Clove oil, distilled from the unripe blossoms of Eugenia caryophyllata, the chief source of which is East Africa (Zanzibar and Pemba). Specific gravity at 15° C., 1.045-1.061; optical rotation, slightly lævo-rotatory up to -1° 30'; phenols, estimated by absorption with 5 per cent. potash solution, 86-92 per cent.; refractive index at 20° C., 1.5300-1.5360; soluble in 1 to 2 volumes of 70 per cent. alcohol.
The principal constituent of the oil is eugenol, together with caryophyllene and acet-eugenol. While within certain limits the value of this oil is determined by its eugenol content, oils containing more than 93 per cent. phenols are usually less satisfactory in odour, the high proportion of phenols being obtained at the expense of the decomposition of some of the sesquiterpene. Oils with less than 88 per cent. phenols will be found somewhat weak in odour. This oil is extensively used in the cheaper toilet soaps and is an important constituent of carnation soaps. As already mentioned, however, it causes the soap to darken in colour somewhat rapidly, and must not therefore be used in any quantity, except in coloured soaps.
Concrete orris oil, a waxy substance obtained by steam distillation of Florentine orris root.
Melting point, 35-45° C., usually 40-45° C.; free acidity, calculated as myristic acid, 50-80 per cent.; ester, calculated as combined myristic acid, 4-10 per cent.
The greater part of the product consists of the inodorous myristic acid, the chief odour-bearing constituent being irone. The high price of the oil renders its use only possible in the very best quality soaps.
Eucalyptus Oil.—Though there are some hundred or more different oils belonging to this class, only two are of much importance to the soap-maker. These are:—
(i.) Eucalyptus citriodora. Specific gravity at 15° C., 0.870-0.905; optical rotation, slightly dextro-rotatory up to +2°; soluble in 4-5 volumes of 70 per cent. alcohol.
The oil consists almost entirely of citronellic aldehyde, and on absorption with saturated solution of sodium bisulphite should leave very little oil unabsorbed.
(ii.) Eucalyptus globulus, the oil used in pharmacy, and containing 50-65 per cent. cineol. Specific gravity at 15° C., 0.910-0.930; optical rotation, +1° to +10°; soluble in 2 to 3 parts of 70 per cent. alcohol; cineol (estimated by combination with phosphoric acid, pressing, decomposing with hot water, and measuring the liberated cineol), not less than 50 per cent. Besides cineol, the oil contains d-pinene, and valeric, butyric, and caproic aldehydes. It is chiefly used in medicated soaps.
Fennel (sweet) oil, obtained from the fruit of Fœniculum vulgare, grown in Germany, Roumania, and other parts of Europe. Specific gravity at 15° C., 0.965-0.985; optical rotation, +6° to +25°; refractive index at 20° C., 1.515-1.548; usually soluble in 2-6 parts 80 per cent. alcohol, but occasionally requires 1 part of 90 per cent. alcohol.