The Collaborative International Dictionary of English v.0.48:
Vitriol \Vit"ri*ol\, n. [F. vitriol; cf. Pr. vitriol, vetriol,
Sp. & Pg. vitriolo, It. vitriuolo; fr. L. vitreolus of glass,
vitreus vitreous. See Vitreous.] (Chem.)
(a) A sulphate of any one of certain metals, as copper, iron,
zinc, cobalt. So called on account of the glassy
appearance or luster.
(b) Sulphuric acid; -- called also oil of vitriol. So
called because first made by the distillation of green
vitriol. See Sulphuric acid, under Sulphuric.
Blue vitriol. See under Blue.
Green vitriol, ferrous sulphate; copperas. See under
Oil of vitriol, sulphuric or vitriolic acid; -- popularly
so called because it has the consistency of oil.
Red vitriol, a native sulphate of cobalt.
Vitriol of Mars, ferric sulphate, a white crystalline
substance which dissolves in water, forming a red
White vitriol, zinc sulphate, a white crystalline substance
used in medicine and in dyeing. It is usually obtained by
dissolving zinc in sulphuric acid, or by roasting and
oxidizing certain zinc ores. Formerly called also vitriol