_Peppermint oil_ (_oleum menthæ piperitæ_) is obtained from the fresh flowering peppermint, _Mentha piperita_, natural order _Labiatæ_. In commerce, German, English, American and Japanese peppermint oils are distinguished. As regards fineness, the German oil is inferior to the English and better kinds of American oils, but superior to the Japanese. The best and most expensive oil is the English so-called "Mitcham oil of peppermint," which dissolves in 50 parts of 50 per cent. spirit of wine and possesses a fine, pure taste, it being for this reason preferred by distillers for the fabrication of liqueurs. For perfuming purposes, however, the American as well as the German oils are very suitable. Of American oils that of H. G. Hotchkiss, L. B. Hotchkiss, Hale & Parshall, and Fritzsche Bros. enjoy a high reputation. The Japanese oil is distinguished from the rest by a peculiar train-oil-like odor and taste, and is in but little demand. Crude oil of peppermint is yellowish to greenish and contains much mucus; it has therefore to be subjected to another distillation with water. The rectified oil is clear as water, limpid, of a strong but pleasant odor and a specific gravity of 0.900 to 0.902. Old oil thickens and then shows an acid reaction. The greater portion of the oil congeals at the freezing point of water; many kinds, however, requiring but slight cooling in order to become solid. The solid portion of the oil, _Menthol_, (C_{10}H_{12},H_{2}O) is a colorless, finely crystallized body with an intense odor of peppermint. It melts at 107.6° F., is quite fluid at an ordinary temperature and boils at 413.6° F. Menthol is found in all oils of peppermint most abundantly in the Japanese oil, which contains from 50 to 55 per cent. of it. Mitcham oil is also very rich in menthol, it containing from 40 to 45 per cent., while the American oil contains only from 20 to 25 per cent. American, German and English oils of peppermint may be distinguished as follows: By adding to 5 or 6 drops of the oil, 25 to 30 drops of pure white concentrated sulphuric acid, _American oil of peppermint_ becomes heated and emits vapors, the mixture acquiring a dark brownish red coloration. After mixing with 8 to 10 cubic centimeters of 90 per cent. alcohol, the fluid becomes turbid, pale yellowish brown, or reddish brown, and on boiling clear pale brown. When mixed with sulphuric acid, _German oil of peppermint_ becomes heated without emitting vapors, becomes yellowish red, not very dark, and turbid. After diluting with alcohol, the fluid becomes turbid and yellowish red, and on boiling somewhat more transparent and currant-red. _English oil of peppermint_ treated in the same manner as the others with sulphuric acid becomes very slightly heated without any emission of vapor. After diluting with alcohol, it becomes clear and raspberry red.