turd
National Hazard
Posts: 800
Registered: 5-3-2006
Member Is Offline
Mood: No Mood
|
|
*cry* My P_red decomposed! *cry*
A few years ago I stored some 100g of perfectly fine P_red in a metal can. Yesterday I dug it out just to discover that there are holes in the can and
the phosphorus transformed into a sticky gooey mass. Worse: it doesnt seem work in HI/P-reductions anymore.
What happened?
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Some of it oxidised into P2O4 (P4O10 whatever) which absorbed water to to give phosphoric acids.
Try stirring it with water , letting it settle, and decant off the water. Repeat several times, then dry the remaining red P.
|
|
|
turd
National Hazard
Posts: 800
Registered: 5-3-2006
Member Is Offline
Mood: No Mood
|
|
Sounds plausible, but I wonder why the HI/P-reduction failed completely?
I've never done this before - do I have to dry it under vacuum to prevent more oxidation?
|
|
|
garage chemist
chemical wizard
Posts: 1803
Registered: 16-8-2004
Location: Germany
Member Is Offline
Mood: No Mood
|
|
Boil with NaHCO3 solution, then filter and wash with water, dry without heat, and store it airtight from now on. Red P is air-sensitive and gets
sticky and wet very quick when exposed to air.
|
|
|
Maya
Hazard to Others
Posts: 263
Registered: 3-10-2006
Location: Mercury
Member Is Offline
Mood: molten
|
|
That doesn't make sense, why do matchbook strike covers not get sticky when exposed to air?
\"Prefiero ser yo extranjero en otras patrias, a serlo en la mia\"
|
|
|
hashashan
Hazard to Others
Posts: 255
Registered: 10-10-2006
Member Is Offline
Mood: No Mood
|
|
they are coated anyway so they arn't exposed to air directly.
|
|
|
halogen
Hazard to Others
Posts: 372
Registered: 18-4-2004
Member Is Offline
Mood: No Mood
|
|
If they were coated so as to be impervious to air, than how does it have such an effect on matches as can only be supplied by contact with red P ?
F. de Lalande and M. Prud'homme showed that a mixture of boric oxide and sodium chloride is decomposed in a stream of dry air or oxygen at a red heat
with the evolution of chlorine.
|
|
|
hashashan
Hazard to Others
Posts: 255
Registered: 10-10-2006
Member Is Offline
Mood: No Mood
|
|
when you slide the match on the box you grind down the coating also
|
|
|
Zinc
Hazard to Others
Posts: 472
Registered: 10-5-2006
Member Is Offline
Mood: No Mood
|
|
But then there is no coating at that place so it should oxidise there but it doesn't.
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Red phosphorous freshly made has some white phosphorous left mixed in with it. This is removed by boiling with aqueous alkali, a shorter boil will
leave a bit of white phosphorous behind. For chemical applications this generally isn't a problem, but if left exposed to air the white phosphorous
portion slowly oxidises, leading to the results that started the thread.
Boil for a longer time period and more of the white phosphorous is removed, making it stabler in air, but raises the cost.
|
|
|
Maya
Hazard to Others
Posts: 263
Registered: 3-10-2006
Location: Mercury
Member Is Offline
Mood: molten
|
|
Ha! You can also make incredible amounts of poisonous phosphine gas this way!
\"Prefiero ser yo extranjero en otras patrias, a serlo en la mia\"
|
|
|
Zinc
Hazard to Others
Posts: 472
Registered: 10-5-2006
Member Is Offline
Mood: No Mood
|
|
I think that phosphine is pyrophoric.
|
|
|
Maya
Hazard to Others
Posts: 263
Registered: 3-10-2006
Location: Mercury
Member Is Offline
Mood: molten
|
|
EXACTLY!!!!!!!!!!!!!!!!!!!!!!!!
give the man a cigar
Drop a small lump of white P into a NAOH soln and watch the smoke rings!!!!!
Classic, I much prefer WP to RP
\"Prefiero ser yo extranjero en otras patrias, a serlo en la mia\"
|
|
|
turd
National Hazard
Posts: 800
Registered: 5-3-2006
Member Is Offline
Mood: No Mood
|
|
Thanks everybody. I could recover some of the P by washing with water. Lesson learned.
| Quote: | Originally posted by not_important
Red phosphorous freshly made has some white phosphorous left mixed in with it. |
Mine was commercial, I don't think it contained appreciable amounts of P<sub>4</sub>. I'm a fan of DIY, but making some 100g of P_red?
Ugh. :S
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
