THE EXTRACTION OF ODORS.
Excepting the articles made in Turkey and India (especially oil of
rose), most aromatic substances are manufactured in southern France
and the adjoining regions of Italy, while a few (oils of peppermint
and lavender) are produced in England; a few also (oils of peppermint,
spearmint, wintergreen, sassafras, etc.) in the United States. However,
as we have stated above, it is possible to cultivate some plants from
which odors are extracted in the warm sections of this country, and
to obtain the most expensive perfumes from them. Among these plants
our experience leads us to suggest violets, roses, reseda, lavender,
mints, syringa, lilac, and several others to which the climate is
adapted.
The methods by which the odors can be extracted from the plants differ
according to the physical properties of the raw material and the
chemical composition of the aromatic substance. We shall here briefly
describe the methods thus far known, and at the same time add our
own experience in this most important part of the art of perfumery.
The aromatic substances are obtained by pressure, by distillation,
by maceration (infusion), by absorption (enfleurage) through air or
through carbonic acid, and by extraction.
PRESSURE.
Certain aromatic substances that occur in large amounts in some
parts of plants, are best obtained by pressure. The rinds of certain
fruits contain an essential oil in considerable quantities inclosed
in receptacles easily distinguished under the microscope. When these
vegetable substances are subjected to strong pressure, the oil
receptacles burst and the essential oil escapes. The force is usually
applied through a screw press with a stout iron spindle; the vegetable
substances being inclosed in strong linen or horse-hair cloths, placed
between iron plates, and subjected to a gradually increasing pressure.
Comparative experiments have shown us that even with the most powerful
presses a considerable, amount of oil is lost owing to the fact that a
large number of oil receptacles remain intact. For this reason, when
oil is to be extracted by pressure, a hydraulic press is preferable,
as it develops greater power than any other press. In the hydraulic
presses used for this purpose the piston fits exactly into a hollow
iron cylinder with sieve-like openings in its circumference. The
vegetable substances are filled into this cylinder; when the pressure
is applied, the fluids escape through the perforations, and the
residue forms a compact woody cake which is then free from oil.
Besides the essential oil, watery fluid is expressed, the whole
appearing as a milky liquid, owing to the admixture of vegetable
fibres, mucilage, etc. It is collected in a tall glass cylinder which
is set in a place free from any vibration. After remaining at rest for
several hours the liquid separates into two layers, the lower being
watery and mixed with mucilage, that floating on top being almost
pure oil. The latter is separated, and finally purified by filtration
through a double paper cone in a funnel covered with a glass plate.
[Illustration: FIG. 4.]
It is best to separate the water and oil in a regular separatory
funnel, or in a simple apparatus illustrated in Fig. 4. It is made
by cutting the bottom from a tall flask, and fitting into the neck
by means of a cork a glass tube having a diameter of one-fourth to
one-half inch. A rubber tube with stop-cock is fastened to the glass
tube. By careful opening of the stop-cock, the watery fluid can be
drained off to the last drop.
To the perfumer this method is of little importance, since it is
applicable only to a few substances which, moreover, give cheap odors.
Still, the possession of a hydraulic press is advisable to every
manufacturer who works on a large scale, as it is useful also in the
preparation of several fixed oils frequently employed in perfumery, for
instance, oils of almonds, nuts, etc.
[Illustration: FIG. 5.]
[Illustration: FIG. 6.]
Fixed oils are best extracted in so-called drop presses, the material
having first been comminuted between rollers. These are arranged
as shown in section in Fig. 5, and in ground plan in Fig. 6. The
apparatus consists of two smooth or slightly grooved iron cylinders
A and B, respectively four feet and one foot in diameter, which can
be approximated or separated by means of set screws. The material is
placed into the trough F containing a feeding roller moved by the belt
P. The scrapers FF, pressed against the cylinders by means of weighted
levers, free the rollers from adhering pieces.
The drop presses Figs. 7 and 8 consist of a hydraulic press with
cylinders A and piston B; the troughs E are movable by means of rings
between two vertical columns and every trough has a circular gutter _d_
for the reception of the expressed oil. The iron pots G have double
walls, the inner of which has a series of openings at its upper part;
these pots are filled with the bruised material to be pressed and after
this has been covered with a plate of horse-hair tissue are set in the
press.
[Illustration: FIG. 7.]
[Illustration: FIG. 8.]
As the piston rises, the troughs E sink into the pots, the escaping oil
collects in the gutters _d_ and thence passes into a receptacle. After
pressing, the piston is allowed to sink back, the pots G are drawn
aside (Fig. 8) to tabular surfaces, and other pots are substituted for
the exhausted ones. These drop presses are suitable for the extraction
of all fixed oils and also volatile oils present in orange and lemon
peel, etc.
DISTILLATION.
Many odors or essential oils possess the remarkable property that their
vapors pass so largely with that of boiling water that they can be
extracted in this way (by “distillation”) from vegetable substances,
though the essential oils have a boiling-point far above that of water.
Distillation can be employed for a large number of substances; for
instance, the essential oils present in cumin, anise, lavender, fennel,
mace, nutmeg, etc., are extracted exclusively in this manner.
[Illustration: FIG. 9.]
For the extraction of odors in this way, according to the quantities of
material to be worked, different apparatuses are used, some of the most
important of which will be here described.
For manufacturers who run without steam and are obliged to use a naked
flame, the adjoining apparatus (Fig. 9) will be advantageous.
It consists of a copper boiler A, the still, set in a brick furnace.
The latter is so constructed that the incandescent gases strike not
only the curved bottom of the still, but also its sides through the
flues Z left in the brickwork. The still, whose upper part projects
from the furnace, has an opening O on the left side, closed air-tight
with a screw, which serves for refilling with water during distillation
when necessary. To the margin of the still is fitted steam-tight the
helm H, made of copper or tinned iron, having a prolongation, the tube
R. The latter is joined to the conical projection _v_ which terminates
in the worm K. In some apparatuses this projection is omitted and the
tube immediately joins the worm. The latter is made of tinned iron and,
as the cut shows, is arranged in coils and supported by props _t_ in
the wooden or metal condenser F. The condenser bears above a short bent
tube _b_, and below, immediately over the bottom, an elbow tube _e_,
long enough to reach above the edge of the condenser, as indicated in
the cut.
The vegetable substances to be distilled can be put immediately into
the still and covered with water; but in this case it is advisable
to use a stirrer which must be kept moving until the water boils,
otherwise the material might burn at the bottom. But this accident can
also be prevented by applying a perforated false bottom to the still
above the flues, or by inclosing the material in a wire-sieve basket C.
[Illustration: FIG. 10.]
In place of the basket C the apparatus can also be provided with an
additional vessel containing the material to be distilled. In the still
A (Fig. 10) the water is brought to boiling, the steam rises through
the second still B in which the material is spread on a perforated
bottom. The steam laden with the vapors of the essential oil passes
through the tube R into the condenser.
It is very advantageous, and in large establishments altogether
indispensable, to use steam in the distillation of essential oils. Fig.
11 represents the arrangement of such an apparatus. The still B (which
in this case may be made of stout tinned iron) stands free and is
provided with a wooden jacket M for the purpose of retaining the heat.
Immediately above the curved bottom is a perforated plate on which the
material rests. The tube D which enters the bottom of the still is
connected with the boiler which furnishes steam at moderate tension.
H is the faucet for the admission of steam; H. is the faucet by which
the water escapes from the still at the end of the operation. After the
still is filled with the material, the faucet H is opened gradually and
a continuous stream of steam is allowed to pass through the still until
the operation is finished.
[Illustration: FIG. 11.]
When working with an open fire, as soon as vapors appear at the lower
end of the worm (Fig. 9), cold water is admitted through the tube _ne_;
as the cold water abstracts heat from the vapors and condenses them, it
becomes warm, rises to the surface, and escapes through _b_, so that
the worm is continually surrounded with cold water. If for any reason
the saving of cold water is an object, its flow may be so regulated
that the vapors are just condensed, the warm distillate being allowed
to cool in the air. When working with steam, the cold water must be
admitted the moment the steam-cock is opened, and the flow of cold
water should be ample during the distillation, which in this case is
much shorter.
The large apparatuses here described are generally used, especially
for the extraction from vegetable substances of odors present in
considerable quantity, for instance, mace, nutmeg, cloves, cinnamon,
etc., or from bulky material as the various flowers. For very expensive
odors, smaller apparatuses are often employed, the construction of
which resembles that of the ones described. For this purpose small
glass apparatuses are very suitable; they are illustrated in Fig. 12.
The still, a retort A, consists of a spherical vessel with a bottle
neck _t_ which is either closed with a cork or carries a thermometer
or glass tube, and with a lateral tube, the neck of the retort,
connected with the adapter _r_. The latter passes into the condenser
C. At the lower end of R is the bent adapter _v_ under which is placed
the receptacle for the distillate. The tube C is closed with corks,
at its lower end is the ascending tube _h_, and at its upper end the
descending tube _g_. During the distillation cold water flows in
through _h_ which cools the tube _r_ and escapes at _g_. The tube C,
as will be readily understood, acts like the condenser in the larger
apparatuses above described. In order to prevent the breaking of the
retort, it is not heated over a flame, but is set in a tin vessel B
filled with water. The comminuted vegetable material is inserted with
water through the up-turned neck of the retort into the latter; the
vessel B is filled with water which is raised to the boiling-point.
[Illustration: FIG. 12.]
During distillation we obtain at the lower end of the condenser pure
water and essential oil. When larger quantities are to be distilled
it is advisable to use a Florentine flask as a receptacle for the
separation of the oil and water (Fig. 13). It consists of a glass
bottle from the bottom of which ascends a tube curved above; the latter
rises high enough to bring the curvature slightly below the neck of the
flask. During the distillation the flask becomes filled with water W,
on which floats a layer of oil O; the excess of water escapes through
_a_ at _d_ until the flask finally contains more oil and very little
water.
[Illustration: FIG. 13.]
When producing essential oils on a large scale, instead of the frail
Florentine flasks it is advisable to use separators, the construction
of which is illustrated in Fig. 14. They consist of glass cylinders,
conical above and below, supported on a suitable frame. The water
accumulating under the oil is allowed to escape by opening the
stop-cock; when the first separator is filled with oil, the succeeding
distillate passes through the horizontal tube into the next separator,
etc.
[Illustration: FIG. 14.]
When the distillation is carried on in an ordinary still, we obtain,
besides the essential oil, a considerable quantity of aromatic water,
that is, a solution of the oil in water.
An apparatus which obviates the losses caused thereby is that of
Schimmel described below, which is well adapted to the manufacture on a
large scale. The apparatus is patented.
The nearly spherical still D (Fig. 15) is surrounded by a jacket M;
the inlet steam tube R is connected with a branch _r_ which enters the
interior of the still as a spiral tube with numerous perforations,
while R opens into the space M. When _r_ is opened, distillation takes
place by direct steam; when R is opened, by indirect steam; when both
faucets are opened, the still is heated at the same time with direct
and indirect steam.
[Illustration: FIG. 15.]
The vapors rising from the still D pass through the helm C and the tube
A into the worm K; the fluid condensed in the latter drops into the tin
Florentine flask F, the aromatic water flowing from the latter passes
back into the still D through the Welter funnel T and is distilled over
again, so that the entire distillation can be effected with very little
water, and it is continued until the water escaping from the Florentine
flask is freed from oil and odorless.
When working with superheated steam, it is necessary to set under the
funnel tube T a vessel twice the size of the Florentine flask, which is
provided with a stop-cock above and below. The lower cock is closed,
the vessel is allowed to fill with water from F, then the upper cock is
closed, the contents being allowed to escape into D by opening, when
the cocks are again reversed.
The use of superheated steam is important especially with material
which gives up the contained oil with difficulty, such as woods.
[Illustration: FIG. 16.]
For freeing the essential oil completely from water we use a so-called
separating funnel (Fig. 16). This consists of a glass funnel T resting
on a suitable support G, which is closed above with a glass plate
ground to fit, drawn out below into a fine point S, and provided with a
glass stop-cock H. The contents of the Florentine flask are poured into
the funnel which is covered with the glass plate and allowed to stand
at rest until the layer of oil O is clearly separated from the water W.
By careful opening of the stop-cock the water is allowed to escape and
the oil is immediately filled into bottles which are closed air tight
and preserved in a cool and dark place.
MACERATION (INFUSION).
Some odors, like those of cassie, rose, reseda, syringa, jasmine,
violets, and many other fragrant blossoms, cannot be obtained by
distillation as completely or as sweet-scented as by the process
of maceration which is in general use among the large perfumers in
southern France. This process is based on the property of fats to
absorb odorous substances with avidity and to yield them almost
entirely to strong alcohol. According to the fat employed for the
maceration of the flowers—a solid fat like lard or a liquid like olive
oil—odorous products are obtained which are known either as pomades
or as perfumed oils (huiles antiques). By repeatedly treating fresh
flowers with the same fat the manufacturer is able to perfume the
pomade or oil at will, and in the factories these varying strengths
are designated by numbers; the higher numbers indicating the stronger
products.
The process of maceration is very simple. The fat is put into porcelain
or enamelled iron pots which are heated, in a shallow vessel filled
with water, to 40 or at most 50° C. (104-122° F.); the flowers are
inclosed in small bags of fine linen and hung into the fat, where they
are allowed to remain for from one-half to two days. At the end of that
time the bags are removed, drained, expressed, refilled with fresh
flowers, and replaced in the fat. This procedure is repeated twelve to
sixteen times or oftener, thus producing pomades or oils of varying
fragrance.
[Illustration: FIG. 17.]
As the odors are much superior when the flowers are only a short
time in contact with the fat, it is better to use an apparatus for
continuous operation (Fig. 17). It consists of a box K made of tin
plate, which is divided into from five to ten compartments by vertical
septa and can be closed water tight by a lid to be screwed on. The
septa have alternate upper and lower openings. The compartments contain
each a basket of tinned wire filled with the flowers for maceration,
then the lid is closed and the box heated in a water bath to 40 or
50° C. (104-122° F.). The stop-cock H in tube R is now opened. This
admits melted fat or oil from a vessel above to the first compartment
in which it rises through the basket filled with flowers whose odor it
abstracts. The additional fat coming from above drives it over through
the opening O_{2} into compartment 2, where it comes in contact with
fresh flowers, passes through O_{3} into the third compartment, and so
on through 4 and 5, until it finally escapes through R_{1} well charged
with odor. According to requirements a larger number of compartments
may be employed.
When all the fat has passed through the apparatus, it is opened, the
basket is removed from compartment 1, the basket from No. 2 is placed
in 1, that from 3 in 2, etc.; basket 1 is emptied, filled with fresh
flowers, and placed in compartment 5, so that every basket gradually
passes through all compartments to No. 1. In this way the fat rapidly
absorbs all the odor.
The odorous substances are abstracted from the pomades or huiles
antiques by treatment with strong alcohol (90-95%) which dissolves the
essential oils but not the fats. The huiles antiques with the alcohol
are placed in large glass bottles and frequently shaken. In order to
abstract the odors from pomades, the latter are allowed to congeal and
are divided into small pieces which are inserted into the bottles of
alcohol. A better plan is to fill the pomades into a tin cylinder with
a narrow opening in front and to express the pomades, by a well-fitting
piston, in the shape of a thin thread which thus presents a large
surface to the action of the alcohol, thus hastening the absorption
of the odor. The alcoholic solution obtained after some weeks is then
distilled off at a low temperature. We shall recur to this hereafter.
No matter how long the fats are left in contact with alcohol, they do
not yield up to it all the odor, but retain a small portion of it and
hence have a very fragrant smell. They are, therefore, brought into
commerce as perfumed oils or pomades bearing the name of the odorous
substance they contain: orange flower, reseda pomade or oil, etc.; they
are highly prized and are sometimes used again for the extraction of
the same odor.
Some odors cannot bear even the slight rise of temperature necessary
for their extraction by the method of maceration or infusion. For these
delicate odors one of the following methods may be employed.
ABSORPTION OR ENFLEURAGE.
In this method the absorbing power of fat is likewise used for
retaining the odors, but the flowers are treated with the fat at
ordinary temperatures. This procedure which is employed especially in
southern France is carried out as follows. The fat (lard) is spread to
a thickness of about one-quarter inch on glass plates G one yard long
and two feet wide, which are inserted in wooden frames R and sprinkled
with flowers F (Fig. 18). The frames are superimposed (the cut shows
two of the frames) and left for from one to three days, when fresh
flowers are substituted for the wilted ones, and so on until the pomade
has attained the desired strength.
[Illustration: FIG. 18.]
This procedure is very cumbrous and tedious and therefore had better be
modified thus: In an air-tight box K (Fig. 19) we place a larger number
of glass plates _g_ covered with lard drawn into fine threads by means
of a syringe. This box is connected with a smaller one K_{1} which is
filled with fresh flowers and provided with openings below and above,
O and O_{1}. The latter, O_{1} communicates by a tube with box K, at
whose upper end is a tube _e_ terminating in an exhaust fan so that the
air must pass through the apparatus in the direction indicated by the
arrows. A small fan V driven by clockwork will answer. The air drawn
from K_{1} is laden with odors and in passing over the fat as shown
by the arrows gives them up completely to the fat. The use of this
apparatus has very important advantages: the absorption is effected
rapidly, requires little power, and the flowers do not come at all into
contact with the fat which therefore can take up nothing but the odors
present in the air.
[Illustration: FIG. 19.]
Instead of charging the fat with odors by either one of the methods
here described, carbonic acid can also be employed with advantage, by
means of the apparatus illustrated in Fig. 20. The large glass vessel
G contains pieces of white marble M upon which hydrochloric acid is
poured at intervals through the funnel tube R. A current of carbonic
acid is thus developed, which passes through a wash bottle W filled
with water, then through the tin vessel B containing fresh flowers,
and finally into a bottle A filled with strong alcohol and set in cold
water, after which it escapes through the tube _e_. The carbonic acid
absorbs the aromatic vapors from B and leaves them in the alcohol which
absorbs them. (G, R, W are made of glass, B of tin.)
[Illustration: FIG. 20.]
EXTRACTION.
This method is based on the fact that some volatile liquids such as
ether, chloroform, petroleum ether, or bisulphide of carbon possess the
property of rapidly extracting the aromatic substances from flowers;
when they are evaporated at a gentle heat they leave the pure odors
behind. In our opinion this process is the best of all for the perfumer
and it is to be regretted that it is not more generally used.
As a rule we employ either petroleum ether or bisulphide of carbon (see
above, pp. 65, 66) because these products are cheaper than ether or
chloroform.
The apparatus we use for this purpose is illustrated in Fig. 21. It
consists of a cylinder C made of tinned iron, which is provided above
with a circular gutter R terminating in a stop-cock _h_ and which
can be closed by a lid D bearing a stop-cock _o_. A tube _b_ with a
stop-cock _a_ enters the bottom of the cylinder. The latter is filled
with the flowers, the volatile liquid (petroleum ether, bisulphide
of carbon, etc.) is poured over them, the lid is put on, and the
gutter R filled with water, thereby sealing the contents of the vessel
hermetically.
After the extraction, which requires about thirty to forty minutes,
stop-cock _o_ is opened first, then stop-cock _a_, and the liquid
is allowed to escape into the retort of the still (Fig. 12). If the
extraction is to be repeated, the water is allowed to escape from the
gutter through _h_, the lid is opened, and the solvent is again poured
over the flowers.
For operation on a larger scale the glass retorts are too small and
should be replaced by tin vessels (Fig. 22) having the form of a
wide-mouthed bottle F; they are closed by a lid D which is rendered
air tight by being clamped upon the flange of the vessel (R) with iron
screws S, a pasteboard washer being interposed; a curved glass tube
connects the apparatus with the condenser of Fig. 12.
[Illustration: FIG. 21.]
[Illustration: FIG. 22.]
The solutions of the aromatic substances are evaporated in these
apparatuses at the lowest possible temperature, the solvent being
condensed and used over again. The heat required is for ether about
36° C. (97° F.), for chloroform about 65° C. (149° F.), for petroleum
ether about 56° C. (133° F.), and for bisulphide of carbon about 45° C.
(113° F.). If it is desired to obtain the aromatic substances pure from
an alcoholic extract of the pomades made by one of the above-described
processes—which is rarely done since these solutions are generally
used as such for perfumes—a heat of 75 to 80 C. (167 to 176° F.) is
required.
Another extraction apparatus illustrated in Fig. 23 is well adapted to
operations on a large scale. Its main parts are the extractor E and the
still B. The former is set in a vat W continually supplied with cold
water. The still B is surrounded with hot water in the boiler K.
To start the apparatus the cone C is removed, the vessel E is filled
with the material to be extracted, and C is replaced. The faucets H_{2}
and H_{4} are opened, the solvent is poured into the still through the
latter, when these faucets are closed and those marked H and H_{1} are
opened.
[Illustration: FIG. 23.]
The water in K is heated until the contents of B are in brisk
ebullition; the vapor rises through RH, is condensed on entering E and
falls in small drops on the material. This fine rain of the solvent
dissolves the aromatic substances and flows back into B, where it is
again evaporated, and so on.
At the end of the extraction the faucets H and H_{1} are closed and
H_{2}, is opened. The vapors of the solvent pass through it into a worm
where they are condensed; the essential oil remaining in B is drained
off by opening H_{3}.
For still larger operations more perfect apparatuses are employed,
such as those of Seiffert and Vohl. Seiffert’s apparatus (Fig. 24)
consists of a battery of jacketed cylinders; steam circulates in the
space between the cylinders and the jackets. Each cylinder contains a
plate covered with a wire net on which the flowers to be extracted are
placed. All the cylinders having been filled and closed, the solvent is
admitted from a container above, through S and _a_ into C^2; when this
is filled the liquid flows through _a_^2_b_^3_c_^n into C. The solution
saturated with essential oil leaves the apparatus through _d_^n and
_p_ and enters a reservoir. The course of the liquid is aided by the
suction of an air-pump acting on _p_.
When the reservoir contains an amount of fluid equal to that in C^n,
_d_^n is closed, _a_^n is opened, and C connected with C^1 through
_b_^n and _c_^1. That the contents of C^2 are completely extracted is
shown by the fact that the liquid appears colorless in the glass tube
inserted in _b_^2; _a_^1 and C^2 are closed; _a_^2 and C^3 are opened,
thereby excluding C^2 from the current of bisulphide of carbon which
then flows through C^3C^nC^1. In order to permit the free flow of
the bisulphide of carbon through S despite the exclusion of C^2, the
faucets _a_^1_a_^2_a_^3_a_^n must be two-way cocks; in one position
they connect S with _b_; in the other they close _b_ and leave the
passage through S open.
[Illustration: FIG. 24.]
In order to collect the bisulphide of carbon present in the extracted
residue in C^2, faucet _g_^2 is opened and the bisulphide of carbon
allowed to escape through _h_. The faucet _e_^2 in tube L on being
opened admits compressed air to C^2, thus hastening the outflow. If
nothing escapes below, faucets _f_^2 and _f_^x are opened, steam enters
through tube D between jacket and cylinder; the bisulphide of carbon
vapor passes through _g_^2 and _h_ into the worm. After the expulsion
of the bisulphide of carbon, C^3 is emptied, refilled, connected with
C^1, and bisulphide of carbon admitted from C^3 in the manner above
described.
An extraction apparatus which has been much recommended of late is the
so-called “Excelsior Apparatus” made by Wegelin and Huebner, Halle a.
S., which can be worked with any desired solvent. The construction of
the apparatus (Figs. 25 and 26) is as follows.
[Illustration: FIG. 25.]
[Illustration: FIG. 26.]
The solvent is admitted to the reservoir R in the lower part of the
condenser B through the tube indicated in the figure. The material
to be extracted having been filled into the cylinder A through the
manhole, the apparatus is closed. The cold water is admitted to the
condenser by opening a faucet. The three-way cock shown in Fig. 25 is
so placed as to open a communication of the overflow tube with A. The
faucet at the lower end of the reservoir R is now opened sufficiently
and the solvent passes into A from above, and as it descends takes
up more and more oil, flows through the sieve-plate, and escapes
through the tube at the bottom of A through the three-way cock, the
overflow tube, and the drain tube into the accumulator C. The opening
of a faucet now admits steam to the heating coil, when the solvent
evaporates, leaving the oil or fat behind. It is condensed in B,
again returns to R, whence it passes once more through the faucet
into the extractor A. The vessel C and the tubes leading to A and C
are surrounded with felt to prevent loss of heat. A sample taken from
the small cock at the foot of A (it has a small plate in the interior
of the tube) will show when the extraction in A may be looked upon as
finished. The solvent is distilled off or recovered from the residue
in A in the following manner. First the faucet in R is closed. The
three-way cock A is set to establish direct communication between A and
C, thus cutting off the overflow tube. Hence all the solvent in A flows
into C for distillation, while the oil is left behind. Steam being
admitted to the residue, the solvent rises as vapor through the upper
tube from A to B and collects in a liquid state in R. To drive off the
last traces of the solvent from the fat or oil obtained, steam is blown
into C by opening the valve. Besides the solvent, watery vapor enters B
and forms a layer of water in R under the solvent. By taking a sample
from the test-cock of the reservoir C which has an internal small
plate, the termination of the process is ascertained. The gauge tube at
the reservoir shows the level of the solvent and water. The water is
drawn off by opening the faucet at the lower end of the reservoir. A is
emptied through the manhole and by draining the oil from C through the
discharge cock. The tube R is closed by a light valve so as to prevent
evaporation of the solvent. All the apparatuses work without pressure
so that there is no danger from overstrain.
[Illustration: FIG. 27.]
[Illustration: FIG. 28.]
The solutions of the essential oils in bisulphide of carbon are
distilled off in the steam still illustrated in Fig. 27; the steam
enters at _h_, the water of condensation escapes at _d_, the liquid
to be distilled enters at _e_ from a container at a higher level. The
boiling is kept uniform by the stirring arrangement _hg_. After the
bisulphide of carbon is distilled off, air is passed through the oil by
the curved tube _a_ which has fine perforations, so as to evaporate the
last traces of the solvent.
In Vohl’s apparatus (Fig. 28), arranged for petroleum ether, the
extraction is effected with the boiling fluid; hence this apparatus
is better adapted for the cheaper oils than for the finest oils from
flowers. The apparatus consists of two extractors A A, the accumulator
B, and the condenser C. Petroleum ether is allowed to flow over the
substances to be extracted, by opening the faucets _mm_, _vh_, closing
_ogw_E, and opening _o_, the course being through _ux_ to B. When B
is two-thirds full, the flow of petroleum ether is cut off, steam
is admitted through _y_ and the contents of B are brought to the
boiling-point. The vapors pass through _g_ and are condensed in _f_
until the contents of A reach the boiling-point of the solvent, when
the vapors pass through _i_ into C, and after closing _m´_ the liquid
passes through _ml_ into the inner cylinder of the extraction apparatus
and returns through _uxx_.
After the contents of A are extracted, _m´_ is opened, _m_ closed, and
steam is admitted through _d_ into the jacket of A; the vapors of the
solvent force the liquid part of the contents through _ux_ into B.
Overfilling of B is prevented by allowing the vapors of the solvent to
escape at the proper time into the condenser through _p_ by opening
_q_. Then _v_ is closed, _q_ opened, and the steam present in A drawn
off by an exhaust applied to _p_; as soon as _p_ begins to cool, all
the petroleum ether is distilled off, the steam is cut off at _d_, and
the extract evacuated through _t_. The contents of B are brought into a
still through D and E.
[Illustration: FIG. 29.]
By employing greater pressure the extraction can also be effected by
what is called displacement; the material to be extracted is placed
in a stout-walled vessel S (Fig. 29) which is connected by a narrow
tube at least ten yards long with the vessel F containing the solvent.
Stopcock H is first opened, then stop-cock H_{1} which is closed as
soon as fluid begins to flow from it. After the liquid has remained in
contact with the material for from thirty to sixty minutes, H_{1} is
opened very slowly, the liquid is allowed to escape and is displaced
with water which is made to pass out of F in the same way as the
solvent, until the latter is completely displaced from S.
After the solvent has been distilled off, the less volatile essential
oil remains in the still almost pure, containing only traces of wax,
vegetable fat or coloring matter which are of no consequence for our
purposes. The last remnants of the solvent cannot be expelled by
distillation, but by forcing through the essential oil a current of
pure air for fifteen or twenty minutes. The essential oils then are of
the purest, unexceptionable quality.
[Illustration: FIG. 30.]
In the case of delicate oils it is better to use carbonic acid in place
of air for expelling the last traces of the solvent, as the oxygen
may impair the delicacy of the fragrance. For this purpose we use the
apparatus illustrated in Fig. 30. In the large bottle A carbonic acid
is generated by pouring hydrochloric acid over fragments of white
marble. The carbonic acid passes into the vessel B filled with water
which frees it from any adhering drops of hydrochloric acid; then into
C filled with sulphuric acid to which it yields its water so that only
pure carbonic acid escapes through the fine rose at the end of tube
D which is made of pure tin, and as it passes through the oil in E
it carries off the last traces of the volatile solvent. In its final
passage through the water in F it leaves behind any oil that may have
been carried with it.
As all the aromatic substances change in air by the gradual absorption
of oxygen, and lose their odor—become resinified—these costly
substances must be put into small bottles which they completely
fill, and be preserved in a cool dark place, as light and heat favor
resinification. The bottles must be closed with well-fitting glass
stoppers.
Aromatic waters or eaux aromatisées, such as jasmine water (eau de
jasmin), orange-flower water (eau de fleurs d’oranges, eau triple de
Néroli, aqua naphæ triplex), etc., are made by distillation of these
flowers with water and show a faint but very fine odor. When they
contain, besides, dilute alcohol they are called spirituous waters
or esprits. Those brought into commerce from southern France are of
excellent quality.
THE YIELD OF ESSENTIAL OILS.
The quantities of essential oil obtainable from the vegetable
substances vary with the amount present in each. The following table
shows the average quantities of oil to be obtained from 100 parts of
material.
Material. Name of Plant. Mean Yield
per 100 Parts.
Ajowan seed Ptychotis Ajowan 3·000
Alant root Inula Helenium 0·600
Allspice Myrtus Pimenta 3·500
Almonds, bitter Amygdala amara 0·400-0·700
Angelica seed Archangelica officinalis 1·150
Angelica root, Thuring. " " 0·750
" " Saxon " " 1·000
Anise seed, Russian Pimpinella Anisum 2·800
" " Thuring. " " 2·400
" " Morav. " " 2·600
Anise seed, Chili Pimpinella Anisum 2·400
" " Spanish " " 3·000
" " Levant " " 1·300
Anise chaff " " 0·666
Arnica flowers Arnica montana 0·040
Arnica root " " 1·100
Asafœtida Ferula Asafœtida 3·250
Avens root Geum urbanum 0·040
Basilicum herb, fresh Ocymum basilicum 0·040
Bay leaves Pimenta acris 2·300-2·600
Bear’s berry Uva ursi 1·010
Beech tar Betula alba 20·000
Bergamots ab. 3·400
Betel leaves Piper Betle 0·550
Bitter almond meal Amygdala amara 0·950
Buchu leaves Barosma crenulata 2·600
Butter-bur oil Tussilago Petasites 0·056
Calamus root Acorus Calamus 2·800
Camomile, German Matricaria Chamomilla 4·000-6·000
" Roman Anthemis nobilis 3·000
Caraway seed,
Cult. German Carum Carvi 4·000
" Dutch " " 5·500
" East Prussian " " 5·000
" Moravian " " 5·000
Wild German " " 6·000-7·000
" Norwegian " " 6·000-6·500
" Russian " " 3·000
Cardamoms, Ceylon Elettaria Cardamomum 4·250
" Madras " " 4·300
" Malabar " " 1·750
" Siam " " 1·350
Carrot seed Daucus Carota 1·650
Cascarilla bark Croton Eluteria 1·500
Cassia flowers Cinnamomum Cassia 3·500
Cassia wood " " 0·285
Cedar wood Juniperus virginianus 0·700-1·000
Celery herb Apium graveolens 0·200
Celery seed " " 0·300
Chekan leaves Myrtus Chekan 1·000
Cinnamon, Ceylon Cinnamomum zeylanicum 0·900-1·250
" white Canella alba 1·000
Cloves, Amboina Caryophyllus aromaticus 19·000
" Bourbon " " 18·000
" Zanzibar " " 17·500
" stems " " 6·000
Common wormwood herb Artemisia Abrotanum 0·040
" " root " " 0·100
Copaiva balsam, Para Copaifera officinalis 45·000
" " East Ind. Dipterocarpus turbinatus 65·000
Coriander seed,
Thuringian Coriandrum sativum 0·800
Russian " " 0·900
Dutch " " 0·600
East Indian " " 0·150
Italian " " 0·700
Mogadore " " 0·600
Crisp mint herb Mentha crispa 1·000
Cubebs Piper Cubeba 12·000-16·000
Culilaban bark Laurus Culilavan 3·400
Cumin seed, Mogadore Cuminum Cyminum 3·000
" " Maltese " " 3·900
" " Syrian " " 4·200
" " East Indian " " 2·250
Curcuma root Curcuma longa 5·200
Dill seed, German Anethum graveolens 3·800
" " Russian " " 4·000
" " East Indian Anethum Sowa 2·000
Elder flowers Sambucus niger 0·025
Elemi resin Icica Abilo 17·000
Eucalyptus leaves, dry Eucalyptus globulus 3·000
Fennel seed,
Saxon Foeniculum vulgare 5·000-5·600
Galician " " 6·000
East Indian Foeniculum Panmorium 2·200
Galanga root Alpinia Galanga 0·750
Galbanum resin Galbanum officinale 6·500
Geranium Pelargonium odoratissimum 0·115
Ginger root,
African Zingiber officinale 2·600
Bengal " " 2·000
Japan " " 1·800
Cochin China " " 1·900
Hazel root Asarum europæum 1·100
Heracleum seed Heracleum Sphondylium 1·000
Hop flowers Humulus Lupulus 0·700
Hop meal, lupulin " " 2·250
Hyssop herb Hyssopa officinalis 0·400
Iva herb Iva moschata 0·400
Juniper berries,
German Juniperus communis 0·500-0·700
Italian " " 1·100-1·200
Hungarian " " 1·000-1·100
Laurel berries Laurus nobilis 1·000
Laurel leaves " " 2·400
Laurel, Californian Oreodaphne californica 7·600
Lavender flowers,
German Lavandula vera 2·900
Linaloe wood Elaphrium graveolens 5·000
Lovage root Levisticum officinale 0·600
Mace Myristica fragrans 11·000-16·000
Marjoram herb, fresh Origanum Majorana 0·350
" " dry " " 0·900
Marsh-rosemary oil Ledum palustre 0·350
Massoy bark Massoia aromatica
Masterwort root Imperatoria Ostruthium 0·800
Matico leaves Piper angustifolium 2·400
Matricaria herb Matricaria Parthenium 0·030
Melissa herb Melissa officinalis 0·100
Michelia bark Michelia nilagirica 0·300
Milfoil herb Achillea Millefolium 0·080
Musk seed Hibiscus Abelmoschus 0·200
Mustard seed,
Dutch Sinapis nigra 0·850
German " " 0·750
East Indian " " 0·590
Pugliese " " 0·750
Mustard seed, Russian Sinapis juncea 0·500
Myrrh Balsamodendron Myrrha 2·500-6·500
Myrtle Myrtus communis 0·275
Nigella seed Nigella sativa 0·300
Nutmegs Myristica fragrans 8·000-10·000
Olibanum resin Boswellia, var. spec 6·300
Opoponax resin Pastinaca Opoponax 6·500
Orange peel, sweet Citrus Aurantium 2·500
Orris root Iris florentina 0·200
Parsley herb Apium Petroselinum 0·300
Parsley seed " " 3·000
Parsnip seed Pastinaca sativa 2·400
Patchouly herb Pogostemon Patchouly 1·500-4·000
Peach kernels Amygdalus persica 0·800-1·000
Pellitory root Valeriana celtia 1·000
Pepper, black Piper nigrum 2·200
Peppermint, fresh Mentha piperita 0·300
Peppermint, dry " " 1·000-1·250
Peru balsam Toluifera Pereiræ 0·400
Pimpernel root Pimpinella saxifraga 0·025
Poplar sprouts Populus niger 0·500
Rhodium wood Convolvulus Scoparius 0·050
Rose flowers, fresh Rosa centifolia 0·050
Rosemary Rosmarinus officinalis 1·550
Rue herb Ruta graveolens 0·180
Sage herb, German Salvia officinalis 1·400
" " Italian " " 1·700
Santal wood,
East Indian Santalum album 4·500
Macassar " " 2·500
West Indian Unknown 2·700
Sassafras wood Sassafras officinalis 2·600
Savin herb Juniperus Sabina 3·750
Snakeroot, Canadian Asarum canadense 2·800-3·250
" Virginian Aristolochia Serpentaria 2·000
Star-anise, Chinese Illicium anisatum 5·000
" Japanese Illicium religiosum 1·000
Storax Liquidambar orientalis 1·000
Sumbul root Ferula Sumbul 0·300
Tansy herb Tanacetum vulgare 0·150
Thyme Thymus Serpyllum 0·200
" dry " " 0·100
Valerian root, German Valeriana officinalis 0·950
" " Dutch " " 1·000
" " Japan Patrinia scabiosæfolia
Vetiver root Andropogon muricatus 0·200-0·350
Violet flowers Viola odorata 0·030
Water-yarrow seed Phellandrium aquaticum 1·300
Wintersweet marjoram Origanum creticum 3·500
Worm seed Artemisia maritima 2·000
Wormwood herb Artemisia Absinthium 0·300-0·400
Zedoary root Curcuma Zedoaria 1·300
Fresh flowers as a rule contain more aromatic material than wilted
ones; the yield of dried herbs, leaves, etc., is usually greater than
that of the fresh, because the latter contain much water which is
lost in drying. When such vegetable materials cannot be worked fresh,
which is best, they should be completely dried, spread on boards, at
a moderate temperature in the shade and preserved in dry airy rooms,
special care being had to guard against mould.