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Picric Acid

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Author	Topic: Picric Acid
Zanx Frequent Poster	posted January 09, 2000 09:44 AM I made some picric acid using the aspirin method (which I don't suggest, as I got a poor yield, although maybe it's because of the impurities of my chemicals), and then I tried to purify it using Mega's method at his site. ("To purify, dissolve the picric acid in 1 L of boiling water per 15 g of crystals, filter while hot and allow to cool slowly. Any heavy droplets of brown oil which dissolve slowly during this boiling should be discarded."-From Mega's site) I dissolved approximately 3.8 g (it should be 3.75 g)of the picric acid in 250 ml of boiling water, filtered while hot, and than allowed the filtered solution to cool. Nothing has crystallized out yet, and it's at room temperature, and has been for hours. My question is, how can I get the picric acid to precipitate out of the water. Could you boil away water until it gets so concentrated that the picric acid crystallizes out? Would that be dangerous, and would it even work? Maybe I am just a fool and I did something wrong in the purification process. Please point out any mistakes I have/might have made. Should the solution be cooled even more or for a longer period of time? Thank you for any help.
nbk2000 Moderator	posted January 10, 2000 12:44 AM Boil it down in a glass (NOT METAL!) container. Freezing won't do it. You shouldn't have done any more to it than a slight wash with ice cold distilled water in the filter. ------------------ "The knowledge that they fear is a weapon to be used against them." www.50megs.com/nbk2000
Zanx Frequent Poster	posted January 10, 2000 08:04 AM Thanks NBK, I boiled it down in a beaker and it crystallized nicely.
megalomania Administrator	posted January 15, 2000 02:39 AM Recrystallization is more of an art than a science. Sometimes things go horribly wrong (I am reminded of a chemistry comic strip where the crystallization fairy appears at night to taunt chemists with glimpses of crystal land, wher all lost crystals go). Try the standard, cool in ice bath, scratch beaker surface with stirring rod, add a seed crystal, and perhaps try dissolving in a minimum amount of solvent instead (ethyl alcohol will dissolve picric acid good). ------------------ Visit Megalomania's Explosives and Stuff at http://surf.to/megalomania
Zanx Frequent Poster	posted January 15, 2000 07:31 AM Ok, cool. Thanks Mega. Would isopropyl alcohol (70%) dissolve picric acid also?

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