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 water with difficulty; but if boiled in water a turbid liquor was yielded which in the boiled condition continually threw up a sort of skin or scum. This was taken off with a skimmer and dried; it was naturally called Cream of Tartar.

Paracelsus and other chemists distilled this cream and got an oil from it which they called oil or spirit of tartar. It was chiefly a pyro-tartaric acid with some empyreumatic constituents. It was a thin, light yellow, bitter tasting but rather tart, and pleasant smelling oil, and was credited with remarkable penetrating powers. It was used in disorders of the ligaments, membranes, and tendons. Particularly surprising to them was the fact that the residue of a distinctly acid substance was a strong alkali. This "salt of tartar" was found to yield another oil called oleum tartari per deliquium, or lixivium tartari, which was the name by which it was called in the Pharmacopœia. Salt of tartar and cream of tartar together yielded the tartarum tartarisatus. It was when making this that Seignette produced by accident his double tartrate of potash and soda, now familiarly known as Rochelle salt.

Visitando Interiora Terræ Rectificando Invenies Occultum Lapidem Veram Medicinam. (Visiting the interior of the earth you may find, by rectifying the occult stone, the true medicine.) This acrostic is first found in the works attributed to Basil Valentine.

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,