152 COHESION OF LIQUIDS. 



oil passes over. At 360 it boils but on losing 

 its essential oil, it becomes more tenacious, and 

 requires a temperature of 500 F. to make it boil 

 thus, passing from the state of a volatile to that 

 of a fixed oil. 



The oil of anise is composed of 10 atoms carbon, 

 6 of hydrogen, and 1 of oxygen, making its proxi- 

 mate atom equal to 74 while the oil of pepper- 

 mint consists of C 10 H 10 O, making its compound 

 equivalent 78: so that in their atomic constitution 

 they resemble naphthalin, forming a medium be- 

 tween the more volatile oil of lemons, and those 

 termed fixed. 



According to Dumas, the oil of cloves is com- 

 posed of 20 atoms carbon, to 13 of hydrogen, and 

 5 of oxygen, making its proximate atom 173. It 

 is accordingly very difficult to volatilize, like the 

 fixed oils from which it is probable, that their 

 atomic constitution is similar, and determines 

 their tenacity. 



When the volatile oils are exposed to the atmos- 

 phere, they absorb oxygen, by which they become 

 resinous and concrete. The oil of turpentine is 

 thus converted into rosin. By absorbing oxygen, 

 the fixed oils become rancid, and much more 

 rapidly in warm than cold weather during which 

 process, carbonic acid is produced, and heat 

 evolved, as in fermentation. Hence, the spon- 

 taneous combustion of cotton goods which have 

 imbibed oily matter. They all give out great 



