The vitriols enjoyed an enormous reputation in medicine, at least until their chemical composition was definitely explained by Geoffrey in 1728. It was certainly known that the green vitriols contained iron, and they were sometimes named vitriol of Mars; that the blue vitriols contained copper, which obtained for them the designation of vitriol of Venus; and the white was understood to be associated with calamine, though by some it was supposed to be only green vitriol which had been calcined. The name of vitriol cannot be traced further back than to Albertus Magnus in the thirteenth century. He expressly applies the term to atramentum viride, the Latin name for sulphate of iron. Presumably it was given to the salt on account of its glassy appearance. The alchemists, on distilling these vitriols found that they always yielded a spirit or oil, to which they naturally gave the name of spirit or oil of vitriol. In Greek the vitriols were called chalcanthon, as they were extracted from brass; the common name in Latin was atramentum sutorium, because they were employed for making leather black. Dioscorides states that this substance is a valuable emetic, should be taken after eating poisonous fungi, and will expel worms. Pliny recommends it for the cure of ulcers, and Galen used it as a collyrium. There was a good deal of confusion between the vitriols and the alums, and the Greek stypteria and the Latin alumens were often an aluminous earth combined with some vitriol. Pliny gives a test for the purity of what he calls alum, which consists in dropping on it some pomegranate juice, when, he says, it should turn black if it is pure. Evidently his alum contained sulphate of iron. Paracelsus declared that, with proper chemical management, vitriol was capable of furnishing the fourth part of all necessary medicine. It contained in itself the power of curing jaundice, gravel, stone, fevers, worms, and epilepsy. Mayerne was another strong advocate of the medicinal virtues of vitriol. According to him it possessed the most diverse properties. It was hot and cold, attenuative and incressant, aperitive and astringent, coagulative and dissolvant, corroborative, purgative, and sudorific.