EXTEACTION OF AROMA. 23 



fact that the heat, being applied directly, has a tendency to char or 

 burn the materials adjacent to the bottom, and thus appreciably affect 

 the quality of the aromatic product distilled over. 



This method has been largely superseded in modern times by dis- 

 tillation with steam, the principles of which depend upon the prop- 

 erty of the steam as it passes through the charged apparatus to 

 carry with it the volatile portion of the plant in the form of vapors, 

 which are condensed, together Avith the excess of watery vapor, and 

 deposited in the receiving vessel. The three steps in the process are 

 (1) the distilling, (2) the condensing of the vapors, and (3) the col- 

 lecting of the oil. Even though the boiling points of the volatile 

 oils separated by distillation from plants may be considerably 

 higher than the temperature of steam, the odors are readily liberated 

 by the passing steam and carried over. 



APPARATUS. 



The apparatus required for the three processes which collectively 

 constitute steam distillation is of comparatively simple construction, 

 consisting of (1) a still, (2) a still head (cover for body), (3) a con- 

 denser, and (i) a receiver. 



The body of the still, or the receptacle In which is placed the 

 material from which the oil is to be extracted, gives best results when 

 cylindrical in form and may be constructed of various materials, 

 preferably copper. However, some stills are made with wooden 

 bodies. Galvanized iron heavily tinned on the interior is a suitable 

 material, principally because of its cheapness and durability. The 

 still may be constructed of any size desirable, provided the other 

 parts, the condenser and the receiver, are in proportion, depending 

 upon the amount of material to be used and the extent of production 

 desired. 



In figure 4, A represents the still, B the still head, or cover, C the 

 condenser, and D the receiver. Through the side of the still at the 

 point E passes a galvanized steam pipe from three-fourths to 1 

 inch in diameter, extending downward and finally terminating in 

 the middle of the still, as shown by the dotted line. A spigot, F, 

 is attached to the bottom of the still for draining the collectecf water 

 from the apparatus. About 3 inches from the bottom of the still is 

 placed a coarse screen, //, fastened to a wooden frame, which acts 

 as a support for the herb or plant part to be distilled. Encircling 

 the top of the still is an iron collar, which may be conveniently con- 

 structed of angle iron, to which the copper or the metal is securely 

 attached. 



The still head, or cover, B, is of the same material as the still and 

 is slightly conical in shape, with an exit tube terminating in a uni(m, 

 at which point connection may be made with the condenser. Around 



195 



