2,4-DNPH is used in a practical exam for U.K. students to complete their “A-level” to complete high school. Students would react an aldehyde or ketone with 2,4-DNPH to produce a colored 2,4-dinitrophenylhydrazone. The experiment had been discontinued but was recently reintroduced. Some schools “have retrieved questionable 2,4-DNPH ‘from the dusty back shelves of the chemical store,’ ” Chemistry World says. If the material dries out, it becomes sensitive to friction and shock. Simply removing the container lid could result in an explosion. That’s why the disposal method of choice is a controlled detonation, as also often happens with dried picric acid.
The solid is supplied damp or ‘wetted’ to minimise the risk of dust/air explosion. Keep solid damp at all times. Stand the bottle of damp solid inside a larger container that also contains a little tap water in the bottom (~ 1 cm depth). Label both the inner and outer containers.
If solid may have become dry, do NOT attempt to open the bottle. Contact CLEAPSS.
Or, if you’re not in the U.K., probably whoever handles your hazardous waste disposal.