416 COMPOUND PRODUCTS. CHAP. I. 



Pinus ; in the leaves of labiate plants, such as 

 Mint, Rosemary, Marjoram ; and of the odorous 

 UmbellifertE, such as Chervil, Fennel, Angelica ; and 

 of plants with compound flowers, such as Worm- 

 wood. They are found also in the flower itself, as 

 in the flowers of Chamomile and the Rose ; and in 

 the fruit, as in that of Pepper and Ginger ; and in 

 the external integuments of many seeds, but never 

 in the cotyledon. They are extracted by means of 

 expression or distillation, and are extremely numer- 

 ous ; and perhaps every plant possessing a pecu- 

 liar odour possesses also a peculiar and volatile oil. 

 The aroma of plants therefore, or the substance 

 from which they derive their odour, and which is 

 cognizable only by the sense of smell, is perhaps 

 merely the more volatile and evaporable part; of 

 their volatile oil, disengaging itself from its com- 

 binations. 



Properties Volatile oils arc characterized by their strong and 

 aromatic odour, and rather acrid taste. They are 

 soluble in alcohol, but are not readily converted 

 into soaps by alkalies. They are very inflammable, 

 and are volatilized by a gentle heat. Like fixed 

 oils their specific gravity is generally less than that 

 of water, on the surface of which they will float; 

 though in some cases it is found to be greater than 

 that of water, in which they consequently sink. 

 They are much in request on account of their 

 agreeable taste and odour, and are prepared and sold 



