Specific gravity at 15° C., 1.180-1.187; optical rotation, Gaultheria oil, up to -1°, Betula oil, inactive; ester as methyl salicylate, at least 98 per cent.; refractive index at 20° C., 1.5354-1.5364; soluble in 2-6 volumes of 70 per cent. alcohol.
Besides methyl salicylate, the oil contains triaconitane, an aldehyde or ketone, and an alcohol.
Ylang-ylang oil, distilled from the flowers of Cananga odorata, the chief sources being the Philippine Islands and Java. Specific gravity at 15° C., 0.924-0.950; optical rotation, -30° to -60°, and occasionally higher; refractive index at 20° C., 1.496-1.512; ester, calculated as linalyl benzoate, 27-45 per cent., occasionally up to 50 per cent.; usually soluble in 1/2 volume of 90 per cent. alcohol.
The composition of the oil is qualitatively the same as that of Cananga oil, but it is considerably more expensive and therefore can only be used in the highest grade soaps.
Artificial and Synthetic Perfumes.
During the past few years the constitution of essential oils has been studied by a considerable number of chemists, and the composition of many oils has been so fully determined that very good imitations can often be made at cheaper prices than those of the genuine oils, rendering it possible to produce cheap soaps having perfumes which were formerly only possible in the more expensive article.
There is a considerable distinction, however, often lost sight of, between an artificial and a synthetic oil. An artificial oil may be produced by separating various constituents from certain natural oils, and so blending these, with or without the addition of other substances, as to produce a desired odour, the perfume being, at any rate in part, obtained from natural oils. A synthetic perfume, on the other hand, is entirely the product of the chemical laboratory, no natural oil or substance derived therefrom entering into its composition.
The following are among the most important bodies of this class:—
Amyl salicylate, the ester prepared from amyl alcohol and salicylic acid, sometimes known as "Orchidée" or "Trèfle". This is much used for the production of a clover-scented soap. It has the specific gravity at 15° C., 1.052-1.054; optical rotation, +1° 16' to +1° 40'; refractive index at 20° C., 1.5056; and should contain not less than 97 per cent. ester, calculated as amyl salicylate.
Anisic aldehyde, or aubépine, prepared by oxidation of anethol, and possessing a pleasant, hawthorn odour. This has the specific gravity at 15° C., 1.126; refractive index at 20° C., 1.5693; is optically inactive, and dissolves readily in one volume of 70 per cent. alcohol.