THE ESSENCES OR EXTRACTS EMPLOYED IN PERFUMERY.
The term _essence_ or _extract_ in perfumery means a solution of an
aromatic substance in strong alcohol. These solutions are generally
made as concentrated as possible and in this form find application in
the manufacture of handkerchief perfumes and of certain odors bearing a
special name. The so-called extrait d’œillet, extract of pink, or the
favorite perfumes known as new-mown hay have nothing in common with
either pink or hay except the name; like many other odors, both are
merely mixtures of different essences or extracts.
Besides the manufacture of true perfumes, essences or extracts are
also used for scenting fine soaps, sachets, mouth washes, etc. For the
latter, too, use is often made of the so-called aromatic waters (eaux
aromatisées) which are obtained as a by-product in the distillation of
fragrant plants, and have a very fine odor owing to the small amount
of the aromatic substance they hold in solution. To this class belong
orange-flower water (Aqua Naphæ triplex, eau de fleurs d’oranges),
peppermint water (Aqua Menthæ, eau de menthe), and many others.
Essences or extracts can be made in two ways: in the case of aromatic
substances which are obtainable in the pure state—that is, essential
oils—by dissolving them in strong alcohol in definite proportions;
in the case of aromatics combined with a fatty substance by one of
the processes described above, by treating the pomade (lard, or other
perfectly bland, sweet, and in itself odorless fat combined with the
aromatic) or huile antique (fixed oil holding the aromatic substance
in solution) with the strongest alcohol.
According to the action of the alcohol upon the pomade or huile antique
at ordinary or higher temperature, the process is called cold or warm
infusion. Cold infusion furnishes the odor in a much more delicate and
superior form than the warm. The cold infusion requires for complete
solution of the aromatic four to six weeks; the warm, ten to fourteen
days. Although the former consumes a much longer time, it is to be
preferred, as the heat injures the odor. Pomades or huiles antiques are
never completely exhausted by a single treatment with alcohol. Even
when heat is employed they always retain a portion of the aromatic with
great tenacity; a second and third infusion still abstracts odor from
them, and finally nothing remains but pure fat with a pleasant odor
which is stained and sold commercially as pomade under the name of the
respective odor—violet, orange flower, reseda, etc.—or else is used
over again in the factory for the extraction of flowers.
Experience has shown us that it is best to infuse the pomades or huiles
antiques twice in the cold and to use the two fluids united for the
finest perfumes; the residue by warm infusion furnishes an essence of
second quality, and superior pomades or fragrant oils. The infusion is
generally effected in strong glass bottles of a capacity of three to
five gallons; about five to six quarts of cologne spirit being poured
over six to eight pounds or pints of fat or huile antique.
In treating huiles antiques all parts of the oil should be brought into
contact with the alcohol as much as possible, hence the bottles must
be frequently shaken; a better plan is to bring the tightly closed
bottles into an apparatus in which they are constantly agitated by
rotation. Such an apparatus is easily made by placing the bottles in
an inclined position between two rods fastened to a common axis which
is kept revolving. The adjoining illustration (Fig. 32) shows such a
contrivance which is required also in the manufacture of perfumes. The
rotation may be effected by clockwork, water power, or any other motor.
[Illustration: FIG. 32.]
Pomades being solid must be divided into small pieces which may be done
with a knife, but the following procedure is more suitable and less
laborious. The pomade is placed in a tin cylinder four inches wide and
about a foot high, which is open at one end, the other being closed
with a tin plate having several fine openings. The cylinder filled with
pomade is set upon the bottle containing the alcohol for extraction,
and the pomade is pressed through the openings in the shape of thin
threads by means of a piston.
In this way, of course, the pomade acquires a very large surface and
rapidly yields the aromatic substance to the alcohol. The odor of
the pomade differs according to the length of time which it has been
subjected to the flowers, and on being treated with alcohol furnishes
extracts of corresponding strength. This should be borne in mind in the
manufacture of perfumes which are intended to be uniform in quality.
After two cold and one warm infusion of the pomade, it may be made to
yield some more aromatic material by heating it carefully to its exact
melting-point, when extract again appears on the surface and can be
poured off by gentle inclination of the vessel.
In the following pages we give the proportions by weight and
measure employed by the most important French, English, and German
manufacturers for their pomade extracts or solutions of the essential
oils in alcohol. As to the latter we again repeat that it must be over
88 to 90% strength according to Tralles or even stronger, and that it
must be absolutely free from any trace of amyl alcohol (potato fusel
oil), the least amount of which impairs the delicacy of the odor. In
this country (the United States) there is no difficulty whatever in
obtaining alcohol of proper strength. The market offers scarcely any
other but that of 94%. Of course deodorized alcohol, or so-called
Cologne spirit should be used. Grain and wine spirits are the kinds
which when rectified are to be preferred to all others. All the citron
oils (_i.e._, oils of lemon, bergamot, and those with similar odor),
rose oils (oils of rose, geranium, and rhodium), and many other sweet
scents are most fragrant when dissolved in pure spirit of wine, while
the odors from the animal kingdom and those of violet (violet and orris
root) smell sweetest when dissolved in grain spirit.
The essences prepared from pomades or huiles antiques usually contain
in solution some fat which is best removed by cooling. To this end the
vessels containing the essences are placed in a vat and surrounded with
pellets of ice and crystals of chloride of calcium. By this mixture the
temperature can be reduced below-20° C. (-4° F.), and after some time
the fats are deposited in a solid form at the bottom of the vessel.
This is then taken from the vat and the essence carefully poured from
the sediment.
The alcoholic extracts of the pomades or solutions of the aromatics are
called essences or extracts (French, extraits); the solutions obtained
from resins and balsams are usually termed tinctures.
While some extracts, owing to their strong odor, can be used only when
diluted with alcohol, others are employed in perfumes as such. Pure
extracts (extraits purs) are those containing only a single odor and
are but rarely used as perfumes; the latter are usually mixtures of
several, often a great many odors.