Extraction by distillation. Subtle fragrances, Light fragrances,
Subtle fragrances, Light fragrances, Exquisite scents.
It is often taken advantage of, to extract the oils from flowers and fruits, the property they have to volatilize. Therefore, in the copper retort (see p. 295) of a copper still, the root, bark, leaves, or flowers from which one wishes to extract the essence are introduced; enough water is added so that the material is bathed in it; then, after a few hours of maceration, the distillation process is carried out.
The steam, laden with the essential oil and condensed in the coil, goes into a container shaped like a carafe with a narrowing neck towards the top;
- Florentine vase at the base which has a spout rising along the simple receptacle body.
main of the container, but which does not rise as high as its neck. Through this design, the oil, usually lighter than water, gathers in the neck, and the water flows out through the end of the spout as the distillation progresses. This container is called a Florentine vase, after the city where it was invented. The oil is extracted from it using a pipette.
To avoid loss of essence, Messrs. Desmarets and Mero have modified the shape of the Florentine vase (fig. 216), so that the essence flows into a flask, as it is produced, through a small conduit B made at the upper part of the test tube A constituting the container. The water flows out through the swan neck C. The distillation product is collected at the exit of the coil rosemary, rose, orange tree, etc. - We are going to explain what is necessary
to know about this process, according to Mr. J. P. Durvelle, perfumer chemist.
The vaporization of fragrances
Essences, although having a much higher boiling point than water, have the property of vaporizing with steam. This vaporization is not instantaneous, but it always requires a certain amount of time, as most of the time the essence is not contained in the plants or plant parts in a simple mixture state, but it is mechanically trapped by cell walls, woody tissue, etc.
Through appropriate preparation for the nature of each material, part of the essence is more or less exposed to be able to escape without obstacles, as crushing tears the cells so that the essence can easily gather in droplets. However, cell tearing is often only partial, and the essence cannot break through the membranes of the utricles and the cellular tissue except with the heat that expands it.
When all the essence is finally set free, it still requires sustained contact with water, and it is only when the plants are well penetrated by steam that it dissolves and carries away the essence.
To give the steam more penetration strength and therefore shorten the distillation time, it is often brought to a high temperature; but this method must be used with great caution as most fragrances alter under the influence of high temperatures.
Furthermore, high temperatures often produce in distillation the same effect as "shots of fire," if they do not bring them about; the essence then takes on a boiler taste that depreciates it.
These accidents frequently occur in open fire distillation. If the plants are in direct contact with the heated walls of the still, they heat up, burn, and undergo a kind of dry distillation. The products of such distillation have a repulsive odor, and since they are volatile, they penetrate the condensed product and impart their bad odor to it.
Properties of stills
In regions where water is scarce, a very simple way to remedy this is to constantly return the waters flowing from the Florentine vase to the retort. The return of these waters to the apparatus becomes even a necessity when the distilled essence is of high value and very soluble in water; it is the only way to avoid the losses that could result from the dissolution and mixing of the essence in the condensed water.
The devices used for distilling essences come in
many and varied shapes; however, the various systems are always based on the same principle. From a functional point of view, the distillation devices are either simple, meaning that the distillation work is intermittent and interrupted by reloading when a charge is depleted, or continuous, meaning they are continuously fed by a pump and a reservoir.
Simple distillation stills are the only systems used by essence manufacturers; they are either open fire or steam, and involve more or less substantial detail modifications,
Let us briefly explain the different parts of an apparatus, using the swan neck apparatus as a model (fig. 217).
This apparatus consists of four main pieces: the retort, the head, the swan neck, and the condenser or coil.
The retort or boiler is tin-plated copper and enters the furnace up to about three-quarters of its height, where it is equipped with a rim to hold it in place; on this rim is attached a socket with its screw cap a which is used to introduce liquid to replace the evaporating one without stopping the distillation. The retort of the open fire apparatus is usually equipped with a ring for supporting the water bath; it also has two handles to facilitate handling. In the bottom of the retort, a perforated round grid with legs that support and keep it about 8 to 10 centimeters away from the bottom is placed.
The water bath is a copper vessel, tinned on the inside only.