Oil of fennel, from whatever variety of the drug obtained, consists of Anethol (or Anise-camphor)
| C₆H₄ |  | OCH₃ |
| CH·CH·CH₃, |
and variable but less considerable proportions of an oil, isomeric with oil of turpentine. Anethol is obtainable from fennel in two forms, the solid and the liquid; crystals of the former are deposited when the oil is subjected to a somewhat low temperature; the liquid anethol may be got by collecting the portion of the crude oil passing over at 225° C. The crystals of anethol fuse between 16 and 20°; the liquid form of anethol remains fluid even at -10° C. By long keeping, the crystals slowly become liquid and lose their power of reassuming a crystalline form.
Three varieties of oil of fennel are found in commerce, namely the oils of Sweet Fennel and Bitter Fennel offered by the drug-houses of the south of France; their money value is as 3 to 1, the oil of sweet fennel, which has a decidedly sweet taste, being by far the most esteemed. The third variety is obtained from Saxon fennel, especially by the manufacturers of Dresden and Leipzig.[1180] We have been supplied with type-specimens of the first two oils by the distillers, Messrs. J. Sagnier, fils, & Cie., Nîmes; a specimen of the third has been distilled in the laboratory of one of ourselves.
Oil of fennel differs from that of anise by displaying a considerable rotatory power. We found the above-mentioned specimens, examined in a column 50 mm. long, to deviate the ray of polarized light to the right thus:—
| Oil of | Sweet Fennel | 29°·8 |
| ” | Bitter ” | 4°·8 |
| ” | German ” | 9°·1 |
The rotatory power is due to the hydrocarbon contained in the oil; we ascertain that anethol from oil of anise is devoid of it.
Fennel fruits contain sugar, yet their sweetness or bitterness depends on the essential oil rather than on the presence of that body. The albumen of the seed contains fixed oil, which amounts to about 12 per cent. of the fruit.
Uses—Fennel fruits are used in medicine in the form of distilled water and volatile oil, but to no considerable extent. The chief consumption is in cattle medicines, and of the oil in the manufacture of cordials.