Oleum Aurantii Corticis (U. S. P.)—Oil of Orange Peel.

Preparations: Spirit of Orange - Compound Spirit of Orange - Wine of Orange
Related entries: Aurantii Amari Cortex (U. S. P.)—Bitter Orange Peel - Aurantii Dulcis Cortex (U. S. P.)—Sweet Orange Peel - Oleum Bergamottae (U. S. P.)—Oil of Bergamot

"A volatile oil obtained by expression from the fresh peel of either the bitter orange, Citrus vulgaris, Risso, or the sweet orange, Citrus Aurantium, Linné (Nat. Ord.—Rutaceae). It should be kept in well-stoppered bottles, in a cool place"—(U. S. P.).
SYNONYM: Essential oil of orange peel.

Source and Preparation.—There are in commerce two oils of orange peel, viz.: OLEUM AURANTII DULCIS, Oil of sweet orange peel, and OLEUM AURANTII AMARI, Oil of bitter orange peel. Both are included in the official oil. They are prepared in southern Europe by at least five different methods: (1) by rupturing the superficial portion of the rind, thus liberating the oil from the glands; (2) by forcibly twisting the fresh rind and collecting the oil upon sponges, and afterward squeezing the contents of the saturated sponges into a suitable vessel; (3) by grating the exterior of the rind and expressing; (4) by putting the scrapings into hot water and skimming off the oil; (5) by distillation of the residues after expression, which yields an inferior product.

Chemical Composition.—Both oils are composed chiefly (to 90 per cent) of dextro-limonene (Wallach, 1884). In addition the oil of sweet orange peel contains, according to Semmler (1891), a small quantity of geranial (citral), and an aldehyde of lower boiling point (Power, Essential Oils). The oil of orange peel is under further chemical investigation. Ninety per cent of the oil distills between 175° and 180° C. (347° and 354° F.).

DEXTRO-LIMONENE occurs chiefly in orange and lemon oils; also found in oils of caraway, dill and elsewhere; laevo-limonene in American oil of peppermint and a few other oils. Both modifications are identical in every respect except their optical antagonism. Combined in equi-molecular quantities, they form a terpene nearly identical with dipentene which is inactive. Limonene is a colorless liquid of a pleasant lemon odor: its specific gravity at 15° C. (59° F.) is 0.846; boiling point 175° to 176° C. (347° to 348.4° F.). Being an unsaturated terpene, 1 molecule absorbs 4 atoms of bromine, forming therewith a characteristic addition product which melts at 104.5° C. (220° F.) (Wallach, 1887).

Description and Tests.—Chemically, and in most other particulars, these two oils are similar. Their flavor differs somewhat, and that from the bitter oranges undergoes change more quickly on exposure. Oil of sweet orange peel is generally preferred in making elixir of orange. The best is the Sicilian oil, though not all is made in Sicily. That from Bigarade orange is known in France as Essence de Bigarade, and regarded the most valuable; that from the Portugal or Sweet orange is called Essence de Portugal. Oil of orange peel is officially described as "a pale yellowish liquid, having the characteristic, aromatic odor of orange, and an aromatic and, when obtained from the bitter orange, somewhat bitter taste. Specific gravity, about 0.850 at 15° C. (59° F.). Its optical rotation should not be less than 95° to the right in a 100 Mm. tube, and at a temperature of about 15° to 20° C. (59° to 68° F.). Soluble in about four times its volume of alcohol, this solution being neutral to litmus paper; also soluble in all proportions, in absolute alcohol or in carbon disulphide, and in an equal volume of glacial acetic acid. When kept for some time the oil should not develop a terebinthinate odor or taste (absence of oil of turpentine or of other oils containing pinene)"—(U. S. P.). Both oils have the same specific gravity (0.848 to 0.854, Schimmel & Co.).

Action and Uses.—This agent is employed for perfuming or flavoring medicines. Its properties are those of an irritant, and it is somewhat narcotic. Those who prepare the oil are subject to mental confusion, muscular debility, neuralgia, headaches, disordered digestion, and erythema, papules, and vesicles upon the skin.

King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.