The most dangerous is probably the sulfuric and nitric acid. Sulfuric acid has earned its nickname “oil of vitriol.” 99% sulfuric will burn through paper in seconds. Skin and paper have a lot in common. Didn’t play much with the nitric acid, but I’ve heard it’s angry. You really only need a small amount to help the hydrochloric acid dissolve the gold. Also sulfur dioxide is hella nasty smelling.
Nitric acid is the single hardest ingredient to get. I found a seller on eBay. I think you can make nitric acid with store bought chemicals though, but I never had to do that.
Other ingredients:
Hydrochloric acid - sold as concrete cleaner Sulfuric acid - sold (diluted) as battery acid. Easy to concentrate with a condenser. Unlike HCl, you can get like 99% purity through distillation. Copper Chloride - Drop some copper into a bath of hydrochloric acid and hydrogen peroxide Sulfur Dioxide - Mix sodium metabisulfite with an acid. Sodium metabisulfite is commercially used in some food/beverage preservatives. I bought a bag of it of amazon that was marketed towards brewers. SO