We apply the term perfume—which really means a fumigating material—to those substances which make an agreeable impression upon our sense of smell; the French call them briefly odeurs, i.e., odors. The high degree of development at present attained by this industry in France and England is the cause of the fact that all perfumes are generally sold under French or English names, which must be borne in mind by manufacturers in this country.

Perfumes or scents, however, exert not only an agreeable impression on the olfactory organ, but their effect extends to the entire nervous system, which they stimulate; when used in excess, they are apt to cause headache in sensitive persons; the laborers in the chemical factories where these substances are produced on a large scale, occasionally even suffer by reason of their stimulating action on the nerves. For this reason perfumes should never be employed otherwise than in a very dilute condition; this necessity arises from a peculiarity of the odorous substances which when concentrated and pure have by no means a pleasant smell and become fragrant only when highly diluted. Oil of roses, of orange flowers, or of jasmine, in fact nearly all aromatic substances, have an almost disagreeable odor when concentrated; only in an extremely dilute state they yield those delightful scents which we admire so much in the blossoms from which they are derived.

It will be easier to understand the almost incredible productiveness of perfumes if we cite as an instance that a few centigrams of musk placed on a sensitive scale can for years fill a large hall with their characteristic odor without showing an appreciable loss of weight, and still particles must separate from the musk and become evenly diffused through the air of the hall because the odor is perceptible throughout every part of it.

It would be an error, however, were we to assume that all aromatic substances possess the same degree of productiveness; some of them, as for instance the odorous principle of orris root, have a comparatively faint smell—a fact which must be borne in mind in the combination of perfumes. Even odors having a very similar effect on the olfactory nerves differ widely in their intensity; for instance, true oil (attar) of roses possesses an intensity more than twice as great as that of the rose geranium; many authorities agree in giving the proportion as three to eight, the first figure being that of rose oil, the second that of oil of rose geranium. Therefore, in order to produce perfumes of equal intensity (having the same effect on the olfactory nerves), we must dissolve in an equal quantity of the menstruum either three parts by weight of the attar of roses or eight parts of the oil of rose geranium.

In the prescriptions for the preparation of perfumes given in this book, these proportions have been carefully weighed; but it will be the office of the trained olfactory sense of the manufacturer to modify them for the various kinds of perfumery in such a way as to produce a truly harmonious pleasant odor.

Although we know many aromatic substances, we are still in ignorance as to the preparation of certain decidedly agreeable odors. Thus no one at present is able to produce the refreshing odor of the sea borne along on the wind, any more than we are able to reproduce the scent exhaled by the forest, especially after a warm rain; chemistry, though it has done much in the domain of perfumery, has thus far thrown no light upon it. Even certain vegetable odors—for instance, the delightful perfume exhaled by some AroideÆ and PrimulaceÆ—we cannot as yet preserve unchanged in perfumery. This opens an illimitable field for future activity to the progressive manufacturer.

In a book devoted to the production of perfumes it would certainly be in place to say something about the physiological relations of the olfactory sensations; but unfortunately this interesting part of physiology is still enveloped in great obscurity. All we know positively on this subject is that many particles of the odorous bodies evaporate and must come in contact with the olfactory nerves in order to produce the sensation of odor. There is no lack of experiments seeking to draw a parallel between sensations of smell and those of hearing, and, as is well known, we speak of a harmony and dissonance of odors as we do of tones. Piesse, the renowned perfumer, has even made an attempt to arrange the different odors in a “harmonic scale” having the compass of the piano, and to deduce therefrom a law for the mixture of the several aromatic substances. This attempt, although very ingenious, still lacks a scientific foundation. Piesse endeavors to combine the several scents like tones to produce chords in different scales; the chords of odors are to agree with those of tones. Thus far, however, no proof has been furnished that the olfactory nerve and the acoustic nerve have the same organization, and under this supposition alone could Piesse’s system be accepted as correct.

The Division of Aromatic Substances According to their Origin.

The majority of the substances used in perfumery are derived from the vegetable kingdom, but some come from the animal kingdom, and for others which do not occur complete in nature we are indebted to chemistry. As is well known, most blossoms possess a decided odor, which is extremely fragrant in some; yet it is not the blossoms alone, but in different genera various parts are distinguished by agreeable odors. In some plants the fragrant substances are contained in every part, as in different pines and the mints; in others, only in the fruits (nutmeg, vanilla), while the other parts are odorless; in certain plants only the rinds of the fruits contain an aromatic substance (oranges, lemons). In the Florentine Iris the entire plant is odorless—only its root stock possesses an agreeable, violet-like scent; while, for instance, in the camphor-tree an aromatic substance exists in the wood, in the cinnamon laurel in the bark, in the clove-tree mainly in the closed buds.

But taking the aromatic plants all together, we find that it is particularly their flowers which contain the finest odors, and that the majority of perfumes are prepared from their blossoms.

From the animal kingdom we take for the purposes of perfumery only a very small number of substances, among which, moreover, some peculiar relation exists; while, for instance, all men would call the odor of violets, roses, vanilla, etc., agreeable, the odor of some animal substances is decidedly obnoxious to many persons, though others like it—an observation which can be verified often with reference to musk.

With the advancement of science, chemical products find application in ever increasing numbers; among them are substances which owe their origin directly to the vegetable kingdom, while others, such as nitrobenzol and pine-apple ether, are only indirectly derived from it.

From what has been stated, we learn that our attention must be directed particularly to those scents which are derived from the vegetable kingdom. To the manufacturer of perfumery, however, it is a matter of importance whence the plants are obtained which he uses for the preparation of the odors; a very slight change in the soil often makes a great difference in the quality of one and the same species; we see this quite clearly in our ordinary strawberry. While the wild fruit is but small in size it has a delightful aromatic flavor, and the same species transplanted into gardens attains much greater size but possesses only a faint aroma not to be compared with that of the wild variety. The Lombardian violet is large and beautiful, but the German has a much more pleasant odor. On the other hand, the blossoms of the orange-tree obtained from the plants cultivated in pots cannot be compared with reference to their odor with these growing in the Riviera, the strip of coast land of the Mediterranean from Marseilles to Genoa. Altogether the last-named region and the south of France may be called the true garden of the perfumer; in the neighborhood of Grasse, Cannes, Nice, Monaco, and some other towns, extensive plots of ground are set with aromatic plants such as orange-trees, Acacia farnesiana, jasmine, violets, etc., whose products are elaborated in large, well-appointed chemical factories solely devoted to the extraction of their odors. The proximity of the sea-coast, with its favorable climate almost free from frost, permits the cultivation of southern plants, while in the more elevated parts of the country the adjoining Maritime Alps cause a more changeable climate which adapts them to certain other sweet-scented plants.

The great value of the annual production of the French flower farms at Cannes, Grasse, and Nice will be evident from the following figures. The harvesting and elaboration of the flowers at the points named give employment to fifteen thousand persons, and the average annual production is:

From these flowers were manufactured: 500,000 kgm. of pomades and essences, 1,000,000 litres of orange-flower water, 100,000 litres of rose water, and 1,200 kgm. of oil of roses.

Besides, in more northern countries we find here and there quite an extensive cultivation of aromatic plants; this is the case, for instance, in England, where lavender, crisp mint, and peppermint are planted on a large scale solely for their perfume. In northern Germany, too, we sometimes find caraway and sweet flag cultivated, for their peculiar odors only, in special fields.

As stated above, the place of growth of a plant exerts a powerful influence on the quality of the odors developed in it; this circumstance may be the reason why certain scents are prized most highly when they are derived from some definite regions, because the buyer is sure that the product from such places is of superior excellence.

Thus we find that English oils of lavender and peppermint are valued more highly and bring better prices than those from other points of production; some places even have, as it were, acquired a monopoly of certain odors. While the factories at Cannes produce the most perfect odors of roses, orange flowers, jasmine, and cassie, those at Nice are famous for the finest odors of violet, reseda (mignonette), and tuberose, and those of Italy for the odors of bergamot and orris root.

Unfortunately there are in the United States no extensive places of cultivation for odoriferous plants, although certain localities are very well adapted to the growth of violets, mignonette, roses, syringa, lavender, etc. Peppermint, however, is grown on a large scale in some parts of New York State and in Michigan. Of course such an enterprise, in order to be profitable, requires the intelligent co-operation of planters and duly qualified chemists, besides well-furnished laboratories and a considerable amount of capital; but under these conditions the prospects of gain are good.

At present the manufacturers of perfumery are almost entirely dependent upon English and French factories for their supply of odors. Owing to the absence of competition, the prices for the products, excellent though they are, are high, and become still more so when the crops are short. These conditions would be materially altered under active competition.

As indicated above, the odors used in perfumery may be divided into three distinct groups according to their origin. These groups are:

1. Odors of vegetable origin.

2. Odors of animal origin.

3. Odors of artificial origin—chemical products.

Before describing the preparation of true perfumes, it is necessary to become acquainted with the several raw materials required in their manufacture; that is to say, the simple odorous substances, their origin, their preparation, and their peculiar qualities. Besides these odorous raw materials, the art of perfumery makes use of a number of chemical and mineral products, whose quality largely influences that of the perfume to be made. These, therefore, likewise call for an appropriate description. Among these auxiliary substances are alcohol, glycerin, fixed oils, and solid fats, which play an important part not only in the preparation of the perfumes, but also enter into the composition of many. The liquid handkerchief perfumes always contain a large quantity of alcohol, the scented hair oils consist largely of fixed oils, while solid fats of animal or vegetable origin occur in the so-called pomades. As we shall see, the actual odors, owing to their extraordinary productiveness, constitute generally only a small percentage of the perfumes; the greatest bulk is usually either alcohol, fixed oil, or solid fat.

Hence, as the last-named substances, aside from the odoriferous materials, form the foundation of all articles of perfumery, the manufacturer must devote particular attention to their purity, and their qualities must be discussed in detail.