Volatile oils are the odorous principles found in various plant parts.
When they are exposed to air at ordinary temperatures they evaporate, therefore they are called volatile oils, ethereal oils, or essential oils. As a result, they are usually colorless, particularly when fresh, but with age they may oxidize and resinify, thus becoming darker. Therefore, storage should be in a cool, dry place, tightly stoppered, preferably full in amber glass containers. The preceding is taken from The Aromatherapy Practitioner Correspondence Course . Is obtained by steam distillation of the flowers and yields ca.