I’m watching Alien right now and they’ve just discovered its blood is acid. Hollywood has taught me that contact with acid will disintegrate matter or, if a whole person is dipped into it, turn him into a villain.
What are the effects of acid? How fast do the worst common acids burn through matter, if they do? How does it happen?
Do extreme bases have a similar effect?
Real acids do not work that way!
Ahem … sorry, I channeled Morbo there for a second.
You could start with Wikipedia. Briefly, acids are a class of ionic compounds that ionize to release a H+ ion. (Not really, but that is the shorthand basic chemistry uses to describe the phenomena.) The hydrogen ion is very reactive to many materials, but what it will “eat” through depends more on this reactivity that some abstract concept of “strength”
Here’s one that really confused the kids in school – common acids don’t attack plastic – even though I could burn that plastic with a flame or glass – even though I could smash a glass vessel to pieces with a hammer. Some metals (like zinc, magnesium and aluminum) are attacked by acids, but dense strong metals that we build durable structures out of, like prison bars, are not particularly reactive – plot line of Prison Break notwithstanding. Or else acid rain would be constantly, gradually, weakening the structure.
An acid either puts a proton on what it touches or takes away electrons. In the case of Alien, it protonates things, because the aliens, AFAIK are water based. The resulting protonated species are transient and will rearrange. Some acids, like sulfuric, can work very fast. Sulfuric will actually heat up and cause physical burns in addition to protonating things. Hydrochloric acid is not too bad. There are stronger acids than sulfuric. They can become very difficult to handle.
Yep, bases (alkalis) are on the other side of the spectrum as acids and can be just as caustic, depending on what they’re reacting to. Lye, or sodium hydroxide is a common one, and used in soap.
See the pH scale. Pure water is neutral, and is in the middle of the scale at 7. The lower this number drops from 7, the more acidic; the higher it climbs from 7, the more alkali.
Also,see here. 
There are acids and there are acids. There are 2 important factors, concentration and ionization. Concentrated sulfuric acid, which ionizes highly, can be very destructive. In addition to chemical reactions. It pulls water out of things. Highly dilute it is pretty mild. Concentrated hydrochloric acid is nothing to mess with.
Vinegar is nothing but dilute acetic acid with a little impurities. Acetic acid does not ionize highly. Fats can be broken down into their fatty acids which are quite mild.
‘‘Do extreme bases have a similar effect?’’ Ever hear of lye? It is sodium hydroxide. Again concentration and ionization potential are important. Lye will take your skin off, but people use ammonia for cleaning. We spread lime on our gardens.
On thing on dilute acids and bases. Something harmlessly dilute when spilled can become concentrated if the water evaporates, but it doesn’t. I used to work with dilute potasium hydroxide in methanol. It could quickly become concentrated and the methanol was bad too.
And some can make your life unpleasant in other ways. Hydrogen fluoride is the classic example. I’ve worked with a lot of acids but never HF and don’t want to. That stuff scares the crap out of me.
Vinegar is an example of a common household acid, as mentioned above. All your cans of soda have phosphoric acid. You can buy a fairly concentrated solution of HCl (the manufacturer marks it as muriatic acid, presumably as to not alarm the consumer) to use as a toilet cleaner. There’s just three examples off the top of my head.
For another example. T316 stainless steel doesn’t stand up to a lot of acids, even in fairly dilute concentrations. But I’ve routinely cleaned it with a 10% phosphoric acid solution.
From a quick web search, it seems that the pH of blood is typically about 7.4. Thus, it is a bit on the basic side of neutrality.
And, not all acid eats through metal or is even dangerous to the body in any significant way. There are some acids that we drink with no ill effect, including ascetic acid (vinegar), ascorbic acid (vitamin C), and citric acid (major component of citrus fruit and juice, including lemons, limes, and oranges). Concentration, often measured in “molarity” is important as well in determining whether or not your sample of acid is dangerous.
There are a few acids, especially the so-called “strong” acids that ionize almost completely in water, that can be dangerous, including hydrochloric acid, hydrofluoric acid, and sulfuric acid, but the human stomach produces some hydrochloric acid for digestion’s sake so it isn’t 100% hostile to life.
Other bases include ammonia (a common household cleaner), and bleach (another common household cleaner that can be more dangerous).
do not ever ever mix ammonia and bleach!
There’s also a general rule that acids taste sour and bases taste bitter. I believe that the sour receptors in the tongue actually respond to acids specifically as their mechanism of actuation, so in a sense the “sour” flavor could also be described as an “acidic” flavor. This is why lemons taste sour - because they’re full of acid!
Hydrofluoric acid, despite being one of the nastiest chemicals you’ll ever hear of, is actually a weak acid. Hydrochloric acid, on the other hand, is the strongest acid you’re ever likely to hear of, but if you spill hydrochloric acid on yourself, you can walk leisurely over to the sink to wash it off, and won’t get anything worse than a very mild rash.
Another example: If you take sulfuric acid and dilute it down to the same pH as Coca-Cola, it’ll still be plenty bad enough to give you chemical burns. Clearly, there’s a lot more to how nasty an acid is than just pH.
Every acid also has quirks to its individual chemistry. For instance, nitric acid and sulfuric acid are both strong acids, and both will burn flesh. Sulfuric acid will do absolutely nothing to copper, but nitric acid will attack it with a vengeance, producing very large quantities of very noxious gas in the process.
Indeed, and that is one reason it is so insidious; you may never know you got splashed by it since you won’t feel a thing until it’s too late.
I used to work with the stuff and had an… incident.
in a beaker wrapped by an ice pack, put in three parts of stongest HCl (12 molar.) then drop-by-drop, put in one part strongest nitric acid (16 molar.) mix and you have aqua regia. it can dissolve even gold and platinum.
Strong nitric and sulphuric acid mainly burn flesh by their dessicant effect - they react strongly and exothermically with water. Pouring concentrated sulphuric acid into water will cause momentary boiling at the point of contact (you can hear it). Carbohydrates such as sugar in strong sulphuric acid will have the water portion ripped right out of them leaving a black skeleton of “sugar charcoal”. So spilling strong sulphuric acid on yourself will dessicate your skin, generating heat locally in the process. That said, wash it off quickly enough and all you get is a brown stain.
Ah, but how well does it dissolve flesh? 12 molar HCl is about 36%, the normal commercial concentrated acide, and 16 molar nitric is about 70%, slightly stronger than the normal concentrated acid. Nitric is also available as white fuming and red fuming, both of which are much stronger and very nasty. The commercial strength nitric is as strong as you can get it by distillation.
Aqua regia made with standard concentrated reagents will burn a person slightly less rapidly than the nitric on its own since the relatively dilute HCl reduces the total acid concentration. Unless you’re wearing gold armour of course…
Strong bases attack flesh by reacting with fats (plenty in your skin) to form soap. The burns are reportedly intially less painful than acid burns but tend to be more serious in the long run. Cement powder left on skin for long periods of time can cause burns, so be careful.
Sulfuric acid is the strongest acid by any measure I am aware of. Anything stronger is defined as a super acid.
Ionization constants can be found at http://www.cem.msu.edu/~reusch/OrgPage/acidity.htm
Para toluene sulfonic acid isn’t in that chart, but if I remember correctly it has the highest ka of anything.
“Muriatic acid” is also sold by the gallon jug in swimming pool supply stores. It’s pretty common to add a quart or so to a backyard-sized pool every few weeks. I’ve spilled it on myself many times with no overt ill effects. Ditto battery acid from a car battery. Go wash it off & you’re fine. Don’t wait 10 minutes and don’t get it in your eyes or mouth though.
Para toluene sulfuric acid doesn’t even qualify as a super acid, although it’s close. You may be thinking of triflic acid. Even that doesn’t come close to the strongest acid. “Magic acid” is probably the strongest commercially available, but then there are the carboranes that prof. Christopher Reed at Riverside is working on. I think those might be the strongest acids in the world.
Quoth LSLGuy:
OK, I’ll take your word on it. I was speaking from experience about hydrochloric not being acutely dangerous, but I’ve never spilled battery acid (which I think is sulfuric) on myself.
Whate ever ‘‘super acids’’ are and ka may be different things.
