Inside Baseball: How acids work in game

One of the great things about hypertext versus a book is that you can link detailed information for those who really, really, really want an 'inside baseball' type information set, and like the 'shape of spells' information I provided, the following is used in the (totes non-existent) Grand Grimoire as a link in individual spell descriptions that use acid.

Acid and Alkali Information:

Acids and alkalis are some of the most dangerous substances in the game, and for the most part do the same kind of burning, disfiguring damage, often in the form of a splash from a broken vial or a magically constructed glob.

Unlike most other attacks in the game, these chemical attacks cannot be healed with regeneration abilities, only being able to be healed by a cleric's cure, the natural healing of time or by hacking off the entire area and then regenerating.

Unless otherwise stated in a description, both acidic and alkaline attacks are considered to be with a weak, not particularly persistent substance that reacts with flesh, wood, leather and similar materials to do 2d4 points of damage, or 1 point if it is a mild splash. This damage is rarely disfiguring, and if it hits water it will heat the water up a little, but do no real damage to things living in the water as long as there is 100 or more times as much water as there is substance.

Rather than have a separate category for acids and alkali, both ends of the pH spectrum are protected from by oil of acid resistance, scrolls of acid protection and the like. The substances are treated the same way except for when they encounter each other and in the amount of damage they do. They are treated as poison (more accurately poison-like compounds) that do disintegration and/or burning damage to the flesh, which can be disfiguring.

Items have saving throws against acid by name, but when they are affecting living beings, they are treated slightly differently, using the best possible category for the attack.  Acid that is suspended in the air, as well as that spit out by dragons and other creatures is saved against as a breath weapon, acid that is created by a spell is saved against by spells, acid that is hurled as a grenade-like does not get a save, but may be avoided because of a good armor class or protection. When there is doubt as to which saving throw to use against acid, the PPD (paralyzation, poison, death magic) number should be used, unless the description says otherwise.

Categories of acid:

Like poisons, acids are given a category, a number that roughly corresponds to the pH of the substance. Because the pH scale is logarithmic, and because the normal human body is slightly resistant to alkaline substances, the scale works as follows (note there is no Category 7, which would correspond roughly to water.) This table does not precisely correspond to pH, and the damage given would represent a highly purified sample, something very hard to get below 4 or above 10. Diluted samples will do a fraction of the damage, based on how dilute they are:

Acid Category	Description	Damage (per full dose)	Damage (Splashing)	Damage (Continuing)
6	Very mild acid	1	0	0
5	Common Acid	2d4	1	1d4
4	Strong Acid	10d8	2d4	2d8
3	Very Strong Acid	8d20	4d10	4d10
2	Extremely Strong Acid	10d100	2d100	2d100
1	Ancient Black Dragon Spit*	(24d4+12)X300	24d4+12	0
8	very mild alkali	1	0	1
9	common alkali	1d6	1	1d6
10	strong alkali	10d6	3d6	3d6
11	Very Strong Alkali	6d100	1d100	1d100
12	Extremely strong Alkali	6d100 X10	6d100	3d100

*Inside the dragon, prior to being released as a breath weapon that does 24d4+12 per 'hit'

A full dose of damage is taken by falling into the purified acid, being hit dead on with a pure sample thrown as a grenade-like missile, swallowing it, etc. Splashing damage occurs with a near miss as detailed on the section on grenade-like missiles. Continuing damage is damage on successive rounds with acid that is persistent. Many in-game acids are non-persistent, reacting instantly with air and vanish in one round. Continuing damage can be caused by the acid clinging to the skin of a target after s/he is removed from the acid, and lasts until the acid is removed or 2d6 rounds have elapsed. Being immersed in acid would do 'full dose' damage on each round until the target was fully dissolved. Diluted acid samples will persist less time and have no or very little continuing damage.

Reactions with Water:

Unless it is described as an acid-like substance, acids (unless they are already very dilute) react to water with a great deal of heat. Attacking a creature made of water with these substances should be saved against as disintegration or death magic (whichever is worse) and do 50% of their total full-dose damage even if just splashed upon, and that damage is in the form of boiling and steaming (the acid damage itself is mitigated by dilution). If dropped into a large body of water, 50% damage (again, from heat) occurs in a 10ft radius, 25% in the next 5ft (a total 30ft radius) and none (although the water heats up) outside a sphere that is 60ft wide.

Neutralization Reactions :

When something basic is hit with something acidic (or vice versa) the regular acid damage should occur, plus an additional 50% damage as if hitting a water-based creature with acid, and the creature will bubble as gas expands. If an inanimate object, these bubbles have a 50% chance of exploiting a critical flaw in the object and disintegrating it (perhaps even 'exploding' it, although the shrapnel won't be propelled far or hard) per round of continuing damage. The continuing damage length is halved.

Disfiguration Reactions :

Disfiguration occurs when acid interacts with the flesh and melts it, creating holes, pits and other gory-looking damage. Disfiguration is not a guarantee with most acid attacks, and indeed, the majority of acid accidents in the real world, just as with the majority of burns, are superficial or first degree burns, the acid spreading out and interacting with the first layer of skin. These are painful, but ultimately heal without scarring. Disfiguration should only be considered as a possibility if the acid attack is a called shot or does greater than one-fourth of the creature's total points in damage (unless the disfiguration is specifically noted in the attack, as with some spells.) Lasting charisma (or comeliness) damage isn't any more likely with acid scarring than with burn scarring, and like burn scarring, is healed by magical healing and time.