Vitriol
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Vitriol is the name that alchemists gave to sulfuric acid. The name was also used for various sulfate salts, such as copper (II) sulfate (blue vitriol, or rarely Roman vitriol), zinc (II) sulfate (white vitriol), Iron (II) sulfate (green vitriol), Iron (III) sulfate (vitriol of Mars), or cobalt (II) sulfate (red vitriol).
Oil of vitriol is concentrated sulfuric acid so named due to its oily appearance.
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Extraction
In antiquity, the vitriol salts were extracted from the runoff that collected inside mines of sulfide ores; the sulfates were formed naturally by the action of air on the wet sulfide minerals, and washed down by percolating water.
Uses
Manufacture of sulfuric acid
The famous Persian alchemist al-Razi (864-930) discovered sulfuric acid by the dry distillation of vitriol salts, thus setting in motion a chain of discoveries that would form the foundation of modern chemistry and chemical engineering. (Nowadays the reverse process is generally used, namely the metal sulfates are made by reacting oxide or other metal compound with the acid, which is obtained by other means).
Agriculture
Blue (copper) and, to a lesser extent, white (zinc) vitriol are still occasionally used as chemical defensives in agriculture. In typical applications, a solution of the vitriol is mixed with lime (calcium carbonate) to produce a fine copper carbonate suspension, which is sprayed on the plant.
Iron-gall ink
Green (Iron (II)) vitriol was much used in the middle ages to make writing iron-gall nut ink.