THE SPECIAL CHARACTERISTICS OF AROMATIC SUBSTANCES.
In a preceding chapter on the chemical properties of the vegetable
substances many of their characteristics have been described. In this
place we need only describe the physical properties of the essential
oils, and with some of them to lay stress on those peculiarities by
which they are specially differentiated. This knowledge is of the
greatest importance to the manufacturer of perfumery because no
single individual is in a position to prepare all aromatic substances
himself, but must rely on commerce for some of them; and in no group of
chemicals is adulteration as frequent and as difficult of demonstration
as among the aromatics. These adulterations are carried so far that
many essential oils occurring in commerce under certain names often
have nothing in common with the substance for which they are sold but
the name.
OIL OF CASSIE.
The oil of Acacia farnesiana is greenish-yellow and viscid; the density
and boiling-point, which are of the greatest importance with reference
to the genuineness of an essential oil, are not yet accurately known.
Moreover, this oil never occurs in commerce as such, but its odor is
present in perfumes, fixed oils, and pomades.
OIL OF ANISE
should be colorless or faintly yellow; a dark yellow color indicates
old and inferior quality. The characteristics of this oil are the odor,
its aromatic sweet taste, and especially the property of solidifying
at a comparatively high temperature, 10-15° C. (50-59° F.), which
is due to the separation of a stearopten, anethol. Oil of anise is
frequently adulterated with or replaced by oil of star-anise. The easy
solidification of the oil of anise is not always proof of its good
quality, for the oil from anise chaff, which congeals at a still higher
temperature, is sometimes mixed with it, and this has a less fine odor
than that distilled from the seed. One part by weight of oil of anise
is soluble in an equal weight of alcohol of 94%.
OIL OF BERGAMOT
has a pale yellow color which becomes greenish when the oil is kept in
copper vessels, and a strong agreeable odor. This oil requires the
greatest care in its preservation, as it abstracts oxygen from the air
with extreme rapidity, when it changes its superior odor so that it can
hardly be distinguished from oil of turpentine.
OIL OF BITTER ALMOND (OLEUM AMYGDALE AMARÆ),
when pure, is a colorless, refractive liquid which is heavier than
water. The vessels in which this product is preserved must be stoppered
air-tight, for in the air the oil very quickly changes into a white,
odorless mass of crystals consisting of benzoic acid.
Oil of bitter almond is formed by the action of the amygdalin upon the
emulsin present in the fruit, bitter-almond meal being deprived of
fat and left in contact with water for some hours at from 40-45° C.
(104-113° F.). Besides oil of bitter almond, sugar and prussic acid are
likewise formed. The crude oil distilled from the meal is freed from
the prussic acid by agitation with ferrous chloride and lime-water, and
redistillation.
OIL OF CAJEPUT (OLEUM CAJUPUTI)
has usually a greenish color, and has a burning, camphoraceous and at
the same time cooling taste. It has a peculiar odor resembling that of
camphor and rosemary.
OIL OF CALAMUS (OLEUM CALAMI).
This oil, which is very viscid and of a yellow or reddish color, must
usually be mixed with other essential oils in order to furnish pleasant
perfumes.
OIL OF CHAMOMILE (OLEUM CHAMOMILLÆ).
Oil of chamomile, from Matricaria Chamomilla (common chamomile), which
is specially characterized by its magnificent dark-blue color, has a
marked narcotic odor and is very high-priced, owing to the small yield
of oil by the flowers. The oil from Anthemis nobilis (Roman chamomile)
has also a blue color which gradually becomes greenish-yellow.
CAMPHOR (CAMPHORA).
This essential oil differs from the others mainly by being firm and
crystalline at ordinary temperatures. Chinese or Japanese camphor melts
at 175° C. (347° F.) and boils at 205° C. (401° F.). Camphor is seldom
used alone, as its odor is hardly fragrant; but it finds frequent
application in the preparation of mouth washes, toilet vinegars, etc.
In commerce so-called Borneo camphor is also met with (though rarely),
which closely resembles the Chinese in appearance and other qualities,
but is more friable and melts at 189° C. (388·4° F.).
OIL OF CASCARILLA
is not used pure in perfumery, the bark being generally employed
instead.
OIL OF CASSIA (OLEUM CASSIÆ)
has a yellow color, gradually becoming dark reddish-brown, and an odor
resembling that of oil of cinnamon, but the odor is not so fine, nor
so strong, as that of the latter. The taste of the oil is of special
importance: while that of true oil of cinnamon is burning though sweet,
oil of cassia has a sharper taste, and this taste is considered by some
a good mark of recognition of the rather common adulteration of true
oil of cinnamon which is much more costly.
OIL OF CEDAR.
This oil, obtained from the wood of the Juniperus virginiana (not from
the true cedar, Cedrus Libani), is clear like water, has a pleasant
odor, and differs from most essential oils by congealing at a very low
temperature (-22° C. or-8° F.) and by its uncommon resinification in
contact with air.
OIL OF CITRON.
Oil of citron is usually merely a synonym for “oil of lemon.” But in
perfumery it has been customary to designate the oil of lemon which was
extracted by the écuelle process, as “oil of citron-zeste” or “oil of
citron,” while “oil of lemon” meant the distilled oil. Since there is
no difficulty at the present time in obtaining all the hand-pressed oil
that may be required, and of the finest quality, there is no longer any
necessity for making the before-mentioned distinction.
OIL OF LEMON (OLEUM LIMONIS, OLEUM CITRI)
is one of the most important essential oils for the perfumer as well
as the manufacturer of liqueurs, confectioner, etc. The oil is pale
yellow, and of a very strong refreshing odor which it loses rapidly
in contact with the air, when it acquires a disagreeable odor of
turpentine and gradually resinifies. This change is particularly marked
under the influence of light. Its spec. grav. is 0·850 at 20° C. (68°
F.). It is soluble in an equal volume of strong alcohol or glacial
acetic acid. The hand-pressed oil has a much finer aroma than that
obtained by distillation.
OIL OF CITRONELLA.
This oil is hardly ever made in Europe, since it is imported in
excellent quality and at low prices from India and especially the
island of Ceylon. (See above, p. 29.)
OIL OF LEMON-GRASS.
This oil, which is imported in considerable quantities from India
(chiefly Ceylon), is colorless and possesses a very pleasant odor of
lemon which at the same time recalls that of roses and still more that
of geranium, which is not rarely adulterated with it. (See above, p.
33.)
OIL OF CORIANDER (OLEUM CORIANDRI)
has a pale yellow color and a burning, sharp, aromatic taste. Like
oil of cubebs (oleum cubebæ), oil of dill (oleum anethi), and oil of
fennel (oleum fœniculi) which latter also has a rather low congealing
point (-8° C. or +17° F.), this oil is used less in perfumery than
for scenting soap and in the manufacture of liqueurs. But it should
be noted that these oils, as well as those of bergamot, caraway,
star-anise, and some others, could well be employed for cheap perfumes
and for scenting soap. Oil of dill also finds application alone in the
preparation of some face washes, and the dried fennel herb in cheap
sachets.
OIL OF LILAC
can be made at slight cost from the flowers, as the raw material is
obtainable without much trouble; it forms a yellow, strong-scented oil.
In perfumery, however, use is generally made only of the pomade made
from the fresh flowers or the alcoholic extract prepared from it. Or
else the odor is imitated by means of terpineol, which is now on the
market under the name of lilacin.
OIL OF GERANIUM.
It is necessary to distinguish clearly between oil of true geranium
distilled in Southern France and Algiers from species of Pelargonium;
and Turkish oil of geranium, also known as Palmarosa oil, oil of
geranium grass, oil of Rusa grass, etc., which is distilled in India
from ginger grass. (See above, p. 33.)
The first-mentioned oil has a much finer aroma than the second. The two
oils are frequently confounded, even in prominent works of reference.
When oil of geranium or of rose geranium is directed to be used, the
French (or Algerian, or Spanish) oil should be employed. These cost
more than twice as much as the so-called Turkish or palmarosa oil.
OIL OF HELIOTROPE.
This oil which does not yet occur in commerce (we find merely the
pomade and the alcoholic extract of the latter) has been made by
the author experimentally; the most suitable method was found to be
extraction with petroleum ether. As the plant, Heliotropium peruvianum,
the source of this delightful odor, is frequently cultivated in
our gardens, the preparation of the oil by this method is to be
recommended, being less expensive and more rapid than by the use of
fat, while the product obtained with petroleum ether is as fine as that
extracted by alcohol from the pomade.
OIL OF ELDER (OLEUM SAMBUCI).
The remark made under the head of oil of lilac applies equally to this
oil. For the benefit of those who wish to make this oil in its pure
form we may add that it is absolutely necessary to select only the
freshest flowers, otherwise the odor will be very much impaired.
OIL OF JASMINE,
not to be confounded with the oil of Syringa or German jasmine
(Philadelphus coronarius), is colorless or yellowish and has a very
strong, almost narcotic odor. It is one of the most valuable and at the
same time most expensive aromatic substances employed in perfumery.
Genuine oil of jasmine can be obtained only from Southern France at
very high prices. What is usually sold as “oil of jasmine” is a fixed
oil impregnated with the aroma of jasmine.
OIL OF CHERRY-LAUREL
is not used as such in perfumery; at most cherry-laurel water may be
employed. But as this has the odor of oil of bitter almond and as
the presence of some prussic acid, on account of which the officinal
cherry-laurel water is used, is of no value to the perfumer and is,
in fact, undesirable, owing to its poisonous quality, we substitute
in all cases a corresponding quantity of oil of bitter almond for
cherry-laurel water.
OIL OF CULILABAN (OLEUM CULILAVANI)
is light brown, somewhat viscid; the odor recalls that of the oils of
cinnamon, sassafras, and clove. It has been used for scenting soap.
OIL OF CARAWAY (OLEUM CARI)
is light yellow and has an aromatic odor and burning taste. In
perfumery it is used only for very cheap odors and for scenting soap;
it finds its chief application in the manufacture of liqueurs.
OIL OF LAVENDER (OLEUM LAVANDULÆ).
This oil is of great importance to the perfumer and is imported in
unsurpassed quality from England (Mitcham); it is light yellow, has a
burning sharp taste, and is exceedingly sensitive to light and air,
under the action of which it loses its refreshing odor in a very brief
time and acquires a common smell recalling that of turpentine.
The buyer of this oil should take care to secure the true oil of
lavender (from Lavandula vera); for the oil of spike-lavender is sold
under the same name. This, prepared from Lavandula Spica, has a similar
odor to the genuine, but cannot be compared with it in delicacy. For
this reason, too, the difference in the price between the two is
considerable. True English oil of lavender costs ten times as much
as oil of spike-lavender. The English brand of the true oil is of so
excellent a quality that it brings four or five times as much as the
best French oil, which is sold under the name of huile de lavande des
Alpes. Yet during the last decade or so the French oil of lavender
flowers has become so much improved in quality that it has become a
serious rival to the Mitcham oil.
OIL OF WALLFLOWER
made from the flowers of the well-known garden plant, and
OIL OF LILY
likewise from the ornamental plant, are, strange to say, not
manufactured in any place, to our knowledge. Experiments made by us in
this direction prove that the odors of these plants can be obtained
either by absorption or, more readily, by extraction. The perfumes thus
far occurring under these names are always combinations of different
scents which, though pleasant, have but little in common with the
plants whose names they bear.
In this connection we may say that the perfumes sold under the names
of various flowers often have no relation to them, but are mixtures
of various odors. While it cannot be denied that perfumes may be made
in this manner which resemble those of the respective plants, it is
unquestionably an imperfection in the art of perfumery that these
odors are not really made from the flowers mentioned. To give another
characteristic instance, we may add that the delightful odor of the
well-known lily of the valley (Convallaria majalis)—a plant which grows
wild abundantly in many of our forests—has not yet been produced, and
that even imitations of this odor, which in delicacy and fragrance
stands next to those of the rose and violet, are seldom met with in
commerce.
OIL OF LEMON (OLEUM LIMONIS),
obtained from the fruits of the lemon-tree, is one of the most
important products, both statistically and economically, of the Citrus
family. In German works there is often a confusion between “oil of
citron” and “oil of lemon,” it being supposed by the authors that the
“Citronen-öl” is derived from the citron (Citrus medica), and the
“Limonen-öl” from the lemon (Citrus Limonum). There is, indeed, some
oil made, occasionally, from the citron, but it does not figure in
price-lists. The oil of the lemon, on the other hand, is very commonly
called “Citronen-öl,” and the fruit itself “Citrone.” Hence, when
“Citronen-öl” is quoted in a formula, it may be assumed at once that
oil of lemon is intended. It is very liable to resinify, when it loses
its fragrance.
OIL OF SWEET BAY (LAUREL) (OLEUM LAURI)
is green, and usually mixed with the fixed oil of the same plant. It
finds more frequent application in the manufacture of liqueurs than
in perfumery; but as it has a pleasant odor it might well be used for
cheap perfumes. But in that event it must be freed from the fixed oil
by distillation.
OIL OF MAGNOLIA,
likewise, has not yet been prepared as such. The remarks made above
under the head of oils of lily and wallflower apply also to this odor.
The so-called magnolia perfumes are mixtures of different odors.
OIL OF MARJORAM (OLEUM MAJORANÆ).
Oil of marjoram, which is obtained by distillation from the dried
herb, has a strong aromatic odor. It is mentioned as having often been
used in perfumery for scenting soap instead of oil of thyme, whose
odor, moreover, is very similar to that of marjoram, but this is a
mistake, due to the fact that ordinary oil of thyme has long been sold
under the name of oil of origanum. True oil of marjoram costs about
twelve dollars a pound, while oil of thyme (so-called oil of origanum)
is worth only about eighty cents. It is rarely employed for volatile
perfumes.
OIL OF MELISSA.
The oil of Melissa officinalis, owing to the very small yield, is quite
expensive. It is used only for the preparation of some perfumes which
owe their peculiar qualities to this strong odor. This oil must not
be confounded with the spurious oil of melissa, also called oil of
citron-melissa, which is identical with oil of lemon grass (see page
30).
OILS OF MINT.
Although all the mints possess an agreeable odor, only three varieties
find extensive application. There are the oils from Mentha piperita,
peppermint; Mentha viridis, spearmint; and Mentha crispa, crispmint.
The oils of English manufacture are highly esteemed, but the United
States also produces them of excellent quality. At one time the
cultivation of mints, particularly peppermint, was greatly extended,
with the expectation of deriving satisfactory profit from the
enterprise. It has, however, been conclusively shown that the market
cannot absorb more than a certain quantity of these products; and that
any over-production brings loss and disappointment to the investor.
Beside the three kinds of mint above mentioned, there is another
species, Mentha arvensis, a native of Japan, which is extensively
cultivated there, and is the chief source of the menthol of commerce,
so well known as an efficient remedy for neuralgia, migraine, etc., in
form of menthol cones. The three varieties of the mint oils previously
mentioned are distinguished, aside from their pleasant odor, by the
property of leaving a very refreshing and cooling taste in the mouth,
and for this reason they form the most important constituent of all
fine mouth washes.
True oil of peppermint, Oleum Menthæ piperitæ, when pure is colorless,
very mobile, of a burning sharp taste which is followed by a peculiar
coolness. The commercial product is usually pale green. Oil of
crispmint, Oleum Menthæ crispæ, which in Europe is often sold to
novices as oil of peppermint, has always a more or less yellow color
and resembles the oil of peppermint in its properties, but it is less
fine and cheaper. The same is true of the oil of spearmint, but this
has a very characteristic odor and taste, distinctly different from
peppermint.
As above stated, the oils of mint are extensively used for mouth
washes, also for scenting soap, in liqueurs and pastils, but rarely in
handkerchief perfumes.
OILS OF MACE AND NUTMEG (OLEUM MACIDIS AND OLEUM MYRISTICÆ).
These oils are prepared either from the seed coat (Oleum Macidis)
or the nutmeg itself (Oleum Myristicæ). Oil of mace generally has
a yellowish-red color in tint varying from dark to light and even
colorless. Its taste is agreeable and mild and the odor exceedingly
strong. Like oil of nutmeg, it is extensively used in the manufacture
of liqueurs and for scenting soap. The oil prepared by distillation
from the nutmeg is, when fresh, almost colorless or at most faintly
yellow, of a burning sharp taste, and an aromatic odor. Like oil of
mace, it is used in the manufacture of liqueurs and soaps and also in
many perfumes.
In India a third valuable product is obtained from the nutmeg by
expression of the ripe fruits and is called nutmeg butter. This
is bright yellow and consists of a true fat and an essential oil.
Its odor is very pleasant and a very superior soap can be made by
saponification of this valuable product with soda lye.
OIL OF MYRTLE.
This oil is of a greenish color and very mobile, but it is not a
commercial product; the manufacturer must prepare the oil himself from
the leaves, though the yield is small. The articles sold as so-called
essence of myrtle are always mixtures of different odors. Southern
France, however, exports at high prices a myrtle water (eau des anges)
which is really made by distillation of the leaves with water.
OIL OF NARCISSUS.
As to the odor to which this flower owes its fragrance we may repeat
what we have said just now with reference to the oil of myrtle: we
have never succeeded in obtaining this oil in commerce. The so-called
essence of narcissus, though a very pleasant mixture, contains no trace
of the true oil. As to
OIL OF PINK,
the same remark applies: the compositions sold under the name of
essence d’œillet, however, have a very striking odor of pink.
OIL OF CLOVE (OLEUM CARYOPHYLLI).
This oil when fresh is colorless, but soon becomes yellowish or brown.
It is heavier than water in which it sinks and is characterized by an
exceedingly strong burning taste and a spicy odor. It remains at least
partly fluid at a very low temperature, namely,-20° C. (-4° F.).
OIL OF ORANGE FLOWERS (OLEUM NAPHÆ, OLEUM NEROLI),
commercially known also under the French names huile de fleurs
d’oranges, huile néroli, huile néroli pétale, is obtained from the
flowers of the orange-tree in Southern France, where the orange is
specially planted for this purpose. The odor of the oil varies with the
mode of its preparation; that obtained by distillation with water has
a different odor from that made by maceration with fat and extraction
with alcohol. The latter variety of oil as such, however, is not
found in commerce, the alcoholic extract entering at once into the
composition of the perfumes.
The French manufacturers of this oil, which is of great importance in
perfumery, distinguish several varieties. The most valuable is the oil
from the flowers of Citrus vulgaris (or Citrus Bigaradia), the true
bitter orange (or Seville orange) tree. This is the so-called néroli
bigarade. That called néroli pétale is obtained from the same flowers
carefully deprived of their floral envelopes, so that only the petals
are subjected to distillation. Much cheaper than these two is the oil
of petit grain which is distilled from the leaves and sometimes also
unripe fruits of various trees of the Citrus order.
All these oils are among the most delicate; when fresh they are
colorless and have a peculiar bitter taste; exposed to light and air
they assume a reddish tint and undergo rapid resinification. They
should, therefore, be preserved in particularly well-closed vessels in
a dark, cool place.
Not to be confounded with these oils is the
OIL OF ORANGE,
of which there are two kinds, one from the bitter orange, known also
as Oil of Orange, Bigarade, and the other from the sweet orange, also
known as Oil of Portugal. Both are extracted from the peel of the fruit
by mechanical means. Both oils of orange peel are golden yellow, and
have a pleasant, refreshing odor recalling that of the fruit. They
find application for scenting soap, in toilet waters, and in some true
perfumes. When oil of orange or oil of orange peel is mentioned in any
formula, without further specification, the oil of _bitter_ orange peel
should be used.
OIL OF PATCHOULY.
This oil, which might be manufactured with advantage in India, the
home of the plant, is, strange to say, not imported from that country,
but is distilled in Europe from the dried herb. Fresh oil of patchouly
is brown in color, very viscid, almost like balsam, and surpasses all
other essential oils in the intensity of its odor. Owing to the strong
odor, pure oil of patchouly must really be called ill-smelling; only
when highly diluted does the odor become pleasant, and then forms a
useful ingredient of many perfumes as the fundamental odor in the
harmony.
OIL OF SYRINGA.
Oil of false jasmine, from the flowers of Philadelphus coronarius,
is not made as such; in Southern France, however, the flowers
are frequently used for the preparation of a cheap pomade known
commercially as orange-flower pomade. A personal experiment made with
the view to obtain the pure odor by extraction of the flowers with
petroleum ether has shown that this plant is suitable for making very
fine preparations, both handkerchief perfumes and pomades.
OIL OF ALLSPICE,
of a burning sharp taste and odor, is colorless, but is hardly ever
used for the purposes of the perfumer—at most for soaps—but all the
more frequently in the manufacture of liqueurs, and particularly also
in that of artificial bay-rum.
OIL OF SWEET PEA
has not been made thus far, though there is no doubt that this perfume,
too, can be prepared pure from the alcoholic extract of the pomade.
The properties of the oil should resemble those of the finest néroli
pétale.
OIL OF RUE (OLEUM RUTÆ).
This oil, obtained by distillation of the herb, is colorless or pale
yellow, of a very strong, penetrating odor; it is used in some washes,
but more particularly as an ingredient in the manufacture of artificial
cognac, for which purpose the plant is specially cultivated in France.
OIL OF RESEDA (MIGNONETTE).
The delightful odor of this plant which formerly could only be fixed by
maceration in fat may be readily prepared by extraction with petroleum
ether. Yet special precautions should be taken that nothing but
portions of the flowers, carefully picked off, and no green leaves are
extracted. The oil thus obtained has a yellow color and a disagreeable
odor which changes into the well-known pleasant smell of the flower
when highly diluted with alcohol.
OIL OF ROSE (OLEUM ROSÆ),
also known as attar or otto of rose. The various species of roses give
different odors. The commercial Turkish, Persian, and Indian oils of
rose (which latter is never exported)—which, by the way, are very
generally adulterated even at their point of production—are derived
mainly from Rosa damascena, and when highly diluted yield the pleasant
odor of our ordinary garden roses. The rose oils having the odor of the
moss rose, tea rose, or dog rose are made almost exclusively in France
and in commerce do not appear pure but generally in the form of pomades
or alcoholic solutions known as essences de roses.
True rose oil is yellowish or yellow, or else greenish, and varying
from liquid almost to the consistence of butter. Between these
extremes there are all possible gradations. A comparatively very high
congealing-point is a characteristic of oil of rose. It becomes almost
solid at 14 to 20° C. (57 to 68° F.). The portion separated during
solidification is colorless, markedly crystalline, and, strange to say,
almost odorless. Pure oil of rose smells disagreeably narcotic, only
the very dilute solution shows the incomparable fragrance.
Much superior to the oils of rose which are prepared from rose leaves
(either fresh or salted) are those obtained by maceration or extraction
with petroleum ether. Those perfumes sold under the name of various
species of rose, such as moss rose, etc., are combinations of rose oil
with other aromatics.
OIL OF RHODIUM.
This bright yellow light oil is obtained by distillation of the wood of
Convolvulus Scoparius. At times this oil is scarce in commerce. It has
a faint but decided odor of rose.
OIL OF ROSEMARY (OLEUM ROSMARINI).
This oil is obtained by distillation from the herb of the rosemary
plant as a thin, pale green fluid with an aromatic odor and spicy
taste. It is used as an ingredient in some old renowned handkerchief
perfumes—for instance, Cologne water—also for flavoring soaps and
liqueurs.
OIL OF SAGE (OLEUM SALVIÆ),
from the flowers of Salvia officinalis, is yellowish, with an odor
somewhat similar to that of oil of peppermint, but far less intense.
Like the latter it imparts a pleasant coolness to the mouth and hence
is used in some mouth washes.
OIL OF SANTAL (OLEUM SANTALI).
The oil of santal wood (also called sandal-wood oil) has a thick,
honey-like consistence and an agreeable, rose-like odor. Formerly
it was sometimes used for the adulteration of oil of rose, but can
also very well be used alone for several perfumes and fumigating
preparations.
OIL OF SASSAFRAS (OLEUM SASSAFRAS)
is yellow, spicy, with a burning odor and taste; in the cold it
crystallizes only in part. The odor of this oil recalls that of fennel.
The purest form of it, or rather substitute for it, is safrol, its main
constituent, which is, however, now extracted more economically from
crude oil of camphor, in which it likewise forms an ingredient.
OIL OF MEADOW-SWEET (OLEUM SPIRÆÆ).
Several species of Spiræa, and especially Spiræa ulmaria, furnish very
pleasant odors. This oil consists mainly of salicylic aldehyde.
Despite its pleasant odor and the facility of its production, this
substance has thus far found little application in perfumery. The
natural oil of meadowsweet, owing to its extremely high price, can
hardly ever be used.
OIL OF STAR-ANISE (OLEUM ANISI STELLATI; OLEUM ILLICII)
resembles in its properties the oil of anise, even in its odor; but
all connoisseurs agree that the odor of the oil of star-anise far
surpasses that of the oil of anise, hence the former is used especially
for fine perfumes. This preference, however, does not extend to all
preparations. For certain liqueurs, such as anisette, the oil obtained
from common anise (Saxon anise) is usually preferred. Many also regard
the odor of star-anise as inferior to that of fine European anise.
OILS OF THYME (OLEUM THYMI).
The essential oils of thyme (chiefly Thymus vulgaris) and some related
plants are very frequently used for scenting cheap soaps. The oils of
these plants are light yellow, and so similar in odor that it is not
possible to distinguish them except by direct comparison.
OIL OF VANILLA,
or, more correctly, vanilla camphor, the true odorous constituent
of vanilla, also called vanillin, is a crystalline substance with a
delightful odor, melting at 76° C. (169° F.). This is now extensively
made artificially from the cambium sap of pines, the coniferin being
converted by chemical processes into vanillin. One ounce of good
vanillin is equivalent to about forty ounces of best Mexican vanilla
beans.
OIL OF VIOLET
has thus far been produced in but very small quantities from the
alcoholic extract of the true violet pomade; it has a greenish color
and when pure a narcotic odor not to be recognized as that of the
flower. The pleasant odor of violets manifests itself only in extreme
dilution.
OIL OF VERBENA
is yellow, with a very pleasant odor of lemons. Its price being quite
high, it is usually adulterated with oil of lemon-grass, or else
the latter is sold under the name of oil of verbena (see p. 30). In
fact the odors of the two oils are so similar that they are easily
confounded.
OIL OF VETIVER (OLEUM IVARANCHUSÆ),
from Andropogon muricatus (see p. 30), is viscid, reddish-brown, with a
very strong and lasting odor.
OIL OF WINTERGREEN (OLEUM GAULTHERIÆ).
This product is obtained by distillation from the leaves and twigs
of Gaultheria procumbens or else by distilling the bark or leaves
of Betula lenta with water, in which case the oil is generated by
the action of the water, as it does not pre-exist in the birch,
and, moreover, in this case the oil consists of nothing but methyl
salicylate. It differs, like oil of meadowsweet, very markedly from
the other aromatic substances and mainly consists of a so-called
compound ether. It is a salicylate of methyl, boils at 220° C. (428°
F.), is much heavier than water (specific gravity 1·173 to 1·184), and
dissolves readily in alcohol and other solvents. It is used chiefly for
scenting soap; the perfumes sold as wintergreen are usually mixtures of
different substances which contain no oil of wintergreen.
OIL OF YLANG-YLANG (OLEUM UNONÆ ODORATISSIMÆ)
is imported from Manilla. It is colorless or yellowish, and has a most
delightful characteristic odor, which is rather fugitive if not made
resistant by other substances. It forms an important constituent of
several of the most favorite and expensive essences.
OIL OF HYSSOP (OLEUM HYSSOPI)
is colorless, but rapidly becomes yellow in the air. It is used in some
very cheap perfumes and in the manufacture of liqueurs.
OILS OF CINNAMON (OLEUM CINNAMOMI).
Commercially we find chiefly three varieties of essential oils which
are designated as: oil of Ceylon cinnamon, oil of Chinese cinnamon or
oil of cassia, and oil of cinnamon leaves. Oil of Ceylon cinnamon,
sometimes called “true oil of cinnamon,” made from the bark of the
twigs of the cinnamon laurel and formerly imported mainly from Ceylon
but now distilled in large amounts in Germany from imported cinnamon
“chips,” is rather viscid, golden yellow to reddish-brown in color, of
a burning though sweet taste. In the air it gradually absorbs oxygen,
when it becomes dark red, thicker, and of weaker flavor. Oil of Ceylon
cinnamon, which should always be used in perfumes or liqueurs when
simply “oil of cinnamon” is directed, has a specific gravity of 1·030
to 1·035 at 15° C. (59° F.) and boils at about 240° C. (464° F.). Its
chief constituent upon which its aroma depends is cinnamyl aldehyde.
Oil of Chinese cinnamon, or oil of cassia, has for a very long time,
up to within a few years, always reached the market in a more or less
adulterated state, a regular practice of the Chinese exporters being
to dissolve ordinary resin in it (claiming afterward that the “resin”
was caused by the oxidation of the oil through age) and often also to
add petroleum to it. These frauds have been well shown up by Schimmel
& Co., of Leipsic; and in consequence thereof, the quality of oil of
cassia exported from China has been greatly improved. Oil of cassia
when pure has a specific gravity of 1·060 to 1·065, and should contain
not less than seventy-five per cent of cinnamyl aldehyde.
Oil of cinnamon leaves is an inferior product, often used for
adulterating oil of Ceylon cinnamon. It does not deserve notice by the
perfumer.
As an appendix we may add in this connection a description of the
OIL OF TURPENTINE (OLEUM TEREBINTHINÆ),
because it must be called an important substance to know for the
perfumer, inasmuch as it is very frequently used for the adulteration
of different essential oils. Oil of turpentine, which is obtained from
incisions into the bark of different fir and pine trees, the exuding
resin being distilled with water, comes into commerce from various
sources. Different sorts are distinguished, but to the perfumer only
the rectified oil of turpentine, oleum terebinthinæ rectificatum, is
important. Oil of turpentine has a yellowish color and a decidedly
disagreeable, resinous, and burnt taste. By repeated distillation,
especially over quicklime or chloride of lime (bleaching powder), it is
finally obtained as a colorless, very refractive liquid with a density
of 0·855 to 0·870 and a boiling-point at 160° C. (320° F.). Its odor
is peculiar, but not easily distinguished from that of old essential
oils, such as oils of caraway, anise, etc. One peculiarity of oil of
turpentine is that its odor is easily masked by that of other essential
oils, so that, for instance, a comparatively large quantity of oil of
turpentine needs the addition of but little oil of anise to impart to
the entire mixture a rather pronounced odor of anise. This peculiarity
has led to the frequent employment of rectified oil of turpentine for
the adulteration of other essential oils.