One thing I always wonder is what exactly does HCl dissolve in the stomach, and how does it not destroy the nutritional value of the food?
The gastroduodenal epithelium (stomach surface) is covered by a sticky mucus layer into which bicarbonate is secreted by surface epithelial cells. This bicarbonate-mucus layer creates a pH gradient with a near-neutral pH at the epithelial surfaces in stomach and duodenum, providing the first line of mucosal protection against luminal gastric acid.
We only learned this in the last 20 years so it’s relatively new science
Edit: either I misread the question or it was edited
Acids destroying whatever they touch is mostly a "kiddie" version of reality. 99.9% of acids found outside of chemistry labs and industrial settings are no more dangerous or destructive (as acids) than soda pop, lime juice, or human vomit (all of which are acids).
The reason is that some far stronger and/or more dangerous acids occasionally show up in household settings. Example: "battery acid", splashed on the skin, can cause horrific & life-long damage in seconds. Teaching kids to stay far away from anything labeled "Acid" is kinda like teaching 'em not to play with fire.
> The reason is that some far stronger and/or more dangerous acids occasionally show up in household settings. Example: "battery acid", splashed on the skin, can cause horrific & life-long damage in seconds.
I had to look up "battery acid"; turns out it's sulfuric acid, which is well known to be very dangerous.
Of course, so is hydrochloric acid, which is the acid in human vomit. The destructiveness of the solution is not determined by the acid -- we use HCl because it is extremely destructive! -- it is determined by the acid's concentration.
Note that vomiting more than a normal amount (say, because you're bulimic) will cause noticeable acid damage to your teeth.
I'd say you're at the "know enough to be dangerous" phase. The destructiveness of concentrated H2SO4 (sulfuric acid) to flesh is at least as much due to its extremely exothermic hydrophilic behavior as to its low pH. Hydrofluoric acid is typically weak (pH-wise) as an acid, but is a horrific delayed-action contact poison. Concentrated nitric acid is a dangerously powerful oxidizer, or worse. Yet concentrated phosphoric acid is arguably less dangerous than propane.
[DISCLAIMER - Neither HN nor I are in any way responsible if you pop any statement in this item your empty little head, and head off in search of your very own Darwin Award. If you have no professional safety training in handling dangerous and/or highly-concentrated acids, then you should completely avoid them.]
What point are you trying to make in response to the observation "99.9% of acids found outside a lab may be no more dangerous or destructive than human vomit, but that isn't particularly meaningful since the acid in human vomit is highly dangerous and destructive"?
For a specified acid, both concentration and pH are fairly good, one-dimensional, metrics of how relatively dangerous/destructive various solutions are. (Or at least "to within household common sense". Anyone competent to cook spaghetti should understand that "10 gallons" or "boiling hot" would make the solution far worse than "3 drops" or "ice cold".)
What set me off was that your comment seemed far too close to "concentration is a good, one-dimensional, measure of how dangerous/destructive acids are." (Without the "specified acid" and "relatively" qualifiers.) That (or a similar statement with "pH" instead of "concentration") is the sort of "logical" simplification that kiddies and idiots can far too easily latch on to, when they're thinking about doing cool & dangerous things.
(So - NO, kiddies. The fact that 5% acetic acid is vinegar, which is safe to splash on your salad, does NOT make (say) 5% hydrofluoric acid safe in any way at all. Stay the hell away from the latter, unless you want to look like a cheap horror movie extra for the rest of your might-be-kinda-short life.)
> What point are you trying to make [...] 99.9% of acids found outside a lab [...] than human vomit [...]
Technically, vomit is (horribly impure) hydrochloric acid. But for household safety purposes? Any good 11-year-old babysitter can safely clean up baby barf, using only routine baby-care supplies. But handling high-molar HCl, let alone dealing with spills of the stuff? That's a completely different world.
In fact it's not true. For 98% suplhuric acid, you have at least 30 seconds to wash it away with just water and have no consequence at all (eyes is a different story, that's where it's actually seconds), and battery acid is only 35% or less.
And a really good stage magician can have a random audience member shoot him in the head with a loaded gun, and catch the bullet in his teeth, too. That I've heard, you don't see that trick performed too often. Because sometimes it goes horribly wrong.
This is consistent with the supposition that low pH is needed to kill some pathogens.
An interesting fact is that humans have a stomach pH in the scavenger range. This is consistent with the supposition that, before becoming the most successful hunters of this planet, for a long time humans had been mainly scavengers, who scared the other scavengers and predators by throwing sticks and stones, and then consumed completely the leftovers by breaking the long bones and the skulls with stones.