Tuco Salamanca inspecting a piece of "meth" (actually mercury(II) fulminate).

Fulminated mercury...and a little tweak of chemistry.
― Walter White explaining his "meth" to Tuco.

Mercury(II) fulminate, or fulminated mercury is an explosive substance with the chemical formula Hg(CNO)2. The substance was used as an example of an explosive chemical by Walter White during chemistry class in the episode "Crazy Handful of Nothin'""​. A bagful of it looks like crystal meth. Later in that episode, he uses a finger sized crystal of it to blow up Tuco Salamanca's headquarters, and uses a bagful of it to acquire $50,000 to cover the stolen pound of meth ($35,000) and injuries to Jesse Pinkman, and negotiate a sales agreement.

Preparation

Mercury(II) fulminate is prepared by dissolving mercury in nitric acid and adding ethanol to the solution.

Silver fulminate can be prepared in a similar way, but this salt is even more unstable than mercury fulminate; it can even explode under water and is impossible to accumulate in large amounts because it detonates under its own weight.

Decomposition

The explosion caused by Walt's fulminated mercury.

The thermal decomposition of mercury(II) fulminate can begin at temperatures as low as 100°C, though it proceeds at a much higher rate with increasing temperature. As with other mercury salts, the decomposition of mercury fulminate is complex, possible reaction for the decomposition of mercury(II) fulminate yields carbon dioxide gas, nitrogen gas, and a combination of metallic mercury and relatively stable mercury salts:

4 Hg(CNO)2 → 2 CO2 + N2 + HgO + 3 Hg(OCN)CN
Hg(CNO)2 → 2 CO + N2 + Hg
Hg(CNO)2 → :Hg(OCN)2 (cyanate and / or isocyanate)
2 Hg(CNO)2 → 2 CO2 + N2 + Hg + Hg(CN)2

Trivia

  • Although theoretically it's possible to grow crystals of mercury fulminate as big as those seen in the episode, especially given Walt's experience in crystallography, it takes time, and a massive amount of mercury fulminate is required for this task, as the compound itself is not very soluble.
  • Whether a piece of fulminated mercury thrown on the floor can generate the explosion shown in "Crazy Handful of Nothin'""​​ is one of the myths tested in MythBusters' Breaking Bad special. When thrown with human force, the 50-gram piece of fulminated mercury they tested failed to explode; though it exploded once fitted with a blasting cap, it did not produce an explosion sufficient to blow out windows as seen on the show. They also determined that any explosion the size of the one showed in the episode would severely incapacitate or even kill everyone in the room, not to mention set off the rest of the fulminate crystals, which would no doubt kill everyone in the room.
    • Likewise, as shown in the same episode, the detonation produces a massive shower of metallic mercury dust, which would cover most of the objects and places in the room. Anything not made of iron/steel, platinum, tantalum or tungsten will soak up the mercury and break down over the course of days, especially if the air moist. The amount of mercury vapors in the room would poison anyone spending long periods of time there, making the building a severe health hazard.
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