Pelargonium. Pelargonium odoratissimum. Rose geranium.

Pelargonium. Pelargonium odoratissimum Willd. Rose Geranium. (Fam. Geraniaceae.)— The Pelargoniums, commonly referred to as geraniums, are indigenous to South Africa and largely cultivated as decorative plants. Some of the species are cultivated for the distillation of the volatile oil, in France, Spain, Algiers, and the Island of Reunion. According to Guibourt, several species of Pelargonium yield a volatile oil by distillation, closely analogous in odor to that of the rose: the species above named, P. capitatum Ait., and P. roseum Willd., the last being regarded as a variety of P. radula Ait. (Hist. Nat. des Drogues, 4e ed., iii, 52.) The oil is obtained from the leaves. Recluz obtained from thirty-five ounces of P. odoratissimum W., two drachms of a volatile, crystallizable oil. (Merat and De Lens, Dict. de Mat. Med., iii, 368.) According to Septimus Piesse, one cwt. yields about two ounces. (See A. J. P., xxvi, 368.) The oil which occurs in commerce, purporting to be the oil of P. odoratissimum, is fluid at ordinary temperatures, of a pale brownish-yellow color, and the characteristic odor of the plant, merely recalling that of the rose. This oil is now much used in perfumery. Piesse states that, as this oil is used to adulterate that of roses, so is it in its turn adulterated with the cheaper oils of species of Andropogon. (See p. 1517.) (A. J. P., xxvi, 368.) It appears, however, that the oil known as oil of palmarosa (see Oil of Citronella), distilled in India, is the one which is used most largely to adulterate oil of rose and oil of rose geranium. According to Baur, the oil is shipped in large copper flasks from Bombay to the Red Sea, and thence to Constantinople and Kizanlik. For Burtell's description of the method of distilling palmarosa oil see Schim. Rep., 1909, 88. Jallard states that the true oil of rose geranium from P. roseum is freely soluble in 70 per cent. alcohol. The oils likely to be used to adulterate it are insoluble in this liquid. If, therefore, six drops of the suspected oil be mixed with 5 mils of 70 per cent. alcohol, there should be no separation. (A. J. P., 1878, 260; from J. P. C.) F. W. Semmler (Ber. d. Chem. Ges., xxiii, 1098) has shown that the chief ingredient in the various geranium oils is an alcohol, geraniol, C₁₀H₁₈O, which boils at from 231° to 232° C. (447.8°-449.6° F.), and has a sp. gr. 0.884 at 15° C. (59° F.). When oxidized by chromium trioxide mixtures, it is changed into citral, C₁₀H₁₆O, an aldehyde found in many of the essential oils, and this when oxidized by silver oxide yields geranic acid, C₁₀H₁₆O₂. The geraniol is both free and combined as tiglic acid ester. The oil also contains citronellol. (Schim. Rep., April, 1897.) Geranium oil is sometimes adulterated with dimethyl sulphide, (CH₃)₂ S. (Schim. Rep., 1909, 55; see also Am. Perf., Jan., 1913.)

The Dispensatory of the United States of America, 1918, was edited by Joseph P. Remington, Horatio C. Wood and others.