In chemistry, vitriol is an archaic name for a sulfate, and vitriol names have the obvious meaning: for example, vitriol of lead is lead sulfate, and so on. The word vitriol comes from the Latin word “vitriolum” for “glassy“, as crystals of several metallic sulfates resemble pieces of colored glass.
Vitriol with no further qualification often means sulfuric acid.
Alchemical diagram from Daniel Stolz von Stolzenberg, Theatrum Chymicum, 1614 representing VITRIOL as the alchemical motto Visita Interiora Terrae Rectificando Invenies Occultum Lapidem (‘Visit the interior of the earth and rectifying (i.e. purifying), you will find the hidden/secret stone’), found in L’Azoth des Philosophes by the 15th century alchemist Basilius Valentinus. This is a backronym, sometimes incorrectly said to be the origin of the word “vitriol”