220 Chemistry. [Lecture 3 1 . 



behind. The same test will of course determine 

 whether they have been adulterated with any of 

 the fixed oils. They are very numerous, and 

 differ in fragrance according to the vegetable 

 which has produced them ; the most common 

 are oil of turpentine, of lavender, and camo- 

 mile. 



Camphor, according to some chemists, be- 

 longs to the class of essential oils, on account of 

 its strong and diffusive smell, being very inflam- 

 mable, and burning with great obstinacy, even 

 sometimes upon the surface of water. Its flame 

 is very white and bright. It impregnates water 

 with its taste and odour, and dissolves very 

 readily in spirit of wine, from which it may be 

 separated by water. In ail these qualities it 

 agrees with the aromatic oils, but differs from 

 them in appearing always in a solid form. 



When exposed to heat, it leaves no feculencies 

 behind, and cannot, like the rest, be resolved 

 into an acid water and charcoal. Instead of 

 b.eing liquefied by heat, it totally evaporates be- 

 fore it becomes liquid: for it is one of those 

 bodies which have their evaporating point below 

 that of their fluidity, while under the pressure of 

 the atmosphere ; but if close corked up, it melts 

 into a transparent fluid. 



To this class may perhaps also be referred 

 balsams and resins, which differ from the oils 

 chiefly in their degree of consistence. Some of 

 the balsams approach in fluidity and tenacity the 



