Dictionary.net

Oils found in aromatic vegetables, and in every part of them, except in the interior of the seeds. The majority are obtained by distillation; but some by expression. They possess unctuosity, inflammability, and viscidity, like the fixed oils; but they are generally odoriferous, pungent, and acrid. The greater part are lighter than water; but some are heavier, and congeal at a moderate temperature. They dissolve, in small quantity, in distilled water, by simple agitation. Almost all are soluble in alcohol. The odour and taste are the usual tests of their goodness. To preserve them, they should be kept in a cool place, in small bottles, quite full and well corked. Volatile oils are possessed of the aromatic properties of the plants whence they are obtained. They are all, when applied externally, stimulant and rubefacient. Pharmaceutical preparations, in which substances are dissolved in volatile oils, (F.) Solutions par les huiles volatiles, are termed by Beral, Myroles.