I suspect that it's just poorly understood Iron Age chemistry, with bits of magic added to it. Some parts of it actually do things, some parts don't.
As for the manipulating and imbuing items with things...the Gnostic schools of the Ancient North seem to have excelled at this, judging by a lot of the stuff in the Coffers. We don't see that in the Three Seas for some reason. Lost knowledge, or is their simply a greater cultural taboo against sorcery in the Three Seas than in the Ancient North, so there's simply no market?