Db33
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What is the smell of red phosphorus?
i read something that said red phosphorus is suppose to be odorless... But the red phosphorus i have smells VERY heavily like matchbooks and has a
very distinct strong smell. Which is correct?
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MeshPL
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Red phosphorus has no smell, but its oxidation and hydrolysis products have some odour. By example phosphine. Smells like garlic. And is a deadly
poison. Don't smell it to much!
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Db33
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i got my RP from Mario who is very trusted so im sure what i have is real RP so why does it have such a strong matchbook smell?
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JJay
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There are a variety of tests you can perform to test for impurities. Red phosphorus is insoluble in carbon disulfide and water, but many potential
contaminants will be soluble.
Do you have any information on its grade or a CoA?
I keep thinking about buying some phosphorus. I know a good source, but I'm not sure I am really prepared to flagrantly import a package that clearly
states "1 kg red phosphorus" on the declaration and pick it up from my mail agent with a straight face. If you spend a lot of time researching the
subject, you'll notice that USPS actually defines "domestic" shipping as shipping within the United Nations and has a policy stating that they'll
deliver anything as long as it doesn't present a serious and actual danger to delivery personnel, but I don't think the DEA exactly feels the same
way, even if they categorize red phosphorus as a Special Surveillance item in their chemical handler's handbook. I would expect no trouble from U.S
law enforcement trading phosphorus mixtures that are less than 80% phosphorus as long as they aren't explosive or anything
I was thinking about picking up some TEMPO from Mario... it is fairly hard to obtain yet entirely legal and wholesome.
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MeshPL
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Even if your phosphorus is pure, it may be possible, that merely exposing it to moisture and air for a short amount of time produces enough phosphine,
to cause that odour. You have no other phosphorus sample to compare your red P to. Neither do I, at the moment. When it comes to old phosphorus
samples, the stench of phosphine is often terrible.
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theAngryLittleBunny
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I wouldn't worry too much, I also bought some red phosphorus, and it does have a smell. Many chemicals which are described as oderless actually have a
smell, for instance if you smell KMnO4, it actually smells kinda sweet in a very weird way. That's because the fine particles can actually enter your
nose.
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Db33
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is there a way to test it to make sure its purely rp?
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JJay
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In addition to the ones I already mentioned, It should dissolve fully in 40% nitric acid, and the resulting phosphoric acid should produce no
precipitate with barium chloride.
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Db33
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i dont have any of those substances, if it is real RP shouldnt upon mixing with iodine immediately produce PI3 and then HI gas? So if i mixed it with
iodine, if it was anything else it wouldnt produce a reaction right?
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Melgar
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To piggyback on this: what is the smell of a strong, hot alkaline solution? Say, hot sodium hydroxide solution? It tends to have a distinctive
smell, reminiscent of soap, but I can't really think of anything in it that would be volatile enough to smell that wouldn't burn your sinus tissue.
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JJay
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Quote: Originally posted by Db33  | | i dont have any of those substances, if it is real RP shouldnt upon mixing with iodine immediately produce PI3 and then HI gas? So if i mixed it with
iodine, if it was anything else it wouldnt produce a reaction right? |
That won't tell you if you have antimony impurities... say, I wonder if you can reduce benzylic alcohols by refluxing them in hydriodic acid with
antimony.
https://en.wikipedia.org/wiki/Antimony_triiodide
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Tsjerk
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Washing with an inert solvent probably helps.
The soap smell of concentrated NaOH is probably soap made in your nose by aerosolic NaOH. Also for example chlorine smell can stay in your nose for
days because of stablely chlorinated proteins in your nose.
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woelen
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Commercial samples of red phosphorus are almost always contaminated with a tiny amount of white phosphorus. It is the white phosphorus, which gives it
the typical smell.
Bad quality red phosphorus may contain so much white phosphorus that it can burst in flame in contact with air without any ignition source. Our member
pyro once had this happen, when taking some red phosphorus from its container, the entire lot bursting in flames.
I have purchased 500 grams of red phosphorus a few years ago and it has the typical smell. This red phosphorus is stated to be 98% and the remainder
almost certainly mainly is white phosphorus, "dissolved" in the red phosphorus.
Recently, I purchased 10 grams of 99.99% red phosphorus for my element collection and this did not have the typical smell. I ampouled most of this red
phosphorus, keeping it good for unlimited time.
From another seller I purchased 100 grams so-called 99.95% red phosphorus. But upon receipt of the material the label only stated that it did not
contain more than 0.05% of non-phosphorus impuritities (there was a whole list of possible impurities like As, Fe, Sb, with low percentages behind
them). So, indeed it was very pure phosphorus, but most likely it was not very pure red phosphorus. It had a very strong smell and I am afraid it
contains a lot of white phosphorus.
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Db33
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i have since learned from a very old and trusted chemist that the smell is very natural for whats called Technical grade Red Phosphorus. Basically its
about 80% pure. So it is not as pure as perhaps some other RP but its good enough for any reaction. Its just a bit smellier.
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Sulaiman
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I have a small (<25g) sample of red P from a northern european supplier so just as another two opinions;
. I thought there was a garlic-like odour (my sense of smell is poor)
. My wife thought that it smells like the stuff that is used wrapped in newspaper to ripen mangoes in Thailand, with a hint of matches.
The powder is very fine and I shook it before testing so some superfine dust would have entered our noses.
EDIT: The stuff my wife was refering to was not calcium carbide ... just tested.
[Edited on 13-3-2017 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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JJay
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I haven't seen red phosphorus since they restricted all purchases in the U.S., but I owned 500 grams of reagent grade RP in 2001. I think I paid $30
for it. It was an odorless fine red powder that had a slightly washed-out look compared to other red phosphorus I was familiar with (perhaps due to
its finely powdered form). On other occasions I've worked with it I remember it being clumpier and smellier; I was honestly kind of disappointed with
the inert, odorless, fine powder when I bought it and sold it when the price spiked due to its impending ban. I've kicked myself several times for
that decision.
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Boffis
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The smell of red phosphorus is due to the formation of phosphine from the reaction of traces of white phosphorus present with water from the air.
Water reacts slowly with white phosphorus forming phosphine and hypophosphorous acid:
4P + 6H<sub>2</sub>O → PH<sub>3</sub> + 3H<sub>3</sub>PO<sub>2</sub>
It is the hydpophosphorous acid that make the red phosphorus damp and clumpy. Alkalis greatly accelerate this reaction and most red phosphorous is now
digested in hot alkali and washed before sale to reduce the white phosphorous content.
White phosphorous also undergoes this reaction on long storage, I have some sticks of white phosphorous that were purchased in 1952 according to the
label and I estimate that more than half of the phosphorus has dissolved. I changed the water some years ago, neutralised the old water with sodium
hydroxide and evaporated it slowly to crystallisation. Sodium hypophosphite is demonstrably present in the crystals but so is a phosphate and possibly
phosphite too, so the reality of the reaction is that it is probably more complex than the equation given above or that atmospheric oxidation of the
hypophosphorous acid occurs.
If your red phosphorus becomes damp or smells, boil it with dilute sodium hydroxide solution, filter, wash with copious water and dry in a warm place.
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Db33
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tahts what i was wondering, if washing it or boiling it would do anything to help.
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tsathoggua1
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I actually rather like the smell of red and white phosphorus. Not that I'd go sticking my nose in it or snorting 'hot-railed' lines (or any other
kind of insufflation for that matter) but the smell of safety match strikers, and of red phosphorus, or WP is not unpleasant. The smell of red I find
more pleasant than of WP.
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woelen
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| Quote: Originally posted by Boffis | | White phosphorous also undergoes this reaction on long storage, I have some sticks of white phosphorous that were purchased in 1952 according to the
label and I estimate that more than half of the phosphorus has dissolved. |
This does not sound good at all.
So, if you have white P under water, then you have a ticking time bomb in your lab? The white P dissolves, according to what you say, releasing PH3.
That gas hardly dissolves in water, so you get pressure buildup in a tightly sealed container and then on a bad day, the container says "boom" and you
have your white P in contact with open air, just waiting to ignite spontaneously on a warm summer day.
Are you really sure about this?
[Edited on 21-3-17 by woelen]
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Boffis
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@woelen, I have never read anything that mentions the slow reaction of water and white phosphorus, it is purely my deduction based on the observed
facts. I am not at home at present but when I return I will photograph the remaining sticks; they look like Swiss cheese sticks. What happens to the
phosphine I don't know but you can certainly smell it when you open the jar. Since the reaction is enhanced by basic conditions but slowly produces
acid maybe it is eventually self moderating in the absence of excess alkali. Also the presence of other radiacal suggests that the reaction may be
much more complex and less than the theoretical amount of phosphine may be produced. Another possibility is that oxygen ingress over the years also
limits phosphine production. It would certainly be interesting to know more but the reading I have done of old texts only really deals with the white
phosphorus/ alkali reaction. One way to find out would be to open a phial of white phosphorus that has been sealed in water under an inert gas for
many years.
@suleman: "EDIT: The stuff my wife was refering to was not calcium carbide ... just tested." Could it be calcium cyanamaide? This stuff tends to smell
slightly of phosphine
[Edited on 21-3-2017 by Boffis]
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tsathoggua1
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Tech grade CaC2 often contains traces of phosphides, potentially sulfides, silicon carbide, with CaC2 being around 80% give or take a few percent, its
pretty ugly stuff to be honest.
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woelen
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@Boffis: I express my concern, because I intend to make a sealed ampoule with white P under water as an element collectors item. In a sealed ampoule
there is no exchange with air, so no oxygen can destroy any PH3 formed and in a sealed ampoule there is not the slighted release of pressure. So, in
time there is buildup of pressure from PH3 and on a bad day it will lead to cracking of the ampoule, exposing the white P to the air and leading to
subsequent fire. Only a very small amount of white P needs to dissolve to have considerable pressure in the ampoule.
So, if this is true, then sealing white P under water in ampoules is not safe and could lead to disaster.
I am looking forward to your pictures.
[Edited on 22-3-17 by woelen]
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