Oil of Partridge-berry (Facti′′tious). See Salicylic acid.
Oil, Pearl. See Amyle (Acetate of), and Essence of Jargonelle pear.
Oil of Pennyroy′al. Syn. Oleum pulegii (Ph. L.), O. menthæ p. (B. P., Ph. E. & D.), O. p. essentiale, L. From the flowering herb of Mentha Pulegium, or the common pennyroyal of our gardens. Pale yellow, growing reddish yellow by age and exposure; antispasmodic, carminative, and emmenagogue. Boils at 395° Fahr. Sp. gr. ·925 to ·931. Prod. 3⁄4 to 1%. (See below.)
Oil of Pennyroyal (American). Syn. Oleum hedeomæ (Ph. U. S.), L. From Hedeoma pulegioides, as the last. Light yellow; closely resembles oil of pennyroyal, for which it passes in the U. S. Sp. gr. ·945 to ·948.
Oil of Pepper. Syn. Oil of black p.; Oleum piperis, O. p. nigri, L. From bruised black pepper (Piper nigrum). Colourless, turning yellow; odorous; pungent; not so hot as the spice. Sp. gr. ·9932. Prod. 1·25% to 1·5%. White pepper (of commerce), 1% (barely).
Oil of Pep′permint. Syn. Oleum menthæ piperitæ (B. P., Ph. L., E., & D.), O. essentialæ m. piperitidis, L. From the fresh flowering herb of Mentha piperita, or garden peppermint. Nearly colourless, or at most a very pale greenish yellow; powerfully odorous;
tastes pungent, at the same time imparting a sensation of coldness to the tongue and palate. Boils at 365° Fahr. Sp. gr. ·902 to ·905. Prod. Fresh flowering herb, ·25% to ·4%; dried do., 1% to 1·25% (fully). In a warm dry season, 5 lbs. of the fresh flowering herb yield 1 oz. of oil; in a wet and unfavorable one, 11 lb. yield barely the same quality.
Pur. The oil of commerce usually contains fully a third part of rectified spirit, and is also frequently adulterated with the oils of rosemary, spearmint, and turpentine. When pure—1. It is soluble in its own weight of rectified spirit.—2. Mixed with 1-4th its volume of nitric acid, a rich purple-red colour is developed.—3. Chromate of potash, in solution, turns it of a deep reddish-brown colour, and converts it into a soft coagulum, which assumes a flaky form when divided with a glass rod, whilst the solution of the salt loses its yellow colour or becomes greenish yellow.—4. With iodine it forms a homogeneous mass, without fulmination. If it explodes with iodine, it contains turpentine. The yellowish, resinous oil, sold under the name of ‘American’ or ‘crude oil of peppermint,’ consists chiefly of oil of turpentine, and on evaporation leaves a residuum of pine resin.
Obs. English oil of peppermint is the best, a fact clearly shown by its price in the market being so greatly above that of the imported oil. The oil distilled at Mitcham, in Surrey (Mitcham oil of peppermint), is the most esteemed. It has usually a very pale greenish colour, which is often imitated by steeping a leaf or two of green mint or parsley in the oil. Old dark-coloured oils are commonly bleached by exposure to the light, to the destruction of a portion of their other properties.
According to a recent and valuable report upon those articles in the Paris Exhibition of 1878, more particularly interesting to the pharmacist, the chemical manufacturer, the perfumer, &c., which lately appeared in the ‘Pharmaceutical Journal,’ the above statement is open to question. Of late years it seems that a considerable industry has sprung up at Arzin in the Department du Nord, in France, where large quantities of libiate plants are cultivated, and subsequently submitted to distillation.