From this story. Some kind of acid, I’d presume?
It’s a common term for sulphuric acid.
The vitriols were the sulphates, white vitriol being zinc sulphate, green vitriol iron suplhate, etc. Vitriolic acid, or vitriol liquor, was the acid that gave rise to the vitriols, i.e., sulphuric acid.
Thanks guys!