According to P. MacEwan the adulteration of wintergreen oil with camphor oil is carried on at a large scale. The presence of camphor oil may be recognized by the specific gravity, 0.900, while that of pure wintergreen oil is, on an average, 1.18. A crude test--which is, however, readily executed--is as follows: Stir a few drops of the suspected oil in water. If pure, the oil in a few seconds sinks to the bottom, but if it contains camphor oil several minutes elapse before it deposits, and there is time to observe that the particles of oil assume different forms, but not a globular one. _Ylang-Ylang oil_ (_oleum unonæ_) is obtained by distilling the flowers of _Unona odoratissima_, indigenous to the Philippine Islands, the Straits of Malacca, and Indian Archipelago. The oil is colorless to yellowish. Its color and specific gravity, however vary very much, according to the season of the year in which it is prepared, the oil distilled in the cold season being more colorless and limpid than that produced in the warm season. The oil has an exquisite odor, partaking of the jasmine and the lilac, and is used in the manufacture of the finest perfumery. Various kinds are found in commerce, that marked "Sartorius" being preferred. The difference in quality of the many kinds of oil found in commerce is chiefly due to the method of preparation and the selection of the flowers, which possess the finest aroma when freshly gathered. In distilling, the first light volatile portions passing over have an incomparable perfume, while the oil distilling over later on possesses an insipid odor. Hence the manufacturer, who only obtains the first portions, will furnish the finest quality of oil, and it is this method of preparation which has gained the "Sartorius" oil its high reputation. While according to Schimmel & Co.'s report, 220 lbs. of fresh ylang-ylang flowers yield 2.64 lbs. of oil, Sartorius for the preparation of his fine oil distils off only about half the quantity. _Conanga oil_ is a poorer quality of ylang-ylang oil, obtained from the same plant. Two varieties are distinguished in commerce, viz: the _Javanese_ and _Indian_. The Java oil is the best, and may be used where ordinary qualities of ylang-ylang oil will do. According to Schimmel & Co.'s report the cheaper Indian oil is very resistant and durable in soaps, especially when combined with licari or linaloë oil. CHAPTER V. RESINS AND BALSAMS. The term _resins_ is applied to certain organic substances which are very closely related to volatile oils, in so far as many of them are formed from the latter by oxidation. As previously mentioned, by exposure to the atmospheric air all volatile oils undergo a change, whereby they thicken and are finally converted into substances possessing the character of resins. In nature most resins also occur mixed with volatile oils.