In a medieval society with minor fantasy elements, a scientifically minded and not-very-ethical character is looking to acquire some strong acid for a "project" of his. He is particularly looking for acids that could burn skin and leave disfiguring scars, such as the concentrated sulfuric or nitric acid used in real-world acid attacks.

However, our "mad chemist" villain lives in a medieval period with Middle Age levels of technology, and that means he has two problems:

  1. Concentrating the acid into a sufficiently harmful substance. The scientific equipment to safely manufacture and concentrate acids (at least in the way a modern society would do it today) is not readily available at the current technology level. Glassware and common simple tools - such as flasks, medieval-style distillation equipment, and vials - are feasibly available in his lab, but titration equipment, digital measuring equipment and other complex modern tools are not. He could feasibly just boil an acid over a heat source, but the question is whether that would make the acid become strong enough to cause the effects he wants.
  2. Getting the materials. To acquire a sufficient amount of material for the concentration process, our chemist would need to find some setting-appropriate creature or animal that produces acidic or basic chemicals naturally - or locate some other natural source that would make sense to exist without being too fantastical, such as a geologically accumulated post-volcanic acid lake.

The question

Given the details above, how would this character go about:

  1. acquiring a source of acid (or the materials to manufacture acid) in a way that is believable for the setting, and
  2. creating and concentrating a sufficient quantity and strength of acid - to the point where the acid could burn or physically scar a person - using only basic scientific tools and the equipment that would be available to him in the time period?

I am tempted to just handwave this bit of the plot as "he just finds a magical creature that has super strong acid glands and uses that to make the acid," but I want to come up with a clever way of producing it that shows the character's malicious ingenuity and scientific prowess.

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    $\begingroup$ If he has glassware, he can feasibly do just about everything. Digital equipment isn't necessary. He may need an inventive streak (and wealth), but most of the materials he needs will be available, and what equipment isn't covered by straight glassware can be worked out by anyone reasonably clever. Precious metals are used in the contact process, but you only need lead for the chamber process. There are modern ones unavailable to him, but only slight efficiency gains are seen with those. If he needs small quantities, there are several other processes besides... the former are industrial scale. $\endgroup$ – John O Jan 15 '20 at 21:27
  • $\begingroup$ Ah, that is valuable input. I'm not a chemist and only know about these processes secondhand, so it's good to know that this is doable in the time period. I am curious what materials he would need, however - i.e. which elements and minerals would he have to find to make a batch of sulfuric acid this way, for example, and would those be available if we assume he has the wealth and influence to get them? $\endgroup$ – Sciborg Jan 15 '20 at 21:31
  • $\begingroup$ Wikipedia knows all. Go look it up, there will be a "manufacturing" section for all mundane chemicals. There are exotic acids that he can't plausibly make, but even in the real world we have trouble with some of those, they tend to remain mostly theoretical. Nitric and sulfuric aren't stretching it at all. $\endgroup$ – John O Jan 15 '20 at 21:35
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    $\begingroup$ Sulfuric (= "vitriol" or "spirit of vitriol") and nitric (= "aqua fortis" or "spirit of niter") acids were known since the antiquity, and were of course available in the Middle Ages. So was aqua regia, a mixture of nitric and hydrochloric acids (called "regal water" because it could dissolve gold). You are asking about substances which were actually available and in use by alchemists during the middle ages. If you are looking for medieval recipes to make them then you should read up on the history of chemistry. $\endgroup$ – AlexP Jan 15 '20 at 21:37
  • $\begingroup$ Good to know, thank you! I admit I'm not skilled in chemistry and honestly had no idea these substances were readily available and completely doable back then. I was worried that this would be implausible the way I presented it. I will go do some more research and iron the rest of it out. You've been a great help! $\endgroup$ – Sciborg Jan 15 '20 at 21:39

Nitric Acid

I mean, this is just one choice among many, but I like the Latin for it (aqua fortis, literally 'strong water'). It's got a pH of 3.01 and is very, very dangerous. Though Latin isn't quite the right language, as this was discovered in the 800s by an Arabic Alchemist, Muhammad ibn Zakariya al-Razi. Preparation is rather easy - superheat a mixture of saltpeter, aluminum salt, and copper sulfate. (I mean, that's one way among many, but that's how Muhammad did it, so that's the one I would recommend. Also, please don't try it at home.)

  • $\begingroup$ This is a great option and well explained, I think I might use this (and I do love the Latin name!) I was worried that powerful acids would not be viable in the setting I described and that I was silly for asking, but other commenters pointed out to me that medieval chemistry is way more advanced than I thought and a lot more doable than I expected it would be. I've been learning a lot from asking this question! :) $\endgroup$ – Sciborg Jan 15 '20 at 21:45
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    $\begingroup$ @Sciborg Mostly what's missing is the scientific method (so it's hit and miss until you figure it out by accident) and understanding of the mechanisms. Reproducibility is just a matter of diligence and engineering instincts. $\endgroup$ – John O Jan 15 '20 at 22:06
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    $\begingroup$ There's a modern misconception that alchemy was just a bunch of loons in towers trying to discover the Elixir of Life or transmutation. That really can't be farther from the truth - ancient alchemists were very competent scientists in their own right, and it's where all of modern chemistry is derived from. They just switched the name to avoid the stigma around the late 1700s. $\endgroup$ – Halfthawed Jan 15 '20 at 22:08
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    $\begingroup$ Same guy is also credited as being the first to produce sulfuric acid, so you can choose that too. $\endgroup$ – Ville Niemi Jan 15 '20 at 23:21

If you really want to handwave away all the details, have your character hire or blackmail an alchemist, who already has the knowledge and equipment to make pretty strong acids.

Making strong acids was one of the hallmarks of a skilled alchemist, and passed down from master to apprentice. See for example https://www.thoughtco.com/alchemy-in-the-middle-ages-1788253 .

You're not showing off the protagonist's scientific prowess, but you are showing off other skills, such as identifying the right person to go to for help. (Many alchemists practiced in secrecy, especially after their profession was banned by the Church in 1317.

But of course a secret known by two people only stays a secret if one of them is dead...

  • $\begingroup$ How is this answering the question? How does the alchemist know how to make strong acids? $\endgroup$ – L.Dutch - Reinstate Monica Jan 16 '20 at 19:30
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    $\begingroup$ That's one of the things alchemists learned in their standard apprenticeship. See for example thoughtco.com/alchemy-in-the-middle-ages-1788253. $\endgroup$ – arp Jan 16 '20 at 19:49
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    $\begingroup$ @arp I came across this answer in the LQP review. You should edit some information from that link into the answer, so that the other users don't vote to delete it. $\endgroup$ – SurpriseDog Jan 17 '20 at 0:28
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    $\begingroup$ Added several paragraphs of supporting information -- I'd thought it was common knowledge that alchemists had significant knowledge of chemistry and access to powerful acids, but apparently I was wrong. $\endgroup$ – arp Jan 17 '20 at 0:50

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