The first to suggest the use of volatile solvents for the extraction of flowers was Robiquet. In a paper2) contributed in 1835 he points out that some plants, such as jonquil, jasmine, heliotrope, and tuberose, in spite of their agreeable fragrance, yield no volatile oil when treated in the ordinary manner. He ascertained that the odoriferous principle of jonquil, could be obtained by extraction with ether and subsequent evaporation of this low-boiling solvent. A year later L. A. Buchner,3) stimulated by the report of Robiquet, ascertained that ether could also be used for the extraction of other flowers with a readily evanescent aroma, such as those of Philadelphus coronarius, Tilia europsea, and Reseda odorata. In 1838 Favrot4) proceeded in like manner with the extraction of the perfume of the flores acaciae (presumably the flowers of Robina pseudacacia?), also of the flowers of Syringa vulgaris.

A more detailed study of the extraction of flowers with volatile solvents was made by Millon5) in Algiers. In addition to ether he recommended chloroform, carbon disulphide, wood alcohol and the low boiling fractions of benzin.

1) Journ. f. prakt. Chetn. II. 64 (1901), 245.

2) Recherches sur /'arome de la jonquille. Journ. de Pharm. 21 (1835), 335; Buchner's Repert. f. d. Pharm. 54 (1835), 249; Pharm. Zentralbl. 1835, 553.

3) Versuche zur Extraktion der Bltiten mit Ather. Buchner's Repert. f. d. Pharm. 56 (1836), 382.

4) Journ. de Chim. med. 1888, 221; Pharm. Zentralbl. 1838, 442.

5) Memoire sur la nature des Parfums et sur quelques fleurs cultivables en A/gerie. Journ. de Pharm. et Chim. HI. 30 (1856), 407; Compt. rend. 43 (1856), 197.

Millon placed the flowers into a percolator (appareil a deplacement) covered them with ether and renewed the menstruum after 10 to 20 minutes. The extract, obtained after evaporation of the ether, he kept in open containers because he thought that the air acted favorably on the odoriferous principle. This, however, was a deception. Unless the solvent is carefully removed with the aid of a vacuum, mere traces of it can be detected if the extract is kept in closed containers. Millon was not ignorant of the fact that the greater part of the extract consists of vegetable wax which is well nigh insoluble in alcohol. Hence he determined the amount of odoriferous sub-stances by ascertaining the difference in weight of the extract before and after treatment with alcohol.

Millon also pointed out that the time of day in which the flowers are collected is an important factor. Thus carnations should be gathered after 2 to 3 hours of intensive sunshine, roses in the morning after they are fully blown, jasmine before sunrise. To a sensitive nose cassie flowers have a different odor according to the time of their collection, morning, noon or evening. Millon recommends that the following flowers be extracted: orange blossom, tuberose, heliotrope, stock and narcissus.

The substitution of petroleum ether for ether, a practice now in common use, was suggested by H. Hirzel1) of Leipzig. His apparatus constructed for this purpose, were patented as early as 1864 in France, England, Austria, and several of the German states. The problem of utilizing on a technical scale the extraction with ether, carbon disulphide, chloroform, and petroleum ether, was developed about the same time by A. Piver.2) The use of methyl chloride as a solvent was recommended by Camille Vincent.3)

In the early seventies, Louis Roure4) devised a method for the preparation of the so called essences concretes, concentrated alcoholic perfumes, obtained by extraction. These were exhibited at the Vienna Exposition in 1873. A very complicated apparatus was patented by Laurent Naudin5) in 1875. This permitted of the vacuum distillation of the solvent charged with the perfume.

However, it is only since the last 25 to 30 years that the method of floral extraction with volatile solvents has found industrial application. It was at that time that Massignon in Cannes erected a battery of extraction apparatus similar to the diffusion apparatus employed in sugar factories. The solvent saturated with the perfume was evaporated in a vacuum still. As menstruum Massignon first used ether, carbon disulphide, methyl chloride, and benzene. Finally he arrived at the conclusion that a petroleum ether of the specific gravity 0,650 was best suited. Later Mas-signon sold his factory and his patents to Leon Chin's. Gradually other factories were equipped with extraction batteries. At the present time there are about 15 larger establishments of this kind in Grasse. In Joffa, Gamier erected a factory for the extraction of cassie flowers, and in Kara-Sarlii near Karlova in Bulgaria, another for the treatment of roses according to the extraction method. Recently a factory has been established for the extraction of cassie flowers and of other flowers cultivated in the island for this purpose.

1) Hirzel's Toiletten-Chemie. III. ed. Leipzig 1874, p. 77.

2) Ibidem p. 79.

3) Pi esse, Chimie des parfums. 1903, p. 69.

4) Berichte von Roure-Bertrand Fils October 1900, 27.

5) Bull. Soc. chim. II. 38 (1882), 586 to 600.

Practically the process of extraction with volatile solvents resolves itself into four steps:

1. Selection and purification of the solvent.

2. The systematic extraction of the flowers.

3. Evaporation of the solvent and production of the vegetable wax saturated with perfume (are parfumee).

4. Recovery of the solvent.

1. Selection and Purification of the Solvent. The solvent most commonly used is petroleum ether of a specific gravity 0,650 (15°). It is purified by consecutive treatment with sulphuric acid and caustic soda, washing with water and rectification with the aid of a column in a still over solid paraffin for the purpose of removing the ligther as well as the heavier fractions. Less frequently benzene is used since it has the disadvantage of yielding a highly colored extract. Carbon disulphide is not serviceable since the extract always retains some of the disagreeable odor of the solvent. Neither has carbon tetrachloride maintained itself. The highprice of ether stands in the way of its general use.