I found the recipe for the superior swallow potion, but I'm missing one important ingredient: Vitriol. I'd guess that this is an alchemy ingredient, but I don't have a recipe for creating it. I also never saw anyone that sells it.
Where can I get some Vitriol?
Best Answer
(Sourced from http://www.gamefaqs.com/boards/702760-the-witcher-3-wild-hunt/71858977)
You're welcome!