PERFUMES AND ESSENTIAL OILS 



345 



The extraction of essential oils from the plants which contain 

 them is accomplished in most cases by a process of distillation 

 with water. The essential oil usually boils at a much higher 

 temperature than water, but the vapour rises with the steam and 

 both are condensed together, the oil then floating to the surface 

 of the water from which it may be separated. The principle of 

 the process may be easily understood by reference to the diagram. 



FIG. 116. DISTILLING AND CONDENSING APPARATUS. 



The body of the still A is generally cylindrical and is of rather 

 large dimensions on account of the usually bulky character of 

 the plant material to be operated on. B is the still head or cover 

 which is usually removable. C is the condenser supplied with a 

 stream of cold water which enters at the bottom by the pipe 

 indicated by the arrow, and being warmed by the steam pipes 

 within escapes at the upper pipe to the drain. D is the receiver 

 in which both essential oil and condensed water are collected, 

 the former remaining above in a separate layer, and the water 

 retaining a small quantity of dissolved essence running off 

 continuously by means of the siphon pipe into another receptacle. 

 E shows where a pipe conveying steam may be driven into the 



