134 MODERN SCIENCE READER 



evaporation of the dissolving agent, yield the less volatile 

 odorous substances in the form of a thin or thick liquid, 

 sometimes even of the consistency of a salve, mostly color- 

 less or pale in color. These substances are generally 

 called essential or volatile oils. They all have the property 

 of being entirely volatile with steam, and for this reason 

 they are easily separated from other substances. The 

 plants are put into stills filled with water, and steam is 

 forced through in such a way that, after it has heated 

 plants and liquid to the boiling point, it can escape into a 

 cooled receiver, where it is condensed. It has by degrees 

 taken from the plants all their essential oil, and carries it 

 with itself into the receiver, where it collects in drops upon 

 the surface of the condensed liquid. From large quan- 

 tities of the distillate these drops can be gathered together 

 and separated from the liquid by pouring off or skimming. 



This method has likewise been long in use in various 

 parts of the world ; it is practised in some places in a very 

 primitive form, and has made possible the production of 

 a great number of fragrant volatile oils. 



The very costly oil, or attar, of roses, is manufactured 

 in Persia, and now especially in Bulgaria. On the island 

 of Luzon, in the Philippines, and in Java is produced 

 from the blossoms of a tree belonging to the family of 

 Anonaceae Cananga odoratatlie no less exquisitely 

 fragrant oil of ylang-ylang, called in Java, oil of cananga, 

 In France neroli oil, an important constituent of eau-de- 

 cologne, is obtained from orange blossoms to say nothing 

 of the numerous oils, less costly, but still valuable, employed 

 in the greatest quantities in the manufacture of perfum- 

 ery, soaps and cordials, as, for example, rose-geranium, 

 peppermint, lavender, etc. 



The volatile oils produced by either method are char- 

 acterized, as has already been remarked, by fixed proper- 

 ties, especially by their individual and very strong odor, 

 which to a certain degree can at once be distinguished 

 from any other. 



