a sulphate of iron, copper, zinc, etc, esp if hydrated (combined with water; see hydrate2)
concentrated sulphuric acid
virulent speech, expression, feeling, etc
This introduction, with its mixture of genius, shrewdness, and vitriol, is a piece of prose not to be missed — Literary World
vitriolic /-ʹolik/ adj
vitriolically adv
[Middle English via French from medieval Latin vitriolum, alteration of late Latin vitreolum, neuter of vitreolus glassy, from Latin vitreus: see vitreous]