Related entry: Citral, Linalool, Oil of rose, Palmarosa oil

C10H18O = 154.144.

Geraniol, C10H18O, is a primary alcohol, isomeric with linalool, and constitutes the chief part of oil of rose and palmarosa oil; it also occurs in appreciable quantities in geranium, citronella, lemon, and many other oils. It is found both in the free state and in the form of esters, and may be obtained by making use of its property of combining with calcium chloride to form a crystalline compound, thus:—The oil is triturated with an equal weight of anhydrous calcium chloride, and the mixture, which becomes heated to 30° to 40°, is cooled in a desiccator. The solid mass thus obtained is triturated with anhydrous ether or benzene, filtered under pressure, washed with ether or benzene, and decomposed with water, the oily liquid which separates washed with warm water, and finally distilled in a current of steam. Geraniol occurs as a colourless, somewhat oily liquid, having a sweet rose-like odour, and becoming oxidised on exposure to the air. Specific gravity, 0.880 to 0.883; boiling-point, 230°; refractive index, 1.4766; optically inactive. On oxidation, it is converted into its aldehyde geranial or citral. By heating with acetic anhydride it yields the acetic ester, CH3COOC10H17, which is a fragrant oil of specific gravity 0.917. Geraniol may be changed to linalool by heating with water to 200° under pressure, whilst it may be obtained from linalool by heating the latter for some time with acetic anhydride.

Use.—Geraniol is used largely in perfumery. It must be distinguished from its aldehyde geranial, C10H16O, which is identical with citral.

The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.