Chainsaw the description?: Hollywood Acid

In films, on TV, and in comic books, an "acid" is any liquid that can eat away at and completely dissolve skin and muscle, leaving only bone (and sometimes not even that). Even stronger "acids" will melt steel, glass, plastic, concrete, and ultimately everything it comes in contact with. Such liquids are almost always either a sickly green or sickly yellow color. They bubble and fizz on the counter or floor when you spill them, give off visible, smoky fumes, and they never dissipate (if a drop of acid eats through the floor, it will continue to eat through things on the next level down, and so on, and so forth...)

This stuff will never be referred to as anything other than "acid," unless it's given some highly scientific name at its introduction, after which it will simply be called "acid." Expect it to show up at least once in any work involving a Mad Scientist. If this stuff is ever spilled on a person or other living creature, say hello to the Nightmare Fuel.

Reality Is Unrealistic, because while acid will eventually dissolve flesh and metals and floors, it will not do so instantly. Also, almost all acid solutions are dangerous not for dissolving flesh but for burning flesh and damaging lungs if breathed in. More can be learned on UsefulNotes.Acid.

See also Poison Is Corrosive and Acid Pool for when this is applied to a Death Trap. A subtrope of Hollywood Science. Has nothing to do with that other kind of acid (which one might do well to distinguish from marijuana).

In Real Life, there are several definitions of an acid. An acid can be a substance that makes more hydrogen/hydronium ions in water (pKa < 7, therefore lowering the pH of pure water (7) when added to the solution). A slightly more advanced and broader definition is a substance that donates a proton in a reaction. For those of you who don't learn your chemistry from movies, the last definition is a substance acts as an electron acceptor. A substance can act as an acid in one situation and as a base in another. For example, you can die if your blood pH wavers more than a tiny bit away from 7.3. To prevent this, your body uses carbon dioxide in water to make what's called a buffer. When you become too acidic, it mops up the hydrogen ions, and when you become basic, it releases more hydrogen ions. No buffer system and a tiny shock to your blood pH could send you into complete thermodynamic equilibrium with the surroundings, thus preventing further non-spontaneous reactions powered by oxidation of various organic chemical compounds of biological origin, in a condition known as acute acidosis or alkalosis.

You encounter acids every day; vinegar is an acid, and citrus juice gets its sharp taste from its acidic nature. Your stomach contains hydrochloric acid to help break down your food. The water you drink was probably treated with phosphoric and sulfuric acid before it was piped to your house. Acids are a normal, natural part of everyday life.

While something with an extreme enough pH number can, in fact, eat through some of the things it is portrayed as eating through given enough time (many acids can dissolve metal), the problem is that bases (high pH) corrode flesh while acids (low pH) burn flesh rather than dissolving it (unless they are very strong). And in Real Life, there is much more to the story than the strength of an acid. Hydrochloric acid is a strong acid (pKa=–7.0), yet HCl solutions are commonly used in high school, and if you spill a bit on your hand, it stings, you just rinse it off for a while. On the other hand, hydrofluoric acid is a weak acid (pKa=3.15), but it will eat right through your glass test tube. And if you get any on your hand, it might not sting because of damage to your nerves, but you better get to a hospital immediately.

Another thing blatantly ignored in most fiction is that acid fumes are dangerous on their own as well. Hydrochloric acid fumes, for example, corrode just as bad as liquid acid and when it's spilled on something vulnerable, it produces chlorine gas which is highly toxic in itself and when it comes into contact with water (like in the inside of human respiratory systems) it goes back to being acid. So of course, 90% of the time the main character investigates the corrosion holes by hovering his head inches above it. (See also Convection, Schmonvection for a similar issue with lava).

The strongest acid in the world is a mixture of antimony pentafluoride and hydrogen fluoride (known as fluoroantimonic acid), and is strong enough to protonate just about anything you throw into the reaction mixture. Even stuff that theoretically doesn't react with acid. According to The Other Wiki, it is 20 quintillion times stronger than pure sulfuric acid.