The Chemistry Must Be Respected

(Heads up! This post contains spoilers for Breaking Bad and Fight Club. Also, this post is intended to explain scientific principles illustrated by a TV show - it is not an instruction manual. Chemicals such as corrosive acids and bases are incredibly dangerous, and you should not attempt any of the processes described in the post.)

As someone who takes great interest in poisons, explosions and fried chicken, I think Breaking Bad is awesome. I am also aware that some of the inconsistencies on the show are probably intentional, or else we’d all have meth labs in our backyards/laundromats/camper vans. 

However, when watching the second episode I leapt from my chair to point at the screen and shout “HYDROFLUORIC ACID IS NOT A STRONG ACID!” (Yes, I am great fun at parties.) Clearly, whoever wrote that script was clearly not respecting the chemistry.

Let’s go back to the second episode of the first season. We’ve all been in Walt’s situation here - you’ve just poisoned a meth dealer and now you need to dispose of the corpse. Mondays, am I right?

“The best thing to do is dissolving [the body] in strong acid,” says Walt, before pilfering jugs of hydrofluoric acid from his school’s storeroom. But Walt is wrong, for several different reasons.

Hydrofluoric acid is not a strong acid - strong, concentrated and corrosive all mean different things. By definition, a strong acid (a common example is hydrochloric acid, HCl, which is the acid in your stomach) dissociates completely in water, forming charged species - ions - of hydrogen and chlorine. Hydrofluoric acid is pretty similar, but it contains fluorine instead of chlorine, so its formula is HF. The fluorine is strongly bonded to the hydrogen and doesn’t dissociate fully in water, which makes it a weak acid. 

In other words, some of the hydrogens are floating around as ions, but a lot of them are still hanging tight with fluorine.

But when we’re talking about acids, “weak” is not the same as “not corrosive.” Whilst hydrofluoric acid doesn’t fully dissociate in water, fluorine itself is highly reactive, and it gets mighty unfriendly when it comes into contact with glass and many metals. Hydrofluoric acid could most definitely eat your bathtub, your tiles and your ceiling before depositing a dead body in your hallway, but that doesn’t make it a strong acid. Also, it will probably dissolve your bathtub long before it actually decomposes a corpse.

Hydrofluoric acid is perhaps not the best way to dissolve a body. Bodies are made up of bones covered in layers of soft, squishy stuff - a mixture of fat, carbohydrates, proteins and nucleic acids. Hydrofluoric acid, though nasty when it comes to metal and glass, is not the quickest way to break down soft, squishy stuff. (Those later episodes where bodies are shown rapidly decomposing in a barrel of acid are using considerable artistic license.) Fun fact: under the right conditions, acidity can even preserve a body in a manner rather similar to pickling.

A better choice would be sodium hydroxide, also known as “that stuff that Tyler Durden poured on his hand in Fight Club" or "what Mexican drug cartels use." Sodium hydroxide reacts with flesh, turning it into a slimy, soapy mess. This process is known as alkaline hydrolysis, and it can be readily sped up with a little heating and pressure. It's a common way to dispose of roadkill and culled livestock.

Incidentally, alkaline hydrolysis produces no atmospheric emissions and the effluent can be safely discharged into a sewer, so one can rest assured that bodies are being disposed of in a clean, green manner. Yeah, science!

Afterwards, you’ll be left with bones and teeth. If you’re itching to open your giant jug of hydrofluoric acid, here's your chance: fluorine and the calcium in the bones will react together to form a mineral known as calcium fluoride, or fluorite. Except for one last problem with this episode...

You probably won’t have a giant jug of hydrofluoric acid. I don’t know what kind of chemistry class Walt’s running, but I doubt the school knows he’s keeping incredibly corrosive liquids just kicking around in his store cupboard. Whilst hydrofluoric acid is an inefficient way to dissolve a body, it’s actually an effective way to seriously injure or kill somebody. Remember when I said that HF would react with the calcium in bones? Well, fluorine doesn’t discriminate between the dead and the living in its ravenous pursuit of calcium. (I really wanted a picture of a zombie fluorine atom to illustrate this point. However, when I googled "zombie fluorine" all I got was conspiracy theories about fluoridated water being used for mind control.)

Once hydrofluoric acid finds its way into the bloodstream, the fluorine bonds to calcium ions, causing more fluorite formation followed by tissue death.

So, to recap: hydrofluoric acid is a weak acid that's still highly corrosive, sodium hydroxide is a better option for liquefying entire human bodies, and now I'm going to re-watch all of the "Bedridden Hank" episodes and see if there's any fluorite in his rock mineral collection.