Alchemy is unscientific by its nature - let's mix random substances to get gold.

You missed the point. Yes, it's unscientific, (well, not entirely - the attempts given knowledge at the time were very scientific, claims of success weren't) but the historical context about how chemistry evolved is still valuable. The whole idea of why it didn't work is scientific information.

We didn't learn alchemy. We learned about alchemy.

That is perfectly scientific. It becomes unscientific is when people pretend it worked, or that they'd ever seen it work.

Materials science follows in the footsteps of the alchemists, keeping alive the grand tradition of mixing random stuff together to see what happens. They too are frequently mixing things together in the hope of getting specific outcomes - usually it doesn't work.

Science is about how people deal with evidence. There wasn't any reason to think that gold couldn't be produced by mixing stuff together in the days when alchemy was popular. After all, a bunch of other substances could be made by mixing things, and it is obviously possible to mix liquids and get solids.

https://en.wikipedia.org/wiki/Goethean_science => https://en.wikipedia.org/wiki/Failure_mode_and_effects_analy...

...okay, forget all the physical and chemical knowledge you have that was discovered after the year 1300 and propose a better method to learn how to produce gold. Where would you even start?

Not by mixing goat piss with hair of a virgin in moonless night.

...how do you know that doesn't work?

Sometimes surprising and interesting things happen when you experiment. Maybe goat piss with hair of a virgin seems weird, but burying shit in your backyard for awhile, digging it up, and mixing it with burnt wood seems pretty odd too when you think about it.

Is that a recipe for gunpowder?

It seems to be missing sulfur, but otherwise - yep.

If memory serves, one of the big reasons for Britain’s naval supremacy for a long time was their discovery and exploitation of large deposits high-quality of saltpeter in India. Before that, they had “saltpeter plantations” with rows of organic waste soaked with human an animal urine and left to dry in the sun. Before that, it was groups of the King’s men going around the countryside and scraping the stone foundations of buildings and cemetery monuments.

My point exactly; people really like to equate "unscientific" with "turned out to be wrong". Chemistry is such a huge field that it's a small miracle we managed to figure out at all, no small thanks to Boyle who actually introduced the very concept of chemical elements.

With an incomplete knowledge of chemistry that wouldn't necessarily be an irrational experiment. For example, urine was a common source of uric acid in pre-modern times. When applied to copper it would produce verdigris. It might be a reasonable hypothesis that whatever allowed urine to change one metal might indicate that it could change other metals into gold.

But it won't produce gold, same like applying aceton to concrete won't produce antimatter.

You don't perform a scientific experiment because you know what the result will be. You perform the experiment to find out what the result is. That's how science works.

Why is that unscientific?