_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 deg. C., 0.870-0.905; optical rotation, slightly dextro-rotatory up to +2 deg.; 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 deg. C., 0.910-0.930; optical rotation, +1 deg. to +10 deg.; 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 Foeniculum vulgare, grown in Germany, Roumania, and other parts of Europe. Specific gravity at 15 deg. C., 0.965-0.985; optical rotation, +6 deg. to +25 deg.; refractive index at 20 deg. 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. The chief constituents of the oil are anethol, fenchone, d-pinene, and dipentene. _Geranium oils_, distilled from plants of the Pelargonium species. There are three principal kinds of this oil on the market--the African, obtained from Algeria and the neighbourhood, the Bourbon, distilled principally in the Island of Reunion, and the Spanish. The oil is also distilled from plants grown in the South of France, but this oil is not much used by soap-makers. A specially fine article is sold by a few essential oil firms under the name of "Geranium-sur-Rose," which as its name implies, is supposed to be geranium oil distilled over roses. This is particularly suitable for use in high-class soaps. The following are the general properties of these oils. It will be seen that the limits for the figures overlap to a considerable extent.