9 5 
16. Volatile oil , likewise called essential oil , 
differs from fixed oil, in being capable of evapora- 
tion by a much lower degree of heat ; in being 
soluble in alcohol, and in possessing a very slight 
degree of solubility in water. 
There is a great number of volatile oils, distin- 
guished by their smell, their taste, their specific 
gravity, and other sensible qualities. A strong 
and peculiar odour may, however, be considered as 
the great characteristic of each species ; the vola- 
tile oils inflame with more facility than the fixed 
oils, and afford, by their combustion, different pro- 
portions of the same substances, water, carbonic 
acid, and carbon. 
The following specific gravities of different vo- 
latile oils were ascertained by Dr. Lewis : 
Oil of Sassafras 1094 Oil of Tansy 
Cinnamon 
Cloves 
Fennel 
Dill 
Penny Royal 
Cummin 
Mint 
Nutmegs 
1035 
1034 
997 
994 
978 
975 
97 5 
948 
Carr aw ay 
Origanum 
Spike 
Rosemary 
Juniper 
Oranges 
946 
940 
940 
936 
934 
911 
888 
Turpentine 79& 
The peculiar odours of plants seem, in almost 
all cases, to depend upon the peculiar volatile oils 
they contain. All the perfumed distilled waters 
owe their peculiar properties to the volatile oils 
they hold in solution. By collecting the aromatic 
oils, the fragrance of flowers, so fugitive in the 
common course of nature, is as it were embodied 
and made permanent. 
