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Hydrofluoric acid attacks the silicon oxide in most types of glass. It also dissolves many metals (not nickel or its alloys, gold, platinum, or silver), and most plastics. Fluorocarbons such as Teflon (TFE and FEP), chlorosulfonated polyethylenene, natural rubber and neoprene all are resistant to hydrofluoric acid. Hydrofluoric acid is so corrosive because the fluorine ion is highly reactive. Even so, it is not a 'strong' acid because it does not completely dissociate in water.
I'm surprised Walt settled on hydrofluoric acid for his body-disposal plan, when the well-known method for dissolving... um... flesh... is to use a base rather than an acid. A mixture of sodium hydroxide (lye) with water can be used to liquefy dead animals such as farm animals or roadkill (with obvious extensions to victims of crime). The carcass is reduced to a brownish sludge, leaving only brittle bones. Lye is used to remove clogs in drains so it could have been poured into a bathtub and rinsed away, plus it is much more readily available than hydrofluoric acid. The fumes from reacting large quantities of either hydrofluoric acid or sodium hydroxide would have been overwhelming to our buddies from Breaking Bad.
What Is the Strongest Acid? | Common Acids Quiz
Photo: Chemist with a gun but no pants, in the pilot episode of the AMC drama Breaking Bad. (Doug Hyun/AMC)
Comments
“I suspect most chemistry teachers don’t keep big jugs of hydrofluoric acid in their labs”
At least one did. When I was in high school (70’s), the chemistry teacher disappeared several weeks into a new school year. Didn’t resign or get fired — just stopped showing up, apparently having left town with no notice.
Eventually a new teacher was hired, and I became a lab assistant under him. One responsibility was keeping the chemicals storage closet in order. On the floor were kept several big jugs of hydrofluoric acid — far more of it than any other acid we had. The new guy couldn’t figure out why his predecessor had stocked it. There was no conceivable use for it in high school chem, even in small quantities. Hoping to find some use for it, and perhaps a way to dispose of it, he tried pouring a little in a stained porcelain sink in the prep room. It removed the stains. Plus all the glaze on the porcelain. All of us — teacher and lab assistants — were scared to death of the stuff.
As far as I know, the mystery of the missing chemistry teacher and the superfluous hydrofluoric acid was never solved.
I have used HF acid to prepare a porcelain bathtub and ceramic tile for refinishing [this is what the pros use]. It had very little effect on the tub or tile and I was not impressed with it as an etcher.
After I graduated college my first job was in an oil refinery. HF acid was used in a process to remove calcium from crude oil in the refining process. We had to use rubber suits and gloves, special glass lined tanks and on the wall in the lab was a picture of an employee who had used a pair of gloves with a pin hole in the thumb of the right glove. It seems that HF is very active in the concentration used in the refining process. The acid that got through the glove ate his thumb away seemingly from the inside out…
HF eats concrete like it was bread. I suspect that the reader that uses the HF for etching old bathtuhs is using a lesser concentration. And I wonder if the acid has a shelf life in the diluted state?
One lungful of the gas from 70% hydrofluoric acid is enough to kill a person, and getting the same concentration of the acid on just 2% of skin results in death. It is very scary stuff!
I agree that a base such as NaOH would have been a better choice, I suppose dissolving the tub made for better drama…
Geologists use HF to break down silicate rocks. Geochemists will use 20-30 mL at a time to dissolve a few mg of mineral separates to prepare samples for U-Pb dating, for example.
In grad school I had a project that involved breaking down 10s of grams of quartz at a time, so I used HF by the liter, so I was the only one in my department who placed orders for 4 gallon cases of the stuff.
Since it is a weak acid exposure, even to the concentrated acid, does not immediately cause the type of burns a strong oxidizer might.
The problem comes later, as the fluoride ions are a great calcium scavenger. Over time they work their way through soft tissues and attack bone. The solution is to flood the exposure with a source of calcium.
We used to keep tubes of calcium gluconate gel in the lab. A friend was exposed to a tiny amount through a pinhole in a glove; he went to the emergency room later that evening when he became aware of the exposure (near the tip of his finger), and he was treated with a local injection of calcium gluconate…
It is too bad some people here think HF is such a joke. It isn’t! It is extremely dangerous in concentrated form and should be handled as if it were a bomb. HF is a calcium seeker. If it comes in contact with skin it will cause irreversible tissue/bone damage, not to mention the highly toxic effect of the “raw” fluorine ion. I would not even want to work with the dilute form without the proper gear. It WILL eat through glass, porcelain, rock, and metal by the way. Don’t toy with it, or use it unless you respect it!
Although I never used it,I worked in an industry where one of the affiliates in Canada had a tragic accident involving a project worker. He had splashed some HF on his face. The stuff is like the “blob that ate N.Y.”. It took him several days to die an extremely painful death. It literally penetrates into tissues, blanching the surface skin in those areas while doing so. There is little one can do to relieve the pain while the patient is dying.
If one has some (even a little) splashed upon the skin, immediately have a co-worker take the victim to a shower and hose/etc him down with “copious” amounts of cold water for at least a half hour. Injections/infiltrations into the affected skin area of calcium gluconate have been mentioned as a possible antidote, but obviously, there has not been that much practical experience.
The stuff is nasty / lethal… a word to the wise…
I don’t think that NaOH is a good choice. Please remember that during chemical reaction with body and NaOH we have high, basic pH so there is huge chance for creating ammonia, which is dangerous for health even in small amounts.
Unfortunately HF don’t dissolve human body. There is only one chance to do it and I mean oxidation. Instead HF we can use sulphuric acid, which has oxygen. Oxygen can destroy most of chemical bonds between proteins in body.
So in my opinion, if something is acid, it doesn’t mean that it can dissolve body. We need oxygen to do it.
PS. Sorry for my awful language, I’m still learning English
Good insight, Doc. Ya, the chemistry angle is what hooked me to Breaking Bad, so I appreciate the “real” aspect. I only noticed two jugs of HF acid. However, your speculations of a lye based reactant yeilding better results is spot on. My question is: do teachers in high school actually use HF acid for kids, to the extent that they might need a few jugs (looks like 2 1/2 gallons) in a year?
Boy, I know I’m reading too much into this but it is interesting. Thanks!
P.S. – I like your column. Just turned onto it. I will read more in the future
I work in a microfluidics lab, and we use solutions of HF buffered with ammonium fluoride (and other proprietary stuff) to etch micrometer-scale channels in glass and quartz. Our lab, and every lab I know of that uses HF, keeps topical calcium gluconate on hand to apply immediately in the event of exposure. The fluoride ion *loves* calcium, and the idea is to use the calcium in the calcium gluconate to precipitate out the fluoride instead of letting it get calcium from bone, which is what it will do if left to its own devices. This bone reaction is possible because – as the original article mentioned – HF is actually a weak acid, so it mostly passes through flesh as an intact molecule instead of dissociating in water like strong acids would.
While it’s true that HF exposed to just a few % of a person’s skin can cause death, that’s only true for concentrated solutions of it; more dilute ones will instead cause painful burns. Suffice to say that we treat it with respect. We also (fortunately) only work with dilute solutions, both for safety reasons and because concentrated ones produce messier channels; at high concentrations of HF, the kinetically-limited reaction proceeds too quickly, reactants and products can’t be transported to/from etch sites fast enough by stirring, and things get ugly.
I was also flummoxed to see that a high school chemistry storage closet contained a whole bunch of jugs of HF. I doubt any high school would let students anywhere near that stuff, nor would it have a reason to; traditional compounds like HCl and NaOH suit all their acid-base chemistry needs and are far less dangerous.
What makes HF so lethal is the affinity towards Calcium. Any calcium dissolved in the blood stream would become calcium fluoride, solidifying in the veins and arteries and causing pulmonary emboli, etc.
I work in a national lab that uses many acids including HF (48%, 70% conc.). We have to completely suit up with PPE.(Gloves, apron, glasses as well as full hood, sometimes SCBA) We also have first aid traning with calcium glutamate and Zephrin, and if not administered with minuites of a large burn (say 5″x5″). Your a goner.
My fluorine chemist friend says that Hypochlorite (chlorox) is the best/ least fussy way to dissolve tissue. Can anyone second this? My BS chemistry knowledge can’t figure it out.
(I’m just watching this fine series! sorry for being a few years late!)
I would want criminals to use the worst acid
in town also but they do not want obvious extensions
to crime. Criminals would also use the best right!
Your present an ethical issue to crime for the
police to find. Rarely, does society become less
educated in the field of crime.
isnt lye dissolving a bathtube as well?
My guess is that the writers may have taken some leeway, worried about people “trying this at home”.
I use diluted hypochlorite in my job and it readily dissolves tissue. If you heat it to boiling it is incredible. If you provide agitation on top of that you wouldn’t believe it. Put a piece of hotdog in a cup of room temp clorox and time how long it takes to dissolve. Then do it in clorox heated in a microwave, and finally with heated clorox with some form of agitation or vibration. The last one will dissolve the tissue in seconds.
Some of these other posts are crazy.
I’ve only dealt with HF in extremely low concentrations, under a fume hood. And it was just a demonstration to show the strength of the acid.
What if a tanker hauling HF acid wrecked and ruptured the tank, i wonder what the kill radius would be?
Of course depending on the winds, streams, population, and if it the diluted and friendly acid (whats that)!
HF is one of those chemicals that people try to avoid at all costs. It’s extremely dangerous. I have been told that it’s not just the acidid properties of the chemical, but also that it is very volatile and permeates about anything. The way you dissolve the HF into water is by putting HF gas head pressure over water, much the same as HCl. I have much more experience with hydrochloric acid than hydrofluoric acid, and I know how much strong solutions of HCl can off gas. It will put you down on your knees if you are not wearing a respirator. From the training I have had with HF is that it permeates the skin easily and seeks calcium. The effects are accute and long lasting. The fluoride ions won’t stop reacting until they are all used up. There is no equilibrium point, it goes until it’s done. I have also read that it will travel in your blood stream and attack heart valves and such. You may be hurt badly from the immediate exposure, but they must monitor your for hours even days afterward. This is extremely nasty stuff. I do remember, though, my chemistry professor told us if we ever wanted to get rid of a body, HF would do the job. He was a bit of a mad scientist type. If a high school chemistry teacher even has this stuff in a lab, they are putting people’s lives in danger. I don’t seen any reason for that. Many other chemicals out there that show what an acid can do.
My experince with HF comes from my past career in the semiconductor industry where HF is used to clean or etch wafers before and during processing. HF is at “full strength” at 70% just as Hydrochloric acid is 37% at max strenght. HF is best left alone it is very dangerous and can have major health effects lasting well after exposure. If HF contacts the body it goes for the calcium as in the bone, if even a minor amount gets on a hand or finger say not even enough to burn the skin to badley and is rinsed off immediatly you are still in trouble, the stuff is already eating the bone in the contact area and a few days or months later you can suddenly have a broken bone from a minor impact the bone is weakened from calcium depeation and the damage can continue up the bone for a long time, the only solution I am aware of is amputation above the point of progression !!!
The First aid for HF contact was to without delay apply a gel kept at any HF workstation called Calcium Glyconate, ti was in a large toothpaste like tube. The Saftey protocol is to wear at a minimum 2 layers of protection and of 2 different types of material, first were Neopreen or synthetic rubber gloves over the standard clean room latex gloves, and 2 pair of nitrile type gloves , Eye protection required users to not wear contact lenses, and use sealed liquid proof saftey googles, acid bib, and a wrap around style full face Shield, Body protection required two lab aprons one neopreen and one Nitrile acid rated. All of this PPE only was for accidental splashes protection and not for pupose or continued contact with the HF.
By the way the lab used something they called pyrona bath, a mix of conc. sulfuric acid and I think it was High % H2O2 it would completely dissolve any organic or calcium/silicon material in nothing flat, I think its what the “cleaner” in the Little nikita movie used to wash bodies down a drain.
Many chemistry teachers will keep large quantities of acid in order to neutralize solutions after a lab before disposal. When you’re neutralizing the basic product of 20+ students over an entire semester or year, you need a lot of acid.
One big mistake here, is that HF does not work like that. It is not something that “melts” a body like shown in Breaking Bad or Saw 6 for that matter. Even in a 70% concentration, you won’t notice any pain for some time, although by then, the damage is done. This is also one of the things that make it so dangerous. It will of course dissolve a body over time, but HF does not happen fast. 100% Formic or Acetic acid is really good for this, since it does not coagulate, thus preventing and stopping the corrosive and oxidizing effect like a lot of the strong mineral acids do. This is also why NAOH is so good as it is, it does not dry out and keeps reacting.