ODORS AND THE SENSE OF SMELL. 



685 



the molecular edifice. The efforts which have been recently made 

 to fill this void are more difficult to expound and follow than 

 fruitful in applications. 



Six methods of extracting perfumes are known : The first is ex- 

 pression, by means of a special press, which is applicable without 

 too great loss to fruit-skins rich in essential oils, such as orange 

 and citron peel, previously grated. Another method is that of 

 distillation, which consists in heating flowers with water in a 

 boiler. The essential oil is volatilized and is condensed with the 

 vapor of water in a worm and a Florentine receiver. The water 

 usually goes to the bottom and the oil floats. The oils of neroli, 

 rose, patchouli, geranium, lavender, caraway, etc., are obtained in 

 this way. This process is not applicable to the delicate perfumes 

 of the mignonette and the violet ; and for them recourse is had 

 to maceration of the flowers in animal fats or mineral oils, which 

 have the property of absorbing odorous substances, and are then 

 washed in alcohol. The flowers are usually heated in the fat or 

 the oil for a variable number of hours. For perfumes which can 

 not endure a high temperature the petals are placed between two 

 frames of glass coated with fat. This is the process of enfleurage. 

 The pneumatic process, which consists in causing a current of 

 perfumed air or carbonic acid to be absorbed by coatings of lard 

 on glass plates, appears not to have given satisfactory results. 

 Another process consists in dissolving perfumes in very volatile 

 liquids like sulphuret of carbon, chloroform, naphtha, ether, or 

 chloride of methyl, and volatilizing the solvents, which can be 

 done at a low temperature in a vacuum. The last method has 

 given very satisfactory results in the extreme delicacy and great 

 accuracy of its returns. 



