpose is shown in Fig. l. A facility has been provided in the furnace for heating the samples under vacuum, as well as in an inert atmosphere. Materials obtained by this method after continuing the reaction for 16 h in vacuum have exhibited only the prominent lines of Zn 3 P2- Zn3 P2 was also prepared by carbon reduction of Zn3(PO4)2 in air and the yield of Zn3P2 was very poor; it also contained some unreacted Zn3(PO4)2, and so only the material prepared under vacuum/inert atmosphere was used as starting material for crystal growth and film preparation.

  

Although reaction conditions are not mentioned, one method to iron phosphide and subsequently phosphorous is provided below (39) it is unknown if this method of isolation, by heating a phosphide with sulfur to free the phosphorus would work with other phosphides but it would be open up a large window of opportunity.  In addition to the reference below there is a second reference in the thread to using sulfur to free the phosphorous from zinc phosphide (64) (65).

 

...and R.A. Brooman heated a mixture of silica, iron, coal, and calcium phosphate so as to form a fusible slag and iron phosphide. The latter when heated with sulphur, hydrogen sulphide, carbon disulphide, etc., furnished phosphorus.

Inorganic and Theoretical Chemistry: pg 740

 

Section 4

Production of phosphorous from phosphoric acid

 

Phosphoric acid can be reduced to phosphorous with either active metals or with carbon, similar to phosphates.  However there are advantages, the liquid nature of phosphoric acid allows a paste to be made beforehand that is thoroughly admixed and the liquid reaction medium can help speed a reaction.  Additionally temperatures quoted in the literature point to a lower initiation point than with mineral phosphates(16):

  

When an evaporated leachate of bone ash with H2SO4 is heated with charcoal in a porcelain tube, P evolution begins at 740°C, the largest part of P goes over at 960°C and at 1170°C a 92% yield is obtained.

 

By-products of these reactions include water, carbon monoxide, and phosphine.  Phosphoric acid is noted in some sources as being oxidizing such as this one quoted by madscientist(54):

 

The pure acid is a colorless crystalline solid (mp 42.35C). It is very stable and has essentially no oxidizing properties below 350-400C. At elevated temperatures it is fairly reactive toward metals, which reduce it, and it will attack quartz.

 

Polverone is the man who spearheaded this area of research wtih a vengence.  During the course of his inital investigations he prepared a large quantity of phosphoric acid / carbon and used this as the basis for reactions with zinc powder, silica powder, aluminum, and lead.  Highlights are detailed below.

 

From zinc powder / silica powder / phosphoric acid / carbon (36):

 

I tried mixing zinc powder and then zinc powder plus silica powder with the acid charcoal. Both of these reactions went very poorly. I didn't notice any increased production of phosphorus; in fact I couldn't see any production at all since the zinc volatilized and left opaque oxide coatings on the inside of the tube, but neither could I see any white smoke in the light, so I don't think much P was being produced. Some zinc phosphide was formed, evidenced by the scent observed upon adding hot water to the cooled tubes.

 

From aluminum / carbon / phosphoric acid (36):

 

Aluminum worked much better. In the first attempt, I placed cut-up pieces of a soda can's pull tab in the bottom of a test tube and poured the acid charcoal over it. This showed the most rapid and easy production of phosphorus, giving a healthy green combustion front racing up the tube as soon as the bottom reached red heat. The rate of reaction slackened considerably after that first burst, but it was still considerable compared to my earlier efforts. All of the successful reactions leave a white ring (presumably of phosphorus oxides) at the point in the tube where the combustion front spends most of its time; this one's white ring had some visible thickness by the time I was done. I scraped it with a bamboo skewer and the residue seemed to absorb water from the air. This showed an acid reaction with litmus (unsurprising).
 
 For the final reaction I ground 400 mesh aluminum (the only sort of particulate aluminum I have) with the acid charcoal and loaded it into a test tube. There was some exotherm and funny smells even before I applied heat. I ran a very small batch, less than 1 gram of mixture, because I was wary of what might happen in the event of a violent reaction or accidental tube break. The reaction actually seemed harder to initiate than the one using chopped-up soda can bits. It never got as vigorous either, but it did all right.

 

From silica powder / carbon / phosphoric acid (55):

 

I had a lot of acid-impregnated charcoal left after my last experiments. So I maintained heating all night. Today it was slightly less damp than yesterday, but not much. Anyway, I tried again with the charcoal, this time grinding in some silica powder. There was a little bit of phosphorus production. It wasn't much, but it was steady as long as I kept the base of the tube at a bright orange. I can't imagine how many hours it would take to get 100 mg out of a test tube like this, even if I could collect the phosphorus instead of burning it.

 

 From lead wire / phosporic acid(56):

 

2 g of lead wire were placed in a borosilicate test tube along with 1 ml of 85% H3PO4. This was heated in a propane torch flame, carefully at first as water was driven off. Heating was increased, and the lead melted under the acid. After a couple minutes a thin stream of whitish smoke started wisping from the test tube. The smoke had the characteristic smell of burning phosphorus. It occurred to me after a bit to turn off the light, and I saw a mysterious and beautiful site: there was a greenish light appearing about halfway down the test tube. The light moved up and down the tube as the heating was increased and decreased in intensity, probably representing the rate of production of flammable vapor vs. its interaction with the atmosphere. After admiring the green glow for a few minutes, I broke off the experiment.

 

From carbon using microwaves

 

Microwave heating of phosphoric acid and carbon has promise in that both are able to readily absorb microwaves.  The issues to be encountered in this process are aptly described by Polverone(58):

 

The reaction takes place at much lower temperatures than the conventional arc furnace process. The problem (or problems), of course, is that the phosphorus still needs to be protected from oxidation, you need a relatively heat-resistant and microwave-transparent reaction vessel, and it's going to be tough to condense and collect the phosphorus if you're trying to come up with something using a domestic microwave oven.

 

That being the case there is little research done in this vein but there is plenty of talking.  Garage chemist can be quoted as saying "I think that the microwave heating of a charcoal/phosphoric acid mix to produce white phosphorus is the most promising home method for phosphorus production."   Citing that even silver can be melted in a microwave using carbon as a microwave absorbent(61)One member, Halogenstruck actually attempted a small scale reaction (57):

 

I MIXED 100% extra mole/mole charcoal powder and 85% H3PO4 then i put it at the bottom of a test tube, covered by a thin glass wool layer, upside-down inside a cup of water.
 in first 4 or 5 minute, a lot of gas was evolved. but 16min was necessary to allow P ring comes down the tube.
 because P releases very fast but immediately because of heat turns to red/violet P.
 red/violet P melting point or sublimation temperature based on wikipedia is between 416 to 590C.
 therefore it does not come out easily as mixture does not warm very well and needs lengthy heating in microwave to get warm enough all the area inside.

 

The holdup also seems to be making a proper reaction vessel for microwave use as the microwave is easily able to heat the mixture to temperature.  A lot of the discussion revolves around US Patent 6207024 posted by Polverone.

 

Section 5

Miscellaneous methods to produce phosphorous

 

And then there are the rest.  Although the vast majority of the methods to prepare phosphrous are shown in previous sections there are a few that defy the listed classifications. 

 

Electrolysis is one of the more off-beat methods of isolation.  In the thread two different electrolysis procedures are mentioned.  The first is the electrolysis of bone ash (calcium phosphate) in molten cryolite (sodium hexafluoroaluminate)(60).  The second method comes from Gmelin and is by electrolysis of molten sodium hexametaphosphate with a nickel cathode(16).

 

Another interesting reaction noted was what sodium hypophosphite decomposed when heated to give phosphorus and phosphine among other products(62).

 

Red phosphorous is produced by using mercury to reduce phosphrous (III) bromide over the course of several days in a Parr shaker(63).

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  49. Chemical Elements and their Compounds Vol I 1962 Sidgwick pg 730

  50. BromicAcid.  (2004, September 10). Preparation of elemental phosphorous [Msg 98]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=4 (Direct Link)

  51. K.R. Murali, B.S.V. Gopalam. Preparation of Zinc Phosphide: JOURNAL OF MATERIALS SCIENCE LETTERS 5 (1986) 989-990

  52. garage chemist.  (2007, April 7). Preparation of elemental phosphorous [Msg 283]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=12 (Direct Link)

  53. Vulture.  (2002, October 13). Preparation of elemental phosphorous [Msg 21]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65 (Direct Link)

  54. madscientist.  (2002, October 18). Preparation of elemental phosphorous [Msg 26]. Message posted to http:/www.sciencemadness.org/talk/viewthread.php?tid=65&page=2 (Direct Link

  55. Polverone.  (2005, September 7). Preparation of elemental phosphorous [Msg 160]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=7 (Direct Link

  56. Polverone. (2005, May 10). Preparation of elemental phosphorous [Msg 136]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=6 (Direct Link

  57. Halogenstruck. (2010, April 8). Preparation of elemental phosphorous [Msg 483]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=20 (Direct Link

  58. Polverone. (2002, June 28). Preparation of elemental phosphorous [Msg 2]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65 (Direct Link

  59. BromicAcid. (2004. Febuary 13).  Preparation of elemental phosphorous [Msg 56]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=3 (Direct Link

  60. BromicAcid. (2004. Febuary 9).  Preparation of elemental phosphorous [Msg 53]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=3 (Direct Link

  61. garage chemist. (2006. December 26).  Preparation of elemental phosphorous [Msg 254]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=11 (Direct Link

  62. garage chemist. (2007. January 29).  Preparation of elemental phosphorous [Msg 271]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=11 (Direct Link

  63. Sauron. (2006. December 24).  Preparation of elemental phosphorous [Msg 226]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=10 (Direct Link

  64. S.C. Wack. (2006. December 26).  Preparation of elemental phosphorous [Msg 252]. Message posted to http://www.sciencemadness.org/talk/viewthread.php?tid=65&page=11 (Direct Link)

  65. Zhurnal Prikladnoi Khimii 44(2) 429-33 (1971)