354 



ODOROGEAPHIA. 



fermented plant, at as low a temperature as possible, or at least by 

 one at which the oil will not be carried over with the solvent. 

 The tension of the vapour of these oils is not recorded, but the 

 evaporation can be effected by one of the following methods, 

 according to the degree of volatility of the oil. The apparatus 

 required being in each case the same, — a difference only being 

 made in the temperature applied to the retort and the temperature 

 (or degree of cold) applied to the condenser. 



For working on a small quantity of material the apparatus can 

 be arranged as per sketch annexed : — 



The ethereal solution of the oil contained in the aqueous 

 distillate is put into the retort A, which is connected with the 

 receiver B, the connection being made perfectly air-tight by a well- 

 fitting cork covered with wax. The tube G of the receiver (also 

 hermetically connected) is provided with a well-ground tap C, 

 communicating with the air-pump D. "When the air is exhausted 

 by the action of the pump, the tap C is closed ; the difference of 

 temperature between the retort and the receiver (which in this 

 arrangement is also the condenser) causes the distillation to 

 proceed. The liquid to be distilled over is of course the ether or 

 other solvent, and the oil resulting from the operation remains in 

 the retort. 



