Jor
National Hazard
Posts: 950
Registered: 21-11-2007
Member Is Offline
Mood: No Mood
|
|
rxn of P4 with Na in benzene
Until i can start with my project on ibuprofen (I think a few more weeks) I am doing some random experiments. Next week I want to try to make some
sodium phosphide, by dissolving some white phosphorus in warm benzene under a dry CO2 atmosphere and covering it with a watch glass to prevent escape
of the benzene/CO2. Next an excess of sodium (activated by short immersion in a IPA/ligroin mixture, followed by a rinse with ligroin) will be added.
I expect a reaction, albeit a slow one. Does anyone have experience with this? Would the rxn likely be quick, would it be very very slow, or do you
expect no reaction at all? I don't have CS2 and not toluene yet, so that's why I chose benzene as solvent, as ether is too flammable and chlorinated
solvents can't be used with Na.
Also, is a solution of white P (say a 3-4% solution) in benzene above the autoignition point of pure white P also pyrophoric?
|
|
|
woelen
Super Administrator
Posts: 7981
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
I do not expect a solution of white P in benzene to self-ignite, not even well above the autoignition point of white P.
I have done quite a few experiments with white P dissolved in CS2 and even fairly concentrated solutions of this do not self-ignite before really all
CS2 is evaporated. E.g. if you put a few drops of this solution on paper, then the CS2 evaporates, but before the final last bits of CS2 have
evaporated takes well over a minute. Only then there is self-ignition, so there is a fairly long delay between applying the solution of white P and
the moment of self-ignition. I expect your experiment to be safe with respect to this.
Last weekend I tried another reaction, Mg + red P to make phosphide and I mixed in MgO to make the reaction slower. Even if more than 50% of the
volume of the powder mix is MgO, there still is a VERY violent reaction (yellow light was emitted by the reaction mix, once it was ignited). But after
the reaction there indeed is phosphide. The PH3, coming from this Mg3P2 (by adding it to dilute HCl) did not self-ignite when it came in contact with
air, but it very easily can be ignited. It burns with puffs, each puff giving a cloud of white smoke.
|
|
|
AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
Posts: 1986
Registered: 2-3-2011
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by woelen  | | But after the reaction there indeed is phosphide. The PH3, coming from this Mg3P2 (by adding it to dilute HCl) did not self-ignite when it came in
contact with air, but it very easily can be ignited. |
Interesting, all the sources I have read state that the phosphine (PH3) produced by acidifying phosphides spontaneously ignites on exposure to air,
suppossedly due to traces of P2H4 in the gas. I wonder how it is that the phosphine from your procedure is apparently free from any P2H4. Or perhaps
all those articles exaggerated the pyrophoric nature of phosphides. Sometimes there is no substitute for a real experiment.
|
|
|
woelen
Super Administrator
Posts: 7981
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
I think that there is a CHANCE of self-ignition of the material. Sensation-seeking writers then change this into there WILL be self-ignition. I expect
that if I repeat my experiment many times that once every few times there is self-ignition.
A similar experience I had with phosphine made by heating white P in a solution of NaOH. I did this experiment to show self-ignition, but the
self-ignition proved to be very unreliable.
|
|
|
Jor
National Hazard
Posts: 950
Registered: 21-11-2007
Member Is Offline
Mood: No Mood
|
|
I did the experiment today. To a 50mL roundbottom flask was added a stirbar followed by 5mL of benzene. A small piece
(I think about 50-100mg) were added to the benzene. The system was briefly purged with dry CO2 (conc. H2SO4 + NaHCO3), but probably not thoroughly
enough that the system was oxygen free. Next the solution was heated at 50-60 C with an oil bath (the neck of the RBF was covered with a watchglass)
untill all P4 dissolved (some red dirty polymeric stuff remained undissolved).
Next 3 small peices of sodium were activated with 1:1 IPA/Ligroin, washed with ligroin and quickly added to the flask. This resulted in some bubbling
(moisture in the benzene reacting with the Na). As I saw no formation of black sodium phosphide, I added one more piece of white P. Stirring the
solution for a few hours at RT gave no formation of black material, so the benzene solution was poured in the organic waste bottle 
The solution still contained dissolved P4 as when a few drops were put in a 10mL beaker and left to evaporate, smoke of oxides of phosphorus were
formed as a white smoke when the benzene evaaporated.
|
|
|
Random
International Hazard
Posts: 1018
Registered: 7-5-2010
Location: In ur closet
Member Is Offline
Mood: Energetic
|
|
If you need phosphine, you could generate it with sodium hydroxide reaction with white phosphorus, or white phosphorus could react with acid.
Also I saw some type of reduction of calcium phosphate to phosphide in Kings Guide to home chemistry experiments.
There is also on wikipedia that aluminium and phosphorus can be ignited to make aluminium phosphide.
Be very careful if you try anything of that though, it could be explosive reaction with toxic fumes.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
