Essential Oils
. Essential Oils, any of several chemicals that form the odoriferous essences of a number of plants. The term essential oil is also applied to similar synthetic substances prepared from coal tar chemicals, and semisynthetic substances prepared from natural essential oils (see Organic Chemistry ; Petroleum ). SOURCES Essential oils come from the flowers, fruits, leaves, roots, seeds, and bark of many plants. Oil of lavender , for example, is derived from a flower , oil of patchouli from a leaf , and oil of orange from a fruit . The oils are formed in the green (chlorophyll-bearing) parts of the plant, and with plant maturity are transported to other tissues, particularly to the flowering shoots. The exact function of an essential oil in a plant is unknown; it may be to attract insects for pollination , or to repel harmful insects, or it may be simply a metabolic intermediate. The essential oils are volatile liquids , mostly insoluble in water, but freely soluble in alcohol , ether, an