Mercury, Lead, Sulfur, Arsenic, and many acids can all be safely handled.
The chemicals and experiments that cannot, shouldn't be worked on by an amateur.
Arguing against the example instead of the main point seems like a waste of time to me. Just because someone picks a bad example doesn't mean he doesn't have a point. Of course it also doesn't mean he does. And also, I can think of a number of historical examples where mercury was not handled safely. I've heard [not sure I believe it but...] ancient [ie one or two centuries ago] hatmakers created the term "mad as a hatter" by rubbing quicksilver into the felt or something. And I'm sure the ancient romans used lead cooking pots.
Okay time to stop derailing the thread.
Well since this is a simulation, then when it comes to alchemy specifically, you can't get around the fact that it is inherently dangerous. Alchemists work with with mercury, lead, sulfur, arsenic, acids etc. Alchemists even ingest this shit trying to create potions of immorality and what not. Stuff like alchemists fire, oil of impact etc. in D&D is extremely dangerous to all involved. You of course also need to think about the literature that has grown from D&D. There are many cases of organic magical systems in literature where the power is inherently dangerous and must be handled with care or else it will horribly backfire. The balancing of magic in DF should be a matter of how much you are willing to risk for power. The HFS is a perfect example. If you get greedy with the adamantine before your ready for the show to begin, your screwed.
I agree. As long as its logical enough that a player would be able to make an informed decision on whether to do something or not. You know that if you're not careful with adamantine you have a chance of FUN. You know that if you send a naked recruit solo against fifty goblins he'd have a ninety nine percent of death. It shouldn;'t be like each time you perform a ritual you'd be forced to cross your fingers and hope that nothing too bad would happen. There could be some randomisation in, but at the end of the day it should be that every act of magic has a price. Not every porice should icncldue a random chance of failiure, but if they do you should be able to prepeare for it and if you can't and the faiiure is bad you'd either only accept the chance of failiure in emergencies or you'd not use t the spell or make the potion or whatever. And if you decide the price of failiure is something you can handle than that's your choice. But again I'll say that not everything should have more than a one or two percent chance of failure. The ones that do could be using potions dealing with highly unstable ingredients or somonning powerful demons. Other prices can nclude sacrifing sapients or atom smashing a thousand units of candy or whatever or having a one hundred percent chance of causing something bad to happen or whatever.