.132 VEGETABLE SUBSTANCES. 



is formed when skins are tanned and made into 

 leathe7\ 



Wax. — This substance appears to be formed by 

 bees, by some animal process. It is also a vege- 

 table substance, for the polish or varnish of leaves 

 is owing to a coating of wax ; and in some vege- 

 tables in Brazil wax exists in considerable quan- 

 tity; Wax is insoluble in water, but sparingly 

 dissolved by boiling alkohol. It is dissolved rea- 

 dily by the fixed oils, and then forms cerates and 

 ointments. Wax contains a large proportion of 

 carbon, with hydrogen and oxygen. 



Camphor. — This substance is brought chiefly 

 from Japan, and is distilled from a species of laurel. 

 It is white and semitransparent ; it is very inflam- 

 mable, soluble in alkohol, and sparingly so in water. 

 It is very volatile, and capable of converting into 

 an acid, called the camphoric acid, which form 

 ' neutral salts called camphorates. Camphor resem- 

 bles essential oil in many of its properties. 



Bitter principle. — It is supposed that this is a 

 peculiar principle. It exists in many vegetables, 

 particularly in quassia, gentian, hop, &c. When 

 extracted, it is of a brownish yellow colour, and 

 brittle when dry. Its taste is very bitter. It is 

 soluble in water and alkohol. A variety of it is 

 supposed to exist in unroasted coflfee. 



Narcotic priiiciple. — This has lately been called 

 morphine, and is found most abundantly in opium, 

 which consists of this together with several of the 

 principles which have been just described. It is a 

 violent poison when taken internally. When pure 

 it is white, without taste or smell. It is soluble in 

 boiling alkahol, but is scarcely acted upon by water. 



From the rapid progress of chemistry, many 

 other vegetable substances are considered as pe- 



