The acid that really does eat through everything

acid burnThanks to the big screen, many of us think of acids as dangerous, burn-through-anything substances.  Think of those scenes in the Alien movies, where the alien’s blood drips through solid metal, destroying everything in its path.

Of course the vast majority of acids are much more boring.  Vinegar (which contains ethanoic acid) and citric acid (found in, guess what, citrus fruits) are common acids that we eat all the time, and they don’t burn holes in your mouth.  There’s an even stronger acid, hydrocholoric acid (HCl), in your stomach and not only does it not burn you from the inside out (usually), it actually helps you to digest your food and keeps you safe from nasty bacteria.

But there is an acid that’s really, properly scary.  And its name is hydrofluoric acid.

Hydrofluoric acid has the chemical formula HF, but unlike HCl you won’t find this one in a school laboratory, and if it turns up in your stomach you’re in very big trouble.  In true movie-acid style it’s capable of dissolving many materials, and is particularly well-known for its ability to dissolve glass (which is mainly silicon dioxide).  It will also dissolve most ceramics (which contain aluminosilicates: compounds made of chemically-bonded aluminium, silicon and oxygen).  And, like many other acids, it also reacts with metals, so storing it is a bit tricky.  Where do you put something that eats through its container? Well, these days it’s stored in special plastic bottles, but in the 17th century when it was first discovered chemists had to use glass bottles coated inside with wax, and hope the coating was a good one.

HF has been an important industrial chemical for centuries.  It’s used to etch patterns into, and clean, glass and ceramics, and also to dissolve rock samples, for example to extract chemicals or fossils from rocks.  It’s also used to clean stainless steel and, in more recent times, to prepare silicon wafers (used to make silicon chips) in the electronics industries.

The chemist Carl Wilhelm Scheele (him again – he just keeps turning up doesn’t he?) was the first person to produce HF in large quantities in 1771.  Scheele is particularly famous for his bad habit of sniffing and tasting any new substances he discovered.  Cumulative exposure to mercury, arsenic, lead, their compounds, hydrofluoric acid, and other substances took their toll on him and he died on 21 May 1786 at the age of just 43.  And that’s why your science teacher was endlessly telling you not to eat or drink in the laboratory.

So why is hydrogen fluoride so nasty?  For starters the gas is a severe poison that immediately and permanently damages the lungs and the corneas of the eyes – lovely. Hydrofluoric acid solution is a contact-poison that causes deep, initially painless burns which result in permanent tissue death. It also interferes with calcium metabolism, which means that exposure to it can and does cause cardiac arrest (heart attack) and death.  Contact with as little as 160 square centimeters (25 square inches) of skin can kill – that’s about the area of the palm of your hand.

And now for a gruesome and tragic tale: in 1995 a chemist working in Australia was sitting working at a fume cupboard and knocked over a small quantity (100-230 millilitres, about the equivalent of a drinking glass full of water) of hydrofluoric acid onto his lap, splashing both thighs.  He immediately washed his legs with water, jumped into a chlorinated swimming pool at the rear of the workplace, and stayed there for about 40 minutes before an ambulance arrived.  (Should you ever need to know, the proper treatment for HF exposure is calcium gluconate gel: calcium gluconate reacts very quickly with hydrofluoric acid to form non-toxic calcium fluoride, rendering it harmless.)  Sadly, his condition deteriorated in hospital and, despite having his right leg amputated 7 days after the accident, he died from multi-organ failure 15 days after hydrofluoric acid spill.  Remember, that was a spill the size of a glass of water.

Because hydrofluoric acid interferes with nerve function, burns from it often aren’t painful to begin with. Small accidental exposures can go unnoticed, which means that people don’t seek treatment straight away, making the whole thing worse.  Do a Google image search on ‘hydrogen fluoride burns’ and you’ll see some images that will really turn your stomach.

So which would you rather meet?  An alien with acid blood and a habit of laying eggs in your stomach or an invisible gas that destroys your tissues and leaves you, if not dead from multiple organ failure, then suffering with horribly disfiguring burns?  You might stand a better chance against the alien…

71 thoughts on “The acid that really does eat through everything

      • well for the people that know the HF and its effect may be a lot, for the people not familiar with such chemicals this may appear rather as “as little as a glass of water”. It all depends on the observer point.

    • Well, no HDPE isn’t particularly special, but I don’t reckon people store HF in recycled plastic milk bottles😉 They make containers specifically for its storage. So they’re ‘special’ in that sense.

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  4. I have been poison’d with hydrochloric acid and need to know can hydrochloric acid be detected thur a hair test or finger nails or toe nails and what can I do to neutralize this hydrochloric acid because I know it is already in your stomach naturally but this is not a natural hydrochloric acid from inside your stomach. Any ideas because I have been to the ER hospital 6 times n had several medical test run and then I read online that hydrochloric acid can not be detected in low levels in your blood and when the doctors do not see anything in my blood they just don’t want to help me but I have been sick since the end of Feb. 2013 n its now Nov. 20, 2013 and my stool has just now turn’d back to a some what normal color but I am still sick everyday. Can anyone help ?

    • I’m sorry to hear about this. How did you come into contact with it? As this material safety data sheet describes, hydrochloric acid is corrosive and will cause serious damage to your respiratory tract if inhaled, and burns and skin irritation in contact with skin. Obviously it will damage your digestive tract if swallowed. If you swallowed it, the problem may be that it caused internal damage (i.e. burns) that have taken a long time to heal. There probably isn’t any more actual HCl in your system, but the internal damage could still be causing symptoms. However, I’m not an expert. You need to speak to someone who deals with poison control.

    • I don’t know how you would be poisoned with HCl acid as it would cause extreme burns, pain and tissue damage if in concentrated form. If you had any elevated levels in your blood stream that would affect its pH and your metabolism would get thrown out of whack; you would not be typing on the computer and would be in serious medical distress, if not worse. The fact your stool was black may indicate stomach bleed from an ulcer or other medical condition. You don’t describe your symptoms, but seem to be able to function with daily activities, so perhaps the problem is not as serious as you suspect. Please elaborate if you are still concerned.

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  6. im just wondering if it were possible that we could probally use HF to maybe cure cancer. Maybe there is a way to somewhat “calm” down or make the substance weaker so that it is able to kill the cancer cells without harming the human body…
    (Im only 15 years old)

    • It’s an interesting idea. Chemotherapy drugs work along these lines: they’re pretty toxic chemicals on the whole, but in the doses taken to treat cancers they’re less harmful to the body as a whole, although they still cause pretty nasty side-effects. They generally work by preventing cancer cells from multiplying by interfering with their DNA. On the other hand, hydrofluoric acid is toxic because it reacts with blood calcium and removes Ca2+ ions from the blood. Without enough of these, your heart stops working. It doesn’t attack cells as such so it wouldn’t work as a cancer treatment. Also, because your blood calcium is so important, it’s extremely dangerous even in very tiny amounts.

  7. I hate reading but I like learning new things so sometimes cant stop reading but I still hate it, but that was a good read. I like that you’ve put a good amount of information in here so well done. Thank you

    • You can buy it legitimately (for example, Fisher sell it), but you will need some kind of evidence that you’re using it for business or educational use. They won’t sell it to an individual. You might be able to get it by other means, but personally I wouldn’t mess about with a less than legit source. Who knows how it’s been stored, whether the packaging is up to scratch… it’s a genuine risk.

    • Plastic isn’t just one thing. There are lots of types of plastic, and some solvents will dissolve some and not others. For example, propanone (acetone) will dissolve polystyrene very effectively, but it has no effect at all on PET (polyethylene terephthalate). So yes and no, but you need to be clear exactly which plastic you want to dissolve.

  8. I have a several light exposures to tyre cleaner and the pain came after couple of hours, now its night and the pharmacist doesn’t work I’m holding the two fingers in ice and water and I’ve drank tons of milk with neskuik high on magnesium so I have a little blue necrosis spot under my nail can I wait till morning or it will be fatal for my fingers?

    • There isn’t really an acid that ‘eats through’ everything (read the blog post:-) But having said that, lots of acids react with iron. Concentrated sulfuric acid, for example, will do a pretty good job of dissolving iron.

      • The last I heard was that it is perfectly OK to transport concentrated sulfuric acid in mild steel tanks such as railway wagon tanks. It has to be really concentrated as it then creates a non-soluble coating on the steel.

  9. Why can HF dissolve glass and certain plastics even though it isn’t a strong acid? Is it so because it is a hydrohalic acid, and does that mean that strong acids such as HCl, HBr and HI are able to dissolve glass and certain plastics?

    • It’s a specific behaviour for HF. HF can dissolve glass because it reacts with silicon dioxide to form silicon tetrafluoride and hexafluorosilicic acid. The other acids you mention don’t react to form the analogous compounds in the same way.

      Now, this is going to get a bit technical but you did ask, so here goes: the reason HF can behave like this is to do with the nature of its chemical bond. Fluorine is a very small atom, and it’s also the most electronegative element in the periodic table. It actually forms quite a strong bond with the hydrogen (it’s stronger than C-C or C-H bonds, for example), so much so that it doesn’t fully dissociate into ions in water – hence it’s a weak acid, albeit a very nasty one. The big difference in electronegativity between the H and the F results in a large dipole on an HF molecule, with the hydrogen having a partial (but sizeable) positive charge and the fluorine having a partial negative charge.

      When HF meets silicon dioxide, the partially-positive hydrogen attacks the electronegative oxygen, which breaks the HF bond producing a highly reactive fluoride ion. THAT then attacks the silicon (which is an electropositive element), and the result is that the Si-O bond breaks and the compounds I mentioned above start to form. Silicon tetrafluoride is a gas at room temperature, and hexafluorosilicic acid is water-soluble, so the result is that the glass appears to dissolve.

      The chloride, bromide and iodide ions formed by the other acids you mentioned aren’t able to attack silicon in the same way, so it’s safe to keep those acids in glass containers. HF can be stored in most hydrocarbon-based plastics: anything where the bonds are non-polar on the whole. Of course, given its extremely nasty nature, no one wants to store it in anything flimsy or breakable, so as a result it’s mostly kept in nice, thick containers made of polyethylene. Perhaps not surprisingly, if you think about it (polar bonds again), PTFE (polytetrafluoroethylene) is slightly permeable to HF, so that’s not the best choice.

    • Well, it’s easily absorbed through the skin and it causes nerve damage which can make the ‘burn’ seem (initially) painless. In the body it binds with calcium ions. Obviously there is calcium in bone, but calcium ions are also crucial for cardiac function – so exposure can lead to heart failure. For these reasons anyone who’s aware they’ve been exposed to it must get proper medical treatment immediately, whether they think they’ve been harmed or not.

    • Depends on the circumstances… steel is mostly iron, and most strong acids will react with iron. If you ground the steel into small pieces and used a concentrated acid, yes, probably. Pouring acid onto a strip of solid steel? No, although it would damage it. In films if they want this effect they use something like polystyrene painted grey and acetone, I’m told.

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  11. I am so glad that I have found your article. Very interesting information. I was wondering why we clean with vinegar. Now I have answer to my question. It is really important everyday to learn something new. Thank you! Best regards!

    • Hm, not sure what you mean? Swimming pool chemistry is complicated but one of the general aims is to keep the water as close to neutral as possible. What do you mean by swimming pool ‘acid’? If you mix acetone with hypochlorite you might form chloroform, is that what you’re thinking of?

  12. The acid that really eats through just about anything is probably fluoroantimonic acid. (HSbF6) Check it out sometime if you want.😛

    • Re rocks,there are many many ways of dealing with them but a lot depends on the rock. In the case of five ton glaciated boulders shaped like a rugby ball, a good way is to drill them then fit an expansion bolt such as a Rawlbolt. The boulders can then be lifted with a crane.and the bolts can be unscrewed and re-used. Another way is to use a thermic lance and burn or melt the rock away. The use of explosives is another possibility and potholers often use nail-gun cartridges for “cave-shaving” (widening narrow passages) One popular way of attacking rocks is to use a rock-hammer mounted on a swing shovel. Unfortunately it is often claimed that the heavy vibration or recoil causes a lot of excess wear on the swing shovel. In the bad old days navvies tunneled through rock using nothing more than hand-operated tools and gun-powder Hammers and star-drills (drills with an X shaped point) were used to drill blasting holes. (Pneumatic drills and dynamite came later) Good luck!

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    • No, and the volume required to even theoretically dissolve that much rock doesn’t exist. Even with heavy-duty drilling equipment, the furthest anyone’s got through the Earth is just over 12 km. The Earth’s crust (the thinnest, outermost layer) is 35 km, so that’s not even half way through the crust. It’s over six thousand kilometres to the Earth’s core.

    • That’s really interesting! Can you tell us anything about it, or is it top secret? Presumably, it’s got a different composition from ‘normal’ concrete? Also, what’s the application? There can’t be that many places that need to be HF resistant, surely?

      • Our A600 Cold Fusion Concrete™ is being marketed and sold into the petrochem industry throughout the Gulf Coast and soon the world. Many giants of the industry have problems with this acid and our product is solving this by being a true-acid resistant concrete.
        Our Cold Fusion Concrete (CFC), is made from waste products like fly ash, ground granulated blast-furnace slag, minerals and other constituents from around the world. Because of that, we can design mixtures using local products from various regions in the U.S., and almost every continent abroad. It’s GREEN as well!
        Our CFC offers tremendous environmental benefits: decreased CO2 output, energy reduction, and preservation of virgin resources, reduced landfill requirements and profound water savings.
        The production of CFC™ cement does not require heating at all. Instead, various minerals and silicates are blended together, resulting in cement that is of a significantly higher quality than Portland cement.
        We can customize the strength of our concrete by balancing constituent materials.
        The ultimate strength can be achieved within 2 hours using electrical treatment or 4 to 6 hours using heat to meet the 28-day strength with normal curing.
        We also have created a better SFRM cementitious product that blows all the competition away when it comes to fireproofing structural steel.

      • Hm, getting into a bit of a sales pitch now, but okay😉 I still can’t imagine there are that many “giants of the industry” who need HF resistant concrete…

  14. A clip from a 1920’s yachting magazine claims that HF is the best acid for cleaning out the water galleries in marine engines. One article advises using a 3 to 5 percent solution and the other advises 10%. The article states “This acid will also dissolve sand and sand cores that were left in by the manufacturer. Leave the acid in for about five hours then rinse out the block and neutralize the acid with soda”,

    It sounds ideal as with it being a weak acid it will not unduly affect good metal but it will attack rust. Allegedly in some countries a very dilute form is sold in supermarkets as “Metal Cleaner”

    Phosphoric acid is far safer and it “phosphates” iron but whether it will do a good job remains to be seen. Modern engines do not run seawater through the block. Instead they use a heat-exchanger but unfortunately that corrodes instead.

  15. HF seems to be a pretty nasty acid, but can it dissolve rubies (corundum), quartz, topaz and diamonds? These are some of the toughest materials on earth. And what about “superman”: fluoroantimonic acid? Very interesting topic you have here going.

    • Good question… HF famously attacks silicon-oxygen bonds. Quartz is basically silicon dioxide, so it will certainly attack that. Topaz contains aluminium, silicon and oxygen, so it would damage that as well. I can be pretty certain that it won’t attack diamond, because although diamond might look a bit like the other gemstones, it’s very different. It’s made of pure carbon, and as a result the bonds in diamond are completely non-polar. HF doesn’t attack non-polar bonds, which is why it can be stored in polyethylene bottles (or diamond ones, I suppose, if you had the resources!) Finally, ruby. Ruby contains aluminium-oxygen bonds, and they are very polar, however I’m reliably informed (by someone that works in the area) that HF doesn’t etch sapphire, and ruby and sapphire have essentially the same chemical makeup. So I’m going to say it doesn’t attack ruby, and actually I did find a website that mentioned it as a test for fake stones: stones made out of glass dissolve in HF, genuine stones do not. Still, I suggest you don’t experiment with grandma’s engagement ring😉

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