Oleum Geranii. Oil of Geranium.
Synonyms.—Oil of Rose Geranium; Oil of Pelargonium.
Oil of geranium is obtained by distillation from the leaves of Pelargonium odoratissimum, Ait., P. capitatum, Ait., and P. roseum, Willd. (N. O. Geraniaceae), the plants being cultivated for the purpose in France, Algiers, Spain, Réunion (Bourbon), and Corsica. The oil is found in all green parts of the plants, but the greatest yield is obtained from the leaves. It occurs as a colourless, greenish, or brownish liquid, with a pleasant rose-like odour. Specific gravity, 0.890 to 0.906. Saponification value, 45 to 100. The ester percentage, calculated as geranyl tiglinate, in French oils, lies between 23 and 29 per cent., Algerian oils from 25 to 28 per cent., Bourbon oils usually 30 to 35 per cent., with a lower specific gravity (0.885 to 0.895). Oil of turpentine, cedar-wood oil, and fatty oils are used as adulterants of oil of geranium, but they are all insoluble in 70 per cent. alcohol. This oil must not be confused with Indian geranium oil (Palmarosa oil), commonly known as Turkish geranium oil, derived from Cymbopogon Martini (N.O. Gramineae), which contains 75 to 95 per cent. of geraniol and is practically devoid of esters.
Soluble in 70 per cent. alcohol (1 in 2 or 3), except in the case of Spanish oil, which may form a turbid mixture with the alcohol, owing probably to the presence of some fatty oil as an adulterant.
Constituents.—The chief constituent of the oil is geraniol, but citronellol is also present, and mixtures of the two alcohols have been described as "rhodinol" and "reuniol"; linalool is present in the lower fractions of the oil. Spanish oil, which is the most esteemed variety, contains 45 per cent. of geraniol and 25 per cent. of citronellol; African oil contains 60 per cent. of geraniol and 15 per cent. of citronellol; Réunion oil contains about 40 per cent. each of geraniol and citronellol.
Action and Uses.—Oil of geranium is largely employed in perfumery, and it is frequently used instead of oil of rose for perfuming tooth powders, ointments, and other preparations.