Oleum Aurantii. Oil of Orange.

Related entries: Sweet orange peel - Bitter orange peel - Lemon peel - Oil of bergamot - Oil of Neroli

Synonym.—Essence of Orange.

Oil of orange (Oleum Aurantii Corticis, U.S.P., Oil of Orange Peel), is obtained by mechanical means from the fresh peel of the sweet orange, Citrus Aurantium, Linn., and also the bitter orange, Citrus Aurantium var. Bigaradia, Hook. f. (N.O. Rutaceae), chiefly in Calabria and Eastern Sicily. By far the greater part of the oil of commerce is obtained from the sweet orange, but chemically the two oils are practically identical. It is possible, however, to distinguish them by their odour and taste; the oil from the bitter orange is said to be the finer. Oil of orange occurs as a yellow to yellowish-brown liquid, having the characteristic odour of orange, and a mild aromatic taste, bitter in the case of the bitter oil. It deteriorates on keeping, acquiring a disagreeable terebinthinate taste. The addition of 10 per cent. of absolute alcohol to the fresh oil prevents this. It has a neutral reaction. Specific gravity, 0.847 to 0.854 (0.842 to 0.846 at 25°). Rotation, +95° (+92° in the case of the bitter oil) to +98° at 20°. Begins to boil at 175°, about 90 per cent. distilling over below 180°. The physical constants are so balanced that the addition of any of the common adulterants is very easily detected. The waste terpene, however, obtained in the manufacture of terpeneless oil of orange is very difficult to detect, paleness of colour and harshness of odour being almost the only means of doing so. Oil of turpentine and oil of lemon are detected by the rotation. Alcohol lowers the specific gravity. Fractionation detects both turpentine and alcohol. The first 10 per cent. distilled from the oil should give a rotatory power not very different from that of the original oil. The purity of the oil is best judged by the rotation and odour. Distilled oil of orange is an inferior article, the effect of heat and steam being detrimental to the oxygenated compounds, which are of a very delicate nature.

Soluble in alcohol (1 in 7), in all proportions of absolute alcohol, but not always with formation of bright solutions, on account of the presence of waxy, non-volatile substances.

Constituents.—The oil consists of at least 90 per cent. of the terpene d-limonene, C₁₀H16. Other constituents are citral, citronellal, decyl aldehyde, the methyl ester of anthranilic acid, and a stearoptene of which nothing, so far, is known. Traces of linalool and terpineol have also been found.

Action and Uses.—Oil of orange is employed in perfumery, and in the form of Elixir Aurantii as a flavouring agent for mixtures.

Dose.—¼ to 2 decimils (0.025 to 0.2 milliliters) (½ to 3 minims).

PREPARATIONS.

Elixir Aromaticum, B.P.C., C.F., and U.S.P.—AROMATIC ELIXIR. 1 (compound spirit) in 80.

Used as a flavouring agent, 4 mils (1 fluid drachm) being sufficient for 30 mils (1 fluid ounce) of mixture. Dose.—2 to 8 mils (½ to 2 fluid drachms).

Elixir Aurantii, B.P.C.—ELIXIR OF ORANGE. 3 in 1000.

This preparation corresponds to Elixir Simplex of the British Pharmaceutical Conference Formulary, 1894. Elixir of orange is a useful flavouring agent, 1 part by volume being sufficient to flavour 30 to 60 parts of mixture. Dose.—1 to 4 mils (15 to 60 minims).

Elixir Aurantii, C.F.—ELIXIR OF ORANGE, C.F.

Spirit of orange, 4; deodorised alcohol, 25; simple syrup, 40; distilled water, 31; talc, a sufficient quantity. Mix the several ingredients in the order named; shake occasionally, and filter through talc until the filtrate passes perfectly clear.

Spiritus Aurantii, C.F.—SPIRIT OF ORANGE.

Fresh oil of sweet-orange peel, 10; deodorised alcohol, 90.

Spiritus Aurantii Compositus, C.F.—Same as U.S.P., but made with deodorised alcohol.

Spiritus Aurantii Compositus, U.S.P.—COMPOUND SPIRIT OF ORANGE.

Oil of orange, 20; oil of 1emon, 5; oil of coriander, 2; oil of anise, 0.5; alcohol (95 per cent,), to 100. Used chiefly as a flavouring agent; and should be kept in completely filled, well-stoppered bottles, in a cool dark place. Average dose.—6 decimils (0.6 milliliters) (10 minims).

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