When the alchemists began to experiment with tartar their first process would be to distil it. The residue left in their retorts they called the salt of tartar. They knew this substance under other names, salt of wormwood, for instance, but they did not recognise the identity. By treating tartar with vinegar they produced acetate of potash, which they called regenerated tartar. Oswald Crollius, the compiler of the first European pharmacopœia, gave the name of vitriolated tartar to what we now know as sulphate of potash. The iatro-chemists of the next century, who obtained it by various methods, gave to sulphate of potash distinct names which show in what esteem it was held. Among other designations it appears as Specificum purgans, Arcanum duplicatum, Nitrum fixum, Panacea holsatica, and Sel de duobus. Glaser, who produced it from sulphur, saltpetre, and urine distilled together, sold it as Sal Polychrest of Glaser. Cream of tartar was known to the ancients under the name of Fæx Vini, which is the designation for it used by Dioscorides. The tartar of wine was found to be only soluble in 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. VITRIOL. 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.