Some articles are colored intentionally; this remark applies particularly to some soaps which not rarely are stained to correspond to the color of the flower whose odor they bear; for instance, violet soap. Some articles again are used only on account of their color; for instance, paints, hair and whisker dyes. As we shall discuss this subject at greater length in connection with these toilet articles, we merely state here that nowadays every manufacturer can choose between a large number of dyes of any color, all of which are innoxious; hence no perfumer should under any circumstances use poisonous colors. This is a matter of importance with substances intended for immediate contact with the human body such as paints, lip salves, soaps, etc. All of these colors will be described hereafter.
[CHAPTER VII.]
THE EXTRACTION OF ODORS.
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.
Pressure.
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.
Besides the essential oil, watery fluid is expressed, the whole appearing as a milky liquid, owing to the admixture of vegetable fibres, mucilage, etc. It is collected in a tall glass cylinder which is set in a place free from any vibration. After remaining at rest for several hours the liquid separates into two layers, the lower being watery and mixed with mucilage, that floating on top being almost pure oil. The latter is separated, and finally purified by filtration through a double paper cone in a funnel covered with a glass plate.
Fig. 4.