Oil of Patchouli.—The genuine oil is obtained from Pogostemon Patchouli Pellet, a plant cultivated in the Straits Settlements and in Penang. The plant has also been cultivated in the West Indies and in Paraguay. A small amount of oil is also obtained from Microtaena cymosa Prain, a plant cultivated in the mountainous districts of Assam. The patchouli herb is sometimes dried and sent into commerce. It is not infrequently adulterated with a number of other plants, the latter being present to the extent of 80 per cent. It is believed by Arabs, Chinese, and Japanese to possess prophylactic powers. The oil as found in commerce is of two kinds. The best is that distilled in the East in the neighborhood of the patchouli plantations, from selected fresh leaves; the other kind is distilled in Europe from imported leaves; the latter often arrive in a more or less damaged condition, and are frequently adulterated. Oil of patchouli is a thick, brownish-yellow oil with a green tint, and was shown by Gladstone to contain coerulein, an intensely blue compound found in oils of absinthium, calamus aromaticus, matricaria, achillea, etc. The oil has the sp. gr. 0.970-0.990 at 15° C. (59° F.), and is laevorotatory. Rodie states that the odor improves by age and hence perfumers prefer the older oils. It deposits a solid, patchouli alcohol, C15H25O, which crystallizes in hexagonal prisms, melts at 56° C. (132.8° F.), and boils at 206° C. (402.8° F.), while cadinene, C15H24, remains; oil of cedar and oil of cubeb are frequently used to adulterate the oil. They may be detected by fractional distillation. Oil of patchouli is used in perfumery mainly for its valuable property of conferring upon other odors lasting qualities; its characteristic and persistent odor when uncombined is usually not popular among Caucasians.
The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.