Sciencemadness Discussion Board

Brady's Reagent hazards

Wrecking Bereserker - 27-6-2019 at 11:22

2,4-dinitrophenylhydrazine/Brady's reagent/Brosche's reagent actually caused some uproars a few years back about it being shock sensitive and explosive right?what are your experience with it and what is your take on it being in a highshcool chemistry lab
And yes I've seen the periodic video

Ozone - 27-6-2019 at 15:03

I used to use DNPH all the time for EPA method 8315 (aldehydes and ketones via RP HPLC of the adducts). Because it was regulatory (and often trace-level), any background (which is always in DNPH, as provided--formaldehyde, in particular) was unacceptable. So, as per the method, I recrystallized the stuff prior to use (often in 10s of grams), and had no problems.

I've handled it dry (it should be kept as a moist solid, but sometimes you really can't wait and need to purify some of that old stuff...), but carefully...nothing happened, but I can't say it'll be safe in your hands.

That said, I think it's safe enough to handle without too much worry (usual PPE, don't eat it or set fire to it, etc.). It would be perfectly safe to use if provided as a dilute solution (e.g. no student contact with the neat material)--excepting potential toxicity/flammability of the solvent (I made it up in acetonitrile)...which can be worked-around (note that alcohols typically contain some small amount of aldehyde, especially methanol--not a lot, but it matters for analytical work).

Note, the reaction with aldehydes/ketones is pH sensitive, and runs best in acetate buffer at pH 5 (formaldehyde) or citrate buffer at pH 4.5 (pretty much everything else).


Chem Science - 28-6-2019 at 14:15

Here's a video of Periodic Videos About Brady's Reagnet.
Personally i synthesized brady's reagent and never had any problems, but it has been reported detonations and working carefully is the best option. I never used it dry, always in solution in ethanol/H3PO4.And i store it in glass vial in a Zip-lock bag in the fridge.

unionised - 29-6-2019 at 12:52

I used it for roughly 20 years. The first thing I did with the stuff- as purchased with 30% water- was to crystallize it from acetonitrile and I usually kept the stuff dry.
I never had any problem with it.
But the thing about explosives is that just because I got away with abusing it doesn't mean you will.

Tellurium - 30-6-2019 at 09:53

I also used the dry powder before and didn't have any problems. Maybe it's the same exaggeration as with dry picric acid, that got disposed from schools using a bomb squad(Which at least in my country was all the time they found it). Sometimes they even let it explode controlled in the outside of the building using a main charge, because they said transportation would be too dangerous :D I think most of us know, that even with a good blasting cap you have difficulties igniting Picric acid, so friction and slight impact will do NOTHING.

Maybe it's the same for DNPH, but to be honest I haven't done any impact or sensitivity test with it, as I don't have anything here. So just be careful handling it and everything will be ok ;)