2. The systematic extraction of the flowers. The extractors of the mounted extraction batteries are cylindrical vessels, varying in size, but usually of about 500 liter capacity. They contain 3 or 4 low cylinders made of wire gause or of perforated tin, one placed over the other. The extractors are airtight and sealed with a removable cover. The batteries are mounted in one of several ways: either the extractors are all on a level in a circle or a row (fig. 56, p. 254), or in two tiers one over the other (fig. 54, p. 252). With the aid of a pump, the solvent can be passed from one extractor to another.

As a rule, 3 to 4 extractions are made within 24 hours. Hence the menstruum remains in contact with the flowers from 6 to 8 hours. Then the flowers are replaced by fresh ones. However, during the height of the harvest the flowers in the extractors are replaced every 8, or even every 4 to 5 hours. This hastening of the process, however, results in an imperfect extraction.

As a rule, each batch of flowers is extracted three times, more rarely twice or four times. For the third (or last) extraction fresh petroleum ether is used, for the second such which has served for a former third extraction, and for the first extraction (i. e. for fresh flowers) the menstruum which has once served for a second and once for a third extraction. The percolate of each extraction is collected in a separate receiver.

Whether the same batch of flowers is to be extracted two, three, or four times, or even oftener depends upon the nature of the flowers to be extracted and on the views of the manufacturer. There exists also a difference of opinion as to how often the same petroleum ether can be used before it is to be recovered by distillation.

In order to increase the yield, the extractors have been so constructed in several instances as to enable their being warmed. This has resulted in a larger yield of wax but not of odoriferous constituents.

3. EVAPORATION OF THE SOLVENT. The manufacturer operates one or several stills under ordinary pressure or in vacuum. As a rule the bulk of the solvent is recovered in a large still under atmospheric pressure until the temperature has reached a point that would prove detrimental to the fineness of the perfume. The distillation is then continued in a vacuum still and finally concluded in a glass flask.

The last traces of solvent are removed by passing small amounts of alcohol into the molten wax thus causing a violent ebullition.

The floral extracts thus obtained are designated "concrete oils" (essences concretes). The alcoholic extracts prepared from these, according to the method described below, are known as floral extracts (Ger. Bluten extraits; Fr. extraits aux f/eurs); the pure oils remaining after the removal of the alcohol quintessences. 1)

4. Recovery of the solvent. On account of the expense of the solvent, suitable devices are provided to prevent loss. Hence long and well cooled spirals are used to condense the vapors from the stills, the extractors and the reservoirs. The ejectors of the vacuum pump must also be provided with an efficient condenser. If the process is conducted without a vacuum, the petroleum ether losses are less, but evaporation under atmospheric pressure, as already pointed out, results in an impairment of the fragrance of some of the floral constituents.

The solvent adhering to the flowers after their extraction is recovered by passing steam through the extractors which, for this purpose, are connected with the condensers; or by transferring the flowers to a still from which the solvent is recovered by steam.

Yield. The yield varies greatly according to the solvent and temperature employed, also according to the duration of the extraction.

At ordinary temperature, petroleum ether yields for every kilo of flowers the following amounts of concrete oils.

Victoria violets........

1,5 to 1,8 g

Roses..............

1,7 " 2 5

Orange flowers........

2,0 " 4,0 "

Jasmine

1,6 " 2,25 "

Cassie

3,5 " 5,0 "

Mignonette...........

1, 3 " 1,5 "

Removal of the plant wax from the concrete oils. For this purpose the essences concretes, i. e. the extracts obtained by percolation and subsequent evaporation of the solvent, are shaken for several days with strong alcohol, preferably in shaking machines (batteuses). The alcoholic solution, after being separated from the insoluble wax, is cooled for some time to 0°. This causes the separation of the dissolved wax, which is removed by filtration. To the alcoholic filtrate a solution of common salt is added, and the perfume, which has risen to the surface, is separated. If necessary, the last traces of alcohol are removed with the aid of a vacuum.

1) Jeancard et Satie, Abrege de la Chimie des Parfums. Paris 1904, p. 12.

In as much as the plant wax when shaken with alcohol agglutinates to a magma from which the perfume is extracted with difficulty, Massignon1) has suggested to mix it with a very hard and odorless mineral wax, thus yielding a mass that can be broken up in a mortar. The particles then remain suspended in the alcohol and are more readily extracted by it.

Fig. 54. Elevation plan of an extraction battery.

Fig. 54. Elevation plan of an extraction battery.

Description And Operation Of The Extraction

Battery Represented By Fig. 54, P. 252.

In the above plan the extractors are marked E1 and E2. They have a capacity of about 500 1. and are divided into compartments by means of 3 to 4 false bottoms of perforated tin or by means of wire baskets. The air tight covers are provided with two pipes: one of these is used for introducing the solvent, the other for ventilation. The ends of the pipes are flexible and can be screwed to the cover. The bottom of the extractor is slightly conical thus admitting of a complete evacuation of the extract through the pipe fastened to its center. S is a condenser in which the vapors that might otherwise escape are liquified. The condensate collects at V and flows into the reservoir R4.

1) P. Jeancard, Volatile solvents applied to flowers. Americ. Perfumer 1 (1907), 10.

Fig. 55.

Fig. 55.

Side view of an extraction battery by Deroy Fits Aine, Paris.

Vapors that have not been condensed as well as air escape through s. S1 and S" are the respective condensers for the stills A and Ai.

A is a larger still for distillation under atmospheric pressure. It is provided with a glass tube indicating the height of the liquid and with a thermometer. The distillate passes through the condenser S1, into the reservoir R4. The residue is allowed to flow into the container R".

A1 is a vacuum still which can be heated by means of a water bath. It is filled by suction from R". The recovered solvent collects in R'" from which it is pumped to the larger reservoirs.

Fig. 56. Sectional front vien of an extraction battery by Deroy Fils Afne, Paris.

Fig. 56. Sectional front vien of an extraction battery by Deroy Fils Afne, Paris.

Fig. 57. Ground plan of an extraction battery by Deroy Fils Aine, Paris

Fig. 57. Ground plan of an extraction battery by Deroy Fils Aine, Paris.

R1, R2, R3, are reservoirs of about 2000 I. capacity provided with glass tubes showing the height of the contents and with ventilation tubes. With the aid of a pump the contents can be transferred to the extractors.

The extractors are filled from ft' which is provided with an overflow into which the solvent is pumped from the other reservoirs with the aid of pump P.

The pipes are indicated by heavy lines. All parts of the battery and the intersections of the pipes are provided with one-way or several-way stopcocks.

The purified solvent passes through pipe K into the reservoirs R2, R3, R4, which are filled to about 4/5 of their capacity. The flowers are then placed on the false bottoms in the extractors E, the covers are placed in position, the influx and ventilation pipes are adjusted, and the solvent is allowed to flow from ft' into the extractors E1 until the flowers are completely covered. The three extractors E2 are next filled and the flowers are covered with the percolate of the upper tier of extractors, the flowers of which are covered with fresh solvent. In this manner the flowers are commonly extracted three times in succession. These three extractions are made within 24 hours, but in the rush of the floral harvest are sometimes made in 8 hours, or even in 4 to 5 hours.

The percolate of each extraction is stored away separately, reservoir R1 containing the first percolate. After the petroleum ether has been sufficiently saturated with perfume it is recovered first by distillation in the still A, then under diminished pressure in A1, and finally in a glass flask.

The exhausted flowers are allowed to drain well. The menstruum still adhering to them is recovered by steam distillation in the large still.