An illustrated guide on the preparation of white phosphorus.pdf

7/25/2019 An illustrated guide on the preparation of white phosphorus.pdf

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An illustrated guide on the preparation of white phosphorus (P4) from red phosphorus (P)

By Pyro16 August 2013, 3:48AM

-Introduction

White phosphorus is an extremely reactive and hard to get allotrope of phosphorus while red phosphorus is morereadily available from chemical suppliers or matchboxes.In this article I will describe one of the ways to make the white allotrope from the red.the reaction proceeds as follows:

So if red phosphorus is strongly heated the red phosphorus will convert to white phosphorus, but as the double

arrow indicates, this reaction is reversible so it is important to cool down the newly formed white phosphorus assoon as possible.

This article will consist of three parts:the first on the bending of a regular test tube to make a suitable retort, the second on the preparation of whitephosphorus from red phosphorus and the third on the purification of the crude white phosphorus to analyticalgrade white phosphorus

-Reagents

H2SO4PK2Cr2O7dH2O(the amounts used here are not crucial)

-apparatus

-Hotplate
http://www.sciencemadness.org/talk/files.php?pid=295781&aid=25055http://www.sciencemadness.org/talk/files.php?pid=295781&aid=25053http://www.sciencemadness.org/talk/files.php?pid=295781&aid=25104


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-beakers-clamps and stands-stirring rod-spatula-tweezers-test tube (soda lime or 3.3 borosilicate)-thermometer (ideally built into the hotplate)

-bunsen burner/teclu burner-matches-For the first and second part rubber gloves are not recommended as you are working with f ire and in that caserubber will make burns worse, but in the third they are highly recommended! When I was finished mine smeltseriously like P4.-All the appropriate safety equipment. A lab coat is essential, followed by cotton trousers, closed shoes andgoggles or a faceshield

-Part I---Bending a regular test tube to make a suitable retort

I started with a box of 16mmx160mm soda lime test tubes. I prefer soda lime as it is a lot easier to bend. Manypeople prefer 3.3 borosilicate because it's less prone to cracking due to thermal stress but it's more expensiveand If you heat it properly there should be no danger at all of it cracking

you will need to light the burner and turn it to the maximum setting, then take a test tube by each end and hold themiddle in the upper part of the flame, rotate it for about 1-2mins. You should see the flame turning yellow whereit's touching the glass, now gently pull the two ends apart while bending, this will ensure a smooth bend with nokinks that can collect P4.the finished test tube should be bent between 90* and 100*, the closer to 90* the better. It should look somethinglike this:

but ideally it would be closer to 90*.

-Part II---preparation of crude white phosphorus from red phosphorus

With the spatula, put red phosphorus into the bent test tube. put enough in to get a 2-3cm deep layer on thebottom, then place it in a clamp and suspend it above a beaker of warm water (+-50*C) so that the mouth is as farunder water as possible.

I find it unnecessary to mix SiO2 with the red phosphorus, I have never had problems with bumping.

Now start the burner, you want a gentle flame. I set it so there is a little yellow tip on it so its not too hot. Now holdthe base in your hand and tilt it towards the tube, heat the open end first and work back to the closed end (e.g.from left to right on the above picture).


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As soon as the glass gets hot enough the P will ignite. It is nothing spectacular, just a barely visible yellow greenflame which goes out quickly.

In this picture the P is on fire, it is nothing to worry about

now continue heating, the red phosphorus will turn to P4 and you will see the vapors coming up and condensingin the curved part. The glass there is hot enough to keep it molten so once enough has built up it will run down theglass and drip into the beaker

Here the drops of P4 are condensing and dripping down

Warning!:If you overheat it bubbles of P4 vapor will come out of the test tube, catching firethe effectsrange from a big bang to a gentle fizzing sound but will not occur unless you are careless

The P4 that collects in the beaker will be anything from dark red (almost black) to lemon yellow depending on howcarefully you heat.

cleanup (retort)Now that you have your P4 you need to safely remove it from the water without it catching fire.I have two ways.#1:wait for the retort to cool completely and then get a stopper large enough to block the mouth of the tube, thenput in between a pair of tweezers and insert it into the mouth of the retort, loosen the clamp and remove the retort.Then place it somewhere safe (e.g. concrete, sand,...) and gently remove the stopper and let it burn, usually it justsmokes, but better safe than sorry.

#2: again wait for the retort to cool down completely, then get a pipette and gently start bubbling air into the retort,waiting a few seconds between bubbles. the P4 will smoke a bit and sometimes catch fire. then remove the clampfrom the stand and carry the test tube to the safe spot, holding it by the end of the clamp

-Part III---Purification of the crude P4

when the P4 is freshly distilled it is usually orange with lots of other junk.Half fill a pipette with water and then suck in the molten P4 and transfer it to a beaker of dH2O at 50*C. next add5ml of H2SO4 and then 2 spatulas of K2Cr2O7 and stir for about 5-10 mins. then transfer the purer P4 to anotherbeaker of 50*C dH2O and stir for about 20 mins. by then it should be white. If it is then pipette it off to a cleanbeaker of water, cool it and transfer it to a good bottle.

-results

a bottle of nice pure P4

remember to store it in the dark!

-IMPORTANT SAFETY NOTICE!!!

If you wish to try this you have to know a few things about P4:


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-White phosphorus is EXTREMELY flammable and toxic-Red phosphorus is very flammable-high temperatures are used that can result in severe burns-Chromium waste is hazardous for the environment-CrVI is toxic and carcinogenic-98% H2SO4 is extremely corrosive

-burning P and P4 creates lots of corrosive smoke-any drops of molten P4 immediately catch fire if exposed to air-in parts 1&2 NO gloves, molten rubber/plastic is not nice, I speak from experience (molten nylon)-all cotton clothing, faceshield, closed shoes/boots are very important! also have a respirator nearby. a piece ofburning P4 throws smaller bits of burning P4 around and makes a lot of toxic smoke (I speak from experience

here too )

you do not want to be anywhere near here

Should an accident occur, remember these things:-put 1% CuSO4 solution on the affected area, this will give the P4 a brown/black coating, making it easier to cleanoff any small bits of P4 with tweezers.-Remove affected clothing to minimize risk of re ignition

-soak the affected area in a saline solution and keep it moist-visit a (military) doctor is any symptoms of phosphorus poisoning occur.

from the CDC emergency response card:

Quote:

TIME COURSE: Exposure to white phosphorus may cause immediate burns that heal slowly. Systemictoxicity from white phosphorus exposure is classically divided into 3 phases. The first phase, thegastrointestinal phase, occurs a few minutes to 8 hours following white phosphorus exposure. Shockduring this phase may be severe enough to cause death in 24 to 48 hours. The second phase, theasymptomatic phase, follows the first phase and lasts for 8 hours to 3 days. The third phase, the multi-

organ failure and central nervous system injury phase, may begin 4 to 8 days after the second phasebegins, and may end in death.

EFFECTS OF SHORT-TERM (LESS THAN 8-HOURS) EXPOSURE: White phosphorus burns in air andcauses severe burns upon contact with skin or eyes. White phosphorus smoke will also cause eye andrespiratory tract irritation. Other initial adverse health effects are primarily due to gastrointestinalirritation.

EYE EXPOSURE: White phosphorus fumes cause severe irritation and the sensation of a foreign body inthe eye. This leads to excessive tear production (lacrimation), spasmodic blinking (blepharospasm), andincreased sensitivity to light (photophobia). White phosphorus particles are caustic and seriouslydamaging when in contact with tissues. They cause damage to the cornea, including perforation,inflammation of the interior of the eyeball (endophthalmitis), and abnormal turning out of the eyelid(ectropion).

INGESTION EXPOSURE: Stage 1: Feeling of warmth or burning pain in the throat and abdomen


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accompanied by feelings of intense thirst; nausea, vomiting (emesis), diarrhea, and severe abdominalpain; garlic odor to the breath, vomitus, and feces; vomitus and feces may glow (luminesce) and arecapable of causing burns on contact with skin; death may occur within 24 to 48 hours due to completecardiovascular collapse.

INHALATION EXPOSURE: Eye and upper respiratory tract irritation are expected. Delayed onset of

accumulation of fluid in the lungs (pulmonary edema) is possible. Whole-body (systemic) effects mayalso occur. See Ingestion Exposure.

SKIN EXPOSURE: White phosphorus causes severely painful, partial (second degree) to full thickness(third degree) burns, which have a characteristic yellow color and garlic-like odor. Smoke may bereleased from the burn site from the continued burning of white phosphorus or the formation ofphosphoric acid. White phosphorus is highly fat soluble, and easily absorbed through the skin, possiblycausing whole-body (systemic) effects. See Ingestion Exposure

here are other ways to perform step II:http://www.versuchschemie.de/topic,5774,-Wei%DFer+Phosphor.h...http://woelen.homescience.net/science/chem/exps/RedP2WhiteP/...

Conversion of phosphorus, red to white

This webpage describes how red phosphorus can be converted to whitephosphorus fairly easily. Red phosphorus, although not availableeverywhere, still can be purchased in many countries, while white

phosphorus is much harder to find. For that reason, it may be interesting toconvert some red phosphorus into white phosphorus. The purity of thewhite phosphorus, obtained in this way is fairly good, although it certainlycannot reach the quality of commercial samples. The material, obtained inthis way, however, is perfectly suitable for all kinds of spectacularexperiment with white phosphorus.

This experiment is one of the most riskyexperiments from the chemistry section of thiswebsite, due to the large risk of fire. White

phosphorus is EXTREMELY flammable and verypoisonous. It also is corrosive and can give rise to nasty wounds, which areonly healing very slowly. This experiment MUST be conducted outside, withnothing flammable and valuable nearby, or in a very good fume hood, withglass protection wall. Some vapor of white phosphorus may be emitted.These vapors are intensely poisonous. That is another reason why thisexperiment must be conducted outside.
http://www.versuchschemie.de/topic,5774,-Wei%DFer+Phosphor.htmlhttp://www.versuchschemie.de/topic,5774,-Wei%DFer+Phosphor.htmlhttp://woelen.homescience.net/science/chem/exps/RedP2WhiteP/index.htmlhttp://woelen.homescience.net/science/chem/exps/RedP2WhiteP/index.htmlhttp://woelen.homescience.net/science/chem/exps/RedP2WhiteP/index.htmlhttp://www.versuchschemie.de/topic,5774,-Wei%DFer+Phosphor.html


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The main principle behind this experiment is that red phosphorus, whenheated strongly, decomposes and sublimes in the form of P4molecules.The P4can be condensed on a cooler place to white phosphorus. A specialdistillation setup, capable of handling very high temperatures, combinedwith the use of an inert atmosphere, would be required to perform such asublimation of red phosphorus. On a small scale, it can be done with asimple test tube, which is prepared in a special way.

Required chemicals:

red phosphorus

marble chips (calcium carbonate) hydrochloric acid (needed for "safe" cleanup) bleach or calcium hypochlorite (needed for "safe" cleanup)

Required equipment:

test tube, made of Duran glass hot propane torch clamp for test tube

glass wool


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Safety:

See warnings above, this experiment MUST be conductedoutside!

Disposal:

Any white phosphorus waste (e.g. on test tube walls, in a tub, inglass wool, in tissues) must be destroyed. Nothing may remainbehind, due to the extreme risk of fire.A special section of thiswebpage is devoted to the cleanup after performing the experiment.The cleanup itself also is a rather nasty job, but the final result is asafe situation, without risk of fire.

Preparation of special "distillation device"

A test tube must be bent in a special way, such that it contains the partwhere the red phosphorus can be heated and at the same time it containsthe part where the white phosphorus can condense and can be collected.

The test tube must be one of high quality Duran glass. Ordinary glasscertainly will crack in this experiment, with possibly disastrousconsequences.Duran glass is not easily melted, but with a hot propanetorch this is possible, when the test tube is kept in the tip of a narrowroaring flame. The test tube is slowly rotated and the place which must bebent is kept in the roaring flame. At a certain point, the glass starts glowing.

At that point, the test tube can be bent carefully and slowly. If the bendingangle is sufficiently large, then take it out of the flame and let it cool down.

After cooling down, a similar thing is done with the second bend. Useplastic clamps for manipulating the test tube. Although the glass becomes

amazingly hot at the place where it is bent, near the bottom and the top ofthe test tube it only becomes warm, one can even touch it without gettingburnt. But for convenience and safety it is better to use a clamp formanipulating the test tube.

The final result is shown in the picture at the start of the webpage. The redphosphorus is put in the bottom part of the test tube, the - shaped partof the bent test tube collects the condensed and liquid white phosphorus.


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Filling the "distillation device" and preparing for heating

The bent test tube first must be filled with some red phosphorus, and afterthat, it must be flooded with carbon dioxide. The carbon dioxide can beprepared by putting some marble chips in dilute hydrochloric acid and thegas must be delivered into the bent test tube with a thin flexible tube, whichis pushed into the powdered red phosphorus. Be sure to make a lot ofcarbon dioxide, such that really all air in the bent tube is displaced by thegas. Production of carbon dioxide must not be too fast, otherwise the redphosphorus may be blown out of the test tube.

Immediately after that, put some glass wool in the upper part of the testtube, such that the carbon dioxide does not quickly escape from the tube.Immediately after that, attach the test tube to a clamp in a position as

shown in the picture below.


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At the left, one can see the glass wool (most of it is covered by the clamp),at the right, one can see the red phosphorus, which will be heated.


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The test tube must be loosely closed with a piece of glass wool. Do not usea rubber stopper or a tightly fitting cork. Such a stopper might pop out of thetest tube during heating (pressure buildup, due to expanding gas) and thatwill result in instant fire.

Heating the red phosphorus, making white phosphorus

With the setup as described in the section above, the experiment can beperformed relatively safely. One does not have to fear ignition of thephosphorus inside the test tube. The only real risk is cracking of the testtube, while the red phosphorus is heated. If that occurs, then there will beinstant violent fire and burning drops of phosphorus will be sprayedaround.Be prepared for such an event, and assure that you can quicklystep away if this occurs. Also wear adequate eye protection and leathergloves during the heating part of this experiment.If the test tube cracks,then quickly step aside and let the phosphorus burn. Do not try toextinguish the fire, this is nearly impossible. For this reason, this experiment

MUST be performed outside, at a place where a phosphorus fire cannot do


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any harm. White phosphorus burns are particularly nasty, because burningdroplets are sprayed around all over the place.

In order to reduce the chance of cracking of the test tube, first heat theentire part, where the red phosphorus is up to the bend (the right part of thetest tube in the previous picture, the left part in the picture below). Thisheating must be done evenly. After this initial heating, the flame of thepropane torch must be pointed below the red phosphorus and it must bekept at that place for a while. When this is done, one quickly sees formationof yellow/white fumes.

At a certain point, the flame of the torch must be put to full blast, but the testtube may not become so hot that it melts. Slowly, the red phosphorussublimes and impure white phosphorus condenses in the cooler part of the

test tube, which is the - shaped part of the test tube. The result isshown in the picture below.


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The picture shows the remains of the red phosphorus, which is a black solid(impurity of the red phosphorus, this most likely is another allotrope ofphosphorus, which is much less reactive than red phosphorus) and a liquidblob of white phosphorus, which appears red due to contamination with

small particles of red phosphorus. Also, drops of white phosphorus appearon the upper side of the test tube. These can be heated a little as well, inorder to have all the phosphorus collected into a single blob.

At the end of the experiment, all red phosphorus has sublimed, only someblack crud remains, as shown in the picture below, which was taken fromabove.


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The resulting white phosphorus is shown in more detail in the followingpicture:


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When this situation is reached, then let the test tube cool down, with theglass wool still in its opening.Never remove the glass wool, as long as thetest tube is not completely under water! Opening of the test tube will resultin instant fire!

Working up the white phosphorus, purifying to some extent

When the test tube has cooled down, then take it out of the clamp andimmerse it in a tub, full of cold water. When it is completely under water,then the glass wool can be removed and the water flows into the test tubeand air/carbon dioxide bubbles to the surface of the water. When cold wateris used, then the white phosphorus solidifies. Once the test tube is full ofcold water, it can be taken inside, and further workup can be done inside.The picture below shows the test tube, full of cold water, with the solidifiedblob of white phosphorus and the glass wool also inserted again.


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Further working up can be done in a tub, filled with a layer of 10 cm of warmwater. Take water, which is quite warm, but not so hot that you can't standworking in it with your bare hands.

Keep the test tube still full of water(with the glass wool plugged in and thetest tube kept in the same orientation as when it was heated with thepropane torch!) under a tap with hot running water, e.g. while filling the tub,in which further work up is done. The phosphorus will melt again.


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Next, take a small glass beaker and put this in the tub with warm water. Thebeaker must be completely under the warm water, and a few cm of watermust be above the beaker. Keep the test tube with the molten phosphorusunder water, above the beaker, and then remove the glass wool andcarefully pour the white phosphorus into the beaker.All of this must bedone under the warm water, otherwise instant fire will be sprayed around!

Try to avoid pouring in some of the black crud as well. For this reason, it isimportant that during the melting of the white phosphorus, the test tube iskept in horizontal position, such that no white phosphorus by accident flowsto the bottom of the test tube and is contaminated with the black crud.

Once all phosphorus is in a beaker, the beaker can be taken out of the tub.The raw liquid material at the bottom of the beaker looks as follows:


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A small video shows the material in the beaker under a layer of warm water.It is a fairly mobile liquid, which does not stick to the glass. The video canbe downloaded by clickinghere,its download size is approximately 2MByte.

Further purification by filtering

The white phosphorus, as prepared according to the procedure givenabove, already is suitable for many experiments, but one can fairly easilypurify the liquid phosphorus by means of filtering through glass wool underwater.

Again, all work must be done completely under warm water. Never allow airto come in contact with the liquid white phosphorus!

The white phosphorus does not stick to glass. One can easily suck thephosphorus into a glass pipette with 5 to 10 ml volume. In order to do so,the beaker with the phosphorus must be put under warm water again, andthe pipette also must be put under water, assuring that most air is out of it.Under water, first suck in some water, and then suck in all crude white

phosphorus. Next, while keeping all of the material and the pipette underwater, take a piece of glass wool and keep this in front of the opening of thepipette and then carefully press out the phosphorus above the beaker. Ifthis is done, a lot of solid crud remains behind in the glass wool and thewhite phosphorus goes through the glass wool. Only use a thin layer ofglass wool, otherwise you will have to press too strongly, with the risk ofpressing all of the white phosphorus out of the pipette at once, resulting inmany small globules under the water, which need to be collected again.

After this purification step, the phosphorus still is not white. It has a

brown/yellow color after this purification step, but better results cannoteasily be obtained with the simple equipment, used in this experiment. Theyellow phosphorus, obtained in this way, however, is perfectly suitable forsynthesis work, and also for all kinds of experiments, which require whitephosphorus.

The beaker with the purified white phosphorus can be taken out of the tuband the warm water can be replaced by cold water. With this replacementof water, again assure, that the phosphorus does not come in contact withair.
http://www.homescience.net/chem/exps/RedP2WhiteP/liquidP.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/liquidP.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/liquidP.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/liquidP.avi


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Once the phosphorus has solidified and cooled down to 15 C or so (thetemperature of the cold water), it can be transferred to a petri dish, filledwith water. Brief contact with air now does not lead to instant fire anymore.With a sharp knife it can be cut into smaller pieces, while it is under a thinlayer of water in the petri dish. After cutting, the smaller pieces have to beput in a little vial, filled with cold water. Do not take pieces of white

phosphorus in your hands. The pieces may ignite and cause severeburns.Use a pair of tweezers for transferring the small pieces from the petridish to the vial.

The final result is the following, which is approximately 3 grams of whitephosphorus:


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The solid is soft and waxy. A rounded glass stick can easily be pressed intothe solid. A sharp knife fairly easily cuts the solid.

Cleaning up of all tools, glassware and tub

All items, which have been in contact with the white phosphorus, may have

solidified droplets or globules of white phosphorus on them or in them. It isvery important to thoroughly cleanup any remains of white phosphorus.


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Simply wiping off with a tissue and then throwing away of this tissueintroduces an unacceptable risk of fire, especially on warm summer days.White phosphorus can easily ignite when in contact with air, even at roomtemperature.

As a demonstration of the danger, the glass wool, which was in the testtube during heating, is kept in air for a while. The picture below shows howmuch smoke is produced from this piece of glass wool. Knowing that thispiece of glass wool is completely soaked with cold water makes it evenmore scary. Avideoalso shows this smoking of the wet glass wool.Download size is appr. 1.25 MByte.
http://www.homescience.net/chem/exps/RedP2WhiteP/smoking_glasswool.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/smoking_glasswool.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/smoking_glasswool.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/smoking_glasswool.avi


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Throwing such smoking material in the trash bin, introduces a serious riskof fire. Such a fire may occur, hours later, when most of the adhering waterhas evaporated. All white phosphorus hence must be destroyed.

A sure method of destruction is the use of a bleach solution, to which aslight excess of hydrochloric acid is added. One can also use calciumhypochlorite (swimming pool tablets or granules), which is added to 10times its volume of water, and then some hydrochloric acid is added untilthe liquid becomes clear and green/yellow. Bubbles of chlorine will beproduced in the liquid, as if it were a soda drink. Immerse the glass wool inthis liquid for a while. Also pour this liquid into the bent test tube. The tubalso must be treated with this liquid. Any tissues, brushes or whatever isused for cleaning also must be treated with the chlorine-water. Avoidcontact of the chlorine-water with the skin.

Let the chlorine-water do its work for 5 minutes and then replace it withfresh liquid. During the cleaning up, quite some white smoke may beproduced from specks of white phosphorus, which are exposed to air. Thisis not dangerous, but it looks weird and somewhat scary.

Perform the cleaning action outside, or in a very well ventilated room.Chlorine gas is very poisonous and has an extremely choking odor.Fortunately, its warning properties are good. Even at low concentration,chlorine gas is unbearable. Do not make too much of the chlorine-water at

once, use multiple small batches.

After cleaning, all materials must be rinsed with water, and then thematerials which are thrown away can go in the trash bin. The cleaning fluidcan be flushed down the drain and after this, a tub full of water can be usedto rinse away all chlorine-water.

After one minute of standing in the acidic chlorine water, the bent test tubealmost is free of white phosphorus. Only two spots of white phosphorusremain in this particular situation as shown in the picture. After three more

minutes of standing in fresh chlorine water, all orange/brown spots aregone, and only the black material remains. This is not a problem, the blackmaterial is inert.


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The white phosphorus in action

After all this effort it is nice to see how the white phosphorus burns. It isexceptionally easily ignited, and it burns with a heavily smoking flame. Italso burns while spraying around many small droplets, due to boiling of thevery hot droplet of molten phosphorus. This makes white phosphorus fires

exceptionally dangerous.


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The spraying around is nicely demonstrated by the following picture (which I

did not make myself) of burning a much larger amount of white phosphorus.


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A video also demonstrates theburning of white phosphorus.Only a verysmall piece of phosphorus (just a few mm) was put on the tip of the screwdriver, shown in the video, and ignited. Download size is approximately 3.5MByte.

Discussion of results

Red phosphorus and white phosphorus are different allotropes of the sameelement. Red phosphorus consists of phosphorus atoms, arranged in anirregular pattern of atoms. It is an amorphous solid of irregularmacromolecules. In this arrangement, the atoms of phosphorus are fairlytightly bound to the macromolecules structure and this makes the solidquite stable and inert at room temperature. It also makes red phosphorus(like carbon, silicon, and boron) insoluble in any known solvent. If redphosphorus does dissolve in some solvent, then it is part of a chemical

reaction and it is converted to another compound.

White phosphorus consists of P4molecules with a particular structure, inwhich there is considerable strain in the molecule.

When red phosphorus is strongly heated (400 to 500 C) then the largemacromolecular structures are broken down and atoms of phosphorus
http://www.homescience.net/chem/exps/RedP2WhiteP/burning.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/burning.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/burning.avihttp://www.homescience.net/chem/exps/RedP2WhiteP/burning.avi


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escape from the solid. These combine to molecules of P4and at colderplaces, this condenses on the glass.

The strain in the P4molecules makes them so reactive. White phosphoruscan ignite at a temperature as low as 30 C. Red phosphorus must beheated to at least 240 C before it ignites

Documents

An illustrated guide on the preparation of white phosphorus.pdf