ESSENTIAL OILS. 885 



dicine are so prepared. These liquors are improved by a second 

 distillation, or by keeping for some time in a cool place when 

 contained in opaque vessels imperfectly closed, during which 

 some foreign matters which have been distilled along with the 

 oil, disappear. The volatile oils are all very soluble in alcohol, 

 and the more so the less water it contains. With alcohol of 

 0.820, oil of turpentine may be mixed in a large proportion, and 

 such a liquid is sometimes burned in a lamp properly con- 

 structed for the purpose. The oils which contain oxygen, such 

 as those of lavender and peppermint, dissolve more readily in 

 aqueous alcohol than the pure hydrocarbons. Such solutions of 

 essential oils in alcohol are lavender ivater, eau de Cologne^ &c. 

 They are rendered turbid by water, which combines with the 

 alcohol and liberates the oil. Essential oils are soluble in 

 ether. They are capable of dissolving at a high temperature a 

 considerable quantity of sulphur and a small portion of phos- 

 phorus ; and may be combined or mixed with bisulphuret of 

 carbon, chlorides of sulphur, of phosphorus, of carbon and 

 arsenic. They combine with several vegetable acids, such as 

 acetic, oxalic, succinic acids, the oily acids, camphoric and 

 suberic acids. With the exception of oils of cloves, cinnamon 

 and cedar wood, the volatile oils do not combine with salifiable 

 bases ; they differ entirely in this respect from the fixed oils 

 which are saponified by alkalies. After being brayed with 

 sugar the volatile oils dissolve better in water. Volatile oils 

 dissolve all the fat oils, resins, and animal fats. 



Many volatile oils contain no oxygen, and in all of these, 

 with one or two exceptions, the carbon and hydrogen are 

 C 5 H 4 , or some multiple of these numbers ; but the larger pro- 

 portion are oxides. Several of the latter part with their whole 

 oxygen, with a proportional quantity of hydrogen, as water, 

 under the action of anhydrous phosphoric acid, and are con- 

 verted into pure oily hydrocarbons. 



A. ESSENTIAL OILS CONTAINING NO OXYGEN. 

 OIL OF TURPENTINE. 



Formula: C 20 H 16 . It is derived from several kinds of tur- 

 pentine, a semi-fluid resin exuding from the different species of 

 the pine. The turpentine is distilled with water, the oil comes 



