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 - 29-4-2007 at 12:43
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 - 29-4-2007 at 12:50
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 - 29-4-2007 at 14:51
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 - 30-4-2007 at 08:13
That doesn't make sense, why do matchbook strike covers not get sticky when exposed to air?hashashan - 30-4-2007 at 09:19
they are coated anyway so they arn't exposed to air directly.halogen - 30-4-2007 at 14:44
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 ?hashashan - 30-4-2007 at 23:13
when you slide the match on the box you grind down the coating alsoZinc - 1-5-2007 at 02:05
But then there is no coating at that place so it should oxidise there but it doesn't.not_important - 1-5-2007 at 03:01
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 - 1-5-2007 at 07:24
Ha! You can also make incredible amounts of poisonous phosphine gas this way!Zinc - 1-5-2007 at 09:20
I think that phosphine is pyrophoric.Maya - 1-5-2007 at 15:29
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 RPturd - 4-5-2007 at 08:38
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
