26 THE PEODUCTION OF VOLATILE OILS AND PERFUMERY PLANTS. 



METHOD OF OPERATION. 



To charge the still, place the false bottom in the still and pack the 

 herb firmly until completely filled. Place a gasket of asbestos rope, 

 heavy cotton wicking, or other suitable material (previously mois- 

 tened) around the top of the still. Place the cover uj^on the mois- 

 tened gasket and clamp securely with heavy steel clamps. Connect 

 the exit pipe from the top of the still to the condenser by means of 

 the union, as indicated in the diagram. Now conduct steam into the still 

 through the inlet pipe, E^ slowly at first, and regulate afterwards so 

 that the distillate jjassing from the end of the condenser is cold or 

 but very slightly warm. The receiving vessel, Z>, should be previously 

 filled three-fourths full of water and placed under the exit from 

 the condenser. Likewise, the cold water is started flowing through 

 the condenser, as indicated by the arrow. Frequently the oil may be 

 led from the receiver by opening the cock on the side. However, 

 owing to the siphon tube attached to the receiver, overflowing is 

 impossible, since this tube carries off the water which separates in 

 the bottom of the receiver. To ascertain when distillation is com- 

 pleted a few drops of the distillate as it comes from the condenser are 

 collected in a glass test tube. The appearance of oily globules on the 

 surface readily indicates whether appreciable quantities of oil are 

 still passing over. Usually a distillation is comj)leted in from one 

 and one-half to two and one-half hours. 



The advantage of steam distillation over other methods of volatile- 

 oil extraction lies principally in its wide applicability and speed of 

 operation. Most plants or plant parts, with the exception of the 

 flowers in some few cases, may be extracted most readily and most 

 expeditiously and with a minimum amount of labor b}^ the steam- 

 distillation method. The simplicity of the operation is obvious. 

 The removal of the oil is much more complete than by any other 

 process. Furthermore, there is produced as a by-product during the 

 distillation an aqueous distillate which is completely saturated with 

 the oil. The aqueous distillate may in many instances be utilized 

 and sold as an "aromatic water" of commerce, especially in such cases 

 as lavender, orange flowers, rose, etc. The aromatic waters possess 

 excellent odors, largely because of the extreme dilution of the odorous 

 compounds held in solution, and are useful in the perfumery and 

 toilet-preparation industries. "VATien the aqueous distillate from the 

 plant has no marketable value, it may be profitably collected and re- 

 turned to the boiler. In case of a further distillation of the same 

 plant it will materially add to the yield of oil, since the distillate is 

 a saturated solution of the oil. Many oils are extremeh^ soluble in 

 water. Distillates from oils of this class usually augment consid- 

 erablv the vield of oil when returned to the boiler and transformed 

 into steam and oil vapors. 



195 



