# 1911 Encyclopædia Britannica/Perfumery

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​PERFUMERY (Lat. per, through, and fumare, to smoke), the preparation of perfumes, or substances which are pleasing to the sense of smell. Perfumes may be divided into two classes, the first of which includes all primitive or simple odoriferous bodies derived from the animal or vegetable kingdom, as well as the definite chemical compounds specially manufactured, while the second comprises the various “bouquets” or “mélanges” made by blending two or more of the foregoing in varying proportions-toilet powders, dentifrices, sachets, &c. To the former class belong (1) the animal products, ambergris, castor, civet, musk; (2) the essential oils (also called attars), mostly procured by the distillation of the stems, leaves, flowers and other parts of plants; (3) the philicome butters or oils, which are either solid or liquid fats charged with odours by the processes of inflowering or maceration; (4) the odoriferous gum-resins or balsams which exude naturally or from wounds in the trunks of various trees and shrubs, such as benzoin, opoponax, Peru, Tolu, storax, myrrh; (5) the large number of synthetic perfumes which simulate the odour of the natural scents. The second class contains the endless combination of tinctures sold under fancy names which may or may not afford a clue to their composition, such as “comédie française,” “eau de senteur,” “eau de Cologne,” “lavendre ambrée,” “blumengeist.” In general, they are mixtures of a number of perfumes dissolved in alcohol. Strictly speaking, most of the perfumes on the market belong to the second class, since, in most cases, they are prepared by blending various natural or artificial odorous principles.
Natural Perfumes.—The animal perfumes are extremely limited in number. Ambergris (q.v.), one of the most important, is secreted by the sperm whale; musk (q.v.), the best known scent of this class, is secreted by the male musk-deer and other animals-musk-ox, musk-rat, &c.; civet (q.v.) is a musky scent named from the animal which secretes it; and castor or castoreum is a somewhat similar secretion of the beaver (q.v.). More important are the scents yielded by flowering plants. As a general rule fragrant flowers flourish in hot climates, but the more delicate perfumes are yielded by plants having a colder habitat; it must be remembered, however, that some costly perfumes are obtained from the plants of Ceylon, the East Indies, Mexico and Peru. In Europe, Grasse, Cannes and Nice are the centres of the natural perfume industry. Cannes is famous for its rose, acacia, jasmine and neroli oil; Nimes for its thyme, rosemary and lavender; and Nice for its violets. Citron and orange oil come from Sicily; iris and bergamot from Italy; and roses are extensively cultivated in Bulgaria, and in European Turkey. England is unsurpassed for its lavender and peppermint, which flourish at Mitcham and Hitchin.
The natural sources of the attars or essential oils are the different parts of the plants which yield them—the wood (lign, aloe, santal, cedar), the bark (cinnamon, cascarilla), the leaves (patchouli, bay, thyme), the flowers (rose, lavender, orange blossom), the fruit (nutmeg, citron), or the seeds (caraway, almond). Some plants yield more than one, such as lemon and bergamot. They are mostly obtained by distilling that part of the plant in which they are contained with water, or with high pressure or superheated steam; but some few, as those from the rind of bergamot (from Citrus bergamia), lemon (citron zeste, from C. Limonum), lime (C. Limetta), by “expression.” The outer layer of the cortex is rasped off from the unripe fruits, the raspings placed in a canvas bag, and squeezed in a screw or hydraulic press. The attars so obtained are separated from the admixed water by a tap-funnel, and are then filtered. Certain flowers, such as jasmine, tuberose, violet, cassia, either do not yield their attars by distillation at all, or do it so sparingly as not to admit of its collection for commercial purposes; and sometimes the attar, as in the case of orange (neroli), has an odour quite different from that of the fresh blossoms. In these cases the odours are secured by the processes of in flowering (enfleurage) or by maceration. Both depend upon the remarkable property which fats and oils possess of absorbing odours. Enfleurage consists in laying the leaves or flowers on plates covered with a layer of fat. The flowers are renewed every morning, and when the fat has sufficient odour it is scraped off, melted and strained. Maceration consists in soaking the flowers in heated fat; in due time they are strained off and replaced by fresh ones, as in the enfleurage process. The whole of the necessary meltings and heatings of the perfumed greases are effected by means of water-baths, whereby the temperature is kept from rising too high. For the manufacture of perfumes for the handkerchief the greases now known as pomades, butters or philocomes are treated with rectified spirit of wine 6o° overproof, i.e. containing as much as 95% of absolute alcohol by volume, which practically completely abstracts the odour.
The gum-resins and resins have been employed as perfumes from the earliest times. The more important are incense, frankincense and myrrh (q.v.). They are largely used in the manufacture of perfumes, both for burning as pastilles, ribbon of Bruges, incenses, &c., and in tinctures, to which they impart their characteristic odours, affording, at the same time, a certain fixity to other perfumes of a more fleeting nature when mixed with them.
Synthetic Perfumes.—Under this heading are included all perfumes in which artificial substances are odorous ingredients. Although the earliest perfumes of this class were introduced in about the middle of the 19th century, the important industry which now prevails is to be regarded as dating from the 'seventies and 'eighties. Three main lines of development may be distinguished: (1) the chance discovery of substances which have odours similar to natural perfumes; (2) the elucidation of the composition of the natural scents, and the chemical constitution of their ingredients, followed by the synthetic preparation of the substances so determined; and (3), which may be regarded as connected with (2), the extraction and separation of the essential oils yielded by less valuable plants, and their reblending to form marketable perfumes.
The first synthetic perfume was the “essence of Mirbane” introduced by Collas in about 1850; this substance was the nitro-benzene discovered by E. Mitscherlich in 1834. Soon afterwards many esters of the fatty acids simulating the odours of fruits were introduced; and in 1888 Baur discovered the “artificial musks,” which are derivatives of s-trinitrobenzene. The above are instances of the first line of progress. The second line has for early examples the cases of artificial oil of wintergreen, which followed Cahour's discovery that the natural oil owed its odour, in the main, to methyl salicylate, and of artificial oil of bitter almonds which followed the preparation of benzaldehyde from benzal chloride in 1868. The synthesis of coumarin, the odorous principle of hay and woodruff, by Sir W. H. Perkin in 1868; of vanillin, the odorous principle of vanilla, by F. Tiemann and W. Haarmann in 1875; and of ionone, almost identical with the natural irone, the odorous principle of violets, by Tiemann and P. Kruger in 1808, are to be regarded as of the highest importance. Equally important are the immense strides made in the elucidation of the constitution and syntheses of the terpenes (q.v.), a group of compounds which are exceptionally abundant as odorous principles in the essential oils.
The present state of our knowledge does not permit a strict correlation of odour and chemical constitution. One theory regards odour as due to “osmophores” or odour-producing groups, in much the same way as colour is associated with chromophores. Such osmophores are hydroxyl (OH), aldehyde (CHO), ketone (CO), ether (·O·), nitrile (CN), nitro (NO$_2$), &c.; we may also notice the isonitrile group (·NG) associated with an unpleasant odour, and the iso-thiocyanate group (·NCS) to which the mustard oils owe their characteristic smell. The same group, however, is not invariably associated with the same odour, or even any odour at all, as, for instance, in such closely related ​compounds as the members of a homologous series. For example, the lower fatty aldehydes have unpleasant odours, those with ten carbon atoms (and also double linkages, which in itself may affect odour) form some of the most delicate scents, while the higher members are odourless. The absence of odour in the higher members may be possibly associated with the low volatility exhibited by compounds of high molecular weight. Certain osmophores have practically equal effects; for example, benzaldehyde, nitrobenzene, benzonitrile, and phenyl azoimide have practically identical odours, and among the “artificial musks,” a nitro group may be replaced by the azoimido group without the odour being modified. As a general rule, homologues have similar odours, but many exceptions are known. For example the methyl and ethyl ethers of β-naphthol have the odour of neroli; on the other hand, of the esters of anthranilic acid, the methyl has the odour of orange blossoms, the ethyl has a slight odour, and the isobutyl is odourless. The introduction of a methyl group into the benzene ring generally involves little or no change in odour; but when it (and more especially higher alkyl radicals) is introduced into side chains the odour may be entirely changed. For example, benzene and its homologues have similar odours; phthalide is odourless, but the isopropyl and butyl phthalides, in which substitution occurs in the side chain, smell of celery. Especially characteristic are the derivatives of phenylacetylene. This hydrocarbon is distinctly unpleasant; on the other hand, para-ethyl and para-methyl phenylacetylene smell of anise. While the triply-linked carbon system is generally associated with strong and unpleasant odours, the doubly linked system gives pleasant ones. Thus the unpleasant phenylacetylene, C$_6$H$_5$·C⋮CH, is contrasted with styrolene, C$_5$H$_5$·CH.CH$_2$, which occurs in storax, and phenylpropiolic aldehyde with cinnamic aldehyde, C$_6$H$_5$·CH:CH·CHO, which occurs in cassia and cinnamon. The reduction of a double to a single linkage may not destroy odour. Thus hydrocinnamic aldehyde, the reduction product of cinnamic aldehyde, smells of jasmine and lilac, and melilotin, which occurs in yellow melilot (Melilotus officianalis), has the same odour (woodruff) as its oxidation product coumarin. The orientation of the substituent groups in the benzene nucleus also affects odour. In general, the meta compounds are odourless, while the ortho and para may have odour. Thus p-methoxyacetophenone has a pleasant odour, the meta compound is odourless, o-aminoacetophenone, o-aminobenzaldehyde, and o-nitrophenol have strong odours, while the meta and para bodies are odourless. Of the three trinitrobenzenes only the symmetrical form gives origin to perfumes.
The concentration and even the solvent has considerable effect on the odour of a substance. Many of the artificial principles—vanillin, heliotropine, ionone, &c.—have very different odours in strong and in dilute solution; phenyl acetic acid and β-naphthylamine are odourless when solid, but have disagreeable odours when dissolved. Traces of impurities often have the effect of making odourless or pleasant-smelling compounds quite intolerable. Acetylene as generated from calcium carbide, and carbon disulphide prepared from its elements are quite intolerable, though when pure they are, at least, not unpleasant; artificial benzaldehyde must be very carefully purified before it can be used in the preparation of the more delicate scents. In all cases the natural scents are complex mixtures of many ingredients, and a variation in the amount of any one may completely alter the scent. Such mixtures would be difficult to reproduce economically; the perfumer is content with a product having practically an identical odour, with or without the natural substance which it is designed to compete with.
We now give an account of the artificial scents, principally arranged according to their chemical relations. The fatty esters are interesting as providing many of the fruit essences; in fact, by appropriate blending, any fruit odour can be reproduced. Their use, however, is inhibited by the fact that they irritate the respiratory organs, producing coughing and headaches. Isobutyl carbinol acetic ester (amyl acetate), (CH$_2$)$_2$ CH CH$_2$·CH$_2$·OC·CH$_3$, forms when in dilute alcoholic solution the artificial pear oil; a similar odour is possessed by isoamyl-n-butyrate, C$_3$H$_7$·CO$_2$·C$_5$H$_{11}$. n-Octyl acetate, C$_8$H$_{11}$·O$_2$C·CH$_3$, has the odour of oranges. Isoamyl propionate, C$_5$H$_{11}$·O$_2$C·C$_2$H$_5$, and ethyl-n-butyrate, C$_3$H$_7$·O$_2$C·C$_2$H$_5$, have the odour of pineapple, the latter constituting the artificial pineapple oil of commerce. Isoamyl isovalerate, C$_5$H$_{11}$·O$_2$C·C$_4$H$_9$, is the artificial apple oil. Of the fatty ketones, methyl nonyl ketone, CH$_3$·CO·C$_9$H$_{19}$, which is the scent of oil of rue, and methyl ethyl acetone, CH$_3$·CO·CH(CH$_3$) (C$_2$H$_5$), which has the odour of peppermint, receive commercial application. Of exceptional importance in the chemistry of perfumes are the unsaturated open chain compounds containing at least eight carbon atoms. These are chemically considered, along with the related cyclic compounds, in the article Terpenes; here we notice their odours and occurrence in perfumes. Of the alcohols, l-linalol occurs in oil of lavender, bergamot, limet and origanum; d-linalol in coriander; citronellol and geraniol in rose, geranium and pelargonium oils. Of the aldehydes, citral or geranial has the odour of lemons; citronella is the chief constituent of citronella oil. By condensing citral with acetone and treating the product with dilute sulphuric acid, the valuable violet substitute ionone results. This substance is a hydroaromatic ketone, and closely resembles the natural principle irone. By successive treatment with acetic anhydride (to form isopulegol), oxidation to isopulegone, and treatment with baryta citronella yields the cyclic compound pulegone, the chief constituent of oil of penny royal. The olefinic terpenes are generally convertible into methyl heptenone, (CH$_3$)$_2$C:CH(CH$_2$)$_2$·CO·CH$_3$, which has been synthesized from sodium acetonylacetone and amylene dibromide; this ketone occurs in several essential oils, and has the odour of rue. For the occurrence of cyclic terpenes in the essential oils reference should be made to the table below, which contains the names, sources and chief ingredients of the more important essential oils The terpenes are printed in italics, the aliphatic and benzenoid compounds in ordinary type.
The Odophone.—The most important element in the perfumer's art is the blending of the odorous principles to form a mixture which gratifies the sense of smell. Experience is the only guide. It is impossible to foretell the odour of a mixture from the odours of its components. Septimus Piesse endeavoured to show that a certain scale or gamut existed amongst odours as amongst sounds, taking the sharp smells to correspond with high notes and the heavy smells with low. He illustrated the idea by classifying some fifty odours in this manner, making each to correspond with a certain note, one-half in each clef, and extending above and below the lines. For example, treble clef note E (4th space) corresponds with Portugal (orange), note D (1st space below clef) with violet, note F (4th space above clef) with ambergris. It is readily noticed in practice that ambergris is much sharper in smell (higher) than violet, while Portugal is intermediate. He asserted that properly to constitute a bouquet the odours to be taken should correspond in the gamut like the notes of a musical chord—one false note among the odours as among the music destroying the harmony. Thus on his odophone, santal, geranium, acacia, orange-flower, camphor, corresponding with C (bass 2nd line below), C (bass 2nd space), E (treble 1st line), G (treble 2nd line), C (treble 3rd space), constitute the bouquet of chord C.
Other Branches of Perfumery.—As a natural outcome of the development of the perfume industry, scented articles for toilet and other uses are now manufactured in large quantities. Soaps, toilet powders, tooth powders, hair-washes, cosmetics generally, and note-paper have provided material on which the perfumer works. For the preparation of scented soaps two methods are in use; both start with a basis either of fine yellow soap (which owes its odour and colour to the presence of resin), or of curd soap (which is hard, white and odourless, and is prepared without resin). In one process the soap is melted by superheated steam, and while still hot and semi-fluid mixed by means of a stirrer of wood with iron cross-bar, technically called a “crutch,” with the attars and colouring matter. It is then removed from the melting pan to a rectangular iron mould or box, the sides of which can be removed by unscrewing the tie-rods which hold them in position; when cold the mass is cut into slabs and bars with a thin brass wire. In the other or cold process the soap is first cut into chips or shavings by a plane or “chipping machine,” then the colouring matters are added and thoroughly incorporated by passing the soap between rollers; the tinted soap emerges in a continuous sheet but little thicker than paper. he perfumes are then added, and after standing for about twelve hours the soap is again sent through the rolling machine. It is next transferred to a bar-forming machine, from which it emerges as a continuous bar almost as hard as wood. Soap thus worked contains less than 10% of water; that prepared by melting contains 20 and even 30%. The amount of perfume added depends upon its nature, and amounts usually to about 7 or 8%. The finest soaps are always manufactured by the cold process.
Toilet Powders are of various sorts. They consist of rice-starch or wheat-starch, with powdered orris-root in varying proportions, and with or without the addition of zinc oxide, bismuth oxide or French chalk. The constituent powders, after the addition of the perfume, are thoroughly incorporated and mixed by sifting through a fine sieve. Violet powder for the nursery should consist entirely of powdered violet root (Iris florentina), from the odour of which the powder is named. It is of a yellowish tint, soft and pleasant to the touch. The white common so-called “violet powders” consist of starch scented with bergamot, and are in every sense inferior.
Tooth Powders consist for the most part of mixtures of powdered orris-root with precipitated chalk, and some other constituent destined to particularize it as to properties or flavour, such as charcoal, finely pulverized pumice, quassia, sugar, camphor, &c. The perfume of the contained orris-root is modified, if required, by the addition of a little of some perfume. Tooth Pastes are formed of the same constituents as the powders, and are worked into a paste by the addition of a little honey or glucose syrup, which substances are usually believed ultimately to have an injurious effect on the teeth.
Perfume Sachets consist either of a powder composed of a mixture of vanilla, musk, Tonqua beans, &c., one or other predominating as required, contained in an ornamental silk sac; or of some of the foregoing substances spread upon card or chamois leather or flannel after being made into a paste with mucilage and a little glycerin. When dry the card so prepared is daintily covered with various parti-coloured silks for sale. Where the ingredients employed in their manufacture are of good quality these cards, known as “peau d'Espagne” sachets, retain their odour unimpaired for years.
Adulterations.—There is, as might be expected, considerable scope for the adulteration of the “matières premières” employed in perfumery. Thus, in the case of musk, the “pods” are frequently found to be partially emptied of the grain, which has been replaced by hide or skin, while the weight has been increased by the introduction of lead, &c. In other instances the fraud consists in the admixture of refuse grain, from which the odour has been exhausted with spirit, with dried blood, and similar substances, whilst pungency is secured by the addition of ammonium carbonate. Attar of rose is diluted with attar of Palma rosa, a variety of geranium of only a quarter or a fifth of the value. The main adulterant of all the natural essential oils, however, is castor oil. This is a bland neutral body, practically odourless, and completely soluble in alcohol; it therefore presents all the requisites for the purpose.
Bibliography.—See generally, J. C. Sawyer, Odorographia, vol. i. (1892), vol. ii. (1894); G. W. Askinson, Perfumes (Eng. trans. by Isidor Furst, 1892); S. Piesse, Art of Perfumery (1891); Paul Hubert, Plantes à parfumes (1909); M. Otto, L'Industrie des parfums (1909). Synthetic perfumes are treated in detail in C. Deite, Manual of Toilet Soap-making (Eng. trans. by S. I. King, 1905), and in E. J. Parry, Chemistry of the Essential Oils and Artificial Parfumes (2nd ed., 1908). Reference may also be made to T. Koller, Cosmetics (1902). The standard works on the essential oils are given in the article Oils. G. Cohn, Die Riechstoffe (1904), treats the chemistry, and Zwaardemaker, Physiologie des Geruchs (1895), the physiology of perfumes. See also the reports and bulletins of Schimmel & Co. and Rouse Bertrand et Fils.