Assume a dragon, roughly the size of a shire horse. This dragon has a unique breath weapon, that technically "burns" (oxidizes) the target.

Still, I have a hard time imagining how dangerous and damaging would that weapon be against knights (in plate armor) and mundane structures.

A dragon can expel a maximum of 3 liters of aqua regia, after that, they need some time to refill the storage organs. The nitric and hydrochloric acids are kept separate, and only combine shortly before exiting the dragon, and don't even properly combine when the dragon uses their spray mode. Proper aqua regia is only created when the dragon uses the spit or drool modes. Dragons prefer to use their spray mode for combat.

There are two main points to the knight:

  1. How fast will they die from a direct and a grazing hit?
  2. Before that, how fast will they be incapacitated from a direct and a grazing hit?
  • $\begingroup$ What's that about Elon Musk's junk?? $\endgroup$ Commented Jan 23, 2020 at 21:04
  • $\begingroup$ @ArkensteinXII That joke of a flamethrower? $\endgroup$ Commented Jan 23, 2020 at 21:06
  • 3
    $\begingroup$ I feel like oblique references in a question don't lead to clear answers. $\endgroup$
    – jdunlop
    Commented Jan 23, 2020 at 21:44
  • $\begingroup$ In addition, I would say this question has insufficient detail. How far can the dragon spray their acid? What volume of acid? What concentration? How many mols/unit volume at various points? There's a big difference if a "direct hit" delivers one litre of aqua regia, or a hundred. $\endgroup$
    – jdunlop
    Commented Jan 23, 2020 at 21:46
  • $\begingroup$ Still, I have a hard time imagining how dangerous and damaging would that weapon be against knights (in plate armor) and mundane structures Compared with WHAT? since there are no actual dragons, you should explain what a "normal" dragon can do so we can answer. Compared against a dragon that splits sulphuric acid it would not make much of a diference, unless the knights armour is made of gold. $\endgroup$
    – SJuan76
    Commented Jan 23, 2020 at 21:47

1 Answer 1


Weaponised acid is a thing in the natural world (termites vs ants).

As far as your acid spitting dragon, goes, here's what happens when Chlorosulfonax the Acrid faces off against the Immobile Chicken of Endor. A normal, mobile animal will instantly turn and seek to flee the vapours.

This weapon will be of great effect against anything that breathes. The knights, their horses and their horses' footmen will all suffer greatly upon inhaling the dragon's breath. Even though the acid won't dissolve the knights right away, they will suffer terribly: their skin will be burnt; their mucous membranes -- nasal, oral, throat, lungs -- will be burnt, swell up and maybe cause death; they're probably be blinded. If they survive, they will be disfigured & disabled.

Little difference between this and the chemical attacks used in WWI, and that's the avenue of research you'll probably want to go down next.

  • 3
    $\begingroup$ This would be the effect on unprepared knights. The knights preparing to fight the "acid dragon" would cover themselves in wet fabric, greatly reducing the effect of the attack. $\endgroup$
    – Alexander
    Commented Jan 24, 2020 at 19:05
  • $\begingroup$ @Alexander They still breathe, and inhaling nitric acid is lethal. Aside from the damage, it triggers convulsive closure of the airways at concentrations as low as 200ppm (0.4 grams per cubic meter). The resultant dyspnea is 100% disabling, and without treatment death follows within minutes. WITH treatment, death follows 90% within 2 days. $\endgroup$
    – PcMan
    Commented Dec 16, 2020 at 22:21
  • $\begingroup$ @PcMan The knights would be using face masks, of course. $\endgroup$
    – Alexander
    Commented Dec 16, 2020 at 23:20
  • $\begingroup$ @Alexander Knights have access to masks that filter gaseous and sub-micron acidic particulates? WOW. we did not have that until late in WW1. I never knew plate armor for knights came equipped with 19th-century chemical protection. $\endgroup$
    – PcMan
    Commented Dec 17, 2020 at 5:32
  • $\begingroup$ @PcMan first, don't underestimate the effect of multilayer wet cloth. Second, why are we going to have "sub-micron acidic particulates"? This mist, even if dragon is able to produce it, won't travel well in the air. $\endgroup$
    – Alexander
    Commented Dec 17, 2020 at 9:21

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