Poison Is Corrosive

A fairly common trope, where any particularly potent poison is incredibly corrosive as well. This is often used to let a hero identify an attack as poisonous without actually getting poisoned. Alternatively, it can be used to show just how strong a poison is (somehow) by having it dissolve the spoon being used to mix it.

Note that this may be justified (or Hand Waved) in fantasy works, as the characters might not understand that there even is a difference between acid and poison, or might not have a word for acid, or something.

Compare Ate the Spoon, Gargle Blaster, Hollywood Acid.

Anime and Manga

 * In Inuyasha, Sessoumaru's poison claw attacks can dissolve bones. In a story late in the series, Sango also uses a poison strong enough to melt bone, causing significant damage to her weapon in the process.
 * One Piece has several examples of this, most notably, whose powers allow him to create any type of poison he pleases, especially the corrosive variety.
 * In Kaiba, a poison disguised as wine spills and eats through whatever it touches.
 * In Bleach, Loly's Resurreccion has centipede-like tentacles which have a poison that erodes whatever it touches.
 * In Apothecarius Argentum, the title character, Argent is a "Basilisk", a type of Super Soldier who has been exposed to various toxins from birth to the point they're integrated into his body chemistry. In one chapter, in order to escape from a dungeon, he bites open the palm of his hand and uses his blood to weaken the stone walls to the point he can punch through them.

Comic Books

 * In Le Scorpion, Several of Master Poisoner Mejai's poisons are shown to be acidic. Armando uses one to burn through the ropes holding him at one point.

Film

 * In Enchanted, a poison apple eats through a biker's helmet.
 * In The Rock, we see what VX2 does to bare skin. One thing that's not addressed is how atropine can counter a blister agent.
 * This trope shows up repeatedly in Three Stooges episodes.
 * The Dark Knight: When the commissioner's poisoned highball glass gets knocked over it starts eating a hole through his desk.
 * It's never stated to be poison though. It might just have been acid.
 * Murder By Death. One of the glasses of wine is poisoned. When the wine is poured onto a cloth napkin, it burns holes through it.
 * Curse of the Golden Flower: Never actually stated to be poison, but normally you don't try to make people drink acid.
 * Prince of Persia the Sands of Time: The poisoned robe corrodes its wearer's flesh, but somehow not its own cloth or the cloth it's wrapped in when presented to the victim. Perhaps it reacts with sweat.
 * Clash of the Titans (1981). The Stygian Witches say that Medusa's blood is a deadly poison. After Perseus cuts off her head, her blood spews out and melts his shield. That must be one hell of a poison, if it can corrode a gift from the gods.

Literature

 * Harry Potter: Poison from the Basilisk's fangs was a corrosive substance. Justified since the delivery method is through a bite.
 * Discworld plays with this a lot, but most noticeably in Interesting Times.
 * Stephen King's The Eyes of the Dragon featured Flagg preparing a poison which burned away and twisted the bowl of the spoon with which he stirred it. The corrosive power killing before the poison is addressed however, as the poison when mixed with water, wine or ingested by the human body stops it burning holes through stuff, it just kills you an extremely unpleasant manner a day or two later.
 * In the Humanx Commonwealth series, Alaspinian minidrags spit an incredibly potent neurotoxin that has been shown to eat through metal. It's justified in that minidrags have no teeth, so they rely on their toxin's corrosive properties to get it into the bloodstreams of their enemies.
 * In the Temeraire novels, certain breeds of dragon are capable of spraying acid. While some characters early in the story refer to it as poison, neither the dragons nor their handlers make the mistake, making this an in-universe example of the trope.
 * In the Wraeththu novels by Storm Constantine, the title creatures' semen is a caustic poison. This is also true in the Tabletop RPG based on the novels.

Live-Action TV

 * Star Trek: The Original Series episode "The Way to Eden": The plant life of the planet Eden is full of acidic poison.
 * The nerve gas in Season 5 of 24 could eat through door seals. Handwaved in that the nerve gas was mixed with a corrosive element.
 * In the TV version of The Hitchhiker's Guide to the Galaxy, the sequence demonstrating the effect of drinking a Pan-Galactic Gargle Blaster ends with a close-up of the stuff, having been spilled when the drinkers succumbed to unconsciousness, eating a hole in the floor.
 * Mighty Morphin Power Rangers
 * The original series did this a lot when a poison attack was used on the Megazord. It could also shock, as Scorpina's sting did.
 * Power Rangers Mystic Force does this twice in two different episodes. Once, a poisoned apple, seconds after Chip suspects it's no good, instantly blackens and deflates like a balloon. Later, a goblet of poisoned tea eats through a book on the table after it's knocked from the intended victim's hand. All the usual Fridge Logic applies.
 * In Mahou Sentai Magiranger, the Hades God Toad used corrosive poisons as part of his power set.

Tabletop RPG

 * Dungeons and Dragons
 * 1st Edition supplement Deities and Demigods Cyclopedia. The skin of the troglodyte deity Laogzed oozes an acidic poison.
 * 2nd Edition
 * Monstrous Manual. The Eyewing weeps an acidic, poison fluid from its 4-foot wide eye.
 * Dark Sun Monstrous Compendium Appendix 1 Terrors of the Desert. The So-ut's claws secrete an acidic poison that damages targets and their armor.
 * 3rd Edition. Sword And Sorcery's Creature Collection.
 * The High Gorgon envenoms its weapons with an acidic poison partially derived from the poison injected by its snake heads.
 * The Narleth's bite injects an acidic venom that causes paralysis. Multiple bites will cause the victim's flesh and bones to dissolve.
 * The Magic: The Gathering card Poison the Well shows someone carrying water in wooden pails, but where it has spilled out it's eaten holes in the ground. Apparently it's acid poison that only dissolves dirt.
 * Amber Diceless Role-Playing, Shadow Knight supplement.
 * The standard form of the Envenom spell is a poisonous acid that prevents rapid healing and regeneration of wounds.
 * Demons can have a bite which injects a highly caustic poison. It has the same effect on healing/regeneration as the Envenom spell.
 * Hollow Earth Expedition supplement Secrets of the Surface World. A wasp in the Amazon rain forest has a sting with venom so caustic it causes 2nd degree burns.

Video Games

 * Pokémon plays with this. While moves such as Acid are classified as Poisonous Person-type attacks, they are among the only Poison attacks that don't have a chance of poisoning the opponent. But Ground- and Rock-type Pokémon resist Poison-type attacks (Poison-type Pokémon are also weak to Ground-type attacks), and Steel-types are completely immune to Poison.
 * Final Fantasy and similar RPGs can be assumed to use this trope with their poison-elemental attacks. Otherwise, they shouldn't deal any damage to mechanical or otherwise non-living targets. In some entries, such as the first, machines are indeed immune to poison.
 * In MS Saga, the trope is subverted by being reversed: when you're dealing with Humongous Mecha, the "poison" Standard Status Effect takes the form of acid, meaning that Corrosive Stuff Is Poison.
 * World of Warcraft has poisons and acids in the Nature category of magic. And many times if it's poison it's also acidic and vice versa. Though when it comes to some things, how close the two are is weird (mechanical enemies especially, some can be poisoned by a Hunter's Serpent Sting but others are immune, while they can all be harmed by acids; some enemies that are caustic piles of goo can be poisoned but are immune to other types of Nature damage; if you get hit by an acid attack chances are you'll also be poisoned for a duration of time; there's also poison attacks that don't actually poison but only do instant damage, acid attacks that don't do damage but lower your armor and poison that doesn't damage but lowers your speed [in fact one boss battle in the Trial of the Crusader involves having to remove one Jormungar Worm's Paralyzing Poison with another Jormungar's Burning Bile, an acid countering a poison]).
 * The Vindictus MMORPG has an Acidic Poison Pouch item that contains an acidic poison.
 * Runescape has a salesman who sells 'all purpose-poison'. In one quest, you learn that it's used for things like polishing family crests and cleaning fountains.
 * "Toxic Waste" in LEGO Batman. Instakills everyone who steps in it, except for a few specific characters with immunity to poisons.
 * Cassiopeia from League of Legends has an ability called Miasma, which creates a circular pool of poison. It damages anything that walks over it, including robotic entities.

Webcomics

 * In Girl Genius, the poison from the Green Glowy Things.

Western Animation

 * Looney Tunes: The stirring something, then lifting the spoon and watching it dissolve is a repeated gag. Most often with horrible poisons, but also mysterious brews like the Jekyll and Hyde variety, and Gargle Blasters.
 * In one of the Classic Disney Shorts (Mickey's Garden, 1935), Mickey prepared an insecticide at his backyard and the broom he was using to stir it "burned" from being inside it.
 * The Real Ghostbusters: Overdone to the point of parody where a poisoned cup of milk eats through several floors. Given they were living through a mystery author's last novel, the surreality of it was intentional.
 * In Asterix and Cleopatra, the Soecial Iced Arsenic Cake make by Artifis is so toxic that the batter Ate the Spoon - before he added the acid.

Real Life

 * The venom of species of snake contain enzymes that kick-start the digestive process. These hemotoxic venoms and myotoxic venoms cause tissue degradation, such as breaking down the muscles around the heart killing their prey.
 * Some species of spiders have similar venoms, such as the brown recluse spider, which acts to dissolve the flesh of the victim, which is extremely painful.
 * Hydrofluoric acid is very corrosive and highly toxic. It can diffuse through skin and spread fluorine around, creating all kinds of havoc -- mainly by precipitation of calcium fluoride. It gets the calcium from your bones. In other words, it melts your bones from the inside out.
 * It'll also take calcium from your blood, which is even worse. Losing calcium from your bones weakens them. Losing calcium from your blood slows or stops your heart. Direct skin contact with even a small amount of hydrofluoric acid is rarely survivable without prompt treatment. Treatment that you're unlikely to get, because the human body also needs calcium to transmit pain signals, leaving many victims entirely unaware that they've even been exposed until it's too late to do much more than say "poor bastard" and start making funeral arrangements.
 * Nearly any spit-poison is acidic, as its primary function is usually to blind, which a normal poison wouldn't do.
 * Some poisons, most notably arsenic sulfides, will tarnish a silver spoon (due to the sulfur, not the arsenic). This led to some royal families using silver spoons to detect poison.
 * Concentrated potassium cyanide solutions are poisonous and corrosive for steel, copper and some other metals. With help of air even gold may be dissolved.
 * Vesicants (blister agents) are poisons that are not normally corrosive to nonliving matter, but corrode and burn flesh, leaving nasty chemical burns and blisters. Typical examples are mustard gas and giant hogweed sap.