Perfumes and their preparation

by George William Askinson

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.

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.

Fig. 10.

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.

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.

Fig. 11.

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.

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.

Fig. 12.

Fig. 13.

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.

Fig. 14.

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.

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.

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.

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.