The science of Breaking Bad: 4 Days Out

Breaking Bad : Season 2 : Episode 9: “4 Days Out”

Walt prepares his biggest batch yet.

Walt prepares his biggest batch yet.

Walt’s latest prognosis does not look good, and he decides to accelerate his plans to provide for his family by cooking as much as he can in as short a time as possible. In this post, I’ll be talking about batteries.

You can read more about this episode at AMC, IMDb and the A.V. Club.

Random thoughts

So the methylamine is “losing its chemical potency”, eh? If Jesse had paid more attention when Walt was teaching him, he might know that methylamine solutions are fairly stable if kept away from air and sunlight.

There is a nice cooking montage in this episode, showing Allihn-type condensers in reflux operation. Walt and Jesse are also using aluminium foil for something, presumably as an easily-removed catalyst.

Having escaped certain death from dehydration, Walt had better drive extremely carefully now that the Winnebago has no brakes.

Batteries not included

Oddly enough, making a new battery out of the chemicals in the lab was the first thing I would have tried – either that, or trying to charge Walt’s phone using the generator. In any case, Walt builds a fairly functional mercury battery and lives to cook another day.

At the cathode, mercury oxide (Walt calls it mercuric oxide) is reduced to mercury with the help of electrons arriving through the external circuit:

HgO + H2O + 2e → Hg + 2OH

The powdered carbon from the brake pads is there to conduct electrons to the HgO molecules, as pure HgO is an insulator. Elemental mercury is also a highly poisonous liquid, and the presence of a fairly inert powder helps to stop it pooling.

At the cathode, zinc (galvanised materials are coated with zinc to prevent rusting) is oxidised to zinc oxide and generates electrons:

Zn + 2OH → ZnO + H2O + 2e

The water and OH ions are supplied through the potassium hydroxide (KOH) electrolyte, which is effectively a solution of K+ and OH in water (H2O). We therefore have two cycles – H2O and OH through the electrolyte, and electrons through the external circuit. The overall cell reaction looks like this:

Zn + HgO → ZnO + Hg

So the reactions at the anode and cathode balance each other out, giving a continuous flow of electrons through the external circuit. We can visualise the complete reaction like this:

Walt's mercury battery.

Walt's mercury battery.

A typical mercury battery has an open circuit voltage of 1.35 V, and Walt made six of them for a total of 8.1 V. A standard car battery has six 2.1 V lead-acid cells for a total of 12.6 V. Is this enough for a jump start, or did our cooks just get lucky?

For background information on this topic, see the primer on redox.

Elements in the credits

Breaking Bromine
Bad Barium
Created Chromium
Bryan Cranston Bromine
AnNa Gunn Sodium
AAron Paul Argon
DeaN Norris Nitrogen
Betsy Brandt Beryllium
RJ MitTe Tellurium
BOb Odenkirk Oxygen
Krysten Ritter Krypton
KelleY Dixon Yttrium
Robb Wilson King Tungsten
MiChael Slovis No such element
Dave Porter Polonium
Sharon Bialy Sulfur
SherrY Thomas Yttrium
Sam Catlin Calcium
StewArt A. Lyons Argon
Melissa Bernstein Beryllium
John ShiBan Barium
Mark JOhnson Oxygen
Karen Moore Molybdenum
MicHelle MacLaren Helium
Vince Gilligan Vanadium

I’m not sure why Michael Slovis wasn’t assigned iodine (I), carbon (C), hydrogen (H), sulfur (S), oxygen (O) or vanadium (V).


11 Responses to The science of Breaking Bad: 4 Days Out

  1. Sprinkles says:

    They might be using the aluminum foil as an aluminum amalgam to reduce the imine of phenylacetone and methylamine… check this out:

    You’ve got a very very good blog!

    • John says:

      That’s almost certainly what it is – got to give the writers credit for doing their research! I assumed that Walt would have been using a platinum catalyst, but maybe mercury is less easily traceable.

  2. Sprinkles says:

    Yes, for a platinum reduction you need hydrogen inside a stirred pressure vessel, an aluminum amalgam dosent need that because nascent hydrogen is generated in situ and that reduces the schiff is base to the drug.

  3. Sprinkles says:

    I checked the literature over the net and the aluminum amalgam method seems like the method of choice for old school meth cooks, not a surprise since mercury thermomethers and aluminum foil can be get at any supermarket. The people at AMC do their homework!

    Keep the good work with the third season that starts this month, because you’ve got a fan here and sorry for my bad english!

  4. mtskeptic says:

    I would think they had sulfuric acid on hand, battery acid is 65% water & 35% sulfuric acid (according to the interwebs) you can add it to the electrolyte wells in the battery. Kinda dangerous but so’s building a mercury battery.

    • John says:

      Yes, that might have been worth a try – the electrolyte becomes more dilute as the battery depletes, so increasing the H2SO4 concentration might give it some more life.

  5. Kesmark says:

    In 4 Days Out, Walt refers to the cathode as positive and the anode as negative. Instead, a cathode is negative and the electricity flows out from it.

  6. Kesmark says:

    Thanks, John. I double-checked my comment, unfortunately AFTER I posted, and read just that. I appreciate your correction.

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