Potion of acid

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Name	acid
Appearance	random
Base price	250 zm
Weight	20
Monster use	May be used offensively by monsters.

A potion of acid is a type of potion that appears in NetHack.

Generation

In addition to random generation, monsters may generate with the potion of acid as an offensive item.

Applying a horn of plenty can generate a potion of acid 0.3% of the time.

Description

The potion of acid has various effects depending on how it is used:

Quaffing

Quaffing a potion of acid without acid resistance abuses constitution, cures stoning and deals damage to you depending on the potion's beatitude: 1d4 points of damage if blessed, 1d8 points of damage if uncursed, and 2d8 points of damage if cursed. You are then prompted to type-name the potion. Quaffing the potion with acid resistance has no effect.

Throwing and wielding

Hitting a target with a wielded or thrown potion deals the same amount of damage to them as quaffing based on beatitude: 1d4 points of damage if blessed, 1d8 points of damage if uncursed, and 2d8 points of damage if cursed, with no effect on a target that has acid resistance. A monster hit with acid will shriek in pain if they can vocalize, waking nearby monsters. You will be prompted to type-name the potion in these cases if not blind, and monsters will throw this potion at you with the same effects, abusing constitution.

Vapors

Inhaling the vapors from a shattered potion of acid abuses constitution, but has no other effect.

Dipping

Dipping items of a corrosion-vulnerable material such as iron or copper into a potion of acid will corrode those items, and dipping a greased item of any type will cause the grease to wear off, using up the potion and prompting you to type-name it in both cases. Dipping a lichen corpse into a potion of acid will print a unique message and will prompt you to type-name the potion without consuming it.

Acid and water

Acid boils on contact with water of any kind: dipping any potions of acid into a pool or fountain, or else walking into deeper water with a potion of acid in your open inventory, will cause them to explode and deal up to 10 points of damage per potion. Acid inside containers such as sacks, a bag of holding or a cursed oilskin sack will explode if water gets inside them, though you will not take damage. A potion of acid can not be diluted normally as a result, though it is possible for diluted acid to occur, usually as the result of random alchemy. Dipping acid into any other potion will also cause the mixture to explode.

Cancelling acid will turn it into a potion of water.

Iron bars

Iron bars can be dissolved with a wielded or thrown potion of acid, unless they are on a level that prevents digging through them.

Strategy

Though several monsters lack acid resistance, the potion of acid is generally too rare to be of frequent use as a weapon against them even in the early game, and there are various means of working around iron bars that are not on no-digging levels. Overall, acid that is not used to gain a bit of extra damage in encounters is usually kept to cancel and turn into water.

The potion is more often relevant as a stoning cure: though it is fragile, damaging and weighs twice as much as the standard lizard corpse while being much rarer, it does not break any conducts, making it an option for characters maintaining vegan or vegetarian conduct. Even then, unless they are unburdened and can guarantee access to a potion stashed in a waterproofed bag in time, it may be preferable to break the conduct and eat a lizard corpse instead. Milky potions of acid are unsafe to use as a stoning cure, as a ghost generating from the potion will paralyze you long enough to fully render you a statue. Smoky potions of acid are only safe to use on the first turn of stoning: even a wish from a djinni won't save you if your limbs are already stiffening.

Though smoky acid allows a horn of plenty to be used with the Platinum Yendorian Express Card for a slow wish engine, the potion of acid is the second-rarest output after the potion of sickness.

Identification

Dipping a lichen corpse is the most reliable way of informally identifying a suspected potion of acid, and does not use up the potion.

If a monster hit by a potion "shrieks" or "writhes in pain", that potion is a potion of acid, and you will be prompted to type-name it if you were not blind at the time. While holy water can give the same message as acid in some circumstances (e.g. quaffing holy water as a chaotic character), monsters do not use it.

History

The potion of acid first appears in NetHack 3.3.0.

In NetHack 3.4.3 and some earlier versions, including some variants based on these versions, the potion of acid was subject to several bugs that are fixed in later versions and most variants, including a pair of bugs that semi-reliably crash the game:

• If a monster carrying acid is crushed with a drawbridge, or a force bolt or zapped wand of striking blows up the drawbridge underneath it, the game may panic. This was bug C343-179.
• Throwing a potion of acid into water or at iron bars will reliably crash the game. This was bug C343-394.

The ability to melt iron bars with acid and identify acid using lichens was introduced in NetHack 3.6.0.

Origin

An acid refers to any substance with a pH below 7 that can donate hydrogen ions (generally in the form of protons) to other substances. Various acids can have different strengths, and possess several different properties depending on their molecular structure. The following are among the most common acidic properties, which are reflected in NetHack:

• Tasting sour when eaten
• Stinging or burning on contact with skin
• Corroding metals and skin
• Turning blue litmus paper red
• Turning red or orange on a universal indicator

Both the litmus paper and universal indicator tests are the basis for the effect of dipping a lichen corpse into a potion of acid: Litmus is a dye extracted from various species of lichen, particularly Roccella tinctoria, while a universal indicator solution also changes color to red to indicate strong acids (pH of less than 3) and orange or even yellow for weaker acids (pH of 3-6).

Messages

This burns a lot!

You quaffed or were hit by a cursed potion of acid.

This burns <like acid>!

You quaffed or were hit by a uncursed potion of acid.

This burns a little!

You quaffed or were hit by a blessed potion of acid.

This tastes <tangy/sour>.

You quaffed any potion of acid while you have acid resistance; the former occurs if hallucinating.

<foo> <withers/shrieks> in pain!

A monster was hit by a potion of acid; the monster "withers" if it cannot vocalize.

Variants

SLASH'EM

In SLASH'EM, valuable gems can be dipped into potion of acid to make new potions via gem alchemy.

A cursed potion of acid can be found within the Chamber of Junk in the Lawful Quest.

ZAPM

In ZAPM, the equivalent to the potion of acid is the canister of universal solvent.

UnNetHack

In UnNetHack, potions of acid dissolve iron bars when they hit them. Dipping a lichen corpse into a potion of acid will identify it.

EvilHack

In EvilHack, the potion of acid has additional messages when thrown or wielded and smashed, and will auto-identify itself when it hits you or a monster.

The cell by the forge in Goblin Town has a ¹⁄₂ chance of containing a potion of acid. On the last level of the Ice Queen's Realm, the lower-right crystal chest in the central room of the castle has 3 potions of acid.

Though force bolts from a spell or a wand of striking can break iron bars, the potion of acid is still useful to avoid hitting and angering peacefuls on the other side of a set of bars: EvilHack makes avoiding alignment abuse much more important compared to NetHack, especially if you have not yet done your Quest. Using acid to melt bars is the safest method of gaining access to the trap door that leads into Gollum's dwelling, as well as freeing the pegasus to tame after defeating Kathryn the Ice Queen.