A PRACTICAL TREATISE
ON THE
MANUFACTURE OF PERFUMERY:

COMPRISING

DIRECTIONS FOR MAKING ALL KINDS OF PERFUMES, SACHET
POWDERS, FUMIGATING MATERIALS, DENTIFRICES,
COSMETICS, ETC., ETC.,

WITH A FULL ACCOUNT OF THE

VOLATILE OILS, BALSAMS, RESINS, AND OTHER NATURAL
AND ARTIFICIAL PERFUME-SUBSTANCES, INCLUDING
THE MANUFACTURE OF FRUIT ETHERS, AND
TESTS OF THEIR PURITY.

BY

Dr. C. DEITE,
Assisted by L. BORCHERT, F. EICHBAUM, E. KUGLER,
H. TOEFFNER, and other experts.

FROM THE GERMAN BY

WILLIAM T. BRANNT,
EDITOR OF "THE TECHNO-CHEMICAL RECEIPT-BOOK."

ILLUSTRATED BY TWENTY-EIGHT ENGRAVINGS.

PHILADELPHIA:
HENRY CAREY BAIRD & CO.,
INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS,
810 WALNUT STREET.
1892.

Copyright by
HENRY CAREY BAIRD & CO.
1892.

Printed at the COLLINS PRINTING HOUSE,
705 Jayne Street,
Philadelphia, U. S. A.

[PREFACE.]

A translation of the portion of the "Handbuch der Parfümerie-und Toiletteseifenfabrikation," edited by Dr. C. Deite, relating to perfumery and cosmetics, is presented to the English reading public with the full confidence that it will not only fill a useful place in technical literature, but will also prove—for what it is chiefly intended—a ready book of reference and a practical help and guide for the perfumer's laboratory. The names of the editor and his co-workers are a sufficient guaranty of its value and practical usefulness, they all being experienced men, well schooled each in the particular branch of the industry, the treatment of which has been assigned to him.

The most suitable and approved formulæ, tested by experience, have been given; and special attention has been paid to the description of the raw materials, as well as to the various methods of testing them, the latter being of special importance, since in no other industry has the manufacturer to contend with such gross and universal adulteration of raw materials.

It is hoped that the additions made here and there by the translator, as well as the portion relating to the manufacture of "Fruit Ethers," added by him, may contribute to the interest and usefulness of the treatise.

Finally, it remains only to be stated that, with their usual liberality, the publishers have spared no expense in the proper illustration and the mechanical production of the book; and, as is their universal practice, have caused it to be provided with a copious table of contents and a very full index, which will add additional value by rendering any subject in it easy and prompt of reference.

W. T. B.

Philadelphia, May 2, 1892.

[CONTENTS.]

A PRACTICAL TREATISE
ON THE
MANUFACTURE OF PERFUMERY.

[CHAPTER I.]

HISTORICAL NOTICE OF PERFUMERY.

Nature has implanted in man the instinct of finding the odor accompanying decay and putrefaction insufferable, of fleeing from it, and of going in quest of fragrant odors. Hence, in ancient times, perfume substances were highly esteemed, and an offering of them was considered a sign of the most profound reverence and homage. The early nations of the Orient especially used perfume substances in such profusion that the consumption of them by the finest lady of to-day must be called a comparatively moderate one. This may, however, be readily explained, for, on the one hand, the majority of plants which produce the most agreeable perfumes in larger quantity are indigenous to the Orient; and, on the other, the excessive exhalations from the human body, caused by the hot climate, forced the people to search for means to remove, or at least to cover, the disagreeable odor arising therefrom.

Since fragrant odors were agreeable to human beings, it was believed that they must be welcome also to the gods, and, to honor them, perfume substances were burned upon the altars. Besides, as an offering to the gods, perfume substances were extensively used by many nations, especially by the Egyptians, for embalming the dead, the process employed by the latter having been transmitted to us by the ancient authors Herodotus and Diodorus.

Furthermore, a desire for ornamentation and to give to the face and body as pleasing an appearance as possible, is common to all mankind. To be sure, the ideas of what constitutes beauty in this respect have varied at different times and among the various nations. But, independent of the savage races, who consider painting and tattooing the body and face an embellishment, and taking into consideration only the earliest civilized nations, it is astonishing how many arts of the toilet have been preserved from the most ancient historical times up to the present. "In the most ancient historical times, people perfumed and painted, frizzed, curled, and dyed the hair as at present, and, in fact, the same cosmetics, only slightly augmented, which were in use hundreds, nay, thousands, of years ago are still employed to-day."[1] It is especially woman, who everywhere exercises the arts of the toilet, while, with the exception of perfumes and agents for the hair, man is but seldom referred to as making use of cosmetics. The young girls of ancient Egypt used red and white paints, colored their pale lips, and anointed their hair with sweet-scented oils; they dyed their eyelashes and eyelids black to impart a brighter lustre to the glance of the eye, and the mother of the wife of the first king of Egypt is said to have already composed a receipt for a hair-dye.

From the Egyptians, the practices of the toilet, like many other things, were transmitted to the Jews. In Egypt, the Hebrew woman had known the sweet-scented flower of the henna bush, and, finding it also in Judea, it served her as a perfume. In the Bible the henna flower is called kopher, in Greek kypros, and the Cyprian salve, mentioned by Pliny, was prepared by boiling henna flowers in oil and then expressing them.

Painting the face was also practised by the Hebrew women, reference being made to it in II. Kings ix. 30, and Jeremiah v. 30, while painting of the eyes is mentioned in Ezekiel xxiii. 40.

The number of perfume substances known to the ancient Hebrews was but a limited one, they consisting, besides the above-mentioned henna flower, chiefly of a few gum-resins, especially bdellium, olibanum and myrrh.

In ancient times olibanum was, without doubt, the most important perfume-substance. It was introduced into commerce by the Phoenicians, and, like many other substances, it received from them its name, which was adopted by other nations. Thus, the Hebrews called the tree lebonah, the Arabs, lubah, while the Greeks named it, λιβανός and the resin derived from it, the celebrated frankincense of the ancients, λιβανωτόςτς, Latin, olibanum. Regarding the mode of gaining the olibanum, some curious ideas prevailed in ancient times. Thus, Herodotus writes: "Arabia is the only country in which olibanum grows, as well as myrrh, cassia, cinnamon and lederum. With the exception of myrrh, the Arabs encounter many difficulties in procuring these products. Olibanum they obtain by burning styrax, for every olibanum tree is guarded by a number of small-sized winged serpents of a variegated appearance, which can be driven away by nothing but styrax vapors." According to Pliny, who gives a very full account of olibanum, Arabia felix received its by-name from the abundance of olibanum and myrrh found there. He states that olibanum grows in no other country besides Arabia, but it is not found in every part of it. About in the centre, upon a high mountain, he continues, is the country of the Atramites, a province of the Sabeans, from which the olibanum region is distant about eight days' journey. It is called Saba and is everywhere rendered inaccessible by mountains, a narrow defile, through which the export is carried on, leading into an adjoining province inhabited by the Mineans. In Saba itself were not more than 300 families, called the saints, who claimed the cultivation of olibanum as a right of heritage. When making the incisions in the trees, and while gathering the olibanum, the men were prohibited from having intercourse with women and from attending funerals. Notwithstanding the fact that the Romans carried on war in Arabia, none of them had ever seen an olibanum tree. When there was less chance of selling the olibanum, it was gathered but once in the year, but since the increase in the demand, it was gathered twice, first in the fall and again in the spring, the incisions in the trees having been made during the winter. The collected olibanum was brought upon camels to Sabota, where one gate was open for its reception; to turn from the road was prohibited under penalty of death. The priests took one-tenth by measure for the god Sabin, sales not being allowed until their claim was satisfied. The olibanum could be exported only through the territory of the Gebanites, whose King also levied tribute.

Pliny further states that the Arabs did not steal one from another, but for fear of loss those employed in the stores of Alexandria were forced to go naked with the exception of a clout which was sealed. A mask and a thick net were thrown over the head.

To us the practice of anointing the entire body, customary among the ancients, appears very singular. Old Egyptian sculptures represent the guests being anointed at the meal. Among the Jews we find a holy oil with which Aaron and his sons were anointed to consecrate them to the priesthood, Moses prescribing for this holy anointing oil, myrrh, cinnamon, calamus, and oil from the olive tree. Other persons were prohibited from imitating or using this holy oil. The anointing of kings was introduced later on. Though it was prohibited to imitate and use the holy oil, this prohibition did not refer to anointing with oil in general.

That the Greeks also set a high value upon anointing with oil is plainly seen from Homer. When Telemachus visited Nestor, Polycaste, Nestor's youngest daughter, bathed him and anointed him with oil, and when he was the guest of Menelaus, the maids of the latter performed the same service for him, while for Ulysses returning as a beggar, the aged Euryclea prepared a foot-bath and anointed him.

By the addition of fragrant substances to the oil, the sweet-scented ointment, myron, originated. While the anointing with simple oil evidently served as a hygienic measure after the bath, and especially for men in the gymnasium, and before a combat, with the Greeks, ointments were an article of luxury. In Socrates' time the use of sweet-scented ointments had reached such an extent, that Xenophon caused him to speak against it, but, as is the case with all such lectures against fashion, without the slightest success. In Athens the luxury was carried so far that the bacchanalians anointed each part of their body with a special ointment. The oil extracted from the palm was thought best adapted to the cheeks and the breasts; the arms were refreshed with balsam-mint; sweet marjoram supplied an oil for the hair and eyebrows; and wild thyme for the knee and neck. Although to us it would be repugnant to have the entire body anointed, in Athens it was considered beautiful to be glossy with ointments. It is said of Demetrius Phalereus, that in order to appear more captivating, he dyed his hair yellow, and anointed the face and the rest of his body.

From the Asiatics and Greeks the Romans also learned the use of ointments. Pliny cannot say at what time they were introduced in Rome, but states that after the conquest of Asia and the defeat of the King, Antiochus, in the year 565, after the building of Rome, the censors issued an edict prohibiting the sale of foreign ointments. However, this edict was of no use, and the practice spread more and more, Pliny speaking very bitterly about it. Regarding this extravagance in ointments, Plutarch says: "Frankincense, cinnamon, spikenard, and Arabian calamus are mixed together with the most careful art and sold for large sums. It is an effeminate pleasure and has spoiled not only the women but also the men, who will not sleep even with their own wives if they do not smell of ointments and powders." Plutarch further mentions an incident which must have created a sensation even in luxurious Rome, as otherwise it would scarcely have been chronicled for the benefit of posterity. Nero one day anointed himself with costly ointments and scattered some of them over Otho. The next day Otho gave Nero a banquet, and laid in all directions gold and silver tubes, which poured forth expensive ointments like water, thoroughly saturating the guests.

Directions for preparing ointments are contained in Theophrastus's work "On Perfumes," in Dioscorides's "Medica materia," and Pliny's "Historia naturalis." Dioscorides's receipts are the fullest. According to Pliny, a distinction was made between the juice and the body, the latter consisting of the fat oils and the former of the sweet-scented substances. In preparing the ointments, the oil together with the perfuming substances were heated in the water-bath. For instance, rose ointment was, according to Dioscorides, prepared by mixing 5½ lbs. of bruised Andropogon Schœnanthus with a little water, then adding 20½ lbs. of oil and heating. After heating the oil was filtered off, and the petals of one thousand roses were thrown into the oil, the hands with which the rose leaves were pressed into the oil being previously coated with honey. When the whole had stood for one night, the oil was strained off and when all impurities had settled, it was brought into another vessel and fresh rose leaves introduced, the operation being several times repeated. However, according to the opinion of the ancient ointment makers, no more odor was absorbed by the oil after the seventh introduction of rose leaves. To fix the odor, resins or gums were added to the ointments.

A process of distilling volatile oils was also known, the odoriferous matter being caught by spreading wool over the heated perfume-substances. The wool was afterwards subjected to pressure. This process, of course, involved great loss and was available only for substances containing much volatile oil.

Dioscorides also gives directions for making animal fats suitable for the reception of perfumes. Beef-tallow, deer-fat, or the marrow of animals was freed from all membranes, melted together with a little salt in an entirely new vessel, and then poured into clean water, where it was washed by rubbing with the hands, the water being frequently renewed. Then it was boiled with equal parts of sweet-scented wine, and after taking it from the fire it was allowed to stand over night. The next day the cold fat was again boiled in a new vessel, with sweet-scented wine, this operation being repeated until the fat had lost every trace of disagreeable odor, when it was brought in contact with the perfumes.

The consumption of perfume-substances by the ancient Romans must have been enormous. The trade of the ointment makers (ungentarii) was so extensive that the large street Seplasia in old Capua was entirely taken up by it, and the business must have paid well since the prices realized were very high. However, in ancient times the business cannot have been very agreeable, at least not in Greece, as shown by a passage in Plutarch's Life of Pericles: "We take pleasure in ointments and purple, but consider the dyers and ointment makers bondsmen and mechanics."

Red and white paints, in the form of powder as well as of paste, were extensively used by the Roman ladies. Chalk and white lead served for white paint, and minium and carmine for red. Lovers preferred white paints, a pale color being more becoming to them:—

"Palleat omnis amans; hic est

color aptus amanti."—(Ovid.)

For black paints for the eyebrows roasted ant eggs or soot were used.

The Roman ladies paid as much attention to their natural, and also false, hair as the fair ones of to-day. They curled their hair with heated iron instruments, and perfumed them with fragrant oil. If from age, sorrow, or other reasons, the hair was no longer black, it was dyed, and it seems that a considerable number of hair-dyes were known in Rome, amongst them some which are still employed to-day, such as green nutshells and acetate of lead.

After the Romans had seen the blonde German maidens, blonde and red hair became the fashion. To dye the hair blonde sharp alkaline soaps were chiefly used. However, this or some other hair-dye seems to have been very injurious, as it caused the hair to come out. The satirists ridiculed this as well as the wigs, which were worn by men and women to hide baldness, or on account of the color which could not be attained by dyes.

Depilatories were also known to the Romans, the agents employed being called psilothrum and dropax. They were of vegetable origin, but it is not exactly known from which plants they were derived.

For cleaning the teeth the Roman ladies used a dentifrice which does not seem very inviting to us. It consisted of a urine imported from Spain (dens hiberna defricatus urina). To perfume the breath or to hide its bad odor, mouth-washes, perfumed with saffron, roses, etc., were used, or myrrh, mastic from Chios or perfumed pastilles were chewed.

We know but little regarding the use of perfumeries and cosmetics in the Middle Ages. In the wars during the migrations of the nations, but little thought was very likely given to them, but as soon as the nations became again settled and made sufficient progress in culture, the taste for perfumes and other pleasures of life no doubt returned. Our knowledge in this respect is limited to what is contained in the works of physicians of the first centuries. Later on we find receipts for cosmetics in the writings of Arabian physicians, such as Rhazes (end of the 9th to the commencement of the 10th century), Avicenna (end of the 10th to the commencement of the 11th century), and Mesuë (11th century). To the 11th century also belong the works of the celebrated Trotula, "De mulierum passionibus," "Practica Trotulae mulieris Salernitanae de curis mulierum," and "Trotula in utilitatem mulierum," all of which contain receipts for cosmetics. In the 14th century the most celebrated surgeon of the Middle Ages, Guy de Chanlios, did not consider it beneath his dignity to devote a section of his "Grande Chirurgie" to cosmetics. However, it was only in the 16th century that perfumes and cosmetics came again into prominent notice in Italy, which at that time was the country of luxury and art. Giovanni Marinello,[2] a physician, in 1562 wrote a work on "Cosmetics for Ladies," which he dedicated to the ladies Victoria and Isabella Palavicini. In the preface the author expresses the opinion that it is only right and pleasing to God to place the gifts bestowed by him in a proper light and to heighten them. He then proceeds to give perfumes for various purposes, aromatic baths to keep the skin young and fresh, means for increasing the stoutness of the entire body and of separate limbs, and others for reducing them. He further recommends certain remedies for making large eyes small, and small ones large. The chapter on the hair is very fully treated. To prevent the hair from coming out, rubbing with oil, and then washing with sorrel and myrobalan is recommended. For promoting the growth of the hair, the use of dried frogs, lizards, etc., rubbed to a powder, is prescribed. Means for making the hair long and soft and curly are also given, and others recommended for eyebrows and eyelashes. As depilatories lime and orpiment are prescribed. Paints are also classed among general cosmetics. Their use became at this time more and more fashionable, and not only the face, but also the breast and neck were painted.

Catherine of Medici and Margaret of Valois introduced these arts of the toilet into France. That country soon became the leader in this respect, and for many years the greatest luxury in perfumes and cosmetics prevailed there. The golden age for these articles lasted from the commencement of the seventeenth to the middle of the eighteenth century, during which time the mouche or beauty patch also flourished. "There were at that time hundreds of pastes, essences, cosmetics, a white balsam, a water to make the face red, another to make a coarse complexion delicate, one to preserve the fine complexion of lean persons and again one to make the face like that of a twenty-year old girl, an Eau pour nourir et laver les teints corrodés and Eau de chair admirable pour teints jaunes et bilieux, etc. Then there were Mouchoirs de Venus, further bands impregnated with wax to cleanse and smooth the forehead; gold leaf was even heated in a lemon over a fire in order to obtain a means which should impart to the face a supernatural brightness. For the hair, teeth and nails there were innumerable receipts, ointments, etc. However, of special importance were the paints, chemical white, blue for the veins, but, chief of all, the red or rouge, mineral, vegetable, or cochineal. The application of rouge was at that time no small affair, it was not only to be rouged, but the rouge had also to express something—Le grand point est d'avoir un rouge qui dise quelque chose. The rouge had to characterize its wearer; a lady of rank did not wear the rouge like a lady of the court, and the rouge of the wife of the bourgeois was not like either of them nor like that of the courtesan. At court a more intense rouge was worn, the intensity of which was still increased on the day of presentation, it being then Rouge d'Espagne and Rouge de Portugal en tasse. It may seem incredible, but for eight days a violet paint was used and then for a change Rouge de Serkis. Ladies, when retiring for the night applied a light rouge (un demi rouge), and even small girls wore rouge, such being the decree of fashion. The ladies dyed their eyebrows and eyelashes, and powdered their hair, both natural and false, for, about 1750, they commenced wearing wigs and chignons. Powdering was done partially for the purpose of dying the hair after dressing, and partially for decoration; white, gray, red and fiery red powders were in vogue."

To that time fashion also ordained an ever-varying routine in the employment of perfumes; so that the royal apartments were one day fragrant with the scent of the tuberose and the next with that of amber and cloves; and so on consecutively, each succeeding day bringing a change of the reigning odor. In that luxurious age the personal use of perfumes was not confined to the fair sex, but the effeminate gallants of the day gloried in perfuming themselves with the favorite scents of their mistresses or of prominent belles; so that the allegiance was recognized, not as in more chivalrous times by the knight wearing the colors of the fair one who had enslaved him, but by his smelling of the particular odor which she had consecrated to herself.

Philip Augustus, in 1190, granted a charter to the French perfumers, who had formed a guild. This charter was, in 1357, confirmed by John, and in 1582 by Henry III., and remained in force until 1636. The importance of the craft in France is shown by the fact that under Colbert the perfumers or "parfumeurs-gantiers," as they were called, were granted patents which were registered in Parliament. In the seventeenth century Montpellier was the chief seat of the French perfumery industry; to-day it is Paris, and over fifty millions of francs' worth of perfumery are annually sold there. The parfumeurs-gantiers had the privilege of selling gloves of all possible kinds of material, as well as the leather required for them; they had the further privilege of perfuming gloves and selling all kinds of perfumes. Perfumed leather for gloves, purses, etc., was at that time imported from Spain. This leather was very expensive and fashionable, but on account of its penetrating odor its use for gloves was finally abandoned.

In England perfumes were not in general use before the reign of Queen Elizabeth, when they soon became fashionable. Elizabeth had an especially finely developed sense of smell and nothing was more repugnant to her than a disagreeable odor. She had a cloak of perfumed Spanish leather, and even her shoes were perfumed. Perfumed gloves were also fashionable. The city soon imitated the practices of the court, and that an extravagant use was made of perfumeries and cosmetics is plainly seen from the works of the authors of that time, as well as from an act of Parliament passed in 1770. By the latter it is ordained that any woman, no matter of what age or rank, be she maid or widow, who deceives a man and inveigles him into matrimony by the use of perfumeries, false hair, Crépons d'Espagne (a paint), corsets, hooped petticoats, shoes with high heels, and false hips, shall suffer the penalty of the law for procuring, and the marriage shall be null and void.

[CHAPTER II.]

THE PERFUME-MATERIALS FOR THE MANUFACTURE OF PERFUMERY.

Most of the perfume-materials employed by the perfumer are derived from the vegetable kingdom; a few are of animal origin, whilst some are artificially prepared.

Of animal substances only four are used, namely: musk, castor or castoreum, civet, and ambergris; the separation of their characteristic odoriferous substances has, however, not yet been accomplished. The odor of plants is generally due to volatile substances called volatile or essential oils. Their occurrence is not limited to special parts, they being found in the flower, seed, wood, bast, bark, leaves, and root. However, in every plant the oil occurs chiefly in certain organs, and it even happens that the oil differs with the part of the plant whence it is derived. The odors exist already formed in the living plant, or else are generated, as in the instance of bitter almonds, by some reaction between the elements which takes place during fermentation or distillation.

From the strength of the odor of a plant no conclusion can be drawn as to the quantity of volatile oil present. If this were the case, the hyacinth, for instance, would contain more oil than the coniferae, whilst in fact it contains so little that it can be separated only with the greatest difficulty. The odor does not depend on the quantity, but on the quality of the oil; a plant may diffuse but little odor and still contain much volatile oil. Of the various families of plants, the labiatae, umbelliferae, and coniferae are richest in volatile oils.

In every climate plants diffuse odor, those growing in tropical latitudes being more prolific in this respect than the plants of colder regions, which, however, yield the most delicate perfume. Although the East Indies, Ceylon, Peru, and Mexico afford some of the choicest perfumes, Central Europe is the actual flower garden of the perfumer, Grasse, Cannes, and Nice being the principal places for the production of perfume-materials. Thanks to the geographical position of these places, the cultivator, within a comparatively narrow space, has at his disposal various climates suitable for the most perfect development of the plants. The Acacia Farnesiana grows on the seashore, without having to fear frost, which in one night might destroy the entire crop, while at the foot of the Alps, on Mount Esteral, the violet diffuses a much sweeter odor than in the hotter regions, where the olive and the tuberose reach perfect bloom. England asserts its superiority in oils of lavender and peppermint. The volatile oils obtained from plants cultivated in Mitcham and Hitchin command a considerably higher price than those from other localities, this preference being justified only by the delicacy of their perfume. Cannes is best suited for roses, acacias, jasmine, and neroli, while in Nimes, thyme, rosemary, and lavender are chiefly cultivated. Nice is celebrated for its violets, while Sicily furnishes the lemon and orange, and Italy the iris and bergamotte.

The odors exhaled by our own domestic plants have been but little studied, but the southern as well as many northern districts of the United States are well adapted for the cultivation of quite a number of species of plants which might be made to yield highly valuable articles of commerce. Among the plants which might furnish oils for the perfumer's use are, for instance, the wall flower, the Lilly, lilac and mignonette.

Volatile Oils.—The volatile oils are either fluid (actual volatile oils) or solid (varieties of camphor) or solutions of solid combinations in fluid. The latter, on exposure to low temperatures, separate into two portions, one solid, called stearoptene, and the other liquid, called elæoptene. The boiling point of the volatile oils is considerably higher than that of water, but when heated with water they pass over with the vapors. Upon paper, fluid volatile oils produce grease spots, which differ, however, from those caused by fat oils in that they gradually disappear at an ordinary temperature, and rapidly by gentle heating. Most volatile oils are insoluble, or only with difficulty and sparingly soluble, in water, but they impart to the latter their odor and taste. They are readily soluble in alcohol, ether, chloroform, bisulphide of carbon and petroleum-ether, and miscible in every proportion with fats and fat oils. By their solubility in alcohol they differ from most fat oils. When freshly prepared many volatile oils are colorless, but soon turn yellow; some, however, show a distinct color even when fresh. They ignite with greater ease than fat oils and burn with a fierce smoky flame depositing a large amount of carbon. They exhibit a great tendency to absorb oxygen from the air and to gum, the influence of light promoting the process. In specific gravity they range from about 0.75 to 1.17, most of them being specifically lighter than water. Most bodies, under otherwise equal conditions, show always exactly the same specific gravity, the variations being so slight that they may be justly ascribed to errors of observation. However, one and the same volatile oil frequently shows such variations in specific gravity, that we are forced to ascribe this phenomenon to alterations in the constitution of the oil itself. For the exact determination of the specific gravity of a volatile oil, it should, therefore, be subjected to examination immediately after its preparation from the plant or vegetable substance, which should be as fresh as possible. The influence of light upon volatile oils is best shown by the following interesting experiment: If certain volatile oils are distilled in a vacuum or over burnt lime in a current of carbonic acid, it is no longer possible to distinguish, for instance, oil of lemon from oil of turpentine; however, by again exposing the oils to the air, they reacquire their characteristic odor.

According to their elementary composition the volatile oils may be divided into three principal divisions:—

1. Volatile oils free from oxygen, terpene (camphene), or hydrocarbons.

2. Oxygenated volatile oils.

3. Volatile oils containing sulphur.

On account of the facility with which most of the volatile oils absorb oxygen, oils originally free from oxygen are frequently a mixture of hydrocarbons and combinations containing oxygen. The volatile oils varying so much in their physical as well as their chemical properties, a suitable classification of them has thus far been unsuccessful.

Most of the volatile oils contain a liquid hydrocarbon, terpene, which is characterized neither by special taste nor odor, nor is the peculiarity of a volatile oil dependent on it. In the direct distillation of a volatile oil, for instance, lemon oil, this hydrocarbon (citrene), passes first over and can, therefore, be readily separated from the constituents on which depend the peculiarity of lemon oil, and which distil over at a higher temperature. The specific character of an oil is generally due to the portion of the oil containing oxygen. Hence, manufacturers have endeavored to free several of the volatile oils, used for perfumery and the preparation of food, from the worthless terpene and at the same time to obtain them in a concentrated form. Carvol is, for instance, caraway oil freed from carvene (terpene). These concentrated oils are not only purer and more agreeable in odor and taste and more readily soluble in dilute alcohol, but, being more concentrated, an equal volume of them goes much further than ordinary volatile oil. In the price lists these oils are designated as extra strong, patented, concentrated, highly concentrated oils or essences.

All the terpenes occurring in the various oils are combinations having the formula C₁₀H₁₆, or polymeric with it, C₁₅H₂₄, C₂₀H₃₂, etc. These terpenes exhibiting certain deviations in regard to their properties, odor, specific gravity, and boiling points, nearly as many terpenes as there are volatile oils have been distinguished. It is, however, very likely that these deviations may be traced back to fortuitous circumstances, for example, to the admixture of foreign substances occurring together with the terpenes, and that, by a more accurate examination, the number of terpenes entitled to be considered pure chemical combinations will be considerably reduced. By Wallach's labors, the identity of several terpenes formerly considered distinct, has already been established, whilst many others have been found to possess properties in common.

According to the nature and quantity of the odoriferous substances contained in the plants, various methods, namely, expression, distillation, extraction, maceration, and absorption, are employed for the purpose of obtaining them.

Expression.—This is only practicable when the substances are especially rich in oil and of sufficient softness, as in the case with the peel of the orange, citron, lemon, etc. In such instances the material is simply placed in a linen cloth and subjected to a strong pressure until it ceases to yield oil. The press may be of any size according to the quantity to be expressed. For small quantities it generally consists of an iron vessel, having a small opening at the bottom so that the oil may flow out. The material is placed upon a perforated bottom inside of the vessel and covered with a well-fitting iron plate, that can be pressed down by means of a screw. Though the material is fairly exhausted by such a press, for large operations it is advisable to make use of a hydraulic press, which is constructed and managed in exactly the same manner as those used for the expression of fixed oils.

By expression a turbid milky fluid is obtained, which consists of the volatile oil and aqueous substances. The latter are a solution of various extractive substances and salts in water. This fluid, as it runs from the press, is received in tall, narrow, glass vessels and brought into a cool place for clarification. This frequently requires several days, three distinct layers being generally distinguished. On the bottom is a mucous layer consisting of cell substances carried along by the liquid bodies. Over this is a clear fluid consisting of a solution of extractive substances, vegetable albumen, and salts, and upon this floats the volatile oil, being specifically the lightest body, which, by its greater refractive power, can be clearly distinguished from the aqueous fluid.

The oil is separated by bringing all that has been expressed into a bottle provided near the bottom with a lateral neck closed by a cock. After separating the oil from the aqueous fluid, the latter is allowed to escape by opening the cock.

The oil obtained in this manner is still impure, and requires further treatment to remove small vegetable fibres, invisible to the naked eye, which float in them, and cause them to be somewhat opaque and slightly opalescent. By their subsequent decomposition they would also give the oil a disagreeable odor.

There are two methods of obtaining the oil entirely clear, viz., filtration and distillation. Filtration is the cheaper process, but requires special precautions to exclude the air as much as possible to prevent the oil from undergoing injurious changes. By arranging the filtering apparatus so that the oil always comes in contact with only the same quantity of air, the injurious action of the oxygen is reduced to a minimum. It is self-evident that the apparatus should not be placed in the sun, but in a semi-dark, cool place.

Fig. 1.

A filter of simple construction, and performing excellent service, is shown in Fig. 1. It consists of a large glass bottle, F, hermetically closed by a doubly-perforated cork. The neck of the glass funnel T, the upper rim of which is ground smooth, is placed in one of the holes, and a glass tube, r, bent at a right angle, is fitted into the second hole. A thick wooden lid, with a rubber ring on the lower side, is placed upon the funnel, thus closing it air-tight. In the centre of the lid is fitted a glass tube, r´, also bent at a right angle, which is connected with the tube r, by a rubber hose, k. After the funnel has been provided with filtering paper and the oil to be filtered, the lid is placed upon it, and must not be removed, except for the purpose of pouring more oil into the funnel. The air in the bottle F is displaced by the oil dropping into it, and escapes through r, k and r´ into the funnel, and thus only the air in the bottle and funnel can act upon the oil.

The other method for the complete purification of expressed oil is by rectification or distillation with water. For this purpose the oil, together with a little water, is brought into one of the stills described later on, and the oil distilled over. It is sometimes difficult to obtain the last portion of the oil, especially with a still heated by direct fire, and it is therefore preferable to combine it with a fresh quantity of the same oil to be distilled.

Distillation.—There are at present two methods in use. The one is founded upon the direct action of the heat, the other upon the use of steam. The first was formerly in general practice, and is still largely employed in France and England, and to a limited extent in this country. It is, however, very deficient in many respects. As the stills must necessarily be of small capacity, only small quantities can be distilled at one time, and the oils very rarely possess the peculiar odor due to them, and sometimes the odor is even altered. In mixing too little water with the materials to be extracted, there is danger that empyreumatic oils will be formed; a large quantity of water, on the other hand, is of disadvantage, in so far as in case the perfume-materials contain little oil, only a perfumed water, but no oil, will be obtained. In order to avoid these inconveniences, or, at least, to do away with some of them, another plan was devised. The materials to be distilled were spread upon sieves, which were suspended in the upper part of a still, so that they might be penetrated from below. It is true no scorching is possible in this case, as was in the other process when the heating was continued after all the water had evaporated, and the oil retains its proper color, but by this method only small quantities can be extracted at a time. The still generally used for distillation with direct heat resembles so much an ordinary whiskey still as to need no further description here.

Fig. 2.

For the accurate determination of the percentage of volatile oil a vegetable substance will yield, or to obtain the oil from very costly raw materials, the small glass apparatus, Fig. 2, is used. The flask A, with a capacity of up to 5 or 6 quarts, serves for a still. In the tube t, shaped like the neck of a bottle, is inserted by means of a cork, a funnel tube, l, reaching to the bottom of the flask. The neck of the flask passes into the cooling pipe, which lies in a so-called Liebig cooler. This consists of a wide-glass tube, C, into the lower end of which, at h, flows cold water from the reservoir D, displacing the heated water at g. The lower end of the cooling pipe is connected with the neck-shaped tube v, under which stands the vessel for the reception of the distillate. To prevent the cracking of the flask, which might readily happen with the use of direct heat, it is placed in a vessel filled with sand or water.

Fig. 3.

A very good small apparatus for the distillation of volatile oil is shown in Fig. 3. It is known as a siphon still. It consists of a double-walled boiler, surmounted by a still-head, which is provided with a mechanism for keeping the contents of the boiler in motion. This stirring apparatus consists of a perpendicular shaft, bearing a frame work of iron, curved so as to correspond to the interior shape of the still, and on the outside carrying a chain which scrapes over the inner surface of the still while the stirrer is being turned. This may be done either by hand or by steam. The still having been charged with the material to be extracted, is filled up with water to within a few inches of the top of the body of the still, and the latter is heated by admitting steam. The vapors arising are conducted to a cooler situated at a higher level than the still itself, and the condensed liquid is collected in a receiver, where the oil and water separate. This receiver is provided with two faucets, one near the top and the other near the bottom. If the oil passing over is heavier than water, the excess of the latter is removed by the upper faucet; if the oil swims on the water, the lower faucet is regulated so as to allow the water to escape in about the same ratio as it enters the receiver. In either case the condensed water is made to run back into the still, and the loss of oil is, therefore, greatly reduced.

Sometimes a single-walled still is used, and distillation carried on with direct steam. This method is, however, not suitable where the presence of water is necessary, for instance, in the production of oil of bitter almonds.

A simple way of converting an ordinary still into use with steam is shown in Fig. 4. For the helmet of the still A is substituted a cylindrical vessel, B, with an opening in the bottom. The materials to be distilled are brought into B, and rest upon a wire bottom to prevent particles from falling into A. From the upper portion of B a pipe, R, leads to the condenser. As may be seen from the illustration, the still A serves only for the generation of steam. The latter, in passing through B, heats the contents and absorbs the liberated oil, the combined vapors passing into the condenser.

Fig. 4.

This simple modification of the ordinary still affords some advantage, the principal being the avoidance of the condensation of a large quantity of water. This in itself would not amount to much, but it has to be taken into consideration that, though volatile oils are only very sparingly soluble in water, they are nevertheless soluble in it to such a degree as to impart to it their characteristic odor and taste. Such aromatized water can be utilized in the manufacture of liqueurs and perfumery, but to the manufacturer who restricts himself to the production of volatile oils alone, this represents a loss, and it is therefore necessary for him to condense as little water as possible. And this object can only be attained by the use of direct steam.

A simple apparatus for the purpose is shown in Fig. 5. The still b, provided with a helmet, rests free upon a suitable support. To prevent cooling, it is surrounded with a wooden jacket, M. The material to be extracted rests upon a perforated bottom, beneath which enters the pipe HD, which conducts the steam from the boiler. For the more uniform distribution of the steam, it is recommended to let this pipe end in a perforated coil. The water condensed in the apparatus itself is discharged through the short pipe H, placed in the lowest part of the still.

Fig. 5.

An improved apparatus for distilling dry substances by steam has been patented in Germany by Messrs. Schimmel & Co., of Leipzic. The tall conical column at the left (Fig. 6) is the still. About eight inches from the bottom is a perforated diaphragm or false bottom, upon which the material to be distilled is placed by introducing it through the still-head. A perforated coil below the diaphragm projects steam upwards through the mass, which is occasionally agitated from without by means of a horizontal stirring apparatus indicated by the two crosses. Any condensed water which may run back is converted into steam by the heating coil at the bottom. Meanwhile, the mass itself is heated by a long coil lining the body of the still and carrying steam at a high pressure. Whatever of volatile oil is carried forward by the steam passes through the still-head into the cooler on the right, where both oil and steam are condensed, and from where they flow through a small funnel tube into three successive receivers, which are arranged like Florentine flasks, and which retain the volatile oil that has separated. From the last receiver the water, which is still impregnated with oil, enters another reservoir, shown in the illustration only by dots, and from there it flows into a small globular still situated underneath; in which, by means of steam, nearly all the oil still retained is again volatilized with the steam of the water and both again conducted to the cooler.

Fig. 6.

Attempts have been made to effect the distillation of volatile oils without the use of steam by means of hot air, but comparative experiments have shown that less oil is obtained. With the use of steam, the vegetable substances swell up by the absorption of water, and thus afford a free passage to the oil, liberated from the sacs containing it. With the use of hot air, on the other hand, the surface of the plant is completely dried and shrivels to a hard solid mass, which offers considerable resistance to the process of distillation.

This injurious effect of hot air can be somewhat overcome by thoroughly moistening the plants to be distilled, and allowing the hot air, before entering the still, to pass through a pipe filled with sponges constantly kept wet. But this process offers no advantages over that by steam. The apparatus required is far more complicated; and, besides, a ventilator has to be provided for forcing the hot air through the apparatus.

Separation of the oil and water.—As previously mentioned the specific gravity of most volatile oils is less than that of water. This behavior is utilized for the separation of the oil and water, by means of a so-called Florentine flask (Fig. 7). It consists of a glass flask provided near the bottom with a pipe, a, rising vertically to near the neck c of the flask where it is bent downwards as shown in the illustration. The mixed liquid of water and oil drips from the cooling pipe into the flask, and the water w, being specifically heavier, separates from the oil floating on the top, and gradually ascends in the pipe a, finally flowing over at d. Oils specifically heavier than water are caught in receivers provided with a discharge-pipe near the mouth of the flask as shown in Fig. 8.

The oil delivered from the receivers is, however, still mixed with some water, dirt, etc., and for their separation is allowed to stand quietly for some time. The final separation is effected either by simply pouring off the oil, especially if larger quantities have to be handled, or with the assistance of a separator-funnel (Fig. 9). This consists of the glass-funnel T secured to the stand G, and provided with a close-fitting lid, P. The fluid is poured into the funnel, the lid placed in position, and the whole allowed to rest until the water W is completely separated from the oil O. The oil is then separated from the last drops of water by carefully opening the faucet H.

Most volatile oils are obtained by distillation, but this method is not practicable for separating the odoriferous principle of many of the most sweet-scented and delicate flowers, partially because the flowers contain too little oil, and partially because the oil would lose in quality if obtained by distillation.

Fig. 9.

Extraction.—For obtaining the volatile oils by extraction various solvents such as ether, bisulphide of carbon, etc., may be employed. Carefully rectified petroleum-ether is very suitable for the purpose. It completely evaporates at about 122° F., and when sufficiently purified does not possess a disagreeable odor. The process of extraction is briefly as follows: The material to be extracted is treated in a digester with petroleum-ether or one of the above-named solvents. The solution is then drawn off and the solvent evaporated in a still. The recondensed solvent flows immediately back into the digester and further extracts the material contained therein. The operation is repeated until nothing soluble remains. In practice some difficulties are, however, connected with this process since, besides the volatile oils, resins, and coloring and extractive substances are dissolved, which have to be removed, as well as the last traces of the solvent, as otherwise the oil would acquire a foreign odor. Further the solvents mentioned are very volatile and inflammable, requiring the greatest precautions as regards fire. For these reasons the extraction process is not suitable for many purposes, and though at first great hopes were entertained in regard to it, its use is limited to substances with a large content of volatile oil.

Fig. 10.

For extraction on a small scale, the apparatus, Fig. 10, is a very suitable one. It is especially adapted for manufacturers of perfumery, who wish to extract fresh flowers. It consists of a cylindrical vessel, C, of tin plate, provided on the bottom with the stop-cock a and the pipe b. The lid D fits into a gutter, R, running around the edge of C, and is hermetically closed by water in R. The cylinder is filled with the vegetable substance to be extracted, and sufficient petroleum-ether or bisulphide of carbon to cover it, poured in. The lid is then adjusted, the gutter R filled with water and the apparatus allowed to stand quietly for forty minutes. To remove the fluid from the cylinder, the faucet o in the lid is first opened, and then the stop-cock a; the fluid escapes at b, and is caught in a well-closed vessel. The operation may be repeated once or twice, or the vegetable substance is pressed out by means of a wooden plate, and the apparatus filled anew. The faucet h serves for emptying the gutter R.

Fig. 11.

Extraction being finished, the cock o is opened, and then the cock a, and the fluid allowed to run into the flask of the distilling apparatus ([Fig. 2]). For working on a large scale, the flask is, however, too small, and is suitably replaced by a bottle-shaped tin vessel, F (Fig. 11), the conical cover D of which is secured by means of the rubber ring R and iron screw-clamps, S. A bent glass tube fitted into the cover is connected with the cooling-pipe of the apparatus shown in [Fig. 2]. But the oils prepared by extraction are not sufficiently purified by mere rectification, as traces of the solvent adhere tenaciously to them, which can only be removed by passing a current of air through the oil. But contact with air has an injurious effect upon the delicacy of the odor. For expensive oils a current of air should therefore never be used, but one of pure carbonic acid. Fig. 12 shows a suitable apparatus for the purpose. The large bottle A, filled half full with pieces of white marble, is closed with a doubly-perforated cork; through one of the holes is inserted a funnel-tube, and through the other a short tube bent at a right angle. The latter is connected with another tube which reaches to the bottom of the vessel B, in which is also inserted a tube open in the bottom, and a short tube bent at a right angle. Alongside B stands another vessel, C, arranged in the same manner. The tube leading from C is connected with a tin pipe, D, with a rose-like expansion on its lower end. This pipe is inserted in the glass balloon containing the volatile oil. Finally, a pipe leads to the flask F, filled with water.

Fig. 12.

To put the apparatus in operation, strongly diluted hydrochloric acid is poured through the funnel-tube upon the pieces of marble in A, which causes the development of a current of carbonic acid. But as the latter carries along water and hydrochloric acid, it has to be freed from them before coming in contact with the volatile oil. The vessels B and C serve for the purpose. B is half filled with water, while C contains strong sulphuric acid. In B the hydrochloric acid carried along with the current of carbonic acid is retained, while the water is fixed on the sulphuric acid in C. The current of carbonic acid passing out from C is perfectly pure, and enters the volatile oil through the fine perforations in the pipe D. It absorbs the traces of solvent still adhering to the oil, and finally passes out through the water in the bottle F.

Volatile oils obtained by extraction, and purified by a current of carbonic acid, will keep for years without undergoing alteration, if placed immediately in hermetically closed vessels and stored in a dark place. Oils purified by a current of air always become somewhat thickly fluid by storing, and partially lose their fine odor, which is due to the oxygen absorbed during the process.

For the extraction of oil on a larger scale, the apparatus shown in Fig. 13 is very suitable. It consists of two principal parts, the actual extracting vessel E, and the still B. The extracting vessel E sits in a vat containing cold water, W, the arrangement being such that the heated water can be removed and replaced by cold. The still B sits in a boiler, K, filled with hot water.

The apparatus is charged as follows: The conical head C of the extracting vessel E is unscrewed and its connection at H with the pipe R loosened. The extracting vessel is then charged with the vegetable substance, the head C replaced, and the connection with the pipe R restored. The cocks H₂ and H₄ are then opened, and the required quantity of solvent is brought into the still. Both cocks are then closed, and the cocks H and H₁ opened. The water in the boiler is then heated until the contents of the still commence to boil. The vapor of the solvent ascends through the pipe R; on entering the extracting vessel E it is condensed, and after falling as a spray upon the material to be extracted, finally returns impregnated with volatile oil to the still B. Here the solvent is revaporized, and passes again through the material in the extracting vessel, while the extracted oil remains in the still. During the boiling of the solvent the extracting vessel must be suitably cooled by the constant admission of cold water.

Fig. 13.

When extraction is finished, the cocks H and H₁ are closed, and the cock H₂, which is connected with a cooling worm, is opened. The solvent is then evaporated, and regained by condensation. The oil is discharged, from the still through a pipe in the bottom provided with the cock H₃.

The apparatus may also be so arranged that the still B is connected with two extracting vessels which are used alternately, while the contents of one are being extracted the other is emptied and refilled.

Fig. 14.

For working on a very large scale, Heyl's extracting apparatus, shown in Fig. 14, is very suitable. It consists of a battery of four or more cast iron or sheet iron cylinders, A₁ to A₄, communicating with each other and surrounded by steam jackets. The extracting vessels are so arranged that they can be emptied by tilting, which is rather inconvenient, as all the pipes have to be unscrewed. In each cylinder close above the bottom is a perforated plate covered with fine wire-gauze, upon which the material to be extracted is placed. The cylinder is filled to the top, and, after placing a similar plate upon it, the upper opening is closed by a lid suspended to a crane. The cylinder, as well as the lid, is provided with a broad flange, between which is placed a hemp tissue firmly pressed together by 12 clamps to serve for packing. After filling the cylinders with the material to be extracted and arranging the packing, the solvent (bisulphide of carbon) is conducted from a reservoir through the principal pipe, B, to the extracting vessels, and is introduced into A₂ by opening the cock C₂, which communicates with the pipe B. The bisulphide of carbon passes through the bent pipe D₁, enters through the cock E₂, below the false bottom of the cylinder A₂, and, after penetrating the mass and filling the cylinder, runs through the cock C₂ of the bent pipe D₂, and the cock E₃ into the cylinder A₃, reaching the fourth cylinder in the same manner through the cock C₃, the pipe D₃, and the cock E₄. From the last cylinder it passes as a thoroughly saturated oil solution into a reservoir, in which a vacuum has been created to promote the circulation of the fluid in the entire apparatus. After a quantity of oil solution corresponding to the contents of the cylinder A₄ has arrived, the cock G₄ is closed and the cock C₄ opened, whereby the cylinder A₄ is connected with A₁ by the bent pipe D₄ and the cock E₁.

After the exhaustion of the contents of the cylinder A₂, which is recognized by means of the glass tube H₂ placed on D₂ by the fluid running off being colorless, the cocks C₁ and E₂ are closed, and C₂ and E₃ opened, whereby the solvent runs into A₃, and from there to A₄ and A₁; A₂ being omitted. To effect this omission, and at the same time not to prevent the introduction of bisulphide of carbon, C₁, C₂, C₃, and C₄, are so-called two-way cocks, which, when placed in one position, connect the principal pipe B with the branch pipes D, but interrupt a further flow through the principal pipe B; while in the other position they close the pipes D and open the principal pipe B.

The cylinder A₂ is, however, still filled with the solvent and material saturated with it. To remove the solvent, the discharge cock K₂ on the bottom of the cylinder is opened, which communicates with the discharge pipe J, through which the bisulphide of carbon is conducted into a reservoir. The discharge is promoted by opening the cock M₂, connected with the pipe L, and the admittance of compressed air, which displaces the liquid solvent. After the flow of the latter has ceased, the steam cocks on the jacket O₂ and the cylinder P₂ are opened under constant admission of air and simultaneous introduction of steam through the pipe N into the upper part of the cylinder.

The solvent (bisulphide of carbon) converted into vapor by the heat, is conducted together with the aqueous vapor, by the admission of air through the cock K₂, the pipe J, and a cooling pipe placed between the extracting vessels and the reservoir, and collected in a reservoir to be re-used.

On account of the great volatility of bisulphide of carbon, considerable loss would, however, be incurred by the above-mentioned admission of air. To avoid this, the reservoir serving for the reception of the condensed bisulphide of carbon and aqueous vapor is closed, and connected by a pipe with a long, narrow, horizontal cylinder half filled with oil, and provided with a fan-shaft. The vapors of bisulphide of carbon entering the cylinder from the reservoir are absorbed, together with the air by the oil, the surface of which is constantly agitated by the fan-shaft, while the air, rendered entirely inodorous, passes out at the other end. The bisulphide of carbon is finally separated from the oil by distillation and again used.

After the cylinder A₂ is sufficiently steamed, it is emptied and again charged with material and connected with the cylinder A₁; while the other cylinders undergo the same manipulations described above.

Fig. 15.

The saturated oil solution is subjected to distillation, which is readily effected in Heyl's apparatus, Fig. 15. The lower part of the still A of boiler plate is surrounded by the steam-jacket B, into which steam is admitted through C and the condensed water discharged through D. The concentrated oil solution runs from a reservoir, standing at a higher level through the pipe E into the still, the admission of a sufficient quantity being indicated by the gauge F. The bisulphide of carbon brought to the boiling point (114° F.) by the steam introduced into the jacket, vaporizes quickly; the vaporization being still more accelerated by revolving the stirrer H, by means of the crank G. The vapors of bisulphide of carbon escape through four openings in the upper part of the still, into a capacious worm, the lower part of which enters, under water, a reservoir.

Notwithstanding the volatility of bisulphide of carbon, the oil retains a portion of it so tenaciously that a complete separation cannot be accomplished by the introduction of steam into the jacket B. Hence, in order to vaporize the last traces of the solvent, air is introduced into the oil through the pipe K, the lower end of which is perforated. After completed distillation the oil is discharged through L.

Maceration or infusion.—This process is employed for flowers with an inconsiderable content of volatile oil or whose odoriferous substance would suffer decomposition or alteration by distillation. The process is founded on the affinity of odoriferous substances for fatty bodies which, when impregnated with them, are called pomades. These are afterwards made to yield the aroma to strong alcohol, so that finally there is obtained a solution of the volatile oil in alcohol from which the pure oil is obtained by distilling off the alcohol. The fat used, olive oil, lard, etc., should be entirely neutral, i. e., free from every trace of acid. The fats are purified by treating them several times in the heat with weak soda-lye and then washing carefully with water until the last traces of the lye are removed, and the fat shows no alkaline or acid reaction.

With the use of olive oil the so-called "Huiles antiques" are obtained, which are merely solutions of volatile oils in the fixed oil. By the use of lard, etc., the genuine pomades are obtained, which are directly used as expensive articles of perfumery, but in the factories serve as a starting point for the preparation of volatile oils.

The old process of maceration, which is still in use in some parts of France, is as follows: A certain quantity of fat is placed in an enameled iron or porcelain pan provided with a water or steam bath. When the fat is melted, the freshly gathered flowers from which the aroma is to be extracted are thrown in and left to digest for from twelve to twenty-four hours, the fat being kept fluid and stirred frequently. When the flowers are completely exhausted, the fat is strained from them into fresh pots, in which it is again macerated with fresh flowers as before. This operation is repeated ten to fifteen times until the pomade has acquired the desired strength.

Experience, however, has shown that volatile oils prepared by this process possess a finer odor the shorter the time the flowers remain in contact with the fat. Piver has devised an apparatus which reduces the time of maceration to the shortest period possible. The kettle to the left, Fig. 16, supplies the fat heated to the proper temperature, which circulates slowly through the macerating tank, in which a constant temperature of 149° F. is maintained by means of a steam pipe. The macerating tank is divided into compartments, in which baskets containing the vegetable substance to be extracted are suspended. The basket on the left contains the substance which has passed through all the compartments; it is from time to time removed, filled with fresh substance, and then attached to the right, the other baskets being moved to the next compartment to the left. In this way the fresh substance has to traverse each compartment from right to left, while the fat flows slowly from left to right, and saturated with the perfume of the substance collects in the tank on the extreme right.

Fig. 16.

Maceration is employed for the flowers of the orange (citrus aurantum), of the mock orange (Philadelphus coronarius), of the acacia (acacia Farnesiana), of the violet (viola odorata), of the mignonette (réséda odorata), etc.

The process of absorption, or "enfleurage," as it is called by the French, is chiefly made use of for procuring the odoriferous principle of very delicate flowers, the delicious odor of which would be greatly modified, if not entirely spoiled, by the application of heat. The older apparatus employed for the purpose consists of a number of shallow wooden frames of about 15×18 inches, inclosing at half their depth a sheet of glass. The edges of the frame rise about an inch above each surface of the glass, and, being flat, the frames stand securely upon one another, forming often considerable stacks. These frames are called "chassis," those just described being termed "chassis aux vitres," or "chassis aux pomades," to distinguish them from a different form, which is used where oil has to be submitted to the process of absorption. The process in the case of pomade is as follows: Each sheet of glass is uniformly coated with a thin layer of purified grease, care being taken that the grease does not come in contact with the woodwork of the frames. The flowers are then thinly sprinkled, or rather laid, one by one, upon the surface of the fat, where they are allowed to remain one or two days, when they are removed and replaced by fresh ones. The operation is thus continued for twenty-five or thirty days, until the fat is saturated with aroma. The frames charged with fat and flowers are stacked one upon the other, forming, in fact, a number of little rectangular chambers.

For perfuming oils a metal sieve, Fig. 17, is substituted for the glass plate. Upon the sieve a piece of thick cotton cloth saturated with oil is laid, and upon this the flowers are scattered, and left there until fresh ones have to be substituted. The operation is repeated until the oil is sufficiently impregnated with aroma, when the cloth is subjected to pressure and the expressed oil filtered.

Fig. 17.

This process is very tedious, requiring much labor and a long time for the impregnation of the fat or oil, but, notwithstanding its faults, it is still pursued to a great extent, some French firms using 3000 such frames during the season.

With the apparatus, shown in Fig. 18, the process of absorption can, however, be conducted with very little expense of labor and time. It has the further advantage that the flowers do not come in direct contact with the fat, whereby a saving of the latter is effected, and it is less liable to rancidity.

The apparatus consists of a tall wooden box provided with doors which can be hermetically closed. In the box are placed upon brackets a number of glass plates, g, so arranged one above the other that, for instance, those with uneven numbers are on the left side, leaving an open space to the right, while those with even numbers are arranged on the right side with an open space to the left.

From the bottom of the box a pipe passes into a sheet-iron cylinder, K´, filled loosely with flowers, and provided with lateral openings, O and O´. From the lid of the box K ascends a pipe, e, which is connected with a small ventilating apparatus kept in motion by a clockwork and weights. This ventilator when in motion sucks a current of air through the apparatus. The air enters the cylinder K´ at O, and after ascending through the flowers and becoming impregnated with the vapors of the volatile oil enters through the opening O´ into the box K and, in passing in the direction indicated by arrows, over the plates coated with fat, yields its aroma to them.

Fig. 18.

Another apparatus for the same purpose, devised by Piver, is shown in Fig. 19. The fat is converted into thin macaroni-like threads and brought upon wire gauze stretched in frames. The flowers to be extracted are piled upon tinned metallic plates, and the trays containing the fat and the flowers are placed in an air-tight chamber arranged as shown in the illustration. The air in the chamber is made to circulate to and fro by the working of a bellows with which the apparatus is provided, whereby the fat is caused to absorb the odor of the flowers very rapidly and is less liable to rancidity.

Fig. 19.

The absorption process is employed for the flowers of the jasmine (jasminum oderatissimum), the mignonnette (réséda odorata), the violet (viola tricolor), the tuberose (polianthes tuberosa), etc.

Storage of volatile oils.—In storing volatile oils, they should be carefully protected from light and air. Some oils become darker on exposure to light, while others, for instance, lemon oil, become colorless. Most volatile oils, as previously mentioned, absorb oxygen from the air with avidity and combine chemically with it. Thinly-fluid oils become perceptibly more thickly-fluid and finally even rigid, the product of oxidation being a resinous body. Some volatile oils containing aldehydes are converted, by the absorption of oxygen, into acids, cinnamic acid being, for instance, formed in cinnamon oil, and benzoic acid in oil of bitter almonds.

To prevent evaporation, as well as the above-mentioned effects of light and air, the volatile oils should be preserved in not too large glass bottles kept as full as possible, and closed with a good cork, over which it is best to tie a piece of bladder. The bottles should be stored in a cool, shady place. The preservation of the oils is assisted by the addition of 0.5 to 1 per cent. of anhydrous alcohol.

[CHAPTER III.]

TESTING VOLATILE OILS.

Volatile oils are much adulterated, the adulterations consisting chiefly in mixing an expensive oil with a cheaper one and with alcohol; more rarely with chloroform and fat oils. To these adulterations, which have been common for many years, has recently been added the previously mentioned hydrocarbon called terpene or camphene, which is separated in the preparation of concentrated oils.

For the recognition of the quality of a volatile oil, serve first of all its physical properties, especially its color, odor and taste. The specific gravity varies too much and is not always a sufficient criterion. Reagents can only be employed with a few oils. The chemical detection of adulterations is rendered especially difficult by the fact, that most of the volatile oils form a mixture of terpenes with other combinations, in which the separate constituent parts do not appear in fixed, but in changeable proportions, and in which the constituents themselves suffer alteration by storing, air and light.

Odor and taste are so characteristic for every volatile oil as to suffice in most cases. For testing as to odor, bring a drop of the oil to be examined upon the dry palm of one hand and for some time rub with the other, whereby the odor is more perceptibly brought out. To determine the taste, vigorously shake one drop of the oil with 15 to 20 grammes of distilled water and then test with the tongue.

An adulteration with fat oil (poppy oil, castor oil) may be recognized as follows: Place a drop of the suspected oil upon blotting paper and expose it to the heat of the water bath. If it evaporates completely and no stain is perceptible, the oil is pure. But frequently a transparent stain remains with old oils without their being adulterated, which is due to the resin formed by the absorption of oxygen and remaining dissolved in the oil. In this case a transparent ring is generally formed by the concentration of the resin on the edges of the stain. If no tangible results are obtained by this test, pour a few cubic centimeters of the oil upon a watch-crystal and heat it very slowly upon a piece of sheet-iron, until all the odor has disappeared. If the watch-crystal becomes empty in a short time, nothing but volatile oil was present; but if a viscous residue remains, this may consist either of fatty oil or resin, or of both. Treat the residue with strong alcohol; if it dissolves it may be resin or castor oil. Dilute the solution with much water; a white flocculent turbidity indicates resin; the separation of an oily liquid, after standing, castor oil. If the residue remains undissolved, it consists of a fatty oil, generally oil of almond or olive.

The presence of castor oil can be accurately determined by bringing the residue from the watch-crystal into a test-tube by means of a glass-rod, and compounding it with a few drops of nitric acid. A strong development of gas takes place, after the cessation of which, solution of carbonate of soda is added as long as there is any sign of effervescence. If the added oil was castor oil, the contents of the test-tube will show a peculiar odor due to œnanthylic acid formed by the action of nitric acid upon castor oil.

Another method of establishing the presence of fat oil consists in mixing the suspected oil with eight times its quantity of 90 per cent. alcohol (specific gravity 0.823). If the oil is unadulterated a clear solution is formed; if it contains fat oil, the latter remains undissolved. The presence of castor oil, which of the fat oils is chiefly used for adulteration, is, however, not shown by this method, it being also soluble in alcohol.

A permanent stain upon the paper may, however, also be formed by fresh oils obtained by expression from the respective parts of the plant. Thus, lemon oil obtained by expression from the peel, and which has a far more agreeable odor than that produced by distillation, always leaves behind a slight grease-stain.

Detection of alcohol or spirit of wine.—Independent of the alcohol added to assist the preservation of some oils, adulteration with alcohol frequently occurs, especially in expensive oils. With a content of not more than 3 per cent. of alcohol, it suffices to allow one to two drops of the suspected oil to fall into water. In the presence of alcohol, the drop becomes either immediately surrounded with a milky zone, or it becomes turbid or whitish after being for some time in contact with the water. Dragendorff's test is based upon the fact that oils, which are hydrocarbons, suffer no change by the addition of sodium (ten drops of oil and a small chip of sodium), while oils containing hydrocarbons and oxygenated oils cause with sodium a slight evolution of hydrogen gas, and suffer but a slight change during the first five to ten minutes of the reaction. If, however, the oil is adulterated with alcohol, not only a violent evolution of hydrogen gas takes place, but the oil in a short time becomes brown or dark brown, thickly fluid or rigid.

The detection of alcohol by means of fuchsine, which has been frequently recommended, requires special precautions. It must first be ascertained that the oil is free from acids and water; if such is not the case, they must be removed by means of caustic potash. After settling, bring, by means of a dry pipette, about five cubic centimeters of the oil into a dry test-tube about ten millimeters in diameter, without moistening the walls of the upper half of the tube. Then bring, by means of a paper gutter, a few milligrammes of coarsely-powdered fuchsine into the dry part of the obliquely held tube, at a distance of one centimeter from the oil. Now heat gradually over a lamp until the tube begins to tarnish. With pure oil no evaporation is observed, but if the oil contains only 0.1 per cent. of alcohol, every speck of fuchsine will, after heating to boiling and setting aside, be surrounded by a stain produced by the alcoholic solution. The chief requirement for this test is that the oil be free from water. If such is not the case, vapors will be observed, which condense in the upper portion of the test-tube, and dissolve fuchsine, and, after flowing back, sink below the oil with a crackling noise. If the oil contains alcohol, the condensing vapors dissolve fuchsine with greater ease, and in flowing back mix without crackling.

Hager's tannin test is very reliable. Bring into a test-tube 5 to 10 drops of the oil to be examined, add a piece of tannin the size of a pea, shake so that the tannin is moistened by the oil, and let the whole stand at a temperature of 59° to 68° F. In most volatile oils tannin is insoluble, and, if the oil is pure, floats for days on the surface without change. If, however, the oil contains alcohol, the tannin absorbs the latter, according to the quantity present, in 3 to 48 hours, and forms with it a more or less transparent, viscous, tough, or smeary mass resembling a soft resin, which settles on the bottom, and adheres so firmly to it, as well as to the sides of the tube, that it cannot be moved by shaking. The mass may be examined as to its consistency with a knitting needle. Traces of moisture in the oil are not detrimental to the test, the tannin mass separating in the form of a hyaline mass only in few oils, and if this mass is tested with the knitting needle it will be found not tough or smeary, but hard, and may sometimes be divided into small grains. With oil of bitter almonds, cassia oil, and some oils of clove, as well as volatile oil containing an acid, the tannin test is not available. The first two oils even dissolve tannin, and large quantities of it, if they contain alcohol.

The above-mentioned oils may, however, be rendered fit for the tannin test by mixing them with double their volume of benzine or petroleum-ether, and allowing the mixture to stand for two or three days. If, however, the oils contain much alcohol, the tannin is dissolved. The use of powdered tannin is not advisable, because it generally deposits in a thin layer on the bottom, and its alteration is not so perceptible. If, for practical reasons, a content of 0.5 per cent. anhydrous alcohol might be accepted as permissible in a volatile oil, the tannin test would have to be so modified as to mix 10 drops of the oil with a piece of tannin the size of two peas, and allow the whole to stand for one hour. In this time the above-mentioned content of alcohol would yield no result.

Detection of chloroform.—An adulteration with chloroform, if moderate, cannot always be detected by the odor and taste. In most cases, chloroform will considerably increase the specific gravity of the oil. Bring into a test-tube 15 drops of the suspected oil, 45 to 90 drops of alcohol, and 30 to 40 drops of dilute sulphuric acid. After thorough shaking, add 2 or 3 shavings of zinc sheet and heat until a vigorous evolution of hydrogen takes place. After again shaking, set the whole aside, and heat again when the evolution of gas becomes weaker. This heating and gentle shaking of the fluid is several times repeated. After 20 to 25 minutes, compound the fluid with an equal volume of cold distilled water, shake vigorously and filter through a paper-filter moistened with water. Strongly acidulate the filtrate with nitric acid and compound with nitrate of silver solution. If chloroform is present, turbidity or a precipitate of chloride of silver appears.

Detection of benzine.—An adulteration with benzine can be readily detected only in oils specifically heavier than water. The separation of benzine is effected by distillation from a small glass flask in the water bath. The distillate together with an equal volume of nitric acid of 1.5 specific gravity is gently heated in a test-tube. A too vigorous reaction is modified by cooling in cold water, and a too sluggish action quickened by gentle heating (dipping in warm water). If the mixture has a yellow color, dilute it with water, shake with ether, mix the decanted ethereal solution with alcohol and hydrochloric acid, add some zinc and place the whole in a lukewarm place to convert the nitrobenzol formed into aniline. After evolution of hydrogen is done, neutralize with potash lye, shake, take off the layer of ether, let the latter evaporate and add to the residue a few drops of calcium chloride solution. If benzine is present, a blue-violet color reaction takes place.

Adulterations with alcohol, chloroform, and benzine are quantitatively determined by bringing a weighed quantity of the oil into a glass flask so that it occupies about four-fifths of the volume of the flask. Place upon the flask a cork through which has been passed a glass-tube bent at a right angle and provided with a cylindrical glass vessel serving as a receiver and heating in the water bath. If the distance from the level of the oil to the angle of the glass tube in which it inclines downwards, amounts, for instance, to 4.72 inches, and the neck of the flask up to its angle is 2.75 inches high outside of the direct effect of the heat of the water bath, only the above-mentioned adulterants distill over, while the vapor of the volatile oil condenses at a height of 2.75 inches and flows back into the flask. The distillate is weighed and examined as to its derivation. First add one cubic centimeter of it to two or three cubic centimeters of potassium acetate solution of specific gravity 1.197 and shake moderately. If a clear mixture results, alcohol alone is present. If, however, the mixture is not clear, and the distilled fluid sinks down and collects on the bottom of the test-tube, chloroform is very likely present, and if it remains floating upon the acetate solution, benzine. Next bring two to three centimeters of the distillate into a test-tube and add a piece of sodium metal, the size of a pea. If violent foaming, i. e., an evolution of gas, takes place, alcohol is certainly present, and possibly also chloroform and benzine towards which sodium is indifferent. However, in the presence of benzine, the sodium solution would be colorless, and in the presence of chloroform, yellowish and turbid. In case the sodium produces no reaction and alcohol is, therefore, not present, add an equal volume (two to three cubic centimeters) of anhydrous alcohol, and after moderately shaking allow the solution of the sodium and the evolution of gas to proceed, whereby benzine produces a nearly colorless, turbid fluid, and chloroform a yellowish, milky one. Now dilute the fluid with an equal or double volume of water, shake and allow the mixture to stand quietly. In the presence of benzine a colorless, turbid layer collects on the bottom of the fluid, while that collecting in the presence of chloroform is yellowish. In the latter case, i. e., in the presence of chloroform, the aqueous filtrate yields with lead acetate solution a white precipitate (lead chloride and lead hydroxide). The adulterant having thus been recognized, further particulars are learned from the specific gravity of the oil as well as of the distillate.

Adulterations with terpenes or terpene-like fluids, such as are gained in the preparation of concentrated or patent oils, are difficult to recognize. They may be detected by the specific gravity, the terpenes being, as a rule, specifically lighter, their specific gravity varying between 0.840 and 0.870.

The detection of adulterations with volatile oils of a lower quality is very difficult, if not led to it by the odor and taste. Many methods for establishing such adulterations have been proposed, of which the following are the most important:—

I. Test with iodine.—This test is based upon the fact that some oils violently detonate with iodine, while others develop heat and vapors, and others again remain indifferent. For this test pour upon about 0.19 gramme of dry iodine in a watch-crystal 4 to 6 drops of the oil to be examined.

1. A vigorous reaction (detonation) with considerable increase in the temperature and emission of vapors takes place with the following oils: oils of bergamot, lemon, lavender, nutmeg, orange peel, spike, turpentine, wormwood.

2. Such a reaction as mentioned under 1, does not take place with oils of bitter almonds, copaiba, calamus, clove, peppermint, rose.

3. Moderate heating and slight vapors are developed with oils of anise-seed, fennel, camomile, curly mint, marjoram, rosemary, sassafras, thyme.

When an oil of the second series becomes heated with iodine and evolves vapors, it may first of all be adulterated with cheaper oils. This may also be the case when an oil of the third series reacts violently with iodine and evolves vapors with strong heating. Formerly the iodine test was highly valued; it has, however, been shown to be unreliable since it is frequently dependent on the age of the oil.

In place of iodine, Rudolph Eck recommends a very dilute alcoholic iodine solution, which is not discolored by oils of turpentine, while other oils discolor it. Dissolve a drop of the oil to be examined in 3 cubic centimeters of 90 to 100 per cent. alcohol, and add a drop of the iodine solution. The latter is not discolored in the presence of an oil of turpentine. There are also, however, several volatile oils, which do not discolor the iodine solution. Mierzinski mentions the following: All cold-expressed oils from the Aurantiaceæ, further oils of coriander, caraway, galanga, rue, sassafras, rose, rosemary, anise-seed, fennel, calamus, neroli, angelica, wormwood. Hence, this reaction cannot be relied upon.

II. Hoppe's nitroprusside of copper test.—This test sometimes gives good results, but only with hydrocarbons absolutely free from oxygen and oxygenated oils. It is, therefore, not suitable for oils derived from the Aurantiaceæ. The process is as follows: Add to a small quantity of the oil to be examined in a perfectly dry test-tube, 2 to 5 milligrammes of pure nitroprusside of copper previously thoroughly dried and finely pulverized, shake vigorously and gradually heat to boiling. After boiling for a few seconds allow to cool. If the oil is free from oil of turpentine, or another oil containing no oxygen, the precipitate formed is brown, black, or gray, and according to the quantity of the reagent added and the original color of the oil, the supernatant oil will be differently colored and appear more or less dark. If, however, the oil is adulterated with oil of turpentine, the precipitate formed shows a handsome green or blue-green color, while the supernatant oil retains its original color or at the utmost acquires a very slightly darker one. The longer the oil is allowed to stand after settling, the more distinct and beautiful the color of the oil and of the precipitate appears. For the establishment and certain recognition of very small quantities of oil of turpentine in oxygenated oils, it is best to first add very little of the nitroprusside of copper to the oil to be tested, and a larger quantity only after being convinced either of the purity or adulteration of the oil. This is done to be able, on the one hand, better to judge the reaction, if the oil is pure, and, on the other, if it is adulterated, to establish such adulteration with certainty and to approximately estimate the quantity of oil of turpentine present. The less nitroprusside of copper is used, the better small quantities of oil of turpentine can be detected.

Nearly all volatile oils free from oxygen show the same behavior towards nitroprusside of copper; they decompose it, which is not the case with oxygenated oils. The behavior of the latter is shown in the following table:—

If these oxygenated oils are mixed with oils free from oxygen, for instance, oil of turpentine, they show exactly the same behavior as oils free from oxygen; the nitroprusside of copper is not decomposed and retains its gray-green color. If, for instance, oil of cloves is mixed with oil of turpentine, the red coloration by nitroprusside of copper does not appear.

III. Hager's alcohol and sulphuric acid test.—Bring into a test-tube of about 0.5 inch diameter, five to six drops of the oil to be tested and twenty-five to thirty drops of pure concentrated sulphuric acid, and mix the two fluids by shaking, whereby either no heating takes place or a scarcely perceptible one, or the heating is strong or very vigorous and in some cases increased to the evolution of vapors. The mixture is either clear or turbid. After complete cooling, add to the mixture eight to ten cubic centimeters of 90 per cent. alcohol, and after closing the tube with the finger, shake vigorously. The mixture now shows a different color, is clear or turbid, and the deposit formed after standing for one day is also differently colored and either soluble or insoluble in boiling alcohol.

The mixture of oil, sulphuric acid and alcohol is perfectly clear and transparent with oils of bitter almonds, fennel, clove and rose; with anise-seed oil and star anise-seed oil only the alcoholic layer over the mixture of sulphuric acid and oil is clear. The mixture of oil, acid and alcohol is slightly turbid or nearly clear with oils of valerian, peppermint and field thyme. With most of the other volatile oils occurring in commerce, the mixture is more or less milky turbid. Heating of the oil and acid mixtures does not take place with pyrogenous oils (petroleum, benzine) or only to a very slight degree, as with oils of peppermint and mustard.

IV. Hager's guaiacum reaction[3] serves for the detection of oil of turpentine in a volatile oil. By pouring upon as much guaiacum, freshly powdered, as will lie upon the point of a small knife, in a test-tube 1 cubic centimeter (25 drops) of spike oil, and heating nearly to boiling over a petroleum lamp, the oil after being removed from the flame and allowing the undissolved resin to settle, shows a yellow color. By now pouring upon an equal quantity of guaiacum in another test-tube 25 drops of spike oil and 5 drops of rectified oil of t from the flame shows a dark violet color. Various other oils behave in the same manner as spike oil, and hence a content of oil of turpentine can be readily detected in them. Other oils do not exhibit this behavior; but this can be remedied by adding, in testing for oil of turpentine, a few drops of an oil of the first class.

The guaiacum reaction is an ozone reaction and with reference to this, the volatile oils may be divided into three classes:—

a. Oils inclining to the formation of ozone.—Foremost of these is oil of turpentine, especially when rectified. Oils of tansy, rue, mint, juniper, zedoary, etc., show considerably less inclination.

b. Oils which, especially when heated, directly incite the oil of turpentine to form ozone, and to color guaiacum violet or blue.—Such oils are many kinds of oil of citronella, oils of spike, calamus, cedar, etc.

c. Oils with a content of oil of turpentine, which remain indifferent towards guaiacum.—To such oils, if to be tested for oil of turpentine, with the assistance of the guaiacum reaction, a few drops of an oil of the second class have to be added.

V. Hübl's iodine method.—Mr. C. Barenthin has applied Hübl's iodine method for fixed oils to the examination of volatile oils. He uses the following solutions:—

1. Fifty grammes iodine and 60 grammes of mercuric chloride in a liter of alcohol freed from fusel oil, and let stand for 12 hours.

2. Twenty-four grammes of hyposulphite of sodium in a liter of water.

3. A ten per cent. solution of iodide of potassium. Dissolve 0.1 to 0.2 gramme of the volatile oil in 10 cubic centimeters of chloroform, and add first 15 cubic centimeters of the iodine-mercuric chloride solution; let stand three or four hours, and, in case the mixture gets discolored, add a few more centimeters of solution. Now add 10 to 15 cubic centimeters iodide of potassium solution, dilute with 150 cubic centimeters of water, and titrate with hyposulphite till the mixture remains clear for about a minute. The iodide of potassium solution must be added before the water, and the relative proportions between this solution and the iodine-mercuric chloride solution must be 15 to 20 cubic centimeters. The quantity of iodine solution consumed is calculated to iodine for 100 parts and the figure thus obtained is designated as the "iodine number."

Barenthin has in this manner determined the iodine number of several volatile oils; other experimenters, however, for instance, Kremel and Davies,[4] have found different numbers for the same oils, so that this method requires further thorough examination before it can be classed as available.

VI. A. Kremel has endeavored to utilize titration or saponification with alcoholic potash lye for the examination of volatile oils. In his experiments he was guided by the following points: A series of volatile oils contains partially free organic acids, like oils of bitter almonds and cinnamon, and partially aldehydes or other combinations. Now it seems not impossible, that up to a certain limit, the quantities of these combinations in the separate volatile oils remain constant, thus presenting the opportunity of testing the respective oils as to their quality and purity by saponification. In some cases these combinations are the chief bearers of the specific odor, and hence the determination of the "saponification number" becomes of double value. It is, of course, self-evident that not every volatile oil can be saponified, and Kremel admits that, even where saponification takes place, it is not in every case a sure test.

The execution of the method is as follows: Dissolve 1 gramme of the oil to be examined in 2 to 3 cubic centimeters of 90 per cent. alcohol freed from acid, compound the solution with a few drops of phenol-phthalein solution, and titrate the free acid with ½ normal alcoholic potash lye. The milligrammes of caustic potash used are designated the "acid number." After having thus determined the content of acid, add to the same solution 10 cubic centimeters of the same potash lye, heat for ¼ hour upon the water bath, and then titrate back the excess of potash lye with ½ normal hydrochloric acid. In this manner the "saponification number" is obtained. (In some cases when the final reaction is not plainly perceptible, it is advisable to correspondingly dilute with water after heating the alcoholic fluid.) The saponification number, less the acid number, gives the "ether or ester number."

Kremel has in this manner examined a large number of volatile oils and partially obtained surprising results. Rose oil gives a saponification number of 12, and geranium oils one of 40 to 50. While lavender oils give very high saponification numbers, oil of lemons does not. Artificial oil of bitter almonds shows higher saponification numbers than the natural oil. By further compounding the saponified portions of the latter with acid, a crystalline precipitate of benzoin is formed, the quantity of which amounts to from 40 to 50 per cent. of the oil used. Such a precipitate, but only in very small quantities, is also formed in peach kernel oil, but not in other similar oils nor in artificial oil of bitter almonds.

VII. F. R. Williams has recently endeavored to utilize for testing volatile oils Maumené's test, which is based upon the increase in temperature produced in oils by concentrated sulphuric acid, and which gives valuable points for the examination of some fat oils. Of course, the large quantities of oil otherwise prescribed cannot be used. While for the examination of fat oils 50 grammes of oil are mixed with 10 cubic centimeters of concentrated sulphuric acid in a beaker glass wrapped around with cotton, Williams could use only six cubic centimeters of volatile oil. They were brought into a very small beaker glass enveloped in cotton. After reading off the temperature, twelve cubic centimeters of concentrated sulphuric acid were added and the whole stirred with the thermometer until the temperature no longer rose. Numbers were in this manner obtained which might in some cases, for instance, cassia oil, furnish guiding points for judging the purity of the oil.

Planchon proposes the following procedure in order to recognize a volatile oil:—

A. The oil is specifically lighter than water.

1. The substance is solid and only melts at 347° F.: Camphor.

2. The oil at a temperature of over 32° F. contains a crystalline stearoptene.

a. The oil is laevorotatory, the stearoptene melts at 77° F., and, on adding sulphuric acid, a clear solution remains behind: Rose oil.

b. The oil possesses no rotatory power, the stearoptene melts at 50° F., and, on adding sulphuric acid, two layers are formed, only one of which is liquid: Anise-seed oil.

c. The oil is dextrorotatory, the stearoptene melts at 41° F., and, on adding sulphuric acid, a nearly colorless fluid remains behind: Fennel oil.

3. The oil is perfectly fluid and clear at above 32° F.

I. The oil explodes with iodine, emitting violet vapors.

a. The oil thickens in the air and readily forms resin.

It requires for its solution several volumes of alcohol: Oil of conifers.

b. The oil, on exposure to the air, does not thicken and but slowly forms resin.

α. It is dextrorotatory.

The liquid oil dissolves santalin: Oil of the aurantiaceæ.

The thick oil does not dissolve santalin: Mace oil.

β. The oil is laevorotatory.

The oil shows an acid reaction and dissolves in equal parts of alcohol: Lavender oil.

The oil shows a neutral reaction and dissolves in 12 to 15 parts of alcohol: Marjoram oil.

II. The oil gives no explosion with iodine, but shows an increase in temperature with or without emission of red vapors.

a. The oil shows an acid reaction.

α. The blue or green oil shows the acid reaction only indistinctly: Milfoil oil.

β. The colorless or brown oil gives a turbid fluid with sulphuric acid. It is laevorotatory: Spanish marjoram oil.

The oil is rendered but slightly turbid by sulphuric acid; it acquires a red-violet color by nitric acid, has no effect upon the plane of polarization, and has a peculiar odor: Oil of valerian.

b. The oil is neutral.

α. It dissolves with difficulty in alcohol.

β. The oil is miscible in every proportion with alcohol.

1. It is dextrorotatory.

The oil is colorless or yellowish, it thickens on exposure to the air, and dissolves and reduces fuchsine: Caraway oil.

The oil is thick, yellow-brown or red-yellow, and has a peculiar odor: Calamus oil.

2. The oil is laevorotatory.

It is fluid and has an aromatic odor: Rosemary oil.

The oil is thick and very pungent: Cubebs oil.

III. The oil dissolves iodine without vigorous reaction and without an increase in the temperature.

a. The oil is blue and green.

It has an agreeable, camphor-like odor: Camomile oil.

The green oil thickens in the air and is dextrorotatory: Wormwood oil.

The oil is generally green and produces no effect upon the plane of polarization: Cajeput oil.

b. The oil is colorless or yellow-brown.

α. It separates a solid stearoptene at about 32° F.: Rue oil.

β. The oil remains liquid at several degrees below 32° F.

1. Dextrorotatory oils.

The oil shows an acid reaction, and gives with sulphuric acid a somewhat turbid solution, which becomes clear by the addition of alcohol: Dill oil.

The oil gives with sulphuric acid a yellow-red turbid solution, which becomes clear and peach-blossom red by the addition of alcohol: Eucalyptus oil.

2. Laevorotatory oil.

The oil showing an acid reaction becomes thick in the air and has a characteristic odor: Mint oil.

The oil shows a neutral reaction and has a camphor-like odor: Thyme oil.

IV. The oil does not dissolve iodine, does not heat with sulphuric acid, and does not react upon nitric acid. The odor is empyreumatic: Petroleum.

B. The oil is specifically heavier than water.

1. The oil shows an acid reaction.

It is soluble in 30 parts of water, boils at 356° F., and smells of bitter almonds: Oil of bitter almonds.

The oil has an agreeable, sweet odor and boils at from 392° to 431.6° F.: Wintergreen oil.

2. The oil shows a neutral reaction.

a. The oil is laevorotatory.

It becomes blue by the addition of sulphuric acid: Oil of cloves.

b. The oil is optically inactive.

The thick oil gives with sulphuric acid a turbid, black-brown fluid; the odor is agreeable: Cinnamon oil.

c. The oil is dextrorotatory.

The thick oil has an agreeable odor: Sassafras oil.

[CHAPTER IV.]

THE VOLATILE OILS USED IN PERFUMERY.

The volatile oils, as previously mentioned, may be divided into three groups, viz: the pure hydrocarbons, oxygenated oils, and sulphuretted oils. Chemically, this division is, however, of little value, since, among bodies which should be classed according to it in one of the groups, combinations are found which vary very much in a chemical respect, and belong partially in the groups of alcohols, indifferent bodies, acids, etc.

It is, therefore, preferred not to attempt a classification of the volatile oils according to their chemical composition, but simply to enumerate them in alphabetical order.

Acacia, oil of, commonly called oil of cassie. The flowers or buds of the acacia Farnesiana yield a somewhat thickly-fluid, greenish-yellow oil of a very intense but delightful odor. The oil may be obtained either by extraction or absorption. The acacia is cultivated in special plantations along the Riviera di Genova. These plantations being controlled by a few perfumers, the oil is not allowed to reach the market, and does not form an article of commerce. The green-colored extrait d'acacia is a solution of the oil in alcohol.

Almond oil (bitter) (oleum amygdalae amaræ) is obtained by submitting bitter almond cake (left after the expression of the fixed oil from bitter almonds) to distillation with water. The volatile oil does not exist ready formed in the bitter almond, nor in the almond cake, but results from the decomposition of a glucoside called "amygdalin," contained in the cake, under the influence of emulsin and water, the emulsin acting as a ferment, into benzylic aldehyde, glucose and prussic acid. The almond tree grows wild, but is also cultivated in Southern Europe, Africa, Barbary, Palestine and Syria. The bitter almonds brought from Barbary are considered the best. Besides, in almonds, amygdalin occurs in various other plants; for instance, in the leaves of the cherry laurel, the leaves and kernels of the peach, the kernels of the black cherry and other varieties of prunus and amygdalus, they all yielding, after maceration with water, a distillate containing prussic acid and oil of bitter almonds.

Instead of the comparatively expensive bitter almonds, peach kernels freed from their hard shells are extensively used in the fabrication of oil of bitter almonds. The oil is prepared as follows: The press cakes of bitter almonds or peach kernels are ground and soaked about twenty-four hours in twice their weight of water to which one-third their weight of salt has been added. The whole is then submitted to distillation. The temperature of the water should not exceed 113° to 122° F. The emulsin contained in the almonds possesses only within certain limits of temperature the power of decomposing amygdalin, and, if heated to 176° F., becomes inoperative. Hence, if the almond paste is quickly heated to boiling, the emulsin becomes inoperative before all the amygdalin is decomposed, and a portion of it being consequently lost, the yield is insufficient. The distillation of the almond paste is effected in a current of steam.

A portion of the prussic acid formed by the decomposition of the amygdalin adheres tenaciously to the oil. This content of prussic acid makes the oil of bitter almonds exceedingly poisonous, while in itself it is non-poisonous. It can be freed from the prussic acid by shaking with ferrous sulphate (blue vitriol) solution. By then distilling over burnt lime the originally yellow or yellowish oil is obtained colorless. It is then thinly fluid, of a peculiar agreeable odor and strongly nutty taste. Its specific gravity is 1.043 at 59° F., but varies a little with age. It boils at 356° F., and dissolves in 13 parts of water, but more readily in alcohol and ether. In the air it is rapidly converted into benzoic acid by the absorption of oxygen. It has to be carefully protected from air and light and kept in well-closed bottles in a dark place. The crude oil, containing from 2 to 5 per cent. prussic acid, has generally a yellowish color.

Oil of bitter almonds may be prepared artificially in many ways. By allowing chlorine to flow into boiling toluene, the latter is converted into benzyl chloride:-

By withdrawing the chlorine and one atom hydrogen from the benzyl chloride and introducing for it one atom oxygen, the benzyl chloride is converted into benzaldehyde. This conversion is readily effected by continuously boiling, best with the introduction of carbonic acid, 1 part of benzyl chloride with 1½ parts of lead nitrate and 10 parts of water, and finally distilling the benzaldehyde off by steam. The decomposition takes place according to the following equation:—

2[C₆H₅(CH₂Cl)] + Pb(NO₃)2 =
2[C₆H₅(CHO)] + PbCl₂ + N₂O₃ + H₂O.

The crude benzaldehyde thus obtained is agitated with warm solution of acid sodium sulphite, the solution formed thereby is separated from undissolved oily particles and cooled, whereby a combination of benzaldehyde with acid sodium sulphate crystallizes out. This combination is separated from the remaining fluid, decomposed by acid and submitted to distillation, whereby benzaldehyde passes over. Large quantities of benzaldehyde are at present prepared according to this method. The identity of benzaldehyde with oil of bitter almonds has been established by Lippmann and Hawliczek.

Genuine oil of almonds is much adulterated, chiefly with alcohol, nitrobenzole, and various cheaper oils. An addition of 3 to 5 per cent. of alcohol is frequently made by Italian dealers in order to conceal a content of water, which at a low temperature is apt to render the oil turbid. To detect the presence of alcohol, moderately heat a sample of the oil in a distilling apparatus and compound the drops, first passing over with sodium carbonate solution and then with potassium iodide solution. In the presence of alcohol a yellowish crystalline precipitate of iodoform is formed.

An addition of synthetically composed oil might seem of no importance, since the natural oil does not differ from it. However, for very fine perfumery the natural oil cannot be replaced by the artificial, it having been thus far impossible to obtain the latter absolutely chemically pure. It always contains small quantities of undecomposed chlorine combinations which injure the taste and odor. To detect such oil in the natural oil, bring a few drops upon a tuft of cotton and ignite it. Over the burning flame invert a beaker moistened inside with water. On the moist sides of the beaker the soot and hydrochloric acid formed by the combustion of the chlorine combination are precipitated. When the flame is extinguished, the beaker is rinsed out with water, the fluid filtered and tested for chlorine with nitrate of silver. An addition of 10 per cent. artificial oil can in this manner be accurately determined.

If genuine oil of bitter almonds containing prussic acid, be heated with an excess of alcoholic potash lye, and the excess of the latter be neutralized with hydrochloric acid, benzoin amounting to 40 to 50 per cent. of the weight of oil of bitter almonds is, according to A. Kremel, separated. By subjecting artificial oil of bitter almonds to the same treatment, no benzoin is separated, so that the genuine oil can in this manner be distinguished from the artificial. Kremel further found that oil of bitter almonds prepared from apricot kernels, when treated in an analogous manner, yielded considerably less benzoin, and that cherry-laurel oil containing prussic acid, which has been considered identical with oil of bitter almonds, separated no benzoin whatever. Should further experiments prove the constancy of this phenomenon, this reaction would be a convenient means of distinguishing the four products.

An adulteration with nitrobenzole and other volatile oils is recognized by mixing 2 drops of the oil with 100 drops of distilled water, and shaking vigorously. Pure oil must completely dissolve. However, the test yields accurate results only with the use of actually pure distilled water and by accurately observing the above-mentioned proportions. If to 5 cubic centimeters of 90 per cent. alcohol and an equal quantity of distilled water in a test-tube, 10 drops of the oil be added, and, after closing the tube with the finger, mixture be effected by gently turning the tube twice upside down, a clear solution will immediately result if the oil is pure. If, however, it contains nitrobenzole, even only 1 per cent., the latter separates, at first rendering the fluid turbid, but in the course of a minute, when gently agitated, it floats in the form of minute drops upon the fluid, while, when at rest, these drops collect to larger ones on the bottom of the test-tube. If the oil becomes only turbid, adulteration with other volatile oils is indicated. Another test, given by Wagner, is based upon the difference in the specific gravity of mixtures of oil of bitter almonds with oil of mirbane. The specific gravity of commercial oil of bitter almonds varies between 1.040 and 1.043 and that of oil of mirbane between 1.180 and 1.201.

5 c. c. of pure oil of bitter almonds weigh 5.29 grammes.
5 " mixed with ¼ oil of mirbane " 5.39 "
5 " " " ½ " " " 5.57 "
5 " " " ¾ " " " 5.75 "
5 " of pure " " " 5.90 "

Oil of bitter almonds is much used in the fabrication of perfumery. In a pure state its odor is by no means agreeable, but rather strong and stupefying. When strongly diluted it is, however, very pleasant.

Angelica oil is obtained by distillation with water from the root of Angelica Archangelica L., natural order Umbelliferae. The oil is lighter than water, possesses the spicy odor of the root and an aromatic pungent taste. It consists mostly of a terpene which turns the plane of polarization to the right, and boils at 320° F.