Читать книгу Perfumes and Their Preparation - George William Askinson - Страница 8

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The odors occurring in plants have their seat mostly in peculiar receptacles called oil glands in which the aromatic substances are stored and seem to take no further part in the vital processes of the plant. As has been intimated, the parts of the plant in which the aromatic substances are stored differ greatly; but in general it may be said that in most cases the flowers and fruits contain the odors; more rarely they may be found in the roots, in the bark, or in the wood, and in very few instances equally distributed throughout the whole plant. In some cases, however, we can obtain totally different odors from various parts of the same plant; this applies, for instance, to the orange-tree, whose blossoms furnish a different odor from the ripe fruits, and the latter must be distinguished from that obtainable from the leaves. The odorous substances occurring in the vegetable kingdom are either mobile liquids (essential oils), or they have a thicker consistence ranging from that of cream to that of soft cheese (balsams or gum-resins), or they are solid (resins). Aside from the fact that the term “essential oils” is quite incorrect, since the substances called by that name have nothing in common with oils except perhaps the liquid state, we are forced from a chemical standpoint to include among them even solid substances; the well-known camphor, a firm and waxy-looking body, belongs according to all its chemical properties into the same group as the so-called essential oils. The name “essential (or volatile) oils” is due to the fact that the volatile vegetable aromatic substances cause a stain on paper similar to that produced by oils and fats; but the stain made by the former disappears spontaneously after some time, while that due to true oils and fats persists. The disappearance of the stain depends on the evaporation of the vegetable aromatic substances—a quality not possessed by fats. Hence the volatile vegetable aromatic substances, in contradistinction from non-volatile fixed or fatty oils, have been designated as essential or volatile or ethereal oils. Inasmuch as the latter terms are the ordinary trade names for these substances, we are compelled to retain them despite their incorrectness. The French name for essential oils is essences; “essence de lavande,” for instance, is the French name for essential oil of lavender, and not for an alcoholic solution of the oil, as might be inferred from the usually accepted meaning of the English terms “essence of lavender,” “essence of peppermint,” etc., which mean solutions of these essential oils in alcohol.

As the localities where the raw materials—that is, the aromatic plants—are cultivated on a large scale naturally constitute the places of manufacture of essential oils, we find in southern France and in England the most extensive factories devoted exclusively to the preparation of perfumes. In the countries named, a favorable influence is exerted, too, by their situation near the sea, as well as by their trade with tropical lands from which additional aromatic plants are imported.

We have stated above that the manufacture of essential oils forms almost a monopoly in France and England; but there is no doubt that this country (the United States) likewise possesses many localities favorable to the cultivation of certain aromatic plants and the preparation of essential oils from them, so that this branch of industry could be carried on at a profit. For this reason we have in our descriptions devoted some attention to the conditions of growth required by such plants as might be raised here. We even find that some advantages are derived from the hot-house cultivation of some tropical plants.

An exact knowledge of the chemical properties of a substance is in all cases the first and fundamental condition for its preparation; it would appear necessary, therefore, that we should endeavor to gain complete information about the nature of vegetable aromatic substances before we enter upon the description of the various methods of their preparation.