ESSENTIAL OILS 
The natural essential] oils are the volatile, odoriferous oils 
obtained from plants. By volatile is meant that if one of these 
oils is exposed to the air it will gradually evaporate. These 
volatile oils may occur in the bark, root, leaves, or other parts 
of the plant, but usually they are most abundant in the fruits 
or flowers. Many of these essential oils have a pleasant taste 
and a very fragrant odor, like that of fruits or flowers. They 
are employed extensively in the manufacture of various sub- 
stances for which there is a great demand; as in perfumes, 
toilet waters, scents (face and sachet powders), and in essences 
which serve as flavoring materials for confectionery and for 
beverages like lemonade and liqueurs. They are also used in 
medicinal preparations to conceal nauseous odors and tastes. 
Perfumes have been in vogue since the earliest times, and 
records show that the ancient Egyptians introduced perfumes 
in their religious services. In certain countries vast tracts of 
land are devoted to the cultivation of flowers from which 
fragrant perfumes are obtained. In southern France large 
quantities of various flowers are raised commercially for the 
production of natural perfumes. In the French Riviera district 
alone the annual revenue from cultivated flowers such as 
roses, carnations, and violets, is over #24,000,000. Roses are 
cultivated extensively in Bulgaria, while in the Philippines ilang- 
ilang is grown to a certain extent. In the Philippines there are 
a number of perfume plants which are the bases of considerable 
industries in other countries, but which are not so utilized in 
the Philippines. Among these are patchouli, lemon grass, and 
vetiver. 
Various methods such as steam-distillation, extraction with 
fats (preparation of flower pomades), and extraction with vola- 
tile solvents are used to obtain the perfume oils from flowers. 
As in the case of seed oils, the purity of essential oils is ascer- 
tained by determining certain essential-oil constants such as 
the specific gravity, optical rotation, and especially the ester 
number, as the value of many oils depends largely upon the 
presence of a quantity of certain esters. The real value of an 
oil, however, is determined by the exact odor it possesses. This 
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