Excepting the articles made in Turkey and India (especially oil of rose), most aromatic substances are manufactured in southern France and the adjoining regions of Italy, while a few (oils of peppermint and lavender) are produced in England; a few also (oils of peppermint, spearmint, wintergreen, sassafras, etc.) in the United States. However, as we have stated above, it is possible to cultivate some plants from which odors are extracted in the warm sections of this country, and to obtain the most expensive perfumes from them. Among these plants our experience leads us to suggest violets, roses, reseda, lavender, mints, syringa, lilac, and several others to which the climate is adapted.
The methods by which the odors can be extracted from the plants differ according to the physical properties of the raw material and the chemical composition of the aromatic substance. We shall here briefly describe the methods thus far known, and at the same time add our own experience in this most important part of the art of perfumery. The aromatic substances are obtained by pressure, by distillation, by maceration (infusion), by absorption (enfleurage) through air or through carbonic acid, and by extraction.
Certain aromatic substances that occur in large amounts in some parts of plants, are best obtained by pressure. The rinds of certain fruits contain an essential oil in considerable quantities inclosed in receptacles easily distinguished under the microscope. When these vegetable substances are subjected to strong pressure, the oil receptacles burst and the essential oil escapes. The force is usually applied through a screw press with a stout iron spindle; the vegetable substances being inclosed in strong linen or horse-hair cloths, placed between iron plates, and subjected to a gradually increasing pressure. Comparative experiments have shown us that even with the most powerful presses a considerable, amount of oil is lost owing to the fact that a large number of oil receptacles remain intact. For this reason, when oil is to be extracted by pressure, a hydraulic press is preferable, as it develops greater power than any other press. In the hydraulic presses used for this purpose the piston fits exactly into a hollow iron cylinder with sieve-like openings in its circumference. The vegetable substances are filled into this cylinder; when the pressure is applied, the fluids escape through the perforations, and the residue forms a compact woody cake which is then free from oil.