VOLATILE OILS. 4I 



similar in their chemical characters they react similarly 

 physiologically. 



In elemental composition volatile oils are alike. They 

 all contain carboii and Jiydrogen. Most of them con- 

 tain oxygen and a few contain nitrogen or sulphur, or 

 both. !Most of the volatile oils contain many hydro- 

 carbons and other compounds as well. These com- 

 pounds belong to either the aliphatic organic compounds, 

 or to the aromatic series, and a number of classes of 

 these are found. The hydrocarbons are of wide occur- 

 rence, particularly terpenes, CjoH^g. From the stand- 

 point of the perfumer the oxygenated compounds are 

 the most important, since they impart the characteristic 

 odors. 



The other compounds found associated with the 

 hydrocarbons may be alcohols, aldehydes, esters, ke- 

 tones, phenols, phenolethers, lactones, oxides, sulphides, 

 nitriles, and isothiocyanates. 



The hydrocarbons of both aliphatic and aromatic 

 nature are knowTi; heptane, C^H^g, from a species of 

 pine, being the lowest paraffine. The higher hydrocar- 

 bons of this series include many of the waxes and waxy- 

 like coatings of leaves. The wax candles made by the 

 early colonists from the waxberry, or Myrica, represent 

 some of these higher hydrocarbons of this paraffine 

 group. The oils from arnica flowers, from chamomile, 

 dill, caraway, sassafras leaf, wintergreen, sweet birch, 

 and wild bergamot contain members of this series. 



In the aromatic series the more characteristic volatile 

 oils are obtained. Styrene (C^Hg . CH = CH2) represents 

 the lowest of this group. It is found in oil of storax, 

 and probably results from the breaking-down of cinnamic 

 acid. 



The principal aromatic hydrocarbons belong to the 

 class of terpenes, with the general formula C,oH,,. The 

 majority of these are found ready formed in the plant. 



