COMPOSITION OF OILS. 205 



oils are all lighter than water, fluid at common 

 temperature, and very combustible. 



511. Amongst the solid oils maj be mentioned the. 

 oils of palms and cocoa-nuts, and the various vege- 

 table butters. The different waxes, too, of which 

 there are a great number, are closely connected in 

 nature with these solid vegetable oils. These sub- 

 stances all consist of carbon, oxygen, and hydrogen. 



512. The volatile oils, such as those of turpen- 

 tine, lemons, orange-peel, bergamot, sabine, and pep- 

 per, (Stc, are pure hydrocarbons. They contain no 

 oxygen ; while those of cloves, peppermint, caraway, 

 and lavender, &c., contain oxygen. Camphor may be 

 said to be an oxidized volatile oil ; its composition is 

 the same as oil of turpentine, with the addition of 

 one equivalent of oxygen. 



513. When the fixed oils are acted on by bases, 

 they are decomposed, and resolved into certain fatty 

 acids, and a peculiar sweet, uncrystallizable substance 

 called glycerine. Most of these oils are mixtures of 

 three distinct, fatty substances, distinguished by dif- 

 ferent properties ; these are termed stearine, marga- 

 rine, and elaine or oleine, and, when acted on by a 

 base, they are respectively decomposed into glycerine, 

 and stearic, margaric, or oleic acid. 



514. Stearine is a white, friable, crystalline solid, 

 which exists in many of the solid oils ; it melts at a 

 temperature of 130° ; when saponified or heated 

 with a base, such as potash, it is decomposed, and 

 yields a soap, or salt of stearic acid and potash. 



18 



