Lead Picrate (2,4,6-Trinitrophenol, lead salt) Laboratory Synthesis:
It is widely known that Picric Acid should not be allowed to contact metals or their salts due to the danger of formation of metal picrates. Metal picrates are salts of Picric Acid formed by the addition of the metal to the 2,4,6TriNitroPhenol ring at the first hydroxide, as seen on the example to the left (PbO-C6H2(NO2)3 or PbC6H2N3O7). They are all, to some degree, explosive. Their explosive strength is lower than Picric Acid’s own (between 48 and 70% depending on the particular salt), but their sensitivity is much greater, increasing with the weight of the particular metal ion used. For curiosity’s sake I experimented with making a few metal picrates and testing them to evaluate their properties. The most interesting one was Lead Picrate, which’s synthesis I outline below for informational purposes only.
Metal Picrates are sensitive explosives and as such should not be manufactured at all!
C6H3N3O7(aq) + PbO(s) => PbC6H2N3O7(s).
Here all the chemicals used in the synthesis are seen, from left to right, back to front: Picric Acid, Lead Monoxide Methanol, 50mL glass beaker, spatula, glass rod.
The picric acid is dissolved in Methanol and heated until no solid remains. It forms a yellow colored liquid, to which an equal amount of Lead Monoxide is added. The methanol is heated further until boiling commences and stirring is maintained.
Shortly after the mixture begins to boil a reaction takes place which thickens it. Lead Picrate has thus formed. Boiling is continued until the solution becomes a thick emulsion. It is than filtered and washed with Methanol until the residue from the wash is colorless. The filtrate is than allowed to dry.
Lead Picrate forms into a yellow/rust colored powder once it has been dried. Heating at 100C for 2 hours is reported to increase the product’s stability, as it converts it from monohydrate to pure lead picrate.
The product is sensitive to shock (2cm fall from a 2 kilogram block causes detonation in 50% of the attempts (Urbanski), flame, and friction. On burning, it deflagrates violently with a bright yellow flame and large amounts of lead metal vapor are released. Click on the picture to the left to watch the 98Kb .mpg video of a small amount being burnt unconfined. Confined deflagration transits easily into detonation (DDT) which makes this product suitable for use in detonators and/or blasting caps.
Questions? Comments? Suggestions? E-mail me!