Oleum Neroli. Oil of Neroli.
Synonyms.—Oleum Aurantii Floris; Oil of Orange-flower.
Oil of neroli is obtained by distillation with water from the fresh blossoms of the bitter orange tree, Citrus Aurantium var. Bigaradia, Hook. f. (N.O. Rutaceae), and is produced in Southern France. It occurs as a pale yellow liquid, slightly, but distinctly, fluorescent, becoming brownish-red on exposure to light, with an intense and pleasant odour of orange blossoms, and a bitter, aromatic taste. On standing, a paraffin hydrocarbon separates in crystalline flakes, and collects on the surface. The alcoholic solution has a fine, violet-blue fluorescence. When exposed to low temperatures, the oil becomes turbid and occasionally solid from separation of paraffin. Specific gravity, 0.870 to 0.880; rotation, +1° 30' to +5°. The saponification value of good oil lies between 20 and 52. The most frequent adulterants are the oils of bergamot and petit-grain, which, consisting chiefly of the same constituents as neroli oil, are difficult to detect, unless they are present in large quantities, when the specific gravity and ester content are increased. The odour alone is a helpful guide in the valuation of the oil.
Soluble in 80 per cent. alcohol (1 in 1.5 to 2), becoming turbid on the addition of more of the alcohol.
Constituents.—The odour and fluorescence of the oil are due to the methyl ester of anthranilic acid, C6H4(NH2)COOCH3, which occurs in small quantity; its odour in the undiluted state is disagreeable, but very pleasant in largely diluted solutions. Other constituents of the oil are l-linalool (C10H18O), linalyl acetate (C12H20O2), 7 to 18 per cent.; geraniol (C10H18O), limonene (C10H16), and a stearoptene, called neroli camphor, which is odourless and tasteless when pure, and melts at 55°.
Action and Uses.—Oil of neroli is largely employed in perfumery. The watery distillate obtained in its preparation constitutes the orange-flower water of commerce.
Preparations: Violet Powder