Vitriol
a commercial name for sulphuric acid, and for several salts which that acid forms. The term vitriol was in common use among the alchemists, and was derived from vitrium, "glass," on account of the glassy appearance and transparency of copperas or green vitriol (the sulphate of iron).
From copperas the alchemists prepared a strong sulphuric acid by distillation, whence also the acid was termed the oil of vitriol. In addition to these there is yet commercially known blue vitriol, which is a sulphate of copper, and white vitriol, the sulphate of zinc (zinci sulphas of the "Pharmacopeia") much used in medicine.